feat: integrate iroh-gossip for mesh networking, using ALPN for protocol routing and node events to manage gossip topics.

.gitignore

@@ -0,0 +1,17 @@
+# Rust / Cargo
+/target/
+Cargo.lock
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Environment
+.env
+.env.local

Cargo.toml

@@ -0,0 +1,59 @@
+[workspace]
+resolver = "2"
+members = [
+    "lattice-core",
+    "lattice-net",
+    "lattice-cli",
+]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+
+[workspace.dependencies]
+# Workspace crates
+lattice-core = { path = "lattice-core" }
+lattice-net = { path = "lattice-net" }
+lattice-cli = { path = "lattice-cli" }
+
+# CLI
+rustyline = "17"
+
+# Networking (Iroh)
+iroh = { version = "0.95", features = ["discovery-local-network"] }
+iroh-gossip = "0.95"
+
+# Cryptography
+ed25519-dalek = { version = "2", features = ["rand_core"] }
+rand = "0.8"
+
+# Serialization
+prost = "0.13"
+prost-types = "0.13"
+prost-build = "0.13"
+
+# Async runtime
+tokio = { version = "1", features = ["full"] }
+tokio-util = { version = "0.7", features = ["codec"] }
+futures-util = "0.3"
+
+# Utilities
+thiserror = "2"
+tracing = "0.1"
+bytes = "1"
+dirs = "5"
+blake3 = "1"
+hex = "0.4"
+redb = "2"
+uuid = { version = "1", features = ["v4"] }
+chrono = "0.4"
+
+# Testing
+tokio-test = "0.4"
+
+[workspace.lints.rust]
+unsafe_code = "forbid"
+
+[workspace.lints.clippy]
+all = "warn"

core/lattice-proto/.gitignore

@@ -1,3 +0,0 @@
-target/
-blobs/
-identity.key

core/lattice-proto/Cargo.toml

@@ -1,21 +0,0 @@
-[package]
-name = "lattice-proto"
-version = "0.1.0"
-edition = "2021"
-
-[dependencies]
-anyhow = "1.0"
-blake3 = "1.5"
-bytes = "1.5"
-clap = { version = "4.5", features = ["derive"] }
-ed25519-dalek = { version = "2.1", features = ["rand_core"] }
-futures = "0.3"
-hex = "0.4"
-iroh = { version = "0.95.1", features = ["discovery-local-network"] }
-iroh-gossip = "0.95.0"
-iroh-tickets = "0.2.0"
-rand = "0.8"
-serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
-tokio = { version = "1.36", features = ["full"] }
-tracing-subscriber = { version = "0.3.22", features = ["env-filter"] }

core/lattice-proto/src/main.rs

@@ -1,434 +0,0 @@
-use serde::{Serialize, Deserialize};
-use std::collections::HashMap;
-use std::sync::{Arc, Mutex};
-use tokio::sync::{mpsc, Notify};
-use ed25519_dalek::{Signer, Verifier, Signature};
-use iroh::{Endpoint, SecretKey, PublicKey}; 
-use iroh::discovery::mdns::MdnsDiscovery;
-use iroh_gossip::net::Gossip;
-use iroh_tickets::endpoint::EndpointTicket; 
-use iroh_gossip::proto::TopicId;
-use iroh::protocol::Router; 
-use futures::StreamExt;
-use std::io::Write;
-
-// --- Data Structures ---
-
-#[derive(Serialize, Deserialize, Debug, Clone)]
-pub struct Entry {
-    pub path: String,
-    pub content_hash: String,
-    pub author: String,
-    pub timestamp: u64,
-    pub signature: Vec<u8>,
-}
-
-#[derive(Serialize, Deserialize, Debug, Clone)]
-pub enum Message {
-    Update(Entry),
-    WantBlob(String),
-    BlobData(String, Vec<u8>), 
-}
-
-// --- Logic ---
-
-type Db = Arc<Mutex<HashMap<String, Entry>>>;
-
-pub struct Node {
-    pub keypair: ed25519_dalek::SigningKey,
-    pub db: Db,
-    pub blobs_dir: std::path::PathBuf,
-    pub gossip_sender: Option<mpsc::Sender<Message>>,
-    pub neighbors: Arc<Mutex<std::collections::HashSet<PublicKey>>>,
-    pub pending_requests: Arc<Mutex<HashMap<String, Arc<Notify>>>>,
-}
-
-impl Node {
-    pub fn new(blobs_dir: std::path::PathBuf) -> Self {
-        let key_path = std::path::Path::new("identity.key");
-        let keypair = if key_path.exists() {
-             let bytes = std::fs::read(key_path).expect("Failed to read key");
-             ed25519_dalek::SigningKey::from_bytes(bytes.as_slice().try_into().unwrap())
-        } else {
-            let pk = ed25519_dalek::SigningKey::generate(&mut rand::rngs::OsRng);
-            std::fs::write(key_path, pk.to_bytes()).expect("Failed to write key");
-            pk
-        };
-
-        if !blobs_dir.exists() {
-            std::fs::create_dir_all(&blobs_dir).expect("Failed to create blobs dir");
-        }
-
-        Self {
-            keypair,
-            db: Arc::new(Mutex::new(HashMap::new())),
-            blobs_dir,
-            gossip_sender: None,
-            neighbors: Arc::new(Mutex::new(std::collections::HashSet::new())),
-            pending_requests: Arc::new(Mutex::new(HashMap::new())),
-        }
-    }
-
-    pub fn load_peers(&self) -> Vec<PublicKey> {
-        let peers_file = self.blobs_dir.parent().unwrap().join("peers.txt");
-        if !peers_file.exists() {
-            return Vec::new();
-        }
-        let content = std::fs::read_to_string(&peers_file).unwrap_or_default();
-        content.lines()
-            .filter_map(|line| std::str::FromStr::from_str(line).ok())
-            .collect()
-    }
-
-    pub fn save_peer(&self, peer: PublicKey) {
-         let peers_file = self.blobs_dir.parent().unwrap().join("peers.txt");
-         // Avoid duplicates in file trivially by checking if already known in memory?
-         // But restart clears memory.
-         // Just append. Ideally we read all and check, but performance.
-         // Let's just append.
-         let mut file = std::fs::OpenOptions::new()
-            .create(true)
-            .append(true)
-            .open(peers_file)
-            .expect("Failed to open peers file");
-         writeln!(file, "{}", peer).expect("Failed to write peer");
-    }
-
-    pub fn pubkey_hex(&self) -> String {
-        hex::encode(self.keypair.verifying_key().to_bytes())
-    }
-
-    pub fn sign_entry(&self, path: &str, hash: &str, timestamp: u64) -> Vec<u8> {
-        let mut msg = Vec::new();
-        msg.extend_from_slice(path.as_bytes());
-        msg.extend_from_slice(hash.as_bytes());
-        msg.extend_from_slice(&timestamp.to_le_bytes()); 
-        self.keypair.sign(&msg).to_bytes().to_vec()
-    }
-
-    pub fn verify_entry(entry: &Entry) -> bool {
-        let pubkey_bytes = match hex::decode(&entry.author) {
-            Ok(b) => b,
-            Err(_) => return false,
-        };
-        let pubkey_arr: [u8; 32] = match pubkey_bytes.as_slice().try_into() {
-            Ok(a) => a, 
-            Err(_) => return false,
-        };
-        let pubkey = match ed25519_dalek::VerifyingKey::from_bytes(&pubkey_arr) {
-            Ok(pk) => pk,
-            Err(_) => return false,
-        };
-
-        let mut msg = Vec::new();
-        msg.extend_from_slice(entry.path.as_bytes());
-        msg.extend_from_slice(entry.content_hash.as_bytes());
-        msg.extend_from_slice(&entry.timestamp.to_le_bytes());
-
-        let sig_arr: [u8; 64] = match entry.signature.as_slice().try_into() {
-            Ok(a) => a,
-            Err(_) => return false,
-        };
-        let sig = Signature::from_bytes(&sig_arr);
-
-        pubkey.verify(&msg, &sig).is_ok()
-    }
-
-    pub fn put_local(&self, path: String, content: String) -> Entry {
-        let hash = blake3::hash(content.as_bytes()).to_hex().to_string();
-        let blob_path = self.blobs_dir.join(&hash);
-        std::fs::write(blob_path, content).expect("Failed to write blob");
-
-        let timestamp = std::time::SystemTime::now()
-            .duration_since(std::time::UNIX_EPOCH)
-            .unwrap()
-            .as_micros() as u64;
-        
-        let signature = self.sign_entry(&path, &hash, timestamp);
-        
-        let entry = Entry {
-            path: path.clone(),
-            content_hash: hash.clone(),
-            author: self.pubkey_hex(),
-            timestamp,
-            signature,
-        };
-
-        println!("[LOCAL] Writing {} -> {}", path, hash);
-        let mut db = self.db.lock().unwrap();
-        db.insert(path, entry.clone());
-
-        entry
-    }
-
-    pub fn process_update(&self, entry: Entry) -> bool {
-        if !Self::verify_entry(&entry) {
-            println!("[WARN] Invalid Signature for {}", entry.path);
-            return false;
-        }
-
-        let mut db = self.db.lock().unwrap();
-        if let Some(existing) = db.get(&entry.path) {
-            if entry.timestamp <= existing.timestamp {
-                return false;
-            }
-        }
-        
-        println!("[SYNC] Received Update: {} -> {}", entry.path, entry.content_hash);
-        db.insert(entry.path.clone(), entry);
-        true
-    }
-}
-
-// --- Main ---
-
-#[tokio::main]
-async fn main() -> anyhow::Result<()> {
-    tracing_subscriber::fmt::init(); 
-
-    let blobs_dir = std::path::PathBuf::from("blobs");
-    let node = Arc::new(Node::new(blobs_dir));
-    println!("Lattice Node Started. Identity: {}", node.pubkey_hex());
-
-    // Convert Node key to Iroh SecretKey
-    let secret_key = SecretKey::from_bytes(&node.keypair.to_bytes());
-    let node_id = secret_key.public();
-    
-    // Configure MDNS
-    // Note: If build() returns Result, use ?
-    let mdns = MdnsDiscovery::builder()
-         .build(node_id)?; 
-
-    // Bind endpoint
-    let endpoint = Endpoint::builder()
-        .secret_key(secret_key)
-        .discovery(mdns)
-        .bind()
-        .await?;
-        
-    println!("Iroh Node ID: {}", endpoint.secret_key().public());
-    
-    // Spawn Gossip
-    let gossip = Gossip::builder().spawn(endpoint.clone()); 
-    
-    // Spawn Router (The Accept Loop handling Gossip ALPN)
-    let router = Router::builder(endpoint.clone())
-        .accept(iroh_gossip::ALPN, gossip.clone()) 
-        .spawn(); // CORRECTED: No await.
-    
-        
-    // Create and print Ticket
-    let my_addr = endpoint.addr(); // CORRECTED: No ?
-    
-    let ticket = EndpointTicket::new(my_addr); 
-    println!("My Ticket: {}", ticket);
-    
-    let topic_bytes = blake3::hash(b"lattice-test-net").as_bytes().to_owned();
-    let topic_id = TopicId::from_bytes(topic_bytes);
-    
-    // Join 
-    println!("Joining Gossip Topic: lattice-test-net...");
-    
-    // Load persisted peers
-    let initial_peers = node.load_peers();
-    if !initial_peers.is_empty() {
-        println!("Loaded {} persisted peers.", initial_peers.len());
-        // Populate neighbors set specifically for display if desired, 
-        // though NeighborUp will fire when connection is actually established.
-    }
-
-    let (sink, mut stream) = gossip.subscribe(topic_id, initial_peers).await?.split();
-    println!("Joined Gossip Topic: lattice-test-net");
-
-    // Command Loop
-    let (tx_cmd, mut rx_cmd) = mpsc::channel::<String>(100);
-    
-    // Stdin Task
-    tokio::spawn(async move {
-        let stdin = std::io::stdin();
-        loop {
-            let mut line = String::new();
-            if stdin.read_line(&mut line).is_ok() {
-                if tx_cmd.send(line).await.is_err() { break; }
-            }
-        }
-    });
-
-    print!("> ");
-    std::io::stdout().flush()?;
-
-    // Event Loop
-    loop {
-        tokio::select! {
-             Some(line) = rx_cmd.recv() => {
-                 let node = node.clone();
-                 let sink = sink.clone();
-                 let endpoint = endpoint.clone();
-                 let gossip = gossip.clone();
-                 
-                 tokio::spawn(async move {
-                     let parts: Vec<&str> = line.trim().split_whitespace().collect();
-                     match parts.as_slice() {
-                         ["put", path, content] => {
-                             let entry = node.put_local(path.to_string(), content.to_string());
-                             let msg = Message::Update(entry);
-                             if let Ok(msg_bytes) = serde_json::to_vec(&msg) {
-                                 sink.broadcast(msg_bytes.into()).await.ok();
-                                 println!("[GOSSIP] Broadcasted update.");
-                             }
-                         },
-                         ["get", path] => {
-                            let entry_opt = {
-                                let db = node.db.lock().unwrap();
-                                db.get(*path).cloned()
-                            };
-                            
-                            if let Some(entry) = entry_opt {
-                                 let blob_path = node.blobs_dir.join(&entry.content_hash);
-                                 if blob_path.exists() {
-                                     if let Ok(content) = std::fs::read_to_string(blob_path) {
-                                         println!("Content: {}", content);
-                                     }
-                                 } else {
-                                     println!("[MISSING BLOB] Need hash: {}", entry.content_hash);
-                                     
-                                     let notify = Arc::new(Notify::new());
-                                     node.pending_requests.lock().unwrap().insert(entry.content_hash.clone(), notify.clone());
-
-                                     let msg = Message::WantBlob(entry.content_hash.clone());
-                                     if let Ok(msg_bytes) = serde_json::to_vec(&msg) {
-                                         sink.broadcast(msg_bytes.into()).await.ok();
-                                         println!("Requesting blob... waiting...");
-                                         
-                                         // Wait for notification with timeout
-                                         match tokio::time::timeout(std::time::Duration::from_secs(5), notify.notified()).await {
-                                             Ok(_) => {
-                                                 // check again
-                                                 let blob_path = node.blobs_dir.join(&entry.content_hash);
-                                                 if let Ok(content) = std::fs::read_to_string(blob_path) {
-                                                     println!("Content: {}", content);
-                                                 } else {
-                                                     println!("Error reading received blob.");
-                                                 }
-                                             },
-                                             Err(_) => {
-                                                 println!("Timeout waiting for blob.");
-                                                 // Clean up
-                                                 node.pending_requests.lock().unwrap().remove(&entry.content_hash);
-                                             }
-                                         }
-                                     }
-                                 }
-                            } else {
-                                println!("Path not found.");
-                            }
-                        },
-                         ["list"] => {
-                             let db = node.db.lock().unwrap();
-                             for (k, v) in db.iter() {
-                                 println!("{} -> {} (ts: {})", k, v.content_hash, v.timestamp);
-                             }
-                         },
-                         ["connect", arg] => {
-                             use std::str::FromStr;
-                             let topic_bytes = blake3::hash(b"lattice-test-net").as_bytes().to_owned();
-                             let topic_id = TopicId::from_bytes(topic_bytes);
-
-                             if let Ok(ticket) = EndpointTicket::from_str(arg) {
-                                 println!("Connecting via Ticket...");
-                                 let addr = iroh::EndpointAddr::from(ticket);
-                                 let peer_id = addr.id;
-
-                                 // Connect first (ensure transport)
-                                 match endpoint.connect(addr, iroh_gossip::ALPN).await {
-                                     Ok(_) => {
-                                         println!("Connected! Adding to Gossip...");
-                                         match gossip.subscribe(topic_id, vec![peer_id]).await {
-                                             Ok(_) => println!("Subscribed peer to gossip topic!"),
-                                             Err(e) => println!("Gossip subscribe error: {}", e),
-                                         }
-                                     },
-                                     Err(e) => println!("Connection failed: {}", e),
-                                 }
-                             } else if let Ok(peer_id) = PublicKey::from_str(arg) {
-                                 println!("Connecting via Node ID (Discovery) to: {}", peer_id);
-                                 match endpoint.connect(peer_id, iroh_gossip::ALPN).await {
-                                     Ok(_) => {
-                                         println!("Connected! Adding to Gossip...");
-                                         match gossip.subscribe(topic_id, vec![peer_id]).await {
-                                             Ok(_) => println!("Subscribed peer to gossip topic!"),
-                                             Err(e) => println!("Gossip subscribe error: {}", e),
-                                         }
-                                     },
-                                     Err(e) => println!("Connection failed: {}", e),
-                                 }
-                             } else {
-                                 println!("Invalid ID or Ticket");
-                             }
-                        },
-                         ["peers"] => {
-                            let neighbors = node.neighbors.lock().unwrap();
-                            println!("Connected Gossip Peers: {}", neighbors.len());
-                            for peer in neighbors.iter() {
-                                println!("- {}", peer);
-                            }
-                        },
-                        ["quit"] => std::process::exit(0), // Can't break loop from spawn
-                        _ => println!("Unknown command. Usage: put <path> <content> | get <path> | list | connect <ticket_or_node_id> | peers"),
-                    }
-                    print!("> ");
-                    std::io::stdout().flush().ok();
-                 });
-             },
-             Some(res) = stream.next() => {
-                 let event = res?;
-                 match event {
-                    iroh_gossip::api::Event::Received(msg) => {
-                         if let Ok(message) = serde_json::from_slice::<Message>(&msg.content) {
-                             match message {
-                                 Message::Update(entry) => { node.process_update(entry); },
-                                 Message::WantBlob(hash) => {
-                                     let blob_path = node.blobs_dir.join(&hash);
-                                     if blob_path.exists() {
-                                         if let Ok(content) = std::fs::read_to_string(&blob_path) {
-                                             let reply = Message::BlobData(hash, content.into_bytes());
-                                             if let Ok(reply_bytes) = serde_json::to_vec(&reply) {
-                                                sink.broadcast(reply_bytes.into()).await.ok(); 
-                                             }
-                                         }
-                                     }
-                                 },
-                                  Message::BlobData(hash, data) => {
-                                     let blob_path = node.blobs_dir.join(&hash);
-                                      if !blob_path.exists() {
-                                         std::fs::write(blob_path, data).expect("Failed to write blob");
-                                         println!("[SYNC] Received Blob: {}", hash);
-                                         
-                                         // Notify waiters
-                                         if let Some(notify) = node.pending_requests.lock().unwrap().remove(&hash) {
-                                             notify.notify_waiters();
-                                         }
-                                     } 
-                                  }
-                             }
-                         }
-                    },
-                    iroh_gossip::api::Event::NeighborUp(node_id) => {
-                        println!("[GOSSIP] Neighbor Up: {}", node_id);
-                        if node.neighbors.lock().unwrap().insert(node_id) {
-                            node.save_peer(node_id);
-                        }
-                    },
-                    iroh_gossip::api::Event::NeighborDown(node_id) => {
-                        println!("[GOSSIP] Neighbor Down: {}", node_id);
-                        node.neighbors.lock().unwrap().remove(&node_id);
-                    },
-                    _ => {} // Handle Lagged or other future variants
-                 }
-             }
-        }
-    }
-    
-    router.shutdown().await?;
-    Ok(())
-}

docs/architecture.md

@@ -0,0 +1,316 @@
+# Architecture
+
+## Ideas
+
+**Core:**
+- SigChains: Ed25519-signed, hash-chained append-only logs per node.
+- Offline-First: Iroh for networking. Vector clocks identify missing entries on reconnect.
+- Full Replication: All nodes keep all logs until watermark consensus, then prune.
+
+**State:**
+- Log-Based State: KV store derived from entries. Watermarks enable pruning + snapshots.
+- Merkle-ized State: state.db as Merkle tree. O(1) sync checks, efficient diffing, light clients.
+- DAG Conflict Resolution: Entries track ancestry. Forks merge on next write. Tips only in state.db.
+- KV Snapshots: Point-in-time snapshots for log pruning, fast bootstrap, time travel.
+
+**Operations:**
+- Atomic Batch Writes: Multiple key updates as single entry.
+- Conditional Updates (CAS): Update only if current value matches expected hash.
+
+**CRDTs:**
+- LWW-Register: Last-writer-wins for single values.
+- LWW-Element-Set: Set with add/remove, element present if add > remove timestamp.
+
+## Concepts
+
+- Transitive Pairing: Nodes can introduce new nodes to the mesh.
+- Multi-Mesh: A node can participate in multiple meshes (clusters). Each mesh is a group of nodes sharing data.
+- Manifest Store: Joining a mesh means joining a special KV store of type "manifest" that defines the mesh membership. The manifest contains node info (`/nodes/{pubkey}/...`).
+
+## Stack
+
+- rust
+- iroh
+- prost protocol buffers
+- redb (embedded KV store)
+- rustyline (interactive CLI)
+
+### Bootstrap
+
+- New peers request a full state snapshot from their first connection.
+- The snapshot allows them to skip replaying the entire log history.
+- After bootstrap, the node receives incremental updates via gossip.
+
+### Networking
+
+- Designed for mobile clients that may only sync a few times per day.
+- When peers connect, they exchange vector clocks to identify missing entries.
+- Missing entries are fetched via unicast.
+- MAX_DRIFT should be generous (e.g., hours) to accommodate sleeping devices.
+
+Networking modes:
+- Active (servers/laptops on power): Frequent gossip broadcasts, proactive sync.
+- Low-power (mobile/battery): Pull-based sync on wake. Query peers instead of relying on push gossip.
+
+## Parts
+
+### Nodes
+
+- Identified by their Ed25519 public key.
+- Private key stored locally in `identity.key` (not replicated).
+- Node data stored in KV:
+  - `/nodes/{pubkey}/name` = display name
+  - `/nodes/{pubkey}/added_at` = timestamp when added
+  - `/nodes/{pubkey}/status` = `invited` | `active` | `dormant` (removal deletes keys)
+  - `/nodes/{pubkey}/role` = `server` | `device` (optional, hints sync priority)
+- Peer invitation flow:
+  1. Inviter runs `invite <peer_pubkey>` → writes `/nodes/{peer}/info` + `/status`
+  2. Inviter shares their Iroh NodeId out-of-band (QR code, link, text)
+  3. Invited peer runs `join <inviter_nodeid>` → syncs with inviter
+  4. Sync pulls `/nodes/{self}/info` + `/status` → peer is authorized
+  5. `connect` implicitly adds inviter to peer's `/nodes/*` (mutual awareness)
+- Accepting = syncing. The invited peer discovers authorization by receiving the entries.
+- Liveness: Each node tracks `last_seen` locally (from watermark gossip). UI alerts if a peer hasn't been seen for threshold (e.g., 30 days). User decides to mark dormant/disabled.
+- Status effects:
+  - `active`: Normal sync participant, blocks watermark until acknowledged.
+  - `dormant`: Excluded from watermark consensus, can be reactivated.
+  - `disabled`: Permanently removed from mesh.
+- Sync priority: Low-power clients prefer peers marked as `server` or recently active.
+
+Future:
+- Key rotation: Allow nodes to rotate their keypair. Old key signs a "rotation" entry pointing to new key.
+- Secure storage: Support platform keystores (macOS Keychain, Linux Secret Service, TPM) for private key protection.
+
+### Data Model
+
+- Multiple KV stores supported, identified by `store_id` (UUID).
+- Keys: Arbitrary byte arrays (`Vec<u8>`), sorted lexicographically.
+- Values: Arbitrary byte arrays (`Vec<u8>`).
+- Each store defines its own key/value format — applications know their schema.
+- Logs are per `(store_id, author_id)` tuple.
+- State is maintained by tracking the "frontier" (tips) of the causal graph for each key.
+- Entry ordering: by HLC timestamp, then by author ID as tiebreaker.
+
+**Sync vs Causality:**
+- Vector Clocks track log coverage ("I have entries from Node A up to seq 50") — syncing files.
+- DAG Parents track data causality ("This value replaces that value") — resolving key conflicts.
+
+#### DAG Conflict Resolution
+
+Instead of simple LWW where newest timestamp blindly overwrites, every entry tracks its ancestry:
+
+**Data Model:**
+- Each entry includes `parent_hashes` — references to the entries it supersedes
+- History forms a DAG (directed acyclic graph), not a linear chain
+- state.db stores only "tips" (heads) of the graph per key
+
+**Life Cycle:**
+
+1. **Write (normal):** New entry points to previous entry's hash as parent. History is a straight line.
+
+2. **Write (concurrent/offline):** Two nodes edit same key independently, both pointing to same old parent. History forks into two branches.
+
+3. **Read (forked):** System sees multiple valid values. Uses deterministic rule (highest HLC, then author_id tiebreaker) to return one "winner". No error thrown.
+
+4. **Merge (healing):** Next write to that key cites both existing branches as parents. Fork merges back to single tip.
+
+**Example: Partial Write (Branch Extension)**
+
+```
+Initial: Heads = {A, B} where A(ts:100), B(ts:105). Read winner = B.
+
+Offline node C wakes up, only knows A (hasn't seen B).
+C writes "v3" with parent = [A].
+
+Result: Heads = {C, B}. Conflict shifted, not resolved.
+        C(ts:110) > B(ts:105), so C wins reads.
+
+       ┌──> [A] ──> [C:110]
+[Root]─┤
+       └──> [B:105]
+
+Later: A synced node writes D with parents = [C, B].
+Result: Heads = {D}. Fork merged.
+```
+
+This preserves B's work even though C never saw it. Naive LWW would lose B forever.
+
+#### Store Consistency Modes
+
+- **Eventually consistent**: Default. Writes accepted locally, sync happens async. Fast, offline-capable.
+- **Strictly consistent**: Writes require quorum acknowledgment before commit. Slower, requires connectivity.
+
+### Timestamps (Hybrid Logical Clocks)
+
+Timestamps use HLC `<wall_time, counter>` with Causal Clamping:
+
+- Each entry includes an HLC and a reference to its parent (prev_hash).
+- Standard HLC: `new_hlc = max(local_wall_clock, max_seen_hlc + 1)`.
+- On receive: if `entry.hlc > local_wall_clock + MAX_DRIFT`, clamp to `parent.hlc + 1`.
+- All nodes compute the same clamped time from the parent (deterministic).
+- Genesis entries (no parent) with future timestamps are dropped.
+
+Pre-flight check (before signing):
+- Compare local_clock to max_peer_hlc (from recent gossip/entries).
+- If `local_clock > max_peer_hlc + MAX_DRIFT`, use `max_peer_hlc + 1` instead.
+- This catches future-clock nodes before they poison the log.
+
+Authors apply their own entries through the standard receive path to ensure consistent clamping.
+
+### Storage
+
+Each node stores logs as one file per author:
+
+```
+~/.local/share/lattice/
+├── identity.key                            # Ed25519 private key
+├── stores/
+│   └── {store_uuid}/
+│       ├── logs/
+│       │   └── {author_id_hex}.log         # Append-only SignedEntry stream
+│       └── state.db                        # redb: KV snapshot + frontiers
+└── meta.db                                 # redb: global metadata (known stores, peers)
+```
+
+- Logs: Append-only binary files per `(store, author)`, containing serialized `SignedEntry` messages.
+- State DB (redb): Per-store KV state and frontiers. Updated as entries are applied.
+
+#### state.db Tables (per store, redb)
+
+```
+Table              Key                     Value                      Purpose
+─────────────────────────────────────────────────────────────────────────────
+kv                 Vec<u8> (key)           Vec<HeadInfo>              Current tips for each key
+AUTHOR_TABLE      [u8; 32] (author_id)    (u64 seq, [u8; 32] hash)   Per-author frontier tracking
+meta               Vec<u8>                 Vec<u8>                    Store metadata (incl. merkle_root)
+```
+
+`HeadInfo: { value: Vec<u8>, hlc: u64, author: [u8;32], hash: [u8;32] }`
+
+Note: KV stores multiple heads per key to support DAG conflict resolution. Reads pick winner deterministically.
+
+#### meta.db Tables (global, redb)
+
+```
+Table              Key                     Value                      Purpose
+─────────────────────────────────────────────────────────────────────────────
+stores             [u8; 16] (UUID)         u64 (created_at_ms)        Known stores
+meta               "root_store"            [u8; 16] (UUID)            Root store ID (opened on startup)
+```
+
+- **Root Store**: The primary/manifest store for this node, auto-opened on CLI startup
+- **Stores Table**: Tracks all stores this node participates in
+- Manifest stores define mesh membership via `/nodes/{pubkey}/...` entries
+- Data stores hold application data
+
+#### In-Memory Structures
+
+- log_frontiers: `HashMap<AuthorId, (seq, hash)>` — rebuilt from log files on startup
+
+### Operation Flow (put/delete)
+
+```
+1. User calls put("/key", value)
+         │
+         ▼
+2. SigChain.create_entry()
+   - Build Entry with parent_hashes (current tips for key)
+   - Sign it → SignedEntry
+         │
+         ▼
+3. Append to log + Gossip (critical path)
+   - Write to author's log file
+   - Update log_frontiers (in-memory)
+   - Broadcast to peers
+         │
+         ▼
+4. Apply to state.db (background)
+   - Update kv heads (merge parent tips into new tip)
+   - Update applied_frontiers
+   - Update merkle_root hash
+```
+
+Fast path (1-3): durable + distributed. Background (4): queryable state.
+
+### Read Flow (get)
+
+`get(key)` reads directly from local state.db. Reads are eventually consistent — if state.db lags behind the log, the read may return slightly stale data.
+
+### Watermarks
+
+- Nodes gossip their watermarks periodically (throttled).
+- A watermark is a vector clock: how much of each author's log the node has seen.
+- All nodes keep all logs (own + others) for redundancy until watermark consensus.
+- Once all peers have acknowledged entries, they can be pruned and replaced by the snapshot.
+- If a node is offline too long, it re-bootstraps with a fresh snapshot when it reconnects.
+- Note: Consider preserving logs longer than required for redundancy — enables time travel (view state at any point in history).
+
+**Pruning and DAG Parents:**
+- If a new entry references a parent that was pruned, accept it only if strictly newer than snapshot timestamp.
+- Snapshots act as the base; entries referencing parents older than snapshot are roots relative to that snapshot.
+
+### Rich CRDTs (Future)
+
+Instead of a generic scripting language, use specific data types that merge better than LWW.
+
+Extend value types in redb:
+
+```rust
+enum ReplicatedValue {
+    LWW(Vec<u8>),          // Standard Last-Write-Wins (current model)
+    Counter(i64),          // PN-Counter (Increment/Decrement)
+    Set(HashSet<Vec<u8>>), // OR-Set (Observed-Remove Set)
+}
+```
+
+**Counter** (for "storage used" etc.):
+- State is `{node_id: value}` map. Merge = sum all nodes. No conflicts possible.
+
+**OR-Set** (for group membership etc.):
+- Merge = union. Element present if add timestamp > remove timestamp.
+
+**Op Code Compromise**: Use commutative operations instead of a VM:
+
+```protobuf
+message Entry {
+  oneof operation {
+    PutOp put = 1;
+    DeleteOp delete = 2;
+    MergeOp merge = 3;
+  }
+}
+
+message MergeOp {
+  string key = 1;
+  oneof payload {
+    int64 counter_delta = 2;
+    bytes set_add_member = 3;
+    bytes set_remove_member = 4;
+  }
+}
+```
+
+Recommendation: Use Put/Delete for 90% of data. Add CRDT primitives only when needed (concurrent counters, lists) rather than a scripting language.
+
+## Open Questions
+
+### Permissions
+
+Write permissions are enforceable cryptographically:
+- Every entry is signed by author
+- Nodes verify signature before accepting
+- Manifest defines allowed writers: `/nodes/{pubkey}/role` = `writer` | `reader`
+- Entries from non-writers are rejected
+
+Read permissions are not enforceable:
+- Sharing a store = granting read access
+- Encryption adds a layer but doesn't solve revocation (once you have the key, you can read past data)
+- True revocation is impossible — you can't "unread" data
+
+Practical model:
+- Share store = grant read
+- Write access defined in manifest
+- Read-only nodes replicate and verify but can't contribute entries
+
+Future:
+- Capability-based permissions: Explore finer-grained write access (e.g., per-key or per-prefix permissions) via capabilities. Exact mechanism TBD.

docs/roadmap.md

@@ -0,0 +1,217 @@
+# Lattice Roadmap
+
+## Milestone 1: Single-Node Append-Only Log
+
+**Goal:** A single node can create, sign, and persist entries to its own log. No networking yet.
+
+### Deliverables
+
+- [x] HLC timestamps
+- [x] Node identity (Ed25519 keypair, save/load)
+- [x] Entry signing & verification
+- [x] Log file I/O (append, read, hash verification)
+- [x] SigChain (validate entries before appending)
+- [x] Store (redb) — `kv` + `meta` tables, log replay
+- [x] Interactive CLI: `init`, `put`, `get`, `delete`, `status`, `quit`
+
+### Success Criteria
+
+- Can create a new identity
+- Can append entries to local log
+- Can replay log to reconstruct KV state
+- All operations survive restart
+
+### Multi-KV Refactoring (before M2) ✓
+
+- [x] DataDir → `stores/{uuid}/` subdirectories
+- [x] Store → per-store state.db
+- [x] Log paths → `stores/{uuid}/logs/{author}.log`
+- [x] Proto: Entry has store_id (UUID)
+- [x] CLI → `init`, `create-store`, `list-stores`, `use`
+- [x] meta.db stores table (MetaStore)
+- [x] SigChain → validate entry.store_id
+
+---
+
+## Milestone 1.5: DAG Conflict Resolution
+
+**Goal:** Upgrade store from simple LWW to DAG-based conflict resolution per architecture.md.
+
+### Deliverables
+
+- [x] Proto: Add `repeated bytes parent_hashes` to Entry (for DAG causality)
+- [x] Proto: Add `HeadInfo` message for multi-head storage
+- [x] Store: KV table schema → `Vec<u8> → Vec<HeadInfo>`
+- [x] Store: `apply_entry` → track multiple heads, merge parent tips
+- [x] Store: `get` → deterministic winner (highest HLC, author tiebreaker)
+- [x] Store: `get_heads` → inspect all heads for a key
+- [x] EntryBuilder: `.parent_hashes(...)` method for DAG ancestry
+- [x] CLI: Show conflict indicator when multiple heads
+
+### Success Criteria
+
+- [x] Concurrent writes to same key create multiple heads
+- [x] Reads return deterministic winner
+- [x] Next write citing both heads merges fork to single tip
+- [x] All existing tests still pass (71 tests)
+
+---
+
+## Milestone 1.9: Async Refactor
+
+**Goal:** Prepare codebase for concurrent CLI + network operation.
+
+### Deliverables
+
+**Phase 1: Store Actor (sync)** ✓
+- [x] Store actor pattern: dedicated thread owns Store, receives commands via `std::sync::mpsc`
+- [x] StoreHandle wraps channel sender, keeps current API
+- [x] Validate: CLI works as before with actor
+
+**Phase 2: Async Runtime** ✓
+- [x] Add tokio runtime (`#[tokio::main]`)
+- [x] Migrate `std::sync::mpsc` → `tokio::sync::mpsc`
+- [x] Async CLI using `block_in_place` for sync handlers
+
+### Success Criteria
+
+- [x] CLI still works as before
+- [x] Store operations serialized (no data races)
+- [x] Ready for concurrent network tasks
+
+---
+
+## Milestone 2: Two-Node Sync
+
+**Goal:** Two nodes can sync their logs over the network.
+
+### Deliverables
+
+**Phase 1: Sync Logic (no network)** ✓
+- [x] SyncState with AuthorInfo (seq + hash) for hash-based log resumption
+- [x] `Store::sync_state()` → author-to-seq+hash map from AUTHOR_TABLE
+- [x] `SyncState::diff()` → `Vec<MissingRange>` with from_hash for `read_entries_after`
+- [x] Multi-store sync test: compute diff, fetch entries, apply, verify same state
+
+**Phase 2: Iroh Integration**
+
+*Completed:*
+- [x] Node info in root store on init: `/nodes/{pubkey}/info` + `/status`
+- [x] CLI: `invite <pubkey>` to authorize peers
+- [x] CLI: `peers` to list known nodes (with name/added_at info, sorted)
+- [x] CLI: `remove <pubkey>` to remove a peer
+- [x] Iroh endpoint on startup (same Ed25519 key, mDNS + DNS discovery)
+- [x] CLI: `join <nodeid>` - connects to peer, verifies invited
+- [x] Peer verification via `/nodes/{pubkey}/status` check
+
+*Join Protocol (new→existing):* ✓
+- [x] Proto: `JoinRequest` / `JoinResponse` with store UUID
+- [x] Accept handler sends root store UUID in response
+- [x] Join command creates empty store with received UUID (no writes until sync)
+
+*Sync Protocol (bidirectional):* ✓
+- [x] Proto: `PeerMessage` wrapper with `oneof` for message type discrimination
+- [x] `framing.rs` with `MessageSink`/`MessageStream` using `LengthDelimitedCodec`
+- [x] Proto: `SyncRequest`/`SyncResponse` using `SyncState`
+- [x] `Store::read_entries_after(hash)` to fetch log chunks
+- [x] Accept handler: receive SyncState, compute diff, send missing entries
+- [x] Sync command: receive entries, apply to store via `apply_entry`
+- [x] CLI: `sync [nodeid]` command (syncs with all active peers if no nodeid)
+- [x] After sync: node updates own `/nodes/{pubkey}/info` with hostname
+
+*Cleanup*:
+- [x] Move core logic from cmd_join and cmd_sync out of commands.rs (now in `sync.rs`)
+- [x] Add 'invited' state: invite sets 'invited', peer sets 'active' after sync
+
+*Regressions:*
+- [x] Entry ordering: Per-author streaming is correct (hash chain per author, HLC for cross-author).
+- [x] Multi-head sync fixed: SyncState now tracks HashSet of head hashes per author.
+- [x] Sync entry ordering: Entries sent in HLC order (merge-sort across authors) to ensure causal order.
+- [x] `join_mesh` doesn't populate `node.root_store`: Fixed with `complete_join` method.
+
+### Success Criteria
+
+- Node A writes, Node B syncs, both have same state
+- Works offline-first (sync when connected)
+
+**Post-M2 Refactoring:**
+- [x] Unify `node.rs` from `lattice-cli` and `lattice-core`
+- [x] Move network code to `lattice-net`
+
+---
+
+## Milestone 3: Multi-Node Mesh
+
+**Goal:** N nodes form a gossip mesh for real-time sync.
+
+### Deliverables
+
+**Phase 1: LatticeServer Refactor** ✓
+- [x] `LatticeServer` struct in `lattice-net` wrapping `Arc<Node>` + `Endpoint`
+- [x] Move `join_mesh`, `sync_with_peer`, `sync_all` to `LatticeServer` methods
+- [x] Encapsulate accept loop inside `LatticeServer` (via Router + ProtocolHandler)
+- [x] CLI uses `LatticeServer` instead of raw `Node` + `Endpoint`
+- [ ] Integration test: invite → join → sync end-to-end
+- [ ] Periodic background sync with known peers
+- [ ] Track last sync time per peer
+
+**Phase 2: Gossip Protocol** ✓ (iroh-gossip)
+- [x] Router handles both `lattice-sync/1` and `/iroh-gossip/1` ALPNs
+- [x] `NodeEvent::RootStoreActivated` emitted when root store opens
+- [x] Auto-join gossip topic on root store activation
+- [x] Broadcast local entries to gossip topic on commit
+- [x] Receive gossip entries and apply to store
+- [x] Topic ID via `blake3::hash("lattice/{store_id}")`
+- [ ] Gossip bootstrap peers from `/peers/` (needs Prefix Watch)
+
+**Next: Prefix Watch (reactive store updates)**
+- [ ] `store.watch_prefix(prefix) -> Receiver<WatchEvent>`
+- [ ] `WatchEvent::Put { key, value }` / `WatchEvent::Delete { key }`
+- [ ] StoreActor tracks watchers per prefix, emits on matching put/delete
+- [ ] LatticeServer uses `/peers/` watch to update gossip bootstrap peers dynamically
+- [ ] Enables reactive patterns: config changes, presence, app-level subscriptions
+
+---
+
+## Technical Debt
+
+**Logging**
+- [ ] Replace `println!`/`eprintln!` with `tracing` crate (`tracing::info!`, `tracing::error!`)
+- Standard in Rust async ecosystem, used by Iroh internally
+
+**Lifecycle Management (Zombie Tasks)**
+- [ ] Spawned infinite loops (`spawn_node_event_listener`, `spawn_entry_forward_loop`, gossip receive loop) keep running if `LatticeServer` is dropped
+- [ ] Use `tokio_util::sync::CancellationToken` or keep `JoinHandle`s for graceful shutdown
+
+**Error Handling**
+- [ ] Replace `Result<..., String>` with `anyhow::Result` or define `LatticeNetError` enum
+- String errors make it hard to handle specific failure cases
+
+---
+
+## Future
+
+- offline nodes should not delay sync
+- sync command should transitive sync all peers
+- Gossip:
+  - gossip new entries to peers
+  - backfill missing entries from peers (how do peers notice missing entries?)
+  - snapshots for kv store
+  - prune using consensus watermark
+- remove_peer should be a transactional operation on store
+- Watermark tracking & log pruning
+  - Track minimum confirmed seq per author across all peers
+  - Log pruning: remove entries below watermark
+- Multi-KV-Store sync
+- Optimized sync on join. Only transfer current watermark state, then sync missing entries. This would allow pruning. Might need snapshot support in KV store.
+- Mobile (iOS/Android) clients
+- Key rotation
+- Secure storage (Keychain, TPM)
+- Snapshots for fast bootstrap
+- FUSE filesystem mount
+  - Note: FUSE requires u64 inode numbers → maintain `BiMap<u64, Hash>` in redb
+- Merkle-ized State
+  - state.db as Merkle tree with signed root hash
+  - O(1) sync checks (compare root), efficient binary-search diffing
+  - Light clients: fetch value + Merkle proof, verify without full state
+  - Trade-off: write amplification, requires deterministic tree (Patricia Trie / Merkle Search Tree)

docs/storage.md

@@ -0,0 +1,39 @@
+# Storage Format
+
+## Directory Layout
+
+```
+~/.local/share/lattice/
+├── identity.key              # Ed25519 private key (not replicated)
+├── meta.db                   # Global metadata (redb)
+└── stores/{uuid}/
+    ├── logs/{author}.log     # Append-only SignedEntry stream
+    └── state.db              # Per-store KV state (redb)
+```
+
+## meta.db (redb)
+
+| Table   | Key           | Value              | Purpose                      |
+|---------|---------------|--------------------|------------------------------|
+| stores  | UUID (16B)    | created_at (u64)   | Known stores                 |
+| meta    | "root_store"  | UUID (16B)         | Auto-opened on CLI startup   |
+
+## state.db (redb, per store)
+
+| Table   | Key      | Value       | Purpose                |
+|---------|----------|-------------|------------------------|
+| kv      | String   | Vec<u8>     | Key-value data         |
+| meta    | String   | Vec<u8>     | last_seq, last_hash    |
+
+## Log Files
+
+Each `{author}.log` contains length-delimited `LogRecord` messages:
+
+```protobuf
+message LogRecord {
+  bytes hash = 1;         // BLAKE3 hash of entry_bytes
+  bytes entry_bytes = 2;  // Serialized SignedEntry
+}
+```
+
+Hashes are verified on read; corruption causes `LogError::HashMismatch`.

docs/testcases.md

@@ -0,0 +1,37 @@
+# Test Cases
+
+## Timestamp / HLC
+
+### Time-traveling node applies own entry
+- Node X has clock at year 2050
+- Node X creates entry, signs, broadcasts
+- All nodes (including X) should clamp to parent.hlc + 1
+- Verify: X's state.db matches other nodes' state.db
+- Failure mode: X applies using 2050, others use 101 → divergence
+
+### Clamping with no parent (genesis entry)
+- Node X creates first-ever entry with future timestamp
+- All nodes should DROP the entry (no parent to anchor to)
+- Verify: entry is not applied anywhere
+
+### Out-of-order entry arrival
+- Entry B (hlc=91) arrives after Entry A (hlc=100)
+- Both write to same key
+- Verify: A's value wins (LWW with timestamp tracking)
+- Verify: no rollback needed, just comparison on apply
+
+### Clock drift detection
+- Node consistently sees its entries clamped
+- Verify: UI alerts user about clock being ahead
+
+### Clock in past (Pi without RTC, boots at 1970)
+- Node X has clock at 1970
+- Node X receives entries from peers with HLC around 2024
+- Standard HLC: X uses max(1970, peer_hlc + 1) = peer_hlc + 1
+- Verify: X's entries slot in correctly (no special handling needed)
+
+### Pre-flight peer sanity check (future clock)
+- Node X has clock at 2050
+- Before creating entry, X compares local_clock to max_peer_hlc
+- If local_clock > max_peer_hlc + MAX_DRIFT, use max_peer_hlc + 1
+- Verify: X's entry uses sane timestamp, all nodes agree

docs/testing.md

@@ -0,0 +1,74 @@
+# Testing Scenarios (Validation Apps)
+
+These apps test HLC ordering, gossip convergence, and conflict resolution.
+
+## Level 1: Pixel Board (Visual Convergence)
+
+50x50 collaborative grid where users paint pixels.
+
+**Data Model:** `/canvas/{x}_{y}` → `{hex_color}`
+
+**Tests:**
+- Visualize sync disagreements immediately
+- High write volume (log performance)
+- Simultaneous writes (HLC tiebreaker)
+
+**Scenario:** Node A paints all red (offline), Node B paints all blue (offline), connect. Board must be identical on both.
+
+---
+
+## Level 2: Shared Grocery List (LWW Trap)
+
+List with add/check/delete operations.
+
+**Data Model:** `/list/{item_uuid}` → `{ name, status: "needed"|"bought" }`
+
+**Tests:** Exposes LWW weakness (resurrection bug)
+
+**Scenario:**
+1. Alice syncs, sees "Milk", goes offline, marks "bought"
+2. Bob syncs, sees "Milk", deletes it
+3. Reconnect
+
+**Result:** Item either resurrects or vanishes based on timestamp. Forces tombstone pattern.
+
+---
+
+## Level 3: Chat Room (Causal Ordering)
+
+Group chat application.
+
+**Data Model:** `/chat/{channel}/{timestamp}_{node_id}` → `{ msg }`
+
+**Tests:**
+- HLC causal ordering
+- Prefix queries (redb range scans)
+- Gap detection via vector clocks
+
+**Scenario:**
+1. Node A sends "Msg 1"
+2. Node B sees it, replies "Msg 2"
+3. Node C comes online, connects only to B
+
+**Success:** Node C receives "Msg 1" before/with "Msg 2" (transitive sync).
+
+---
+
+## Level 4: Chaos Monkey (Automated Simulation)
+
+Tokio-based simulation harness with in-memory networking.
+
+**Setup:**
+- 5 node threads in one process
+- In-memory network (tokio channels)
+- Chaos monkey randomly: cuts connections, writes random keys, sleeps threads
+
+**Assertion:**
+```rust
+let state_0 = nodes[0].dump_state_hash();
+for i in 1..5 {
+    assert_eq!(state_0, nodes[i].dump_state_hash());
+}
+```
+
+Catches HLC clamping edge cases that manual testing misses.

lattice-cli/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "lattice-cli"
+description = "Interactive CLI for Lattice"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[[bin]]
+name = "lattice"
+path = "src/main.rs"
+
+[dependencies]
+lattice-core = { workspace = true }
+lattice-net = { workspace = true }
+rustyline = { workspace = true }
+hex = { workspace = true }
+thiserror = { workspace = true }
+tokio = { workspace = true }
+shlex = "1"
+serde_json = "1"
+iroh = { workspace = true }
+prost = { workspace = true }
+chrono = { workspace = true }
+tokio-util = { version = "0.7", features = ["codec"] }
+futures-util = "0.3"

lattice-cli/src/commands.rs

@@ -0,0 +1,79 @@
+//! CLI command handlers
+
+use lattice_core::{Node, StoreHandle};
+use lattice_net::LatticeServer;
+
+/// Result of a command that may switch stores or exit
+pub enum CommandResult {
+    /// No store change
+    Ok,
+    /// Switch to this store
+    SwitchTo(StoreHandle),
+    /// Exit the CLI
+    Quit,
+}
+
+/// Helper to call async code from sync command handlers
+pub fn block_async<F: std::future::Future>(f: F) -> F::Output {
+    tokio::task::block_in_place(|| tokio::runtime::Handle::current().block_on(f))
+}
+
+pub type Handler = fn(&Node, Option<&StoreHandle>, Option<&LatticeServer>, &[String]) -> CommandResult;
+
+pub struct Command {
+    pub name: &'static str,
+    pub args: &'static str,
+    pub desc: &'static str,
+    pub group: &'static str,
+    pub min_args: usize,
+    pub max_args: usize,
+    pub handler: Handler,
+}
+
+/// Get all available commands
+pub fn commands() -> Vec<Command> {
+    let mut cmds = Vec::new();
+    
+    // General CLI commands
+    cmds.push(Command { 
+        name: "help", args: "", desc: "Show this help", 
+        group: "general", min_args: 0, max_args: 0, handler: cmd_help as Handler 
+    });
+    cmds.push(Command {
+        name: "quit", args: "", desc: "Exit",
+        group: "general", min_args: 0, max_args: 0, handler: cmd_quit as Handler
+    });
+    
+    // Node commands (operations on the node)
+    cmds.extend(crate::node_commands::node_commands());
+    
+    // Store commands (raw KV operations)
+    cmds.extend(crate::store_commands::store_commands());
+    
+    cmds
+}
+
+fn cmd_help(_node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    let cmds = commands();
+    let mut last_group = "";
+    for cmd in &cmds {
+        if cmd.group != last_group {
+            println!();
+            println!("[{}]", cmd.group);
+            last_group = cmd.group;
+        }
+        let usage = if cmd.args.is_empty() {
+            cmd.name.to_string()
+        } else {
+            format!("{} {}", cmd.name, cmd.args)
+        };
+        println!("  {:18} {}", usage, cmd.desc);
+    }
+    println!();
+    CommandResult::Ok
+}
+
+fn cmd_quit(_node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    println!("Goodbye!");
+    CommandResult::Quit
+}

lattice-cli/src/main.rs

@@ -0,0 +1,121 @@
+//! Lattice Interactive CLI
+
+mod commands;
+mod node_commands;
+mod store_commands;
+
+use lattice_net::LatticeServer;
+use commands::CommandResult;
+use lattice_core::{NodeBuilder, StoreHandle};
+use rustyline::error::ReadlineError;
+use rustyline::DefaultEditor;
+use std::sync::Arc;
+
+#[tokio::main]
+async fn main() {
+    println!("Lattice CLI v{}", env!("CARGO_PKG_VERSION"));
+    println!("Type 'help' for commands, 'quit' to exit.\n");
+
+    let node = match NodeBuilder::new().build() {
+        Ok(n) => Arc::new(n),
+        Err(e) => {
+            eprintln!("Failed to initialize: {}", e);
+            return;
+        }
+    };
+    
+    // Create LatticeServer (creates endpoint and spawns accept loop internally)
+    let server = match LatticeServer::new_from_node(node.clone()).await {
+        Ok(s) => {
+            println!("Iroh:    {} (listening)", s.endpoint().public_key().fmt_short());
+            Some(s)
+        }
+        Err(e) => {
+            eprintln!("Warning: Iroh failed to start: {}", e);
+            None
+        }
+    };
+    
+    let info = node.info();
+    println!("Node ID: {}", info.node_id);
+    println!("Data:    {}", info.data_path);
+
+    if !info.stores.is_empty() {
+        println!("Stores:  {}", info.stores.len());
+    }
+
+    let mut current_store: Option<StoreHandle> = match node.open_root_store().await {
+        Ok(Some(open_info)) => {
+            if open_info.entries_replayed > 0 {
+                println!("Root:    {} (replayed {})", open_info.store_id, open_info.entries_replayed);
+            } else {
+                println!("Root:    {}", open_info.store_id);
+            }
+
+            node.root_store().await.as_ref().cloned()
+        }
+        Ok(None) => {
+            println!("Status:  Not initialized (use 'init')");
+            None
+        }
+        Err(e) => {
+            eprintln!("Warning: {}", e);
+            None
+        }
+    };
+    println!();
+
+    let mut rl = DefaultEditor::new().expect("Failed to create editor");
+    let cmds = commands::commands();
+
+    loop {
+        let prompt = match &current_store {
+            Some(h) => format!("lattice:{}> ", &h.id().to_string()[..8]),
+            None => "lattice:no-store> ".to_string(),
+        };
+
+        match rl.readline(&prompt) {
+            Ok(line) => {
+                let line = line.trim();
+                if line.is_empty() { continue; }
+                let _ = rl.add_history_entry(line);
+
+                let args = match shlex::split(line) {
+                    Some(a) => a,
+                    None => {
+                        println!("Error: mismatched quotes");
+                        continue;
+                    }
+                };
+
+                let cmd_name = args.first().map(|s| s.as_str()).unwrap_or("");
+
+                match cmds.iter().find(|c| c.name == cmd_name || (cmd_name == "exit" && c.name == "quit")) {
+                    Some(cmd) => {
+                        let cmd_args = &args[1..];
+                        if cmd_args.len() < cmd.min_args || cmd_args.len() > cmd.max_args {
+                            println!("Usage: {} {}", cmd.name, cmd.args);
+                        } else {
+                            match (cmd.handler)(&node, current_store.as_ref(), server.as_ref(), cmd_args) {
+                                CommandResult::Ok => {}
+                                CommandResult::SwitchTo(h) => {
+                                    current_store = Some(h);
+                                }
+                                CommandResult::Quit => break,
+                            }
+                        }
+                    }
+                    None => println!("Unknown: '{}'. Type 'help'.", cmd_name),
+                }
+            }
+            Err(ReadlineError::Interrupted | ReadlineError::Eof) => {
+                println!("Goodbye!");
+                break;
+            }
+            Err(e) => {
+                eprintln!("Error: {:?}", e);
+                break;
+            }
+        }
+    }
+}

lattice-cli/src/node_commands.rs

@@ -0,0 +1,313 @@
+//! Node commands - operations on the node (mesh, peers, status)
+
+use crate::commands::{block_async, Command, CommandResult, Handler};
+use lattice_core::{Node, StoreHandle, PeerStatus, Uuid};
+use lattice_net::LatticeServer;
+use chrono::DateTime;
+use std::time::Instant;
+
+pub fn node_commands() -> Vec<Command> {
+    vec![
+        // Store management
+        Command { name: "init", args: "", desc: "Initialize root store", group: "node", min_args: 0, max_args: 0, handler: cmd_init as Handler },
+        Command { name: "create-store", args: "", desc: "Create a new store", group: "node", min_args: 0, max_args: 0, handler: cmd_create_store as Handler },
+        Command { name: "use", args: "<uuid>", desc: "Switch to a store", group: "node", min_args: 1, max_args: 1, handler: cmd_use_store as Handler },
+        Command { name: "list-stores", args: "", desc: "List all stores", group: "node", min_args: 0, max_args: 0, handler: cmd_list_stores as Handler },
+        Command { name: "node-status", args: "", desc: "Show node info", group: "node", min_args: 0, max_args: 0, handler: cmd_node_status as Handler },
+        // Peer management
+        Command { name: "invite", args: "<pubkey>", desc: "Invite a peer", group: "peers", min_args: 1, max_args: 1, handler: cmd_invite as Handler },
+        Command { name: "peers", args: "", desc: "List all peers", group: "peers", min_args: 0, max_args: 0, handler: cmd_peers as Handler },
+        Command { name: "remove", args: "<pubkey>", desc: "Remove a peer", group: "peers", min_args: 1, max_args: 1, handler: cmd_remove as Handler },
+        // Networking
+        Command { name: "join", args: "<node_id>", desc: "Join an existing mesh", group: "network", min_args: 1, max_args: 1, handler: cmd_join as Handler },
+        Command { name: "sync", args: "[node_id]", desc: "Sync with peers", group: "network", min_args: 0, max_args: 1, handler: cmd_sync as Handler },
+    ]
+}
+
+// --- Store management ---
+
+fn cmd_init(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    match block_async(node.init()) {
+        Ok(store_id) => {
+            println!("Initialized with root store: {}", store_id);
+            println!("Node info stored in /nodes/{}/*", hex::encode(node.node_id()));
+            match block_async(node.root_store()).as_ref() {
+                Some(h) => CommandResult::SwitchTo(h.clone()),
+                None => CommandResult::Ok,
+            }
+        }
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            CommandResult::Ok
+        }
+    }
+}
+
+fn cmd_create_store(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    match node.create_store() {
+        Ok(store_id) => {
+            println!("Created store: {}", store_id);
+            match block_async(node.open_store(store_id)) {
+                Ok((handle, _)) => {
+                    println!("Switched to new store");
+                    CommandResult::SwitchTo(handle)
+                }
+                Err(e) => {
+                    eprintln!("Warning: {}", e);
+                    CommandResult::Ok
+                }
+            }
+        }
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            CommandResult::Ok
+        }
+    }
+}
+
+fn cmd_use_store(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let store_id = match Uuid::parse_str(&args[0]) {
+        Ok(id) => id,
+        Err(_) => {
+            eprintln!("Error: invalid UUID '{}'", args[0]);
+            return CommandResult::Ok;
+        }
+    };
+    
+    let start = Instant::now();
+    match block_async(node.open_store(store_id)) {
+        Ok((handle, info)) => {
+            if info.entries_replayed > 0 {
+                println!("Replayed {} entries ({:.2?})", info.entries_replayed, start.elapsed());
+            } else {
+                println!("Switched to store {}", store_id);
+            }
+            CommandResult::SwitchTo(handle)
+        }
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            CommandResult::Ok
+        }
+    }
+}
+
+fn cmd_list_stores(node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    let stores = match node.list_stores() {
+        Ok(s) => s,
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            return CommandResult::Ok;
+        }
+    };
+    let current_id = store.map(|s| s.id());
+    
+    if stores.is_empty() {
+        println!("No stores. Use 'init' or 'create-store'.");
+    } else {
+        for store_id in stores {
+            let marker = if Some(store_id) == current_id { " *" } else { "" };
+            println!("{}{}", store_id, marker);
+        }
+    }
+    CommandResult::Ok
+}
+
+// --- Info ---
+
+fn cmd_node_status(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    println!("Node ID:  {}", hex::encode(node.node_id()));
+    if let Some(name) = node.name() {
+        println!("Name:     {}", name);
+    }
+    println!("Data:     {}", node.data_path().display());
+    match node.root_store_id() {
+        Ok(Some(id)) => println!("Root:     {}", id),
+        Ok(None) => println!("Root:     (not set)"),
+        Err(_) => println!("Root:     (error)"),
+    }
+    
+    // Count peers using node.list_peers()
+    if let Ok(peers) = block_async(node.list_peers()) {
+        let active = peers.iter().filter(|p| p.status == PeerStatus::Active).count();
+        let invited = peers.iter().filter(|p| p.status == PeerStatus::Invited).count();
+        println!("Peers:    {} active, {} invited", active, invited);
+    }
+    
+    CommandResult::Ok
+}
+
+// --- Peer management ---
+
+fn cmd_invite(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let pubkey_hex = &args[0];
+    let pubkey: [u8; 32] = match hex::decode(pubkey_hex) {
+        Ok(bytes) if bytes.len() == 32 => bytes.try_into().unwrap(),
+        _ => {
+            eprintln!("Invalid pubkey: expected 64 hex chars (32 bytes)");
+            return CommandResult::Ok;
+        }
+    };
+    
+    match block_async(node.invite_peer(&pubkey)) {
+        Ok(()) => {
+            println!("Invited peer: {}", pubkey_hex);
+            println!("  Status: {} (will become active after sync)", PeerStatus::Invited.as_str());
+        }
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+fn cmd_peers(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    let peers = match block_async(node.list_peers()) {
+        Ok(p) => p,
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            return CommandResult::Ok;
+        }
+    };
+    
+    if peers.is_empty() {
+        println!("No peers found.");
+        return CommandResult::Ok;
+    }
+    
+    // Group peers by status
+    let mut by_status: std::collections::HashMap<PeerStatus, Vec<&lattice_core::PeerInfo>> = 
+        std::collections::HashMap::new();
+    for peer in &peers {
+        by_status.entry(peer.status).or_default().push(peer);
+    }
+    
+    // Print grouped by status in order: active, invited, dormant
+    let status_order = [PeerStatus::Active, PeerStatus::Invited, PeerStatus::Dormant];
+    for status in &status_order {
+        if let Some(peer_list) = by_status.get(status) {
+            println!("\n[{}] ({}):", status.as_str(), peer_list.len());
+            let mut sorted: Vec<_> = peer_list.iter().collect();
+            sorted.sort_by(|a, b| a.pubkey.cmp(&b.pubkey));
+            for peer in sorted {
+                let added_str = peer.added_at
+                    .and_then(|ts| DateTime::from_timestamp(ts as i64, 0))
+                    .map(|dt| dt.format("%Y-%m-%d").to_string())
+                    .unwrap_or_default();
+                let info_str = match (peer.name.as_ref(), added_str.is_empty()) {
+                    (Some(name), false) => format!(" {} ({})", name, added_str),
+                    (Some(name), true) => format!(" {}", name),
+                    (None, false) => format!(" ({})", added_str),
+                    (None, true) => String::new(),
+                };
+                println!("  {}{}", peer.pubkey, info_str);
+            }
+        }
+    }
+    CommandResult::Ok
+}
+
+fn cmd_remove(node: &Node, _store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let pubkey_hex = &args[0];
+    let pubkey: [u8; 32] = match hex::decode(pubkey_hex) {
+        Ok(bytes) if bytes.len() == 32 => bytes.try_into().unwrap(),
+        _ => {
+            eprintln!("Invalid pubkey: expected 64 hex characters");
+            return CommandResult::Ok;
+        }
+    };
+    
+    match block_async(node.remove_peer(&pubkey)) {
+        Ok(()) => println!("Removed peer: {}...", &pubkey_hex[..10]),
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+// --- Networking ---
+
+fn cmd_join(_node: &Node, store: Option<&StoreHandle>, server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let server = match server {
+        Some(s) => s,
+        None => {
+            eprintln!("Iroh endpoint not started.");
+            return CommandResult::Ok;
+        }
+    };
+    
+    if store.is_some() {
+        eprintln!("Already initialized. Use 'sync' to sync with peers.");
+        return CommandResult::Ok;
+    }
+    
+    let peer_id = match lattice_net::parse_node_id(&args[0]) {
+        Ok(id) => id,
+        Err(e) => {
+            eprintln!("Invalid node ID: {}", e);
+            return CommandResult::Ok;
+        }
+    };
+    
+    println!("Joining mesh via {}...", peer_id.fmt_short());
+    
+    match block_async(server.join_mesh(peer_id)) {
+        Ok(handle) => {
+            println!("Joined mesh! Use 'sync' command to sync entries.");
+            CommandResult::SwitchTo(handle)
+        }
+        Err(e) => {
+            eprintln!("Join failed: {}", e);
+            CommandResult::Ok
+        }
+    }
+}
+
+fn cmd_sync(_node: &Node, store: Option<&StoreHandle>, server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let server = match server {
+        Some(s) => s,
+        None => {
+            eprintln!("Iroh endpoint not started.");
+            return CommandResult::Ok;
+        }
+    };
+    
+    let store = match store {
+        Some(s) => s,
+        None => {
+            eprintln!("No store open. Use 'init' or 'join' first.");
+            return CommandResult::Ok;
+        }
+    };
+    
+    if args.is_empty() {
+        // Sync with all active peers
+        match block_async(server.sync_all(store)) {
+            Ok(results) => {
+                if results.is_empty() {
+                    println!("No peers to sync with.");
+                } else {
+                    let total: u64 = results.iter().map(|r| r.entries_applied).sum();
+                    println!("\nSync complete! Applied {} entries from {} peer(s).", total, results.len());
+                }
+            }
+            Err(e) => eprintln!("Sync failed: {}", e),
+        }
+    } else {
+        // Sync with specific peer
+        let peer_id = match lattice_net::parse_node_id(&args[0]) {
+            Ok(id) => id,
+            Err(e) => {
+                eprintln!("Invalid node ID: {}", e);
+                return CommandResult::Ok;
+            }
+        };
+        
+        println!("Syncing with {}...", peer_id.fmt_short());
+        match block_async(server.sync_with_peer(store, peer_id)) {
+            Ok(result) => {
+                println!("Sync complete! Applied {} entries (peer sent {})", 
+                    result.entries_applied, result.entries_sent_by_peer);
+            }
+            Err(e) => eprintln!("Sync failed: {}", e),
+        }
+    }
+    
+    CommandResult::Ok
+}

lattice-cli/src/store_commands.rs

@@ -0,0 +1,220 @@
+//! Store commands - direct KV operations
+
+use crate::commands::{block_async, Command, CommandResult, Handler};
+use lattice_core::{Node, StoreHandle};
+use lattice_net::LatticeServer;
+use std::time::Instant;
+
+pub fn store_commands() -> Vec<Command> {
+    vec![
+        Command { name: "store-status", args: "", desc: "Show store info", group: "store", min_args: 0, max_args: 0, handler: cmd_store_status as Handler },
+        Command { name: "put", args: "<key> <value>", desc: "Store a key-value pair", group: "store", min_args: 2, max_args: 2, handler: cmd_put as Handler },
+        Command { name: "get", args: "<key> [-v]", desc: "Get value for key", group: "store", min_args: 1, max_args: 2, handler: cmd_get as Handler },
+        Command { name: "delete", args: "<key>", desc: "Delete a key", group: "store", min_args: 1, max_args: 1, handler: cmd_delete as Handler },
+        Command { name: "list", args: "[prefix] [-v]", desc: "List keys (optionally filtered by prefix)", group: "store", min_args: 0, max_args: 2, handler: cmd_list as Handler },
+        Command { name: "author-state", args: "[pubkey]", desc: "Show author sync state", group: "store", min_args: 0, max_args: 1, handler: cmd_author_state as Handler },
+    ]
+}
+
+fn cmd_store_status(_node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, _args: &[String]) -> CommandResult {
+    let Some(h) = store else {
+        println!("No store selected. Use 'init' or 'use <uuid>'");
+        return CommandResult::Ok;
+    };
+    
+    println!("Store ID: {}", h.id());
+    println!("Log Seq:  {}", block_async(h.log_seq()));
+    println!("Applied:  {}", block_async(h.applied_seq()).unwrap_or(0));
+    
+    let all = block_async(h.list(false)).unwrap_or_default();
+    println!("Keys:     {}", all.len());
+    
+    // Show log directory size
+    let (file_count, total_size) = block_async(h.log_stats());
+    if file_count > 0 {
+        println!("Logs:     {} files, {} bytes", file_count, total_size);
+    }
+    
+    CommandResult::Ok
+}
+
+fn cmd_put(_node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let Some(h) = store else {
+        println!("No store selected. Use 'init' or 'use <uuid>'");
+        return CommandResult::Ok;
+    };
+    let start = Instant::now();
+    match block_async(h.put(args[0].as_bytes(), args[1].as_bytes())) {
+        Ok(seq) => println!("OK (seq: {}, {:.2?})", seq, start.elapsed()),
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+fn cmd_get(_node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let Some(h) = store else {
+        println!("No store selected. Use 'init' or 'use <uuid>'");
+        return CommandResult::Ok;
+    };
+    let verbose = args.get(1).map(|a| a == "-v").unwrap_or(false);
+    let start = Instant::now();
+    let key = args[0].as_bytes();
+    
+    if verbose {
+        // Show all heads
+        match block_async(h.get_heads(key)) {
+            Ok(heads) if heads.is_empty() => println!("(nil)"),
+            Ok(heads) => {
+                for (i, head) in heads.iter().enumerate() {
+                    let winner = if i == 0 { "→" } else { " " };
+                    let tombstone = if head.tombstone { "⊗" } else { "" };
+                    let author_short = hex::encode(&head.author).chars().take(8).collect::<String>();
+                    if head.tombstone {
+                        println!("{} {} (deleted) (hlc:{}, author:{})", 
+                            winner, tombstone, head.hlc, author_short);
+                    } else {
+                        println!("{} {} (hlc:{}, author:{})", 
+                            winner, format_value(&head.value), head.hlc, author_short);
+                    }
+                }
+                if heads.len() > 1 {
+                    println!("⚠ {} heads (conflict)", heads.len());
+                }
+                println!("({:.2?})", start.elapsed());
+            }
+            Err(e) => eprintln!("Error: {}", e),
+        }
+    } else {
+        match block_async(h.get(key)) {
+            Ok(Some(v)) => {
+                let heads = block_async(h.get_heads(key)).unwrap_or_default();
+                if heads.len() > 1 {
+                    println!("{} (⚠ {} heads)", format_value(&v), heads.len());
+                } else {
+                    println!("{}", format_value(&v));
+                }
+                println!("({:.2?})", start.elapsed());
+            }
+            Ok(None) => println!("(nil)"),
+            Err(e) => eprintln!("Error: {}", e),
+        }
+    }
+    CommandResult::Ok
+}
+
+fn cmd_delete(_node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let Some(h) = store else {
+        println!("No store selected. Use 'init' or 'use <uuid>'");
+        return CommandResult::Ok;
+    };
+    let start = Instant::now();
+    match block_async(h.delete(args[0].as_bytes())) {
+        Ok(seq) => println!("OK (seq: {}, {:.2?})", seq, start.elapsed()),
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+fn cmd_list(_node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let Some(h) = store else {
+        println!("No store selected. Use 'init' or 'use <uuid>'");
+        return CommandResult::Ok;
+    };
+    
+    // Parse args: [prefix] [-v]
+    let verbose = args.iter().any(|a| a == "-v");
+    let prefix = args.iter().find(|a| *a != "-v").cloned();
+    
+    let start = Instant::now();
+    let result = if let Some(p) = &prefix {
+        block_async(h.list_by_prefix(p.as_bytes(), verbose))
+    } else {
+        block_async(h.list(verbose))
+    };
+    
+    match result {
+        Ok(entries) => {
+            if entries.is_empty() {
+                println!("(empty)");
+            } else {
+                for (k, v) in &entries {
+                    let key_str = format_value(k);
+                    if verbose {
+                        // Show all heads for this key
+                        let heads = block_async(h.get_heads(k)).unwrap_or_default();
+                        println!("{}:", key_str);
+                        for (i, head) in heads.iter().enumerate() {
+                            let winner = if i == 0 { "→" } else { " " };
+                            let author_short = hex::encode(&head.author).chars().take(8).collect::<String>();
+                            if head.tombstone {
+                                println!("  {} ⊗ (deleted) (hlc:{}, author:{})", 
+                                    winner, head.hlc, author_short);
+                            } else {
+                                println!("  {} {} (hlc:{}, author:{})", 
+                                    winner, format_value(&head.value), head.hlc, author_short);
+                            }
+                        }
+                    } else {
+                        // Check for multiple heads
+                        let heads = block_async(h.get_heads(k)).unwrap_or_default();
+                        if heads.len() > 1 {
+                            println!("{} = {} (⚠ {} heads)", key_str, format_value(v), heads.len());
+                        } else {
+                            println!("{} = {}", key_str, format_value(v));
+                        }
+                    }
+                }
+                let prefix_str = prefix.as_ref().map(|p| format!(" (prefix: {})", p)).unwrap_or_default();
+                println!("({} keys{}, {:.2?})", entries.len(), prefix_str, start.elapsed());
+            }
+        }
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+fn cmd_author_state(node: &Node, store: Option<&StoreHandle>, _server: Option<&LatticeServer>, args: &[String]) -> CommandResult {
+    let store = match store {
+        Some(s) => s,
+        None => {
+            eprintln!("Error: no store selected");
+            return CommandResult::Ok;
+        }
+    };
+
+    // Get author: from arg or default to self
+    let author_bytes: [u8; 32] = if args.is_empty() {
+        node.node_id()
+    } else {
+        let hex_str = args[0].trim_start_matches("0x");
+        match hex::decode(hex_str) {
+            Ok(bytes) if bytes.len() == 32 => bytes.try_into().unwrap(),
+            Ok(bytes) => {
+                eprintln!("Error: author must be 32 bytes, got {}", bytes.len());
+                return CommandResult::Ok;
+            }
+            Err(e) => {
+                eprintln!("Error: invalid hex: {}", e);
+                return CommandResult::Ok;
+            }
+        }
+    };
+
+    match block_async(store.author_state(&author_bytes)) {
+        Ok(Some(state)) => {
+            println!("Author: {}", hex::encode(&author_bytes));
+            println!("  seq: {}", state.seq);
+            println!("  hash: {}", hex::encode(&state.hash));
+            println!("  log_offset: {}", state.log_offset);
+        }
+        Ok(None) => {
+            println!("No state for author: {}", hex::encode(&author_bytes));
+        }
+        Err(e) => eprintln!("Error: {}", e),
+    }
+    CommandResult::Ok
+}
+
+fn format_value(v: &[u8]) -> String {
+    std::str::from_utf8(v).map(String::from).unwrap_or_else(|_| format!("0x{}", hex::encode(v)))
+}

lattice-core/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "lattice-core"
+description = "Core types for Lattice: nodes, sigchains, entries, and vector clocks"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+ed25519-dalek = { workspace = true }
+rand = { workspace = true }
+prost = { workspace = true }
+thiserror = { workspace = true }
+bytes = { workspace = true }
+dirs = { workspace = true }
+blake3 = { workspace = true }
+hex = { workspace = true }
+redb = { workspace = true }
+uuid = { workspace = true }
+tokio = { workspace = true }
+hostname = "0.4"
+serde_json = "1"
+
+[build-dependencies]
+prost-build = { workspace = true }
+
+[dev-dependencies]
+tokio-test = { workspace = true }

lattice-core/build.rs

@@ -0,0 +1,9 @@
+use std::io::Result;
+
+fn main() -> Result<()> {
+    prost_build::compile_protos(
+        &["../proto/lattice.proto"],
+        &["../proto/"],
+    )?;
+    Ok(())
+}

lattice-core/src/causal_iter.rs

@@ -0,0 +1,189 @@
+//! Causal Entry Iterator - yields entries in HLC (causal) order
+//!
+//! Implements merge-sort streaming across multiple author queues using a min-heap,
+//! ensuring entries are returned in correct causal order for sync.
+//! Complexity: O(N log K) where N = total entries, K = number of authors.
+
+use crate::proto::{Entry, SignedEntry};
+use prost::Message;
+use std::cmp::Ordering;
+use std::collections::{BinaryHeap, VecDeque};
+
+/// A heap entry that wraps an author queue index and the HLC of its front entry.
+/// Uses Reverse for min-heap behavior (lowest HLC first).
+struct HeapEntry {
+    hlc: (u64, u32),
+    queue_idx: usize,
+}
+
+impl PartialEq for HeapEntry {
+    fn eq(&self, other: &Self) -> bool {
+        self.hlc == other.hlc
+    }
+}
+
+impl Eq for HeapEntry {}
+
+impl PartialOrd for HeapEntry {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for HeapEntry {
+    fn cmp(&self, other: &Self) -> Ordering {
+        // Reverse order for min-heap (BinaryHeap is max-heap by default)
+        other.hlc.cmp(&self.hlc)
+    }
+}
+
+/// Iterator that yields SignedEntry in HLC (causal) order.
+/// 
+/// Takes multiple VecDeques (one per author) and yields entries
+/// from lowest to highest HLC, ensuring causal ordering for sync.
+/// Uses a min-heap for O(log K) per-entry overhead instead of O(K) linear scan.
+pub struct CausalEntryIter {
+    queues: Vec<VecDeque<SignedEntry>>,
+    heap: BinaryHeap<HeapEntry>,
+}
+
+impl CausalEntryIter {
+    /// Create a new iterator from a list of entry queues (one per author)
+    pub fn new(queues: Vec<VecDeque<SignedEntry>>) -> Self {
+        let mut heap = BinaryHeap::with_capacity(queues.len());
+        
+        // Initialize heap with the front entry from each non-empty queue
+        for (idx, queue) in queues.iter().enumerate() {
+            if let Some(entry) = queue.front() {
+                heap.push(HeapEntry {
+                    hlc: Self::get_hlc(entry),
+                    queue_idx: idx,
+                });
+            }
+        }
+        
+        Self { queues, heap }
+    }
+    
+    /// Extract HLC (wall_time, counter) from a SignedEntry
+    fn get_hlc(entry: &SignedEntry) -> (u64, u32) {
+        Entry::decode(&entry.entry_bytes[..])
+            .ok()
+            .and_then(|e| e.timestamp)
+            .map(|t| (t.wall_time, t.counter))
+            .unwrap_or((0, 0))
+    }
+}
+
+impl Iterator for CausalEntryIter {
+    type Item = SignedEntry;
+    
+    fn next(&mut self) -> Option<Self::Item> {
+        // Pop the queue with lowest HLC
+        let HeapEntry { queue_idx, .. } = self.heap.pop()?;
+        
+        // Remove entry from that queue
+        let entry = self.queues[queue_idx].pop_front()?;
+        
+        // If queue still has entries, push its new front back to heap
+        if let Some(next_entry) = self.queues[queue_idx].front() {
+            self.heap.push(HeapEntry {
+                hlc: Self::get_hlc(next_entry),
+                queue_idx,
+            });
+        }
+        
+        Some(entry)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::hlc::HLC;
+    use crate::clock::MockClock;
+    use crate::node_identity::NodeIdentity;
+    use crate::signed_entry::EntryBuilder;
+    
+    fn make_entry(node: &NodeIdentity, seq: u64, clock_ms: u64) -> SignedEntry {
+        let clock = MockClock::new(clock_ms);
+        EntryBuilder::new(seq, HLC::now_with_clock(&clock))
+            .store_id(vec![0u8; 16])
+            .prev_hash(vec![0u8; 32])
+            .put(b"/test".to_vec(), format!("seq{}", seq).into_bytes())
+            .sign(node)
+    }
+    
+    #[test]
+    fn test_empty_iter() {
+        let iter = CausalEntryIter::new(vec![]);
+        assert_eq!(iter.count(), 0);
+    }
+    
+    #[test]
+    fn test_single_queue() {
+        let node = NodeIdentity::generate();
+        let entries: VecDeque<_> = vec![
+            make_entry(&node, 1, 1000),
+            make_entry(&node, 2, 2000),
+        ].into();
+        
+        let iter = CausalEntryIter::new(vec![entries]);
+        let result: Vec<_> = iter.collect();
+        assert_eq!(result.len(), 2);
+    }
+    
+    #[test]
+    fn test_merge_multiple_queues() {
+        let node_a = NodeIdentity::generate();
+        let node_b = NodeIdentity::generate();
+        
+        // Author A: entries at time 1000, 3000
+        let queue_a: VecDeque<_> = vec![
+            make_entry(&node_a, 1, 1000),
+            make_entry(&node_a, 2, 3000),
+        ].into();
+        
+        // Author B: entries at time 2000
+        let queue_b: VecDeque<_> = vec![
+            make_entry(&node_b, 1, 2000),
+        ].into();
+        
+        let iter = CausalEntryIter::new(vec![queue_a, queue_b]);
+        let result: Vec<_> = iter.collect();
+        
+        // Should be in HLC order: 1000, 2000, 3000
+        assert_eq!(result.len(), 3);
+        
+        // Verify order by checking HLC values
+        let hlcs: Vec<_> = result.iter()
+            .map(|e| CausalEntryIter::get_hlc(e))
+            .collect();
+        assert_eq!(hlcs[0].0, 1000);
+        assert_eq!(hlcs[1].0, 2000);
+        assert_eq!(hlcs[2].0, 3000);
+    }
+    
+    #[test]
+    fn test_many_authors() {
+        // Test with 10 authors to verify heap behavior
+        let nodes: Vec<_> = (0..10).map(|_| NodeIdentity::generate()).collect();
+        let queues: Vec<VecDeque<_>> = nodes.iter().enumerate().map(|(i, node)| {
+            vec![make_entry(node, 1, (i * 100 + 50) as u64)].into()
+        }).collect();
+        
+        let iter = CausalEntryIter::new(queues);
+        let result: Vec<_> = iter.collect();
+        
+        assert_eq!(result.len(), 10);
+        
+        // Verify strictly increasing HLC order
+        let hlcs: Vec<_> = result.iter()
+            .map(|e| CausalEntryIter::get_hlc(e).0)
+            .collect();
+        for window in hlcs.windows(2) {
+            assert!(window[0] < window[1], "HLCs should be strictly increasing");
+        }
+    }
+}
+

lattice-core/src/clock.rs

@@ -0,0 +1,62 @@
+//! Clock abstraction for testable time
+//!
+//! Provides a trait for getting the current time, with implementations
+//! for real system time and mock time for testing.
+
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// Trait for getting the current wall clock time in milliseconds
+pub trait Clock: Send + Sync {
+    /// Get the current time in milliseconds since Unix epoch
+    fn now_ms(&self) -> u64;
+}
+
+/// Real system clock implementation
+#[derive(Debug, Clone, Copy, Default)]
+pub struct SystemClock;
+
+impl Clock for SystemClock {
+    fn now_ms(&self) -> u64 {
+        SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .expect("Time went backwards")
+            .as_millis() as u64
+    }
+}
+
+/// Mock clock for testing - returns a fixed time
+#[derive(Debug, Clone, Copy)]
+pub struct MockClock {
+    pub time_ms: u64,
+}
+
+impl MockClock {
+    pub fn new(time_ms: u64) -> Self {
+        Self { time_ms }
+    }
+}
+
+impl Clock for MockClock {
+    fn now_ms(&self) -> u64 {
+        self.time_ms
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_system_clock_returns_reasonable_time() {
+        let clock = SystemClock;
+        let now = clock.now_ms();
+        // Should be after 2025-01-01
+        assert!(now > 1_735_689_600_000);
+    }
+
+    #[test]
+    fn test_mock_clock_returns_fixed_time() {
+        let clock = MockClock::new(12345);
+        assert_eq!(clock.now_ms(), 12345);
+    }
+}

lattice-core/src/data_dir.rs

@@ -0,0 +1,138 @@
+//! Data directory management
+//!
+//! Provides platform-specific paths for Lattice data storage:
+//! - `identity.key` — Ed25519 private key
+//! - `meta.db` — Global metadata (stores table)
+//! - `stores/{uuid}/logs/{author}.log` — Per-store, per-author logs
+//! - `stores/{uuid}/state.db` — Per-store KV state
+
+use std::path::{Path, PathBuf};
+use uuid::Uuid;
+
+const APP_NAME: &str = "lattice";
+
+/// Data directory configuration.
+///
+/// Multi-store layout:
+/// ```text
+/// base/
+///   identity.key
+///   meta.db
+///   stores/{uuid}/
+///     logs/{author}.log
+///     state.db
+/// ```
+#[derive(Debug, Clone)]
+pub struct DataDir {
+    base: PathBuf,
+}
+
+impl DataDir {
+    /// Create a DataDir with a custom base path.
+    pub fn new(base: impl Into<PathBuf>) -> Self {
+        Self { base: base.into() }
+    }
+
+    /// Create a DataDir using the platform-specific data directory.
+    pub fn default_location() -> Option<Self> {
+        dirs::data_dir().map(|d| Self::new(d.join(APP_NAME)))
+    }
+
+    /// Get the base directory path.
+    pub fn base(&self) -> &Path {
+        &self.base
+    }
+
+    /// Get the path to the identity key file.
+    pub fn identity_key(&self) -> PathBuf {
+        self.base.join("identity.key")
+    }
+
+    /// Get the path to the global metadata database.
+    pub fn meta_db(&self) -> PathBuf {
+        self.base.join("meta.db")
+    }
+
+    /// Get the path to the stores directory.
+    pub fn stores_dir(&self) -> PathBuf {
+        self.base.join("stores")
+    }
+
+    /// Get the path to a specific store's directory.
+    pub fn store_dir(&self, store_id: Uuid) -> PathBuf {
+        self.stores_dir().join(store_id.to_string())
+    }
+
+    /// Get the path to a store's logs directory.
+    pub fn store_logs_dir(&self, store_id: Uuid) -> PathBuf {
+        self.store_dir(store_id).join("logs")
+    }
+
+    /// Get the path to a specific author's log file within a store.
+    pub fn store_log_file(&self, store_id: Uuid, author_id_hex: &str) -> PathBuf {
+        self.store_logs_dir(store_id).join(format!("{}.log", author_id_hex))
+    }
+
+    /// Get the path to a store's state database.
+    pub fn store_state_db(&self, store_id: Uuid) -> PathBuf {
+        self.store_dir(store_id).join("state.db")
+    }
+
+    /// Ensure base directory exists.
+    pub fn ensure_dirs(&self) -> std::io::Result<()> {
+        std::fs::create_dir_all(&self.base)?;
+        std::fs::create_dir_all(self.stores_dir())?;
+        Ok(())
+    }
+
+    /// Ensure directories for a specific store exist.
+    pub fn ensure_store_dirs(&self, store_id: Uuid) -> std::io::Result<()> {
+        self.ensure_dirs()?;
+        std::fs::create_dir_all(self.store_logs_dir(store_id))?;
+        Ok(())
+    }
+}
+
+impl Default for DataDir {
+    fn default() -> Self {
+        Self::default_location().unwrap_or_else(|| Self::new("./data"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_custom_path() {
+        let dd = DataDir::new("/custom/path");
+        assert_eq!(dd.base(), Path::new("/custom/path"));
+        assert_eq!(dd.identity_key(), PathBuf::from("/custom/path/identity.key"));
+        assert_eq!(dd.meta_db(), PathBuf::from("/custom/path/meta.db"));
+        assert_eq!(dd.stores_dir(), PathBuf::from("/custom/path/stores"));
+    }
+
+    #[test]
+    fn test_store_paths() {
+        let dd = DataDir::new("/data");
+        let store_id = Uuid::parse_str("a1b2c3d4-e5f6-7890-abcd-ef1234567890").unwrap();
+        
+        assert_eq!(dd.store_dir(store_id), PathBuf::from("/data/stores/a1b2c3d4-e5f6-7890-abcd-ef1234567890"));
+        assert_eq!(dd.store_logs_dir(store_id), PathBuf::from("/data/stores/a1b2c3d4-e5f6-7890-abcd-ef1234567890/logs"));
+        assert_eq!(dd.store_log_file(store_id, "abc123"), PathBuf::from("/data/stores/a1b2c3d4-e5f6-7890-abcd-ef1234567890/logs/abc123.log"));
+        assert_eq!(dd.store_state_db(store_id), PathBuf::from("/data/stores/a1b2c3d4-e5f6-7890-abcd-ef1234567890/state.db"));
+    }
+
+    #[test]
+    fn test_default_location_exists() {
+        // On most systems, default_location should return Some
+        let location = DataDir::default_location();
+        assert!(location.is_some() || true);
+    }
+
+    #[test]
+    fn test_default_impl() {
+        let dd = DataDir::default();
+        assert!(dd.base().to_str().is_some());
+    }
+}

lattice-core/src/entry.rs

@@ -0,0 +1,9 @@
+//! Log entries (atomic operations)
+
+/// An atomic, batched operation in the sigchain.
+///
+/// Entries are the fundamental unit of change in Lattice.
+/// The KV store is a "view" generated by replaying these entries.
+pub struct Entry {
+    // TODO: operation data, signature, prev_hash
+}

lattice-core/src/hlc.rs

@@ -0,0 +1,325 @@
+//! Hybrid Logical Clock (HLC) implementation
+//!
+//! HLCs combine wall clock time with a logical counter to provide
+//! causally consistent ordering even with clock drift.
+
+use std::cmp::Ordering;
+use crate::clock::{Clock, SystemClock};
+
+/// Default maximum drift allowed before clamping (1 hour in ms)
+pub const DEFAULT_MAX_DRIFT_MS: u64 = 60 * 60 * 1000;
+
+/// Hybrid Logical Clock
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct HLC {
+    /// Wall clock time in milliseconds since Unix epoch
+    pub wall_time: u64,
+    /// Logical counter for ordering events at same wall_time
+    pub counter: u32,
+}
+
+impl HLC {
+    /// Create a new HLC with the given wall_time and counter
+    pub fn new(wall_time: u64, counter: u32) -> Self {
+        Self { wall_time, counter }
+    }
+
+    /// Create an HLC from the current system time
+    pub fn now() -> Self {
+        Self::now_with_clock(&SystemClock)
+    }
+
+    /// Create an HLC from the given clock (for testing)
+    pub fn now_with_clock(clock: &impl Clock) -> Self {
+        Self {
+            wall_time: clock.now_ms(),
+            counter: 0,
+        }
+    }
+
+    /// Update this clock upon receiving a message with the given HLC.
+    /// Uses the system clock.
+    pub fn update(&self, received: &HLC) -> HLC {
+        self.update_with_clock(received, &SystemClock)
+    }
+
+    /// Update this clock with an explicit clock source (for testing)
+    pub fn update_with_clock(&self, received: &HLC, clock: &impl Clock) -> HLC {
+        let local_wall_time = clock.now_ms();
+        
+        if local_wall_time > self.wall_time && local_wall_time > received.wall_time {
+            // Local wall clock is ahead of everything, use it
+            HLC::new(local_wall_time, 0)
+        } else if self.wall_time > received.wall_time {
+            // Our last HLC is ahead, increment counter
+            HLC::new(self.wall_time, self.counter + 1)
+        } else if received.wall_time > self.wall_time {
+            // Received HLC is ahead, use it and increment
+            HLC::new(received.wall_time, received.counter + 1)
+        } else {
+            // Same wall_time, take max counter and increment
+            HLC::new(self.wall_time, self.counter.max(received.counter) + 1)
+        }
+    }
+
+    /// Clamp a potentially-future HLC to be at most parent + 1.
+    /// Returns the clamped HLC if the original exceeds max_drift,
+    /// otherwise returns the original.
+    pub fn clamp_future(&self, parent: &HLC, local_wall_time: u64, max_drift_ms: u64) -> HLC {
+        if self.wall_time > local_wall_time + max_drift_ms {
+            // Clamp to parent + 1 (deterministic across all nodes)
+            HLC::new(parent.wall_time, parent.counter + 1)
+        } else {
+            *self
+        }
+    }
+
+    /// Clamp with clock source (convenience method)
+    pub fn clamp_future_with_clock(&self, parent: &HLC, clock: &impl Clock, max_drift_ms: u64) -> HLC {
+        self.clamp_future(parent, clock.now_ms(), max_drift_ms)
+    }
+
+    /// Check if this HLC exceeds the given wall time by more than max_drift
+    pub fn is_future(&self, local_wall_time: u64, max_drift_ms: u64) -> bool {
+        self.wall_time > local_wall_time + max_drift_ms
+    }
+
+    /// Increment this HLC for a new local event
+    pub fn tick(&self) -> HLC {
+        self.tick_with_clock(&SystemClock)
+    }
+
+    /// Increment with explicit clock (for testing)
+    pub fn tick_with_clock(&self, clock: &impl Clock) -> HLC {
+        let now = clock.now_ms();
+        if now > self.wall_time {
+            HLC::new(now, 0)
+        } else {
+            HLC::new(self.wall_time, self.counter + 1)
+        }
+    }
+}
+
+impl Ord for HLC {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match self.wall_time.cmp(&other.wall_time) {
+            Ordering::Equal => self.counter.cmp(&other.counter),
+            other => other,
+        }
+    }
+}
+
+impl PartialOrd for HLC {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Default for HLC {
+    fn default() -> Self {
+        Self::now()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::clock::MockClock;
+
+    #[test]
+    fn test_hlc_ordering() {
+        let a = HLC::new(100, 0);
+        let b = HLC::new(100, 1);
+        let c = HLC::new(101, 0);
+
+        assert!(a < b);
+        assert!(b < c);
+        assert!(a < c);
+    }
+
+    #[test]
+    fn test_hlc_update_received_ahead() {
+        let local = HLC::new(100, 5);
+        let received = HLC::new(200, 3);
+        let clock = MockClock::new(50); // Wall clock behind both
+        
+        let updated = local.update_with_clock(&received, &clock);
+        
+        assert!(updated > received);
+        assert_eq!(updated.wall_time, 200);
+        assert_eq!(updated.counter, 4);
+    }
+
+    #[test]
+    fn test_hlc_update_local_ahead() {
+        let local = HLC::new(200, 5);
+        let received = HLC::new(100, 3);
+        let clock = MockClock::new(50); // Wall clock behind both
+        
+        let updated = local.update_with_clock(&received, &clock);
+        
+        assert!(updated > local);
+        assert_eq!(updated.wall_time, 200);
+        assert_eq!(updated.counter, 6);
+    }
+
+    #[test]
+    fn test_hlc_update_wall_clock_ahead() {
+        let local = HLC::new(100, 5);
+        let received = HLC::new(150, 3);
+        let clock = MockClock::new(500); // Wall clock ahead of both
+        
+        let updated = local.update_with_clock(&received, &clock);
+        
+        assert_eq!(updated.wall_time, 500);
+        assert_eq!(updated.counter, 0);
+    }
+
+    #[test]
+    fn test_hlc_clamp_future() {
+        let future = HLC::new(2050_000_000_000, 0);
+        let parent = HLC::new(100, 5);
+        let clock = MockClock::new(1000);
+        
+        let clamped = future.clamp_future_with_clock(&parent, &clock, DEFAULT_MAX_DRIFT_MS);
+        
+        assert_eq!(clamped.wall_time, 100);
+        assert_eq!(clamped.counter, 6);
+    }
+
+    #[test]
+    fn test_hlc_clamp_within_drift() {
+        let normal = HLC::new(1000, 3);
+        let parent = HLC::new(100, 5);
+        let clock = MockClock::new(900);
+        
+        let clamped = normal.clamp_future_with_clock(&parent, &clock, DEFAULT_MAX_DRIFT_MS);
+        
+        assert_eq!(clamped, normal);
+    }
+
+    #[test]
+    fn test_clock_in_past_uses_received() {
+        // Simulates Pi booting with clock at 1970
+        let old_clock = HLC::new(0, 0);
+        let received = HLC::new(1_700_000_000_000, 5);
+        let clock = MockClock::new(0); // Clock also at 1970
+        
+        let updated = old_clock.update_with_clock(&received, &clock);
+        
+        assert_eq!(updated.wall_time, 1_700_000_000_000);
+        assert_eq!(updated.counter, 6);
+    }
+
+    #[test]
+    fn test_tick_with_mock_clock() {
+        let hlc = HLC::new(100, 5);
+        
+        // Clock behind: counter increments
+        let clock = MockClock::new(50);
+        let ticked = hlc.tick_with_clock(&clock);
+        assert_eq!(ticked.wall_time, 100);
+        assert_eq!(ticked.counter, 6);
+        
+        // Clock ahead: use new wall time
+        let clock = MockClock::new(200);
+        let ticked = hlc.tick_with_clock(&clock);
+        assert_eq!(ticked.wall_time, 200);
+        assert_eq!(ticked.counter, 0);
+    }
+
+    #[test]
+    fn test_now_with_mock_clock() {
+        let clock = MockClock::new(12345);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        assert_eq!(hlc.wall_time, 12345);
+        assert_eq!(hlc.counter, 0);
+    }
+
+    #[test]
+    fn test_hlc_update_same_wall_time_collision() {
+        // Both local and received have the same wall_time (collision branch)
+        let local = HLC::new(100, 5);
+        let received = HLC::new(100, 8);
+        let clock = MockClock::new(50); // Wall clock behind both
+        
+        let updated = local.update_with_clock(&received, &clock);
+        
+        // Should take max(5, 8) + 1 = 9
+        assert_eq!(updated.wall_time, 100);
+        assert_eq!(updated.counter, 9);
+    }
+
+    #[test]
+    fn test_hlc_update_same_wall_time_local_counter_higher() {
+        // Same wall_time, but local has higher counter
+        let local = HLC::new(100, 10);
+        let received = HLC::new(100, 3);
+        let clock = MockClock::new(50);
+        
+        let updated = local.update_with_clock(&received, &clock);
+        
+        // Should take max(10, 3) + 1 = 11
+        assert_eq!(updated.wall_time, 100);
+        assert_eq!(updated.counter, 11);
+    }
+
+    #[test]
+    fn test_is_future() {
+        let hlc = HLC::new(1000, 0);
+        
+        // Within drift: not future
+        assert!(!hlc.is_future(500, 600));
+        
+        // Exactly at drift boundary: not future (>= vs >)
+        assert!(!hlc.is_future(500, 500));
+        
+        // Beyond drift: is future
+        assert!(hlc.is_future(500, 400));
+        
+        // Way in the future
+        let future = HLC::new(2050_000_000_000, 0);
+        assert!(future.is_future(1_700_000_000_000, DEFAULT_MAX_DRIFT_MS));
+    }
+
+    #[test]
+    fn test_system_clock_smoke() {
+        // Ensure SystemClock compiles and returns reasonable values
+        let hlc = HLC::now();
+        // Should be after 2025-01-01 (1735689600000 ms)
+        assert!(hlc.wall_time > 1_735_689_600_000);
+        assert_eq!(hlc.counter, 0);
+    }
+
+    #[test]
+    fn test_default_uses_system_clock() {
+        let hlc = HLC::default();
+        // Should be after 2025-01-01
+        assert!(hlc.wall_time > 1_735_689_600_000);
+        assert_eq!(hlc.counter, 0);
+    }
+
+    #[test]
+    fn test_update_with_system_clock_smoke() {
+        let local = HLC::new(100, 5);
+        let received = HLC::new(200, 3);
+        
+        // This should use the real system clock internally
+        let updated = local.update(&received);
+        
+        // Updated should be greater than both
+        assert!(updated > local);
+        assert!(updated > received);
+    }
+
+    #[test]
+    fn test_tick_with_system_clock_smoke() {
+        let hlc = HLC::new(100, 5);
+        let ticked = hlc.tick();
+        
+        // Should be greater than original
+        assert!(ticked > hlc);
+    }
+}
+

lattice-core/src/lib.rs

@@ -0,0 +1,52 @@
+//! Lattice Core
+//!
+//! Core types for the Lattice distributed mesh:
+//! - **NodeIdentity**: Cryptographic identity with Ed25519 keypair
+//! - **SigChain**: Append-only cryptographically signed log
+//! - **Entry**: Atomic operations in the log
+//! - **SyncState**: Per-author sequence tracking for reconciliation
+//! - **HLC**: Hybrid Logical Clock for ordering
+//! - **Clock**: Time abstraction for testability
+//! - **Proto**: Generated protobuf types from lattice.proto
+//! - **DataDir**: Platform-specific data directory paths
+//! - **SignedEntry**: Entry creation, signing, and verification
+//! - **Log**: Append-only log file I/O
+//! - **Store**: Persistent KV state from log replay
+//! - **CausalIter**: Merge-sort iterator for HLC-ordered sync
+
+pub mod node_identity;
+pub mod node;
+pub mod sigchain;
+pub mod entry;
+pub mod sync_state;
+pub mod hlc;
+pub mod clock;
+pub mod proto;
+pub mod data_dir;
+pub mod signed_entry;
+pub mod log;
+pub mod store;
+pub mod meta_store;
+pub mod causal_iter;
+pub mod store_actor;
+
+// Constants
+/// Maximum size of a serialized SignedEntry (16 MB)
+pub const MAX_ENTRY_SIZE: usize = 16 * 1024 * 1024;
+
+pub use node_identity::{NodeIdentity, PeerStatus};
+pub use node::{Node, NodeBuilder, NodeInfo, StoreInfo, StoreHandle, NodeError, NodeEvent, PeerInfo, JoinAcceptance};
+pub use sigchain::{SigChain, SigChainManager};
+pub use entry::Entry;
+pub use sync_state::{SyncState, AuthorInfo, MissingRange};
+pub use hlc::HLC;
+pub use clock::{Clock, SystemClock, MockClock};
+pub use data_dir::DataDir;
+pub use signed_entry::{EntryBuilder, sign_entry, verify_signed_entry, hash_signed_entry};
+pub use log::{append_entry, read_entries, read_entries_after, LogReader};
+pub use store::Store;
+pub use meta_store::MetaStore;
+pub use proto::HeadInfo;
+pub use uuid::Uuid;
+pub use causal_iter::CausalEntryIter;
+pub use store_actor::{StoreActor, StoreCmd, StoreActorError, spawn_store_actor};

lattice-core/src/log.rs

@@ -0,0 +1,534 @@
+//! Log file I/O for append-only entry storage
+//!
+//! Each author has a log file containing length-delimited LogRecord messages.
+//! LogRecord = { hash: [u8; 32], entry_bytes: SignedEntry }
+
+use crate::proto::{LogRecord, SignedEntry};
+use crate::MAX_ENTRY_SIZE;
+use prost::Message;
+use std::fs::{File, OpenOptions};
+use std::io::{self, BufReader, BufWriter, Read, Write};
+use std::path::Path;
+use thiserror::Error;
+
+/// Errors that can occur during log operations
+#[derive(Error, Debug)]
+pub enum LogError {
+    #[error("IO error: {0}")]
+    Io(#[from] io::Error),
+    
+    #[error("Proto decode error: {0}")]
+    Decode(#[from] prost::DecodeError),
+    
+    #[error("Entry too large: {0} bytes (max {MAX_ENTRY_SIZE})")]
+    EntryTooLarge(usize),
+    
+    #[error("Unexpected EOF while reading entry")]
+    UnexpectedEof,
+    
+    #[error("Hash mismatch: stored hash does not match computed hash")]
+    HashMismatch,
+}
+
+/// Append a SignedEntry to a log file as a LogRecord
+pub fn append_entry(path: impl AsRef<Path>, entry: &SignedEntry) -> Result<u64, LogError> {
+    let path = path.as_ref();
+    
+    let file = OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(path)?;
+    
+    let mut writer = BufWriter::new(file);
+    
+    // Serialize the SignedEntry
+    let entry_bytes = entry.encode_to_vec();
+    
+    if entry_bytes.len() > MAX_ENTRY_SIZE {
+        return Err(LogError::EntryTooLarge(entry_bytes.len()));
+    }
+    
+    // Compute hash
+    let hash: [u8; 32] = blake3::hash(&entry_bytes).into();
+    
+    // Create LogRecord
+    let record = LogRecord {
+        hash: hash.to_vec(),
+        entry_bytes,
+    };
+    
+    // Write length-delimited LogRecord
+    let mut buf = Vec::new();
+    record.encode_length_delimited(&mut buf)
+        .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
+    
+    writer.write_all(&buf)?;
+    writer.flush()?;
+    
+    // Ensure data is physically written to disk
+    writer.get_ref().sync_all()?;
+    
+    // Return new file size
+    let metadata = std::fs::metadata(path)?;
+    Ok(metadata.len())
+}
+
+/// Read all SignedEntry messages from a log file (with hash verification)
+pub fn read_entries(path: impl AsRef<Path>) -> Result<Vec<SignedEntry>, LogError> {
+    read_entries_after(path, None)
+}
+
+/// Read all entries that come AFTER the given hash.
+/// If `last_hash` is None, reads all entries.
+pub fn read_entries_after(path: impl AsRef<Path>, last_hash: Option<[u8; 32]>) -> Result<Vec<SignedEntry>, LogError> {
+    let reader = match LogReader::open(&path) {
+        Ok(r) => r,
+        Err(LogError::Io(e)) if e.kind() == io::ErrorKind::NotFound => return Ok(Vec::new()),
+        Err(e) => return Err(e),
+    };
+    
+    let mut entries = Vec::new();
+    let mut found_start = last_hash.is_none();
+    
+    for result in reader {
+        let (hash, entry) = result?;
+        
+        if found_start {
+            entries.push(entry);
+        } else if let Some(target) = last_hash {
+            if hash == target {
+                found_start = true;
+            }
+        }
+    }
+    
+    Ok(entries)
+}
+
+/// Iterator over entries in a log file
+/// Returns (hash, SignedEntry) pairs
+pub struct LogReader {
+    reader: BufReader<File>,
+}
+
+impl LogReader {
+    /// Open a log file for reading
+    pub fn open(path: impl AsRef<Path>) -> Result<Self, LogError> {
+        let file = File::open(path)?;
+        Ok(Self {
+            reader: BufReader::new(file),
+        })
+    }
+}
+
+impl Iterator for LogReader {
+    type Item = Result<([u8; 32], SignedEntry), LogError>;
+    
+    fn next(&mut self) -> Option<Self::Item> {
+        match read_one_record(&mut self.reader) {
+            Ok(Some(pair)) => Some(Ok(pair)),
+            Ok(None) => None,
+            Err(e) => Some(Err(e)),
+        }
+    }
+}
+
+/// Read a single LogRecord, returning (hash, SignedEntry)
+fn read_one_record<R: Read>(reader: &mut R) -> Result<Option<([u8; 32], SignedEntry)>, LogError> {
+    // Read length-delimited bytes
+    let record_bytes = match read_length_delimited_bytes(reader) {
+        Ok(bytes) => bytes,
+        Err(LogError::Io(e)) if e.kind() == io::ErrorKind::UnexpectedEof => return Ok(None),
+        Err(e) => return Err(e),
+    };
+    
+    // Decode LogRecord
+    let record = LogRecord::decode(&record_bytes[..])?;
+    
+    // Verify hash
+    let computed_hash: [u8; 32] = blake3::hash(&record.entry_bytes).into();
+    let stored_hash: [u8; 32] = record.hash.try_into()
+        .map_err(|_| io::Error::new(io::ErrorKind::InvalidData, "invalid hash length"))?;
+    
+    if computed_hash != stored_hash {
+        return Err(LogError::HashMismatch);
+    }
+    
+    // Decode SignedEntry
+    let entry = SignedEntry::decode(&record.entry_bytes[..])?;
+    Ok(Some((stored_hash, entry)))
+}
+
+/// Read length-delimited bytes from a reader
+fn read_length_delimited_bytes<R: Read>(reader: &mut R) -> Result<Vec<u8>, LogError> {
+    // Read varint length prefix
+    let mut prefix_buf = Vec::with_capacity(10);
+    let mut byte = [0u8; 1];
+    
+    loop {
+        match reader.read_exact(&mut byte) {
+            Ok(()) => {}
+            Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => return Err(e.into()),
+            Err(e) => return Err(e.into()),
+        }
+        prefix_buf.push(byte[0]);
+        
+        if byte[0] & 0x80 == 0 {
+            break;
+        }
+        if prefix_buf.len() > 10 {
+            return Err(io::Error::new(io::ErrorKind::InvalidData, "varint too long").into());
+        }
+    }
+    
+    // Decode the length
+    let len = prost::decode_length_delimiter(&prefix_buf[..])
+        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+    
+    if len > MAX_ENTRY_SIZE {
+        return Err(LogError::EntryTooLarge(len));
+    }
+    
+    // Read the data
+    let mut data_buf = vec![0u8; len];
+    reader.read_exact(&mut data_buf).map_err(|e| {
+        if e.kind() == io::ErrorKind::UnexpectedEof {
+            LogError::UnexpectedEof
+        } else {
+            e.into()
+        }
+    })?;
+    
+    Ok(data_buf)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::clock::MockClock;
+    use crate::hlc::HLC;
+    use crate::node_identity::NodeIdentity;
+    use crate::signed_entry::EntryBuilder;
+    use std::env::temp_dir;
+
+    fn temp_log_path(name: &str) -> std::path::PathBuf {
+        temp_dir().join(format!("lattice_test_{}.log", name))
+    }
+    
+    /// Compute hash the same way append_entry does
+    fn compute_entry_hash(entry: &SignedEntry) -> [u8; 32] {
+        let entry_bytes = entry.encode_to_vec();
+        blake3::hash(&entry_bytes).into()
+    }
+
+    #[test]
+    fn test_append_and_read_single() {
+        let path = temp_log_path("single_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let entry = EntryBuilder::new(1, hlc)
+            .put("/test/key", b"value".to_vec())
+            .sign(&node);
+        
+        append_entry(&path, &entry).unwrap();
+        
+        let entries = read_entries(&path).unwrap();
+        assert_eq!(entries.len(), 1);
+        assert_eq!(entries[0].entry_bytes, entry.entry_bytes);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_append_multiple() {
+        let path = temp_log_path("multiple_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        for i in 1..=5 {
+            let entry = EntryBuilder::new(i, HLC::now_with_clock(&clock))
+                .put(format!("/key/{}", i), format!("value{}", i).into_bytes())
+                .sign(&node);
+            append_entry(&path, &entry).unwrap();
+        }
+        
+        let entries = read_entries(&path).unwrap();
+        assert_eq!(entries.len(), 5);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_read_entries_after() {
+        let path = temp_log_path("after_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let mut entries = Vec::new();
+        let mut hashes = Vec::new();
+        
+        for i in 1..=5 {
+            let entry = EntryBuilder::new(i, HLC::now_with_clock(&clock))
+                .put(format!("/key/{}", i), format!("value{}", i).into_bytes())
+                .sign(&node);
+            hashes.push(compute_entry_hash(&entry));
+            append_entry(&path, &entry).unwrap();
+            entries.push(entry);
+        }
+        
+        // Read entries after hash[1] (second entry) -> should get entries 3, 4, 5
+        let result = read_entries_after(&path, Some(hashes[1])).unwrap();
+        assert_eq!(result.len(), 3);
+        assert_eq!(result[0].entry_bytes, entries[2].entry_bytes);
+        
+        // Read all entries (no hash)
+        let all = read_entries_after(&path, None).unwrap();
+        assert_eq!(all.len(), 5);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_hash_not_found_returns_empty() {
+        let path = temp_log_path("not_found_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"value".to_vec())
+            .sign(&node);
+        append_entry(&path, &entry).unwrap();
+        
+        let fake_hash = [0u8; 32];
+        let result = read_entries_after(&path, Some(fake_hash)).unwrap();
+        assert_eq!(result.len(), 0);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_log_reader_returns_hash() {
+        let path = temp_log_path("reader_hash_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"value".to_vec())
+            .sign(&node);
+        let expected_hash = compute_entry_hash(&entry);
+        append_entry(&path, &entry).unwrap();
+        
+        let mut reader = LogReader::open(&path).unwrap();
+        let (hash, _) = reader.next().unwrap().unwrap();
+        assert_eq!(hash, expected_hash);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_read_empty_file() {
+        let path = temp_log_path("empty_v6");
+        std::fs::remove_file(&path).ok();
+        
+        File::create(&path).unwrap();
+        
+        let entries = read_entries(&path).unwrap();
+        assert_eq!(entries.len(), 0);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_read_nonexistent() {
+        let path = temp_log_path("nonexistent_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let entries = read_entries(&path).unwrap();
+        assert_eq!(entries.len(), 0);
+    }
+
+    // --- Negative Tests ---
+
+    #[test]
+    fn test_corrupted_entry_detected() {
+        use std::io::Seek;
+        
+        let path = temp_log_path("corrupted_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"original".to_vec())
+            .sign(&node);
+        append_entry(&path, &entry).unwrap();
+        
+        // Corrupt the file: change a byte in the middle
+        let mut file = OpenOptions::new().write(true).open(&path).unwrap();
+        file.seek(io::SeekFrom::Start(20)).unwrap();
+        file.write_all(&[0xFF]).unwrap();
+        drop(file);
+        
+        let result = read_entries(&path);
+        
+        match result {
+            Err(LogError::HashMismatch) => (),
+            Err(LogError::Decode(_)) => (),
+            Err(e) => panic!("Expected HashMismatch or Decode error, got: {:?}", e),
+            Ok(_) => panic!("Corrupted entry was accepted!"),
+        }
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_truncated_file() {
+        let path = temp_log_path("truncated_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"data".to_vec())
+            .sign(&node);
+        append_entry(&path, &entry).unwrap();
+        
+        // Truncate file by 1 byte
+        let file = OpenOptions::new().write(true).open(&path).unwrap();
+        let len = file.metadata().unwrap().len();
+        file.set_len(len - 1).unwrap();
+        drop(file);
+        
+        let result = read_entries(&path);
+        
+        match result {
+            Err(LogError::UnexpectedEof) => (),
+            Err(LogError::Io(e)) if e.kind() == io::ErrorKind::UnexpectedEof => (),
+            Err(LogError::Decode(_)) => (), // Also acceptable
+            res => panic!("Expected UnexpectedEof, got: {:?}", res),
+        }
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_append_too_large() {
+        let path = temp_log_path("too_large_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        // Create payload larger than MAX_ENTRY_SIZE
+        let huge_payload = vec![0u8; crate::MAX_ENTRY_SIZE + 100];
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/huge", huge_payload)
+            .sign(&node);
+        
+        let result = append_entry(&path, &entry);
+        
+        match result {
+            Err(LogError::EntryTooLarge(size)) => assert!(size > crate::MAX_ENTRY_SIZE),
+            _ => panic!("Expected EntryTooLarge error"),
+        }
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_read_after_last_element() {
+        let path = temp_log_path("boundary_last_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"val".to_vec())
+            .sign(&node);
+        append_entry(&path, &entry).unwrap();
+        
+        let hash = compute_entry_hash(&entry);
+        
+        // Ask for everything AFTER the only entry
+        let result = read_entries_after(&path, Some(hash)).unwrap();
+        
+        // Result must be empty
+        assert_eq!(result.len(), 0);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_read_entry_exceeding_limit() {
+        let path = temp_log_path("huge_read_v6");
+        std::fs::remove_file(&path).ok();
+        
+        // Write a length prefix claiming the entry is > MAX_ENTRY_SIZE
+        let mut file = File::create(&path).unwrap();
+        
+        let too_big = (crate::MAX_ENTRY_SIZE + 1) as usize;
+        let mut buf = Vec::new();
+        prost::encode_length_delimiter(too_big, &mut buf).unwrap();
+        
+        file.write_all(&buf).unwrap();
+        // Write some dummy bytes (reader should reject before reading these)
+        file.write_all(&[0u8; 10]).unwrap();
+        drop(file);
+        
+        let result = read_entries(&path);
+        
+        match result {
+            Err(LogError::EntryTooLarge(size)) => assert_eq!(size, too_big),
+            _ => panic!("Expected EntryTooLarge before allocating RAM"),
+        }
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_corruption_in_middle_of_stream() {
+        let path = temp_log_path("corruption_middle_v6");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        // Write 3 entries
+        for i in 0..3 {
+            let entry = EntryBuilder::new(i + 1, HLC::now_with_clock(&clock))
+                .put(format!("/key/{}", i), b"val".to_vec())
+                .sign(&node);
+            append_entry(&path, &entry).unwrap();
+        }
+        
+        // Corrupt a byte in the middle of the file
+        let mut file_bytes = std::fs::read(&path).unwrap();
+        let mid_idx = file_bytes.len() / 2;
+        file_bytes[mid_idx] = !file_bytes[mid_idx]; // Bitflip
+        std::fs::write(&path, file_bytes).unwrap();
+        
+        // Reading should fail at some point
+        let result = read_entries(&path);
+        
+        // Must fail with HashMismatch or DecodeError  
+        assert!(result.is_err());
+        
+        std::fs::remove_file(&path).ok();
+    }
+}

lattice-core/src/meta_store.rs

@@ -0,0 +1,177 @@
+//! MetaStore - global node metadata in meta.db
+//!
+//! Tables:
+//! - stores: UUID → created_at (Unix ms)
+//! - meta: "root_store" → UUID (auto-opened on startup)
+
+use redb::{Database, ReadableTable, TableDefinition};
+use std::path::Path;
+use thiserror::Error;
+use uuid::Uuid;
+
+const STORES_TABLE: TableDefinition<&[u8], u64> = TableDefinition::new("stores");
+const META_TABLE: TableDefinition<&str, &[u8]> = TableDefinition::new("meta");
+
+const META_ROOT_STORE: &str = "root_store";
+const META_NAME: &str = "name";
+
+#[derive(Error, Debug)]
+pub enum MetaStoreError {
+    #[error("Database error: {0}")]
+    Database(#[from] redb::DatabaseError),
+    
+    #[error("Table error: {0}")]
+    Table(#[from] redb::TableError),
+    
+    #[error("Transaction error: {0}")]
+    Transaction(#[from] redb::TransactionError),
+    
+    #[error("Commit error: {0}")]
+    Commit(#[from] redb::CommitError),
+    
+    #[error("Storage error: {0}")]
+    Storage(#[from] redb::StorageError),
+}
+
+/// Global metadata store
+pub struct MetaStore {
+    db: Database,
+}
+
+impl MetaStore {
+    /// Open or create meta.db at the given path
+    pub fn open(path: impl AsRef<Path>) -> Result<Self, MetaStoreError> {
+        let db = Database::create(path)?;
+        
+        // Ensure tables exist
+        let write_txn = db.begin_write()?;
+        {
+            let _ = write_txn.open_table(STORES_TABLE)?;
+            let _ = write_txn.open_table(META_TABLE)?;
+        }
+        write_txn.commit()?;
+        
+        Ok(Self { db })
+    }
+
+    /// Register a new store
+    pub fn add_store(&self, store_id: Uuid) -> Result<(), MetaStoreError> {
+        let write_txn = self.db.begin_write()?;
+        {
+            let mut table = write_txn.open_table(STORES_TABLE)?;
+            let now = std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap()
+                .as_millis() as u64;
+            table.insert(store_id.as_bytes().as_slice(), now)?;
+        }
+        write_txn.commit()?;
+        Ok(())
+    }
+
+    /// List all registered stores
+    pub fn list_stores(&self) -> Result<Vec<Uuid>, MetaStoreError> {
+        let read_txn = self.db.begin_read()?;
+        let table = read_txn.open_table(STORES_TABLE)?;
+        
+        let mut stores = Vec::new();
+        for result in table.iter()? {
+            let (key, _created_at) = result?;
+            let bytes: [u8; 16] = key.value().try_into().unwrap_or([0; 16]);
+            stores.push(Uuid::from_bytes(bytes));
+        }
+        Ok(stores)
+    }
+
+    /// Get the root store ID (auto-opened on startup)
+    pub fn root_store(&self) -> Result<Option<Uuid>, MetaStoreError> {
+        let read_txn = self.db.begin_read()?;
+        let table = read_txn.open_table(META_TABLE)?;
+        
+        match table.get(META_ROOT_STORE)? {
+            Some(value) => {
+                let bytes: [u8; 16] = value.value().try_into().unwrap_or([0; 16]);
+                Ok(Some(Uuid::from_bytes(bytes)))
+            }
+            None => Ok(None),
+        }
+    }
+
+    /// Set the root store ID
+    pub fn set_root_store(&self, store_id: Uuid) -> Result<(), MetaStoreError> {
+        let write_txn = self.db.begin_write()?;
+        {
+            let mut table = write_txn.open_table(META_TABLE)?;
+            table.insert(META_ROOT_STORE, store_id.as_bytes().as_slice())?;
+        }
+        write_txn.commit()?;
+        Ok(())
+    }
+    
+    /// Get the node's display name
+    pub fn name(&self) -> Result<Option<String>, MetaStoreError> {
+        let read_txn = self.db.begin_read()?;
+        let table = read_txn.open_table(META_TABLE)?;
+        
+        match table.get(META_NAME)? {
+            Some(value) => Ok(Some(String::from_utf8_lossy(value.value()).to_string())),
+            None => Ok(None),
+        }
+    }
+    
+    /// Set the node's display name
+    pub fn set_name(&self, name: &str) -> Result<(), MetaStoreError> {
+        let write_txn = self.db.begin_write()?;
+        {
+            let mut table = write_txn.open_table(META_TABLE)?;
+            table.insert(META_NAME, name.as_bytes())?;
+        }
+        write_txn.commit()?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::env::temp_dir;
+
+    #[test]
+    fn test_add_and_list_stores() {
+        let path = temp_dir().join("meta_store_test.db");
+        let _ = std::fs::remove_file(&path);
+        
+        let meta = MetaStore::open(&path).unwrap();
+        
+        let id1 = Uuid::new_v4();
+        let id2 = Uuid::new_v4();
+        
+        meta.add_store(id1).unwrap();
+        meta.add_store(id2).unwrap();
+        
+        let stores = meta.list_stores().unwrap();
+        assert_eq!(stores.len(), 2);
+        assert!(stores.contains(&id1));
+        assert!(stores.contains(&id2));
+        
+        let _ = std::fs::remove_file(&path);
+    }
+
+    #[test]
+    fn test_root_store() {
+        let path = temp_dir().join("meta_store_root.db");
+        let _ = std::fs::remove_file(&path);
+        
+        let meta = MetaStore::open(&path).unwrap();
+        
+        // Initially no root store
+        assert_eq!(meta.root_store().unwrap(), None);
+        
+        let root = Uuid::new_v4();
+        meta.set_root_store(root).unwrap();
+        
+        assert_eq!(meta.root_store().unwrap(), Some(root));
+        
+        let _ = std::fs::remove_file(&path);
+    }
+}

lattice-core/src/node.rs

@@ -0,0 +1,985 @@
+//! Local Lattice node API with multi-store support
+
+use crate::{
+    DataDir, MetaStore, NodeIdentity, PeerStatus, SigChain, Store, Uuid,
+    log::LogError,
+    meta_store::MetaStoreError,
+    sigchain::SigChainError,
+    store::StoreError,
+    spawn_store_actor, StoreCmd,
+    node_identity::NodeError as IdentityError,
+    proto::SignedEntry,
+};
+use std::path::Path;
+use thiserror::Error;
+use tokio::sync::broadcast;
+
+#[derive(Error, Debug)]
+pub enum NodeError {
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+    
+    #[error("Store error: {0}")]
+    Store(#[from] StoreError),
+    
+    #[error("MetaStore error: {0}")]
+    MetaStore(#[from] MetaStoreError),
+    
+    #[error("SigChain error: {0}")]
+    SigChain(#[from] SigChainError),
+    
+    #[error("Log error: {0}")]
+    Log(#[from] LogError),
+    
+    #[error("Node error: {0}")]
+    Node(#[from] IdentityError),
+    
+    #[error("Already initialized")]
+    AlreadyInitialized,
+    
+    #[error("Channel closed")]
+    ChannelClosed,
+    
+    #[error("Actor error: {0}")]
+    Actor(String),
+}
+
+pub struct NodeInfo {
+    pub node_id: String,
+    pub data_path: String,
+    pub stores: Vec<Uuid>,
+}
+
+pub struct StoreInfo {
+    pub store_id: Uuid,
+    pub entries_replayed: u64,
+}
+
+/// Result of accepting a peer's join request
+pub struct JoinAcceptance {
+    pub store_id: Uuid,
+}
+
+/// Information about a peer in the mesh
+pub struct PeerInfo {
+    pub pubkey: String,
+    pub name: Option<String>,
+    pub added_at: Option<u64>,
+    pub added_by: Option<String>,
+    pub status: PeerStatus,
+}
+
+/// Events emitted by Node for interested listeners (e.g., LatticeServer)
+#[derive(Clone, Debug)]
+pub enum NodeEvent {
+    /// Root store was activated (opened or set)
+    RootStoreActivated(StoreHandle),
+}
+
+pub struct NodeBuilder {
+    pub data_dir: DataDir,
+}
+
+impl NodeBuilder {
+    pub fn new() -> Self {
+        Self { data_dir: DataDir::default() }
+    }
+
+    pub fn build(self) -> Result<Node, NodeError> {
+        self.data_dir.ensure_dirs()?;
+
+        let key_path = self.data_dir.identity_key();
+        let is_new = !key_path.exists();
+        let node = if key_path.exists() {
+            NodeIdentity::load(&key_path)?
+        } else {
+            let node = NodeIdentity::generate();
+            node.save(&key_path)?;
+            node
+        };
+
+        let meta = MetaStore::open(self.data_dir.meta_db())?;
+        // Set hostname on first creation
+        if is_new {
+            let hostname = hostname::get()
+                .map(|s| s.to_string_lossy().to_string())
+                .unwrap_or_else(|_| "unknown".to_string());
+            let _ = meta.set_name(&hostname);
+        }
+        
+        // Create event channel
+        let (event_tx, _) = broadcast::channel(16);
+
+        Ok(Node {
+            data_dir: self.data_dir,
+            node: std::sync::Arc::new(node),
+            meta,
+            root_store: tokio::sync::RwLock::new(None),
+            event_tx,
+        })
+    }
+}
+
+impl Default for NodeBuilder {
+    fn default() -> Self { Self::new() }
+}
+
+/// A local Lattice node (manages identity and store registry)
+pub struct Node {
+    data_dir: DataDir,
+    node: std::sync::Arc<NodeIdentity>,
+    meta: MetaStore,
+    root_store: tokio::sync::RwLock<Option<StoreHandle>>,
+    event_tx: broadcast::Sender<NodeEvent>,
+}
+
+impl Node {
+    pub fn info(&self) -> NodeInfo {
+        NodeInfo {
+            node_id: hex::encode(self.node.public_key_bytes()),
+            data_path: self.data_dir.base().display().to_string(),
+            stores: self.meta.list_stores().unwrap_or_default(),
+        }
+    }
+
+    pub fn node_id(&self) -> [u8; 32] {
+        self.node.public_key_bytes()
+    }
+    
+    /// Subscribe to node events (e.g., root store activation)
+    pub fn subscribe_events(&self) -> broadcast::Receiver<NodeEvent> {
+        self.event_tx.subscribe()
+    }
+
+    /// Get the secret key bytes for Iroh integration (same Ed25519 key)
+    pub fn secret_key_bytes(&self) -> [u8; 32] {
+        self.node.secret_key_bytes()
+    }
+
+    pub fn data_path(&self) -> &Path {
+        self.data_dir.base()
+    }
+
+    /// Get the node's display name (from meta.db, set on creation)
+    pub fn name(&self) -> Option<String> {
+        self.meta.name().ok().flatten()
+    }
+    
+    /// Set the node's display name.
+    /// Updates meta.db and if root store is open, also updates /nodes/{pubkey}/name
+    pub async fn set_name(&self, name: &str) -> Result<(), NodeError> {
+        self.meta.set_name(name)?;
+        self.publish_name().await
+    }
+    
+    /// Publish this node's name from meta.db to the root store.
+    /// Used after joining a mesh to announce ourselves.
+    pub async fn publish_name(&self) -> Result<(), NodeError> {
+        if let Some(name) = self.name() {
+            let guard = self.root_store.read().await;
+            if let Some(handle) = guard.as_ref() {
+                let pubkey_hex = hex::encode(self.node.public_key_bytes());
+                let name_key = format!("/nodes/{}/name", pubkey_hex);
+                handle.put(name_key.as_bytes(), name.as_bytes()).await?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Get the root store ID
+    pub fn root_store_id(&self) -> Result<Option<Uuid>, NodeError> {
+        Ok(self.meta.root_store()?)
+    }
+    
+    /// Get reference to the cached root store handle (if open)
+    pub async fn root_store(&self) -> tokio::sync::RwLockReadGuard<'_, Option<StoreHandle>> {
+        self.root_store.read().await
+    }
+    
+    /// Open the root store if set. Node owns the handle internally.
+    /// Returns StoreInfo on success, or None if no root store is set.
+    pub async fn open_root_store(&self) -> Result<Option<StoreInfo>, NodeError> {
+        match self.meta.root_store()? {
+            Some(id) => {
+                let (handle, info) = self.open_store(id).await?;
+                
+                // Emit event for listeners (send clone, keep original)
+                let _ = self.event_tx.send(NodeEvent::RootStoreActivated(handle.clone()));
+                
+                // Store original handle (owns actor thread)
+                *self.root_store.write().await = Some(handle);
+                
+                Ok(Some(info))
+            }
+            None => Ok(None),
+        }
+    }
+
+    /// Initialize the node with a root store (fails if already initialized).
+    /// Node owns the store handle internally. Access via root_store().
+    pub async fn init(&self) -> Result<Uuid, NodeError> {
+        if self.meta.root_store()?.is_some() {
+            return Err(NodeError::AlreadyInitialized);
+        }
+        let store_id = self.create_store()?;
+        self.meta.set_root_store(store_id)?;
+        
+        // Open the store and write our node info as separate keys
+        let (handle, _) = self.open_store(store_id).await?;
+        let pubkey_hex = hex::encode(self.node.public_key_bytes());
+        
+        // Store node metadata as separate keys
+        if let Some(name) = self.name() {
+            let name_key = format!("/nodes/{}/name", pubkey_hex);
+            handle.put(name_key.as_bytes(), name.as_bytes()).await?;
+        }
+        
+        let added_at = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
+        let added_at_key = format!("/nodes/{}/added_at", pubkey_hex);
+        handle.put(added_at_key.as_bytes(), added_at.to_string().as_bytes()).await?;
+        
+        // Write status = active
+        let status_key = format!("/nodes/{}/status", pubkey_hex);
+        handle.put(status_key.as_bytes(), PeerStatus::Active.as_str().as_bytes()).await?;
+        
+        // Store the handle - node owns it
+        *self.root_store.write().await = Some(handle);
+        
+        Ok(store_id)
+    }
+    
+    /// Complete joining a mesh - creates store with given UUID, sets as root, caches handle.
+    /// Called after receiving store_id from peer's JoinResponse.
+    pub async fn complete_join(&self, store_id: Uuid) -> Result<StoreHandle, NodeError> {
+        // Create local store with that UUID
+        self.create_store_with_uuid(store_id)?;
+        self.meta.set_root_store(store_id)?;
+        
+        // Open and cache the handle (original stays in cache)
+        let (handle, _) = self.open_store(store_id).await?;
+        let handle_clone = handle.clone();
+        *self.root_store.write().await = Some(handle);
+        
+        // Emit event for listeners
+        let _ = self.event_tx.send(NodeEvent::RootStoreActivated(handle_clone.clone()));
+        
+        // Publish our name to the store
+        let _ = self.publish_name().await;
+        
+        Ok(handle_clone)
+    }
+    
+    // --- Peer Management ---
+    
+    /// Invite a peer to the mesh. Writes their info with status = invited.
+    pub async fn invite_peer(&self, pubkey: &[u8; 32]) -> Result<(), NodeError> {
+        let guard = self.root_store.read().await;
+        let store = guard.as_ref()
+            .ok_or_else(|| NodeError::Actor("No root store open".to_string()))?;
+        
+        let pubkey_hex = hex::encode(pubkey);
+        let my_pubkey_hex = hex::encode(self.node.public_key_bytes());
+        
+        let added_at = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_secs())
+            .unwrap_or(0);
+        
+        // Write added_by
+        let added_by_key = format!("/nodes/{}/added_by", pubkey_hex);
+        store.put(added_by_key.as_bytes(), my_pubkey_hex.as_bytes()).await?;
+        
+        // Write added_at
+        let added_at_key = format!("/nodes/{}/added_at", pubkey_hex);
+        store.put(added_at_key.as_bytes(), added_at.to_string().as_bytes()).await?;
+        
+        // Write status = invited
+        let status_key = format!("/nodes/{}/status", pubkey_hex);
+        store.put(status_key.as_bytes(), PeerStatus::Invited.as_str().as_bytes()).await?;
+        
+        Ok(())
+    }
+    
+    /// List all peers in the mesh with their info
+    pub async fn list_peers(&self) -> Result<Vec<PeerInfo>, NodeError> {
+        let guard = self.root_store.read().await;
+        let store = guard.as_ref()
+            .ok_or_else(|| NodeError::Actor("No root store open".to_string()))?;
+        
+        let all = store.list(false).await?;
+        
+        // Collect unique pubkeys with status
+        let mut peers_map: std::collections::HashMap<String, PeerStatus> = std::collections::HashMap::new();
+        for (key, value) in &all {
+            let key_str = String::from_utf8_lossy(key);
+            if key_str.ends_with("/status") {
+                if let Some(pubkey) = key_str.strip_prefix("/nodes/").and_then(|s| s.strip_suffix("/status")) {
+                    let status_str = String::from_utf8_lossy(value);
+                    if let Some(status) = PeerStatus::from_str(&status_str) {
+                        peers_map.insert(pubkey.to_string(), status);
+                    }
+                }
+            }
+        }
+        
+        // Build PeerInfo for each peer
+        let mut peers = Vec::new();
+        for (pubkey, status) in peers_map {
+            let name_key = format!("/nodes/{}/name", pubkey);
+            let added_at_key = format!("/nodes/{}/added_at", pubkey);
+            let added_by_key = format!("/nodes/{}/added_by", pubkey);
+            
+            let name = store.get(name_key.as_bytes()).await?
+                .map(|b| String::from_utf8_lossy(&b).to_string());
+            
+            let added_at = store.get(added_at_key.as_bytes()).await?
+                .and_then(|b| String::from_utf8_lossy(&b).parse().ok());
+            
+            let added_by = store.get(added_by_key.as_bytes()).await?
+                .map(|b| String::from_utf8_lossy(&b).to_string());
+            
+            peers.push(PeerInfo {
+                pubkey,
+                name,
+                added_at,
+                added_by,
+                status,
+            });
+        }
+        
+        Ok(peers)
+    }
+    
+    /// Remove a peer from the mesh (deletes all their /nodes/{pubkey}/* keys)
+    pub async fn remove_peer(&self, pubkey: &[u8; 32]) -> Result<(), NodeError> {
+        let guard = self.root_store.read().await;
+        let store = guard.as_ref()
+            .ok_or_else(|| NodeError::Actor("No root store open".to_string()))?;
+        
+        let pubkey_hex = hex::encode(pubkey);
+        
+        // Prevent self-removal
+        if pubkey == &self.node.public_key_bytes() {
+            return Err(NodeError::Actor("Cannot remove yourself".to_string()));
+        }
+        
+        // Find all keys for this peer using prefix search
+        let prefix = format!("/nodes/{}/", pubkey_hex);
+        let keys = store.list_by_prefix(prefix.as_bytes(), false).await?;
+        
+        if keys.is_empty() {
+            return Err(NodeError::Actor("Peer not found".to_string()));
+        }
+        
+        // Delete all found keys
+        for (key, _) in keys {
+            store.delete(&key).await?;
+        }
+        
+        Ok(())
+    }
+    
+    /// Get a peer's status
+    pub async fn get_peer_status(&self, pubkey: &[u8; 32]) -> Result<Option<PeerStatus>, NodeError> {
+        let guard = self.root_store.read().await;
+        let store = guard.as_ref()
+            .ok_or_else(|| NodeError::Actor("No root store open".to_string()))?;
+        
+        let pubkey_hex = hex::encode(pubkey);
+        let status_key = format!("/nodes/{}/status", pubkey_hex);
+        
+        match store.get(status_key.as_bytes()).await? {
+            Some(bytes) => {
+                let status_str = String::from_utf8_lossy(&bytes);
+                Ok(PeerStatus::from_str(&status_str))
+            }
+            None => Ok(None),
+        }
+    }
+    
+    /// Set a peer's status
+    pub async fn set_peer_status(&self, pubkey: &[u8; 32], status: PeerStatus) -> Result<(), NodeError> {
+        let guard = self.root_store.read().await;
+        let store = guard.as_ref()
+            .ok_or_else(|| NodeError::Actor("No root store open".to_string()))?;
+        
+        let pubkey_hex = hex::encode(pubkey);
+        let status_key = format!("/nodes/{}/status", pubkey_hex);
+        store.put(status_key.as_bytes(), status.as_str().as_bytes()).await?;
+        Ok(())
+    }
+    
+    /// Verify a peer has one of the expected statuses
+    pub async fn verify_peer_status(&self, pubkey: &[u8; 32], expected: &[PeerStatus]) -> Result<(), NodeError> {
+        match self.get_peer_status(pubkey).await? {
+            Some(status) if expected.contains(&status) => Ok(()),
+            Some(status) => Err(NodeError::Actor(format!(
+                "Peer status is '{:?}', expected one of {:?}", status, expected
+            ))),
+            None => Err(NodeError::Actor("Peer not found".to_string())),
+        }
+    }
+    
+    /// Accept a peer's join request - verifies they're invited, sets active, returns join info
+    pub async fn accept_join(&self, pubkey: &[u8; 32]) -> Result<JoinAcceptance, NodeError> {
+        // Verify peer is invited
+        self.verify_peer_status(pubkey, &[PeerStatus::Invited]).await?;
+        
+        // Get root store ID
+        let store_id = self.meta.root_store()?
+            .ok_or_else(|| NodeError::Actor("No root store configured".to_string()))?;
+        
+        // Set peer status to active
+        self.set_peer_status(pubkey, PeerStatus::Active).await?;
+        
+        Ok(JoinAcceptance { store_id })
+    }
+
+    pub fn list_stores(&self) -> Result<Vec<Uuid>, NodeError> {
+        Ok(self.meta.list_stores()?)
+    }
+
+    pub fn create_store(&self) -> Result<Uuid, NodeError> {
+        let store_id = Uuid::new_v4();
+        self.create_store_internal(store_id)
+    }
+    
+    /// Create a store with a specific UUID (for joining existing mesh)
+    pub fn create_store_with_uuid(&self, store_id: Uuid) -> Result<Uuid, NodeError> {
+        self.create_store_internal(store_id)
+    }
+    
+    /// Set a store as the root store
+    pub fn set_root_store(&self, store_id: Uuid) -> Result<(), NodeError> {
+        self.meta.set_root_store(store_id)?;
+        Ok(())
+    }
+    
+    fn create_store_internal(&self, store_id: Uuid) -> Result<Uuid, NodeError> {
+        self.data_dir.ensure_store_dirs(store_id)?;
+        let _ = Store::open(self.data_dir.store_state_db(store_id))?;
+        self.meta.add_store(store_id)?;
+        Ok(store_id)
+    }
+
+    pub async fn open_store(&self, store_id: Uuid) -> Result<(StoreHandle, StoreInfo), NodeError> {
+        // Check if this store is already cached as root_store
+        {
+            let guard = self.root_store.read().await;
+            if let Some(ref handle) = *guard {
+                if handle.id() == store_id {
+                    let info = StoreInfo { store_id, entries_replayed: 0 };
+                    return Ok((handle.clone(), info));
+                }
+            }
+        }
+        
+        // Not cached, open it fresh
+        self.data_dir.ensure_store_dirs(store_id)?;
+        
+        let author_id_hex = hex::encode(self.node.public_key_bytes());
+        let log_path = self.data_dir.store_log_file(store_id, &author_id_hex);
+        
+        let sigchain = if log_path.exists() {
+            SigChain::from_log(&log_path, *store_id.as_bytes(), self.node.public_key_bytes())?
+        } else {
+            SigChain::new(&log_path, *store_id.as_bytes(), self.node.public_key_bytes())
+        };
+        
+        let store = Store::open(self.data_dir.store_state_db(store_id))?;
+        let entries_replayed = if log_path.exists() {
+            store.replay_log(&log_path)?
+        } else {
+            0
+        };
+        
+        let info = StoreInfo { store_id, entries_replayed };
+        
+        // Spawn actor thread - actor owns store, sigchain, and node copy
+        let (tx, entry_tx, actor_handle) = spawn_store_actor(
+            store_id,
+            store,
+            sigchain,
+            (*self.node).clone(),
+        );
+        
+        // Store the entry sender for gossip
+        let handle = StoreHandle {
+            store_id,
+            tx,
+            actor_handle: Some(actor_handle),
+            entry_tx,
+        };
+        
+        Ok((handle, info))
+    }
+}
+
+/// A handle to a specific store - wraps channel to actor thread
+#[derive(Debug)]
+pub struct StoreHandle {
+    store_id: Uuid,
+    tx: tokio::sync::mpsc::Sender<StoreCmd>,
+    actor_handle: Option<std::thread::JoinHandle<()>>,
+    entry_tx: broadcast::Sender<SignedEntry>,
+}
+
+impl Clone for StoreHandle {
+    fn clone(&self) -> Self {
+        Self {
+            store_id: self.store_id,
+            tx: self.tx.clone(),
+            actor_handle: None, // Clones don't own the actor thread
+            entry_tx: self.entry_tx.clone(),
+        }
+    }
+}
+
+impl StoreHandle {
+    pub fn id(&self) -> Uuid { self.store_id }
+    
+    /// Subscribe to receive entries as they're committed locally
+    pub fn subscribe_entries(&self) -> broadcast::Receiver<SignedEntry> {
+        self.entry_tx.subscribe()
+    }
+
+    pub async fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::Get { key: key.to_vec(), resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn get_heads(&self, key: &[u8]) -> Result<Vec<crate::HeadInfo>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::GetHeads { key: key.to_vec(), resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn list(&self, include_deleted: bool) -> Result<Vec<(Vec<u8>, Vec<u8>)>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::List { include_deleted, resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn list_by_prefix(&self, prefix: &[u8], include_deleted: bool) -> Result<Vec<(Vec<u8>, Vec<u8>)>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::ListByPrefix { prefix: prefix.to_vec(), include_deleted, resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn log_seq(&self) -> u64 {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        let _ = self.tx.send(StoreCmd::LogSeq { resp: resp_tx }).await;
+        resp_rx.await.unwrap_or(0)
+    }
+
+    pub async fn applied_seq(&self) -> Result<u64, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::AppliedSeq { resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn author_state(&self, author: &[u8; 32]) -> Result<Option<crate::proto::AuthorState>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::AuthorState { author: *author, resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    /// Get log directory statistics (file count, total bytes)
+    pub async fn log_stats(&self) -> (usize, u64) {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        let _ = self.tx.send(StoreCmd::LogStats { resp: resp_tx }).await;
+        resp_rx.await.unwrap_or((0, 0))
+    }
+
+    pub async fn sync_state(&self) -> Result<crate::sync_state::SyncState, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::SyncState { resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn read_entries_after(&self, author: &[u8; 32], from_hash: Option<[u8; 32]>) -> Result<Vec<crate::proto::SignedEntry>, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::ReadEntriesAfter { author: *author, from_hash, resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn apply_entry(&self, entry: crate::proto::SignedEntry) -> Result<(), NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::ApplyEntry { entry, resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(NodeError::Store)
+    }
+
+    pub async fn put(&self, key: &[u8], value: &[u8]) -> Result<u64, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::Put { key: key.to_vec(), value: value.to_vec(), resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(|e| NodeError::Actor(e.to_string()))
+    }
+
+    pub async fn delete(&self, key: &[u8]) -> Result<u64, NodeError> {
+        use StoreCmd;
+        let (resp_tx, resp_rx) = tokio::sync::oneshot::channel();
+        self.tx.send(StoreCmd::Delete { key: key.to_vec(), resp: resp_tx }).await
+            .map_err(|_| NodeError::ChannelClosed)?;
+        resp_rx.await
+            .map_err(|_| NodeError::ChannelClosed)?
+            .map_err(|e| NodeError::Actor(e.to_string()))
+    }
+
+}
+
+impl Drop for StoreHandle {
+    fn drop(&mut self) {
+        // Only send shutdown if we own the actor (non-cloned handle)
+        if let Some(handle) = self.actor_handle.take() {
+            let _ = self.tx.try_send(StoreCmd::Shutdown);
+            let _ = handle.join();
+        }
+        // Clones (actor_handle = None) don't send shutdown - actor keeps running
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::env::temp_dir;
+
+    fn temp_data_dir(name: &str) -> DataDir {
+        let path = temp_dir().join(format!("lattice_node_test_{}", name));
+        let _ = std::fs::remove_dir_all(&path);
+        DataDir::new(path)
+    }
+
+    #[tokio::test]
+    async fn test_create_and_open_store() {
+        let data_dir = temp_data_dir("meta_store");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("Failed to create node");
+        
+        assert!(node.info().stores.is_empty());
+        
+        let store_id = node.create_store().expect("Failed to create store");
+        
+        // Verify it's in the list
+        let stores = node.list_stores().expect("list failed");
+        assert!(stores.contains(&store_id));
+        
+        let (handle, _) = node.open_store(store_id).await.expect("Failed to open store");
+        handle.put(b"/key", b"value").await.expect("put failed");
+        assert_eq!(handle.get(b"/key").await.unwrap(), Some(b"value".to_vec()));
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_store_isolation() {
+        let data_dir = temp_data_dir("meta_isolation");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("Failed to create node");
+        
+        let store_a = node.create_store().expect("create A");
+        let store_b = node.create_store().expect("create B");
+        
+        let (handle_a, _) = node.open_store(store_a).await.expect("open A");
+        handle_a.put(b"/key", b"from A").await.expect("put A");
+        
+        let (handle_b, _) = node.open_store(store_b).await.expect("open B");
+        assert_eq!(handle_b.get(b"/key").await.unwrap(), None);
+        
+        assert_eq!(handle_a.get(b"/key").await.unwrap(), Some(b"from A".to_vec()));
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_init_creates_root_store() {
+        let data_dir = temp_data_dir("init_root");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        
+        // Initially no root store
+        assert!(node.root_store().await.is_none());
+        
+        // Init creates root store
+        let root_id = node.init().await.expect("init failed");
+        assert_eq!(node.root_store_id().unwrap(), Some(root_id));
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_duplicate_init_fails() {
+        let data_dir = temp_data_dir("init_dup");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        
+        node.init().await.expect("first init");
+        
+        // Second init should fail
+        match node.init().await {
+            Ok(_) => panic!("Expected AlreadyInitialized error"),
+            Err(e) => match e {
+                NodeError::AlreadyInitialized => (),
+                _ => panic!("Expected AlreadyInitialized, got {:?}", e),
+            },
+        }
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_root_store_in_info_after_init() {
+        let data_dir = temp_data_dir("init_info");
+        
+        // First session: init
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        let root_id = node.init().await.expect("init");
+        drop(node);  // End first session
+        
+        // Second session: root_store should persist
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("reload node");
+        
+        assert_eq!(node.root_store_id().unwrap(), Some(root_id));
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_idempotent_put_and_delete() {
+        let data_dir = temp_data_dir("idempotent");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        node.init().await.expect("init");
+        let store = node.root_store().await;
+        let store = store.as_ref().unwrap();
+        
+        // Get baseline seq after init
+        let baseline = store.log_seq().await;
+        
+        // Put twice with same value - second should be idempotent
+        let seq1 = store.put(b"/key", b"value").await.expect("put 1");
+        assert_eq!(seq1, baseline + 1);
+        
+        let seq2 = store.put(b"/key", b"value").await.expect("put 2");
+        assert_eq!(seq2, baseline + 1, "Second put should be idempotent (no new entry)");
+        
+        assert_eq!(store.log_seq().await, baseline + 1);
+        
+        // Delete twice - second should be idempotent
+        let seq3 = store.delete(b"/key").await.expect("delete 1");
+        assert_eq!(seq3, baseline + 2);
+        
+        let seq4 = store.delete(b"/key").await.expect("delete 2");
+        assert_eq!(seq4, baseline + 2, "Second delete should be idempotent (no new entry)");
+        
+        assert_eq!(store.log_seq().await, baseline + 2);
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+    
+    #[tokio::test]
+    async fn test_set_name_updates_store() {
+        let data_dir = temp_data_dir("set_name");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        
+        // Set initial name
+        assert!(node.name().is_some());
+        let initial_name = node.name().unwrap();
+        
+        // Init creates root store
+        node.init().await.expect("init");
+        
+        // Verify initial name is in store
+        let pubkey_hex = hex::encode(node.node_id());
+        let name_key = format!("/nodes/{}/name", pubkey_hex);
+        {
+            let store = node.root_store().await;
+            let store = store.as_ref().unwrap();
+            let stored_name = store.get(name_key.as_bytes()).await.unwrap();
+            assert_eq!(stored_name, Some(initial_name.as_bytes().to_vec()));
+        }
+        
+        // Change name
+        let new_name = "my-custom-name";
+        node.set_name(new_name).await.expect("set_name");
+        
+        // Verify meta.db updated
+        assert_eq!(node.name(), Some(new_name.to_string()));
+        
+        // Verify store updated
+        {
+            let store = node.root_store().await;
+            let store = store.as_ref().unwrap();
+            let stored_name = store.get(name_key.as_bytes()).await.unwrap();
+            assert_eq!(stored_name, Some(new_name.as_bytes().to_vec()));
+        }
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_invite_peer() {
+        let data_dir = temp_data_dir("invite_peer");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        
+        // Init first
+        node.init().await.expect("init");
+        
+        // Invite a peer
+        let peer_pubkey = [0u8; 32]; // Dummy pubkey
+        node.invite_peer(&peer_pubkey).await.expect("invite");
+        
+        // Verify peer is Invited
+        let peers = node.list_peers().await.expect("list_peers");
+        let invited = peers.iter().find(|p| p.pubkey == hex::encode(peer_pubkey));
+        assert!(invited.is_some(), "Should find invited peer");
+        assert_eq!(invited.unwrap().status, PeerStatus::Invited);
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_accept_join() {
+        let data_dir = temp_data_dir("accept_join");
+        
+        let node = NodeBuilder { data_dir: data_dir.clone() }
+            .build()
+            .expect("create node");
+        
+        // Init first
+        let store_id = node.init().await.expect("init");
+        
+        // Invite a peer
+        let peer_pubkey = [1u8; 32]; // Dummy pubkey
+        node.invite_peer(&peer_pubkey).await.expect("invite");
+        
+        // Accept the join
+        let acceptance = node.accept_join(&peer_pubkey).await.expect("accept_join");
+        assert_eq!(acceptance.store_id, store_id);
+        
+        // Peer should now be Active
+        let peers = node.list_peers().await.expect("list_peers");
+        let peer = peers.iter().find(|p| p.pubkey == hex::encode(peer_pubkey));
+        assert!(peer.is_some(), "Should find peer");
+        assert_eq!(peer.unwrap().status, PeerStatus::Active);
+        
+        let _ = std::fs::remove_dir_all(data_dir.base());
+    }
+
+    #[tokio::test]
+    async fn test_invite_join_sync_flow() {
+        // Node A: creator, Node B: joiner
+        let data_dir_a = temp_data_dir("flow_a");
+        let data_dir_b = temp_data_dir("flow_b");
+        
+        let node_a = NodeBuilder { data_dir: data_dir_a.clone() }
+            .build()
+            .expect("create node A");
+        let node_b = NodeBuilder { data_dir: data_dir_b.clone() }
+            .build()
+            .expect("create node B");
+        
+        // Step 1: Node A initializes
+        let store_id = node_a.init().await.expect("A init");
+        let store_a = node_a.root_store().await;
+        let store_a = store_a.as_ref().expect("A has root store");
+        
+        // Step 2: A invites B
+        let b_pubkey: [u8; 32] = node_b.node_id().try_into().unwrap();
+        node_a.invite_peer(&b_pubkey).await.expect("invite B");
+        
+        // Verify B is invited
+        let peers = node_a.list_peers().await.expect("list peers");
+        assert!(peers.iter().any(|p| p.status == PeerStatus::Invited));
+        
+        // Step 3: B "joins" (complete_join simulates receiving JoinResponse)
+        let store_b = node_b.complete_join(store_id).await.expect("B join");
+        
+        // Verify B has the same store ID
+        assert_eq!(store_b.id(), store_id);
+        
+        // Step 4: A writes data
+        store_a.put(b"/key", b"from A").await.expect("A put");
+        
+        // Step 5: B writes data independently
+        store_b.put(b"/key", b"from B").await.expect("B put");
+        
+        // Each store has its own local state (not synced yet)
+        let a_val = store_a.get(b"/key").await.expect("A get").unwrap();
+        let b_val = store_b.get(b"/key").await.expect("B get").unwrap();
+        
+        // A sees "from A" (its own write wins locally)
+        assert_eq!(a_val, b"from A".to_vec());
+        // B sees "from B" (its own write wins locally)  
+        assert_eq!(b_val, b"from B".to_vec());
+        
+        // Cleanup
+        let _ = std::fs::remove_dir_all(data_dir_a.base());
+        let _ = std::fs::remove_dir_all(data_dir_b.base());
+    }
+}

lattice-core/src/node_identity.rs

@@ -0,0 +1,252 @@
+//! Node identity and cryptographic keys
+//!
+//! Each node has an Ed25519 keypair:
+//! - Private key: stored locally in `identity.key` (never replicated)
+//! - Public key: serves as the node's identity (32 bytes)
+
+use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
+use rand::rngs::OsRng;
+use std::fs;
+use std::io::{self, Read, Write};
+use std::path::Path;
+use thiserror::Error;
+
+/// Errors that can occur during node operations
+#[derive(Error, Debug)]
+pub enum NodeError {
+    #[error("IO error: {0}")]
+    Io(#[from] io::Error),
+    
+    #[error("Invalid key length: expected 32 bytes, got {0}")]
+    InvalidKeyLength(usize),
+    
+    #[error("Invalid signature")]
+    InvalidSignature,
+}
+
+/// A node in the Lattice mesh.
+///
+/// Each node has an Ed25519 keypair used for signing sigchain entries
+/// and establishing trust within the network.
+#[derive(Clone)]
+pub struct NodeIdentity {
+    signing_key: SigningKey,
+}
+
+impl NodeIdentity {
+    /// Generate a new node with a random keypair.
+    pub fn generate() -> Self {
+        let signing_key = SigningKey::generate(&mut OsRng);
+        Self { signing_key }
+    }
+
+    /// Create a node from an existing signing key.
+    pub fn from_signing_key(signing_key: SigningKey) -> Self {
+        Self { signing_key }
+    }
+
+    /// Load a node's identity from a key file, or generate and save if it doesn't exist.
+    pub fn load_or_generate(path: impl AsRef<Path>) -> Result<Self, NodeError> {
+        let path = path.as_ref();
+        if path.exists() {
+            Self::load(path)
+        } else {
+            let node = Self::generate();
+            node.save(path)?;
+            Ok(node)
+        }
+    }
+
+    /// Load a node's identity from a key file.
+    pub fn load(path: impl AsRef<Path>) -> Result<Self, NodeError> {
+        let mut file = fs::File::open(path)?;
+        let mut bytes = Vec::new();
+        file.read_to_end(&mut bytes)?;
+        
+        if bytes.len() != 32 {
+            return Err(NodeError::InvalidKeyLength(bytes.len()));
+        }
+        
+        let key_bytes: [u8; 32] = bytes.try_into().unwrap();
+        let signing_key = SigningKey::from_bytes(&key_bytes);
+        Ok(Self { signing_key })
+    }
+
+    /// Save the node's private key to a file.
+    pub fn save(&self, path: impl AsRef<Path>) -> Result<(), NodeError> {
+        let path = path.as_ref();
+        
+        // Create parent directories if they don't exist
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent)?;
+        }
+        
+        let mut file = fs::File::create(path)?;
+        file.write_all(self.signing_key.as_bytes())?;
+        Ok(())
+    }
+
+    /// Get the node's public key (identity).
+    pub fn public_key(&self) -> VerifyingKey {
+        self.signing_key.verifying_key()
+    }
+
+    /// Get the node's public key as bytes (32 bytes).
+    pub fn public_key_bytes(&self) -> [u8; 32] {
+        self.signing_key.verifying_key().to_bytes()
+    }
+
+    /// Get the signing key for creating signatures.
+    pub fn signing_key(&self) -> &SigningKey {
+        &self.signing_key
+    }
+
+    /// Get the secret key bytes (32 bytes) for Iroh integration.
+    /// WARNING: Handle with care - this exposes the private key material.
+    pub fn secret_key_bytes(&self) -> [u8; 32] {
+        self.signing_key.to_bytes()
+    }
+
+    /// Sign a message.
+    pub fn sign(&self, message: &[u8]) -> Signature {
+        self.signing_key.sign(message)
+    }
+
+    /// Verify a signature against this node's public key.
+    pub fn verify(&self, message: &[u8], signature: &Signature) -> Result<(), NodeError> {
+        self.public_key()
+            .verify(message, signature)
+            .map_err(|_| NodeError::InvalidSignature)
+    }
+
+    /// Verify a signature using a raw public key.
+    pub fn verify_with_key(
+        public_key: &VerifyingKey,
+        message: &[u8],
+        signature: &Signature,
+    ) -> Result<(), NodeError> {
+        public_key
+            .verify(message, signature)
+            .map_err(|_| NodeError::InvalidSignature)
+    }
+}
+
+/// Peer status values used across the system
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum PeerStatus {
+    /// Peer has been invited but hasn't joined yet
+    Invited,
+    /// Peer is active and can sync
+    Active,
+    /// Peer is temporarily inactive
+    Dormant,
+}
+
+impl PeerStatus {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            PeerStatus::Invited => "invited",
+            PeerStatus::Active => "active",
+            PeerStatus::Dormant => "dormant",
+        }
+    }
+    
+    pub fn from_str(s: &str) -> Option<PeerStatus> {
+        match s {
+            "invited" => Some(PeerStatus::Invited),
+            "active" => Some(PeerStatus::Active),
+            "dormant" => Some(PeerStatus::Dormant),
+            _ => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::env::temp_dir;
+
+    #[test]
+    fn test_generate() {
+        let node = NodeIdentity::generate();
+        let pk = node.public_key_bytes();
+        assert_eq!(pk.len(), 32);
+    }
+
+    #[test]
+    fn test_sign_and_verify() {
+        let node = NodeIdentity::generate();
+        let message = b"hello lattice";
+        
+        let signature = node.sign(message);
+        assert!(node.verify(message, &signature).is_ok());
+    }
+
+    #[test]
+    fn test_verify_wrong_message() {
+        let node = NodeIdentity::generate();
+        let signature = node.sign(b"original");
+        
+        assert!(node.verify(b"tampered", &signature).is_err());
+    }
+
+    #[test]
+    fn test_verify_with_different_key() {
+        let node1 = NodeIdentity::generate();
+        let node2 = NodeIdentity::generate();
+        
+        let signature = node1.sign(b"message");
+        assert!(node2.verify(b"message", &signature).is_err());
+    }
+
+    #[test]
+    fn test_save_and_load() {
+        let temp_path = temp_dir().join("lattice_test_identity.key");
+        
+        // Generate and save
+        let node1 = NodeIdentity::generate();
+        let pk1 = node1.public_key_bytes();
+        node1.save(&temp_path).unwrap();
+        
+        // Load and verify same key
+        let node2 = NodeIdentity::load(&temp_path).unwrap();
+        let pk2 = node2.public_key_bytes();
+        
+        assert_eq!(pk1, pk2);
+        
+        // Cleanup
+        fs::remove_file(&temp_path).ok();
+    }
+
+    #[test]
+    fn test_load_or_generate() {
+        let temp_path = temp_dir().join("lattice_test_identity2.key");
+        
+        // Remove if exists
+        fs::remove_file(&temp_path).ok();
+        
+        // First call: generates
+        let node1 = NodeIdentity::load_or_generate(&temp_path).unwrap();
+        let pk1 = node1.public_key_bytes();
+        
+        // Second call: loads existing
+        let node2 = NodeIdentity::load_or_generate(&temp_path).unwrap();
+        let pk2 = node2.public_key_bytes();
+        
+        assert_eq!(pk1, pk2);
+        
+        // Cleanup
+        fs::remove_file(&temp_path).ok();
+    }
+
+    #[test]
+    fn test_verify_with_key_static() {
+        let node = NodeIdentity::generate();
+        let pk = node.public_key();
+        let message = b"test message";
+        
+        let signature = node.sign(message);
+        
+        assert!(NodeIdentity::verify_with_key(&pk, message, &signature).is_ok());
+    }
+}

lattice-core/src/proto.rs

@@ -0,0 +1,78 @@
+//! Generated protobuf types for Lattice
+//!
+//! This module re-exports types generated from `proto/lattice.proto`
+
+// Include the generated code from prost-build
+include!(concat!(env!("OUT_DIR"), "/lattice.rs"));
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_hlc_roundtrip() {
+        let hlc = Hlc {
+            wall_time: 1234567890,
+            counter: 42,
+        };
+        
+        // Encode
+        let mut buf = Vec::new();
+        prost::Message::encode(&hlc, &mut buf).unwrap();
+        
+        // Decode
+        let decoded: Hlc = prost::Message::decode(&buf[..]).unwrap();
+        
+        assert_eq!(decoded.wall_time, 1234567890);
+        assert_eq!(decoded.counter, 42);
+    }
+
+    #[test]
+    fn test_entry_with_ops() {
+        let entry = Entry {
+            version: 1,
+            store_id: vec![1u8; 16],
+            prev_hash: vec![0u8; 32],
+            parent_hashes: vec![],
+            seq: 5,
+            timestamp: Some(Hlc {
+                wall_time: 1000,
+                counter: 0,
+            }),
+            ops: vec![
+                Operation {
+                    op_type: Some(operation::OpType::Put(PutOp {
+                        key: b"/nodes/abc".to_vec(),
+                        value: b"hello".to_vec(),
+                    })),
+                },
+            ],
+        };
+        
+        // Encode
+        let mut buf = Vec::new();
+        prost::Message::encode(&entry, &mut buf).unwrap();
+        
+        // Decode
+        let decoded: Entry = prost::Message::decode(&buf[..]).unwrap();
+        
+        assert_eq!(decoded.version, 1);
+        assert_eq!(decoded.seq, 5);
+        assert_eq!(decoded.ops.len(), 1);
+    }
+
+    #[test]
+    fn test_signed_entry() {
+        let signed = SignedEntry {
+            entry_bytes: vec![1, 2, 3, 4],
+            signature: vec![0u8; 64],
+            author_id: vec![0u8; 32],
+        };
+        
+        let mut buf = Vec::new();
+        prost::Message::encode(&signed, &mut buf).unwrap();
+        
+        let decoded: SignedEntry = prost::Message::decode(&buf[..]).unwrap();
+        assert_eq!(decoded.entry_bytes, vec![1, 2, 3, 4]);
+    }
+}

lattice-core/src/sigchain.rs

@@ -0,0 +1,593 @@
+//! Cryptographic SigChain (append-only signed log)
+//!
+//! A SigChain manages a single author's append-only log. It validates entries
+//! before appending (correct seq, prev_hash, valid signature) and persists to disk.
+
+use crate::log::{append_entry, read_entries, LogError};
+use crate::node_identity::NodeIdentity;
+use crate::proto::{Entry, SignedEntry};
+use crate::signed_entry::{hash_signed_entry, verify_signed_entry};
+use prost::Message;
+use std::path::{Path, PathBuf};
+use thiserror::Error;
+
+/// Errors that can occur during sigchain operations
+#[derive(Error, Debug)]
+pub enum SigChainError {
+    #[error("Log error: {0}")]
+    Log(#[from] LogError),
+    
+    #[error("Invalid signature")]
+    InvalidSignature,
+    
+    #[error("Wrong author: expected {expected}, got {got}")]
+    WrongAuthor { expected: String, got: String },
+    
+    #[error("Wrong store_id: expected {expected}, got {got}")]
+    WrongStoreId { expected: String, got: String },
+    
+    #[error("Invalid sequence: expected {expected}, got {got}")]
+    InvalidSequence { expected: u64, got: u64 },
+    
+    #[error("Invalid prev_hash: expected {expected}, got {got}")]
+    InvalidPrevHash { expected: String, got: String },
+    
+    #[error("Decode error: {0}")]
+    Decode(#[from] prost::DecodeError),
+}
+
+/// An append-only log where each entry is cryptographically signed
+/// and hash-linked to the previous entry, scoped to a specific store.
+pub struct SigChain {
+    /// Path to the log file
+    log_path: PathBuf,
+    
+    /// Store UUID (16 bytes)
+    store_id: [u8; 16],
+    
+    /// Author's public key (32 bytes)
+    author_id: [u8; 32],
+    
+    /// Next expected sequence number
+    next_seq: u64,
+    
+    /// Hash of the last entry (zeroes if empty)
+    last_hash: [u8; 32],
+}
+
+impl SigChain {
+    /// Create a new empty sigchain for a (store, author) pair
+    pub fn new(log_path: impl AsRef<Path>, store_id: [u8; 16], author_id: [u8; 32]) -> Self {
+        Self {
+            log_path: log_path.as_ref().to_path_buf(),
+            store_id,
+            author_id,
+            next_seq: 1,
+            last_hash: [0u8; 32],
+        }
+    }
+    
+    /// Load a sigchain from an existing log file
+    pub fn from_log(log_path: impl AsRef<Path>, store_id: [u8; 16], author_id: [u8; 32]) -> Result<Self, SigChainError> {
+        let log_path = log_path.as_ref().to_path_buf();
+        let entries = read_entries(&log_path)?;
+        
+        let mut chain = Self::new(&log_path, store_id, author_id);
+        
+        for signed_entry in entries {
+            // Verify signature
+            verify_signed_entry(&signed_entry)
+                .map_err(|_| SigChainError::InvalidSignature)?;
+            
+            // Validate author (author_id is in SignedEntry)
+            let entry_author: [u8; 32] = signed_entry.author_id.clone().try_into()
+                .unwrap_or([0u8; 32]);
+            if entry_author != author_id {
+                return Err(SigChainError::WrongAuthor {
+                    expected: hex::encode(author_id),
+                    got: hex::encode(&entry_author),
+                });
+            }
+            
+            // Decode Entry
+            let entry = Entry::decode(&signed_entry.entry_bytes[..])?;
+            
+            // Validate store_id
+            // Note: Empty/malformed store_id becomes [0u8;16], which fails validation
+            // against any real UUID store. This intentionally rejects legacy entries.
+            let entry_store: [u8; 16] = entry.store_id.clone().try_into()
+                .unwrap_or([0u8; 16]);
+            if entry_store != store_id {
+                return Err(SigChainError::WrongStoreId {
+                    expected: hex::encode(store_id),
+                    got: hex::encode(entry_store),
+                });
+            }
+            
+            // Validate sequence
+            if entry.seq != chain.next_seq {
+                return Err(SigChainError::InvalidSequence {
+                    expected: chain.next_seq,
+                    got: entry.seq,
+                });
+            }
+            
+            // Validate prev_hash
+            let expected_prev: [u8; 32] = chain.last_hash;
+            let got_prev: [u8; 32] = entry.prev_hash.try_into()
+                .unwrap_or([0u8; 32]);
+            if got_prev != expected_prev {
+                return Err(SigChainError::InvalidPrevHash {
+                    expected: hex::encode(expected_prev),
+                    got: hex::encode(got_prev),
+                });
+            }
+            
+            // Update state
+            chain.last_hash = hash_signed_entry(&signed_entry);
+            chain.next_seq += 1;
+        }
+        
+        Ok(chain)
+    }
+    
+    /// Get the author's public key
+    pub fn author_id(&self) -> &[u8; 32] {
+        &self.author_id
+    }
+    
+    /// Get the next expected sequence number
+    pub fn next_seq(&self) -> u64 {
+        self.next_seq
+    }
+    
+    /// Get the hash of the last entry
+    pub fn last_hash(&self) -> &[u8; 32] {
+        &self.last_hash
+    }
+    
+    /// Get the log file path
+    pub fn log_path(&self) -> &std::path::Path {
+        &self.log_path
+    }
+    
+    /// Get the current length of the chain
+    pub fn len(&self) -> u64 {
+        self.next_seq - 1
+    }
+    
+    /// Check if the chain is empty
+    pub fn is_empty(&self) -> bool {
+        self.next_seq == 1
+    }
+    
+    /// Validate a signed entry without appending
+    pub fn validate(&self, signed_entry: &SignedEntry) -> Result<(), SigChainError> {
+        // Verify signature
+        verify_signed_entry(signed_entry)
+            .map_err(|_| SigChainError::InvalidSignature)?;
+        
+        // Validate author (author_id is in SignedEntry)
+        let author: [u8; 32] = signed_entry.author_id.clone().try_into()
+            .unwrap_or([0u8; 32]);
+        if author != self.author_id {
+            return Err(SigChainError::WrongAuthor {
+                expected: hex::encode(self.author_id),
+                got: hex::encode(author),
+            });
+        }
+        
+        // Decode entry
+        let entry = Entry::decode(&signed_entry.entry_bytes[..])?;
+        
+        // Validate store_id
+        // Note: Empty/malformed store_id becomes [0u8;16], which fails validation
+        // against any real UUID store. This intentionally rejects legacy entries.
+        let entry_store: [u8; 16] = entry.store_id.clone().try_into()
+            .unwrap_or([0u8; 16]);
+        if entry_store != self.store_id {
+            return Err(SigChainError::WrongStoreId {
+                expected: hex::encode(self.store_id),
+                got: hex::encode(entry_store),
+            });
+        }
+        
+        // Validate sequence
+        if entry.seq != self.next_seq {
+            return Err(SigChainError::InvalidSequence {
+                expected: self.next_seq,
+                got: entry.seq,
+            });
+        }
+        
+        // Validate prev_hash
+        let prev: [u8; 32] = entry.prev_hash.try_into()
+            .unwrap_or([0u8; 32]);
+        if prev != self.last_hash {
+            return Err(SigChainError::InvalidPrevHash {
+                expected: hex::encode(self.last_hash),
+                got: hex::encode(prev),
+            });
+        }
+        
+        Ok(())
+    }
+    
+    /// Append a signed entry to the chain (validates first)
+    pub fn append(&mut self, signed_entry: &SignedEntry) -> Result<(), SigChainError> {
+        // Validate
+        self.validate(signed_entry)?;
+        
+        // Write to log
+        append_entry(&self.log_path, signed_entry)?;
+        
+        // Update state
+        self.last_hash = hash_signed_entry(signed_entry);
+        self.next_seq += 1;
+        
+        Ok(())
+    }
+    
+    /// Create and append a new entry using the node's key
+    pub fn create_entry(&mut self, node: &NodeIdentity, ops: Vec<crate::proto::Operation>) -> Result<SignedEntry, SigChainError> {
+        use crate::clock::SystemClock;
+        use crate::hlc::HLC;
+        use crate::signed_entry::EntryBuilder;
+        
+        let hlc = HLC::now_with_clock(&SystemClock);
+        
+        let mut builder = EntryBuilder::new(self.next_seq, hlc)
+            .store_id(self.store_id.to_vec())
+            .prev_hash(self.last_hash.to_vec());
+        
+        // Add operations
+        for op in ops {
+            builder = builder.operation(op);
+        }
+        
+        let signed = builder.sign(node);
+        
+        self.append(&signed)?;
+        
+        Ok(signed)
+    }
+}
+
+/// Manages multiple SigChains (one per author) for a store.
+/// Provides unified interface for appending entries from any author.
+pub struct SigChainManager {
+    /// Directory containing log files (one per author)
+    logs_dir: PathBuf,
+    
+    /// Store UUID (16 bytes)
+    store_id: [u8; 16],
+    
+    /// Cache of loaded SigChains by author
+    chains: std::collections::HashMap<[u8; 32], SigChain>,
+}
+
+impl SigChainManager {
+    /// Create a new manager for a store's logs directory
+    pub fn new(logs_dir: impl AsRef<Path>, store_id: [u8; 16]) -> Self {
+        Self {
+            logs_dir: logs_dir.as_ref().to_path_buf(),
+            store_id,
+            chains: std::collections::HashMap::new(),
+        }
+    }
+    
+    /// Get or create a SigChain for an author
+    pub fn get_or_create(&mut self, author: [u8; 32]) -> &mut SigChain {
+        self.chains.entry(author).or_insert_with(|| {
+            let author_hex = hex::encode(author);
+            let log_path = self.logs_dir.join(format!("{}.log", author_hex));
+            
+            // Try to load existing log, or create new
+            SigChain::from_log(&log_path, self.store_id, author)
+                .unwrap_or_else(|_| SigChain::new(&log_path, self.store_id, author))
+        })
+    }
+    
+    /// Get the local node's sigchain (for creating new entries)
+    pub fn get(&self, author: &[u8; 32]) -> Option<&SigChain> {
+        self.chains.get(author)
+    }
+    
+    /// Append an entry to the appropriate author's log
+    /// This is the main entry point for all entry writes (from put, sync, etc.)
+    pub fn append_entry(&mut self, entry: &SignedEntry) -> Result<(), SigChainError> {
+        let author: [u8; 32] = entry.author_id.clone()
+            .try_into()
+            .map_err(|_| SigChainError::WrongAuthor {
+                expected: "32 bytes".to_string(),
+                got: format!("{} bytes", entry.author_id.len()),
+            })?;
+        
+        // For synced entries, we can't validate seq/prev_hash since they may arrive
+        // out of order. Just append to the log file directly.
+        let chain = self.get_or_create(author);
+        append_entry(chain.log_path(), entry)?;
+        
+        Ok(())
+    }
+    
+    /// Get the logs directory path
+    pub fn logs_dir(&self) -> &Path {
+        &self.logs_dir
+    }
+    
+    /// Get log directory statistics (file count, total bytes)
+    pub fn log_stats(&self) -> (usize, u64) {
+        if !self.logs_dir.exists() {
+            return (0, 0);
+        }
+        let mut total_size = 0u64;
+        let mut file_count = 0;
+        if let Ok(entries) = std::fs::read_dir(&self.logs_dir) {
+            for entry in entries.flatten() {
+                if let Ok(meta) = entry.metadata() {
+                    if meta.is_file() {
+                        total_size += meta.len();
+                        file_count += 1;
+                    }
+                }
+            }
+        }
+        (file_count, total_size)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::clock::MockClock;
+    use crate::hlc::HLC;
+    use crate::node_identity::NodeIdentity;
+    use crate::proto::{operation, Operation, PutOp};
+    use crate::signed_entry::EntryBuilder;
+    use std::env::temp_dir;
+
+    fn temp_log_path(name: &str) -> PathBuf {
+        temp_dir().join(format!("lattice_sigchain_test_{}.log", name))
+    }
+
+    const TEST_STORE: [u8; 16] = [1u8; 16];
+
+    #[test]
+    fn test_new_sigchain() {
+        let path = temp_log_path("new");
+        let author = [1u8; 32];
+        
+        let chain = SigChain::new(&path, TEST_STORE, author);
+        
+        assert_eq!(chain.author_id(), &author);
+        assert_eq!(chain.next_seq(), 1);
+        assert_eq!(chain.last_hash(), &[0u8; 32]);
+        assert!(chain.is_empty());
+        assert_eq!(chain.len(), 0);
+    }
+
+    #[test]
+    fn test_append_entry() {
+        let path = temp_log_path("append");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let mut chain = SigChain::new(&path, TEST_STORE, author);
+        
+        let clock = MockClock::new(1000);
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .store_id(TEST_STORE.to_vec())
+            .prev_hash([0u8; 32].to_vec())
+            .put("/key", b"value".to_vec())
+            .sign(&node);
+        
+        chain.append(&entry).unwrap();
+        
+        assert_eq!(chain.next_seq(), 2);
+        assert_eq!(chain.len(), 1);
+        assert!(!chain.is_empty());
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_append_multiple() {
+        let path = temp_log_path("multiple");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let mut chain = SigChain::new(&path, TEST_STORE, author);
+        let clock = MockClock::new(1000);
+        
+        for i in 1..=3 {
+            let entry = EntryBuilder::new(i, HLC::now_with_clock(&clock))
+                .store_id(TEST_STORE.to_vec())
+                .prev_hash(chain.last_hash.to_vec())
+                .put(format!("/key/{}", i), format!("value{}", i).into_bytes())
+                .sign(&node);
+            chain.append(&entry).unwrap();
+        }
+        
+        assert_eq!(chain.len(), 3);
+        assert_eq!(chain.next_seq(), 4);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_from_log() {
+        let path = temp_log_path("from_log");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let clock = MockClock::new(1000);
+        
+        // Write some entries
+        {
+            let mut chain = SigChain::new(&path, TEST_STORE, author);
+            for i in 1..=3 {
+                let entry = EntryBuilder::new(i, HLC::now_with_clock(&clock))
+                    .store_id(TEST_STORE.to_vec())
+                    .prev_hash(chain.last_hash.to_vec())
+                    .put("/key", b"val".to_vec())
+                    .sign(&node);
+                chain.append(&entry).unwrap();
+            }
+        }
+        
+        // Reload from log
+        let chain = SigChain::from_log(&path, TEST_STORE, author).unwrap();
+        
+        assert_eq!(chain.len(), 3);
+        assert_eq!(chain.next_seq(), 4);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_reject_wrong_sequence() {
+        let path = temp_log_path("wrong_seq");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let mut chain = SigChain::new(&path, TEST_STORE, author);
+        let clock = MockClock::new(1000);
+        
+        // Try to append with wrong seq (2 instead of 1)
+        let entry = EntryBuilder::new(2, HLC::now_with_clock(&clock))
+            .store_id(TEST_STORE.to_vec())
+            .prev_hash([0u8; 32].to_vec())
+            .put("/key", b"val".to_vec())
+            .sign(&node);
+        
+        let result = chain.append(&entry);
+        
+        assert!(matches!(result, Err(SigChainError::InvalidSequence { .. })));
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_reject_wrong_prev_hash() {
+        let path = temp_log_path("wrong_prev");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let mut chain = SigChain::new(&path, TEST_STORE, author);
+        let clock = MockClock::new(1000);
+        
+        // First entry
+        let entry1 = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .store_id(TEST_STORE.to_vec())
+            .prev_hash([0u8; 32].to_vec())
+            .put("/key", b"v1".to_vec())
+            .sign(&node);
+        chain.append(&entry1).unwrap();
+        
+        // Second entry with wrong prev_hash
+        let entry2 = EntryBuilder::new(2, HLC::now_with_clock(&clock))
+            .store_id(TEST_STORE.to_vec())
+            .prev_hash([99u8; 32].to_vec()) // Wrong!
+            .put("/key", b"v2".to_vec())
+            .sign(&node);
+        
+        let result = chain.append(&entry2);
+        
+        assert!(matches!(result, Err(SigChainError::InvalidPrevHash { .. })));
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_reject_wrong_author() {
+        let path = temp_log_path("wrong_author");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let other_author = [99u8; 32]; // Different author
+        let mut chain = SigChain::new(&path, TEST_STORE, other_author);
+        let clock = MockClock::new(1000);
+        
+        // Entry signed by node but chain expects other_author
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .store_id(TEST_STORE.to_vec())
+            .prev_hash([0u8; 32].to_vec())
+            .put("/key", b"val".to_vec())
+            .sign(&node);
+        
+        let result = chain.append(&entry);
+        
+        assert!(matches!(result, Err(SigChainError::WrongAuthor { .. })));
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_create_entry() {
+        let path = temp_log_path("create");
+        std::fs::remove_file(&path).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let mut chain = SigChain::new(&path, TEST_STORE, author);
+        
+        let ops = vec![
+            Operation {
+                op_type: Some(operation::OpType::Put(PutOp {
+                    key: b"/test".to_vec(),
+                    value: b"hello".to_vec(),
+                })),
+            },
+        ];
+        
+        let signed = chain.create_entry(&node, ops).unwrap();
+        
+        assert_eq!(chain.len(), 1);
+        
+        // Verify it was written
+        let entries = read_entries(&path).unwrap();
+        assert_eq!(entries.len(), 1);
+        assert_eq!(entries[0].entry_bytes, signed.entry_bytes);
+        
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[test]
+    fn test_reject_wrong_store_id() {
+        let path_a = temp_log_path("storeid_a");
+        let path_b = temp_log_path("storeid_b");
+        std::fs::remove_file(&path_a).ok();
+        std::fs::remove_file(&path_b).ok();
+        
+        let node = NodeIdentity::generate();
+        let author = node.public_key_bytes();
+        let clock = MockClock::new(1000);
+        
+        let store_a = [0xAAu8; 16];
+        let store_b = [0xBBu8; 16];
+        
+        // Create valid entry for store A
+        let mut chain_a = SigChain::new(&path_a, store_a, author);
+        let entry = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .store_id(store_a.to_vec())
+            .prev_hash([0u8; 32].to_vec())
+            .put("/key", b"val".to_vec())
+            .sign(&node);
+        chain_a.append(&entry).unwrap();
+        
+        // Try to replay that entry into store B's chain
+        let mut chain_b = SigChain::new(&path_b, store_b, author);
+        let result = chain_b.append(&entry);
+        
+        assert!(matches!(result, Err(SigChainError::WrongStoreId { .. })));
+        
+        std::fs::remove_file(&path_a).ok();
+        std::fs::remove_file(&path_b).ok();
+    }
+}

lattice-core/src/signed_entry.rs

@@ -0,0 +1,284 @@
+//! Signed entry creation and verification
+//!
+//! Provides utilities for:
+//! - Building Entry messages with operations
+//! - Signing entries to create SignedEntry
+//! - Verifying signatures
+//! - Computing entry hashes for prev_hash linking
+
+use crate::hlc::HLC;
+use crate::node_identity::{NodeIdentity, NodeError};
+use crate::proto::{Entry, Hlc, Operation, PutOp, DeleteOp, SignedEntry, operation};
+use ed25519_dalek::{Signature, VerifyingKey};
+use prost::Message;
+use thiserror::Error;
+
+/// Errors that can occur during entry operations
+#[derive(Error, Debug)]
+pub enum EntryError {
+    #[error("Signature verification failed: {0}")]
+    Signature(#[from] NodeError),
+    
+    #[error("Proto decode error: {0}")]
+    Decode(#[from] prost::DecodeError),
+    
+    #[error("Invalid signature length: expected 64 bytes, got {0}")]
+    InvalidSignatureLength(usize),
+    
+    #[error("Invalid public key length: expected 32 bytes, got {0}")]
+    InvalidPublicKeyLength(usize),
+}
+
+/// Builder for creating Entry messages
+pub struct EntryBuilder {
+    version: u32,
+    store_id: Vec<u8>,
+    prev_hash: Vec<u8>,
+    parent_hashes: Vec<Vec<u8>>,
+    seq: u64,
+    timestamp: HLC,
+    ops: Vec<Operation>,
+}
+
+impl EntryBuilder {
+    /// Create a new entry builder with the given sequence number and timestamp
+    pub fn new(seq: u64, timestamp: HLC) -> Self {
+        Self {
+            version: 1,
+            store_id: Vec::new(),
+            prev_hash: vec![0u8; 32],
+            parent_hashes: Vec::new(),
+            seq,
+            timestamp,
+            ops: Vec::new(),
+        }
+    }
+
+    /// Set the store ID (16-byte UUID)
+    pub fn store_id(mut self, id: impl Into<Vec<u8>>) -> Self {
+        self.store_id = id.into();
+        self
+    }
+
+    /// Set the previous entry hash (for sigchain linking)
+    pub fn prev_hash(mut self, hash: impl Into<Vec<u8>>) -> Self {
+        self.prev_hash = hash.into();
+        self
+    }
+
+    /// Set the parent hashes (for DAG ancestry)
+    pub fn parent_hashes(mut self, hashes: Vec<Vec<u8>>) -> Self {
+        self.parent_hashes = hashes;
+        self
+    }
+
+    /// Add a Put operation
+    pub fn put(mut self, key: impl Into<Vec<u8>>, value: impl Into<Vec<u8>>) -> Self {
+        self.ops.push(Operation {
+            op_type: Some(operation::OpType::Put(PutOp {
+                key: key.into(),
+                value: value.into(),
+            })),
+        });
+        self
+    }
+
+    /// Add a Delete operation
+    pub fn delete(mut self, key: impl Into<Vec<u8>>) -> Self {
+        self.ops.push(Operation {
+            op_type: Some(operation::OpType::Delete(DeleteOp {
+                key: key.into(),
+            })),
+        });
+        self
+    }
+    
+    /// Add a raw operation
+    pub fn operation(mut self, op: Operation) -> Self {
+        self.ops.push(op);
+        self
+    }
+
+    /// Build the Entry proto message
+    pub fn build(self) -> Entry {
+        Entry {
+            version: self.version,
+            store_id: self.store_id,
+            prev_hash: self.prev_hash,
+            parent_hashes: self.parent_hashes,
+            seq: self.seq,
+            timestamp: Some(Hlc {
+                wall_time: self.timestamp.wall_time,
+                counter: self.timestamp.counter,
+            }),
+            ops: self.ops,
+        }
+    }
+
+    /// Build and sign the entry, returning a SignedEntry
+    pub fn sign(self, node: &NodeIdentity) -> SignedEntry {
+        let entry = self.build();
+        sign_entry(&entry, node)
+    }
+}
+
+/// Sign an Entry to create a SignedEntry
+pub fn sign_entry(entry: &Entry, node: &NodeIdentity) -> SignedEntry {
+    let entry_bytes = entry.encode_to_vec();
+    let signature = node.sign(&entry_bytes);
+    
+    SignedEntry {
+        entry_bytes,
+        signature: signature.to_bytes().to_vec(),
+        author_id: node.public_key_bytes().to_vec(),
+    }
+}
+
+/// Verify a SignedEntry's signature
+pub fn verify_signed_entry(signed: &SignedEntry) -> Result<Entry, EntryError> {
+    // Parse public key
+    if signed.author_id.len() != 32 {
+        return Err(EntryError::InvalidPublicKeyLength(signed.author_id.len()));
+    }
+    let pk_bytes: [u8; 32] = signed.author_id.clone().try_into().unwrap();
+    let public_key = VerifyingKey::from_bytes(&pk_bytes)
+        .map_err(|_| NodeError::InvalidSignature)?;
+    
+    // Parse signature
+    if signed.signature.len() != 64 {
+        return Err(EntryError::InvalidSignatureLength(signed.signature.len()));
+    }
+    let sig_bytes: [u8; 64] = signed.signature.clone().try_into().unwrap();
+    let signature = Signature::from_bytes(&sig_bytes);
+    
+    // Verify
+    NodeIdentity::verify_with_key(&public_key, &signed.entry_bytes, &signature)?;
+    
+    // Decode entry
+    let entry = Entry::decode(&signed.entry_bytes[..])?;
+    Ok(entry)
+}
+
+/// Compute the BLAKE3 hash of a SignedEntry (for prev_hash linking)
+pub fn hash_signed_entry(signed: &SignedEntry) -> [u8; 32] {
+    let bytes = signed.encode_to_vec();
+    blake3::hash(&bytes).into()
+}
+
+/// Compute the BLAKE3 hash of entry_bytes (alternative for lighter hashing)
+pub fn hash_entry_bytes(entry_bytes: &[u8]) -> [u8; 32] {
+    blake3::hash(entry_bytes).into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::clock::MockClock;
+
+    #[test]
+    fn test_entry_builder() {
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let entry = EntryBuilder::new(1, hlc)
+            .put("/test/key", b"value".to_vec())
+            .delete("/test/old")
+            .build();
+        
+        assert_eq!(entry.version, 1);
+        assert_eq!(entry.seq, 1);
+        assert_eq!(entry.ops.len(), 2);
+    }
+
+    #[test]
+    fn test_sign_and_verify() {
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let signed = EntryBuilder::new(1, hlc)
+            .put("/nodes/abc", b"test".to_vec())
+            .sign(&node);
+        
+        assert_eq!(signed.author_id.len(), 32);
+        assert_eq!(signed.signature.len(), 64);
+        
+        // Verify
+        let entry = verify_signed_entry(&signed).unwrap();
+        assert_eq!(entry.seq, 1);
+        assert_eq!(entry.ops.len(), 1);
+    }
+
+    #[test]
+    fn test_verify_tampered_fails() {
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let mut signed = EntryBuilder::new(1, hlc)
+            .put("/key", b"value".to_vec())
+            .sign(&node);
+        
+        // Tamper with entry bytes
+        signed.entry_bytes[0] ^= 0xFF;
+        
+        assert!(verify_signed_entry(&signed).is_err());
+    }
+
+    #[test]
+    fn test_verify_wrong_key_fails() {
+        let node1 = NodeIdentity::generate();
+        let node2 = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let mut signed = EntryBuilder::new(1, hlc)
+            .put("/key", b"value".to_vec())
+            .sign(&node1);
+        
+        // Replace author with different key
+        signed.author_id = node2.public_key_bytes().to_vec();
+        
+        assert!(verify_signed_entry(&signed).is_err());
+    }
+
+    #[test]
+    fn test_hash_signed_entry() {
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        let hlc = HLC::now_with_clock(&clock);
+        
+        let signed = EntryBuilder::new(1, hlc)
+            .put("/key", b"value".to_vec())
+            .sign(&node);
+        
+        let hash = hash_signed_entry(&signed);
+        assert_eq!(hash.len(), 32);
+        
+        // Same entry should produce same hash
+        let hash2 = hash_signed_entry(&signed);
+        assert_eq!(hash, hash2);
+    }
+
+    #[test]
+    fn test_prev_hash_chaining() {
+        let node = NodeIdentity::generate();
+        let clock = MockClock::new(1000);
+        
+        // First entry
+        let entry1 = EntryBuilder::new(1, HLC::now_with_clock(&clock))
+            .put("/key", b"v1".to_vec())
+            .sign(&node);
+        
+        let hash1 = hash_signed_entry(&entry1);
+        
+        // Second entry links to first
+        let entry2 = EntryBuilder::new(2, HLC::now_with_clock(&clock))
+            .prev_hash(hash1)
+            .put("/key", b"v2".to_vec())
+            .sign(&node);
+        
+        let decoded = verify_signed_entry(&entry2).unwrap();
+        assert_eq!(decoded.prev_hash, hash1.to_vec());
+    }
+}

lattice-core/src/store_actor.rs

@@ -0,0 +1,299 @@
+//! Store Actor - dedicated thread that owns Store and processes commands via channel
+
+use crate::{
+    EntryBuilder, HeadInfo, NodeIdentity, SigChain, SigChainManager, Store, Uuid,
+    hlc::HLC,
+    proto::AuthorState,
+    sigchain::SigChainError,
+    store::StoreError,
+    sync_state::SyncState,
+    proto::SignedEntry,
+    log,
+};
+use tokio::sync::{mpsc, oneshot, broadcast};
+use std::thread::{self, JoinHandle};
+
+/// Commands sent to the store actor
+pub enum StoreCmd {
+    Get {
+        key: Vec<u8>,
+        resp: oneshot::Sender<Result<Option<Vec<u8>>, StoreError>>,
+    },
+    GetHeads {
+        key: Vec<u8>,
+        resp: oneshot::Sender<Result<Vec<HeadInfo>, StoreError>>,
+    },
+    List {
+        include_deleted: bool,
+        resp: oneshot::Sender<Result<Vec<(Vec<u8>, Vec<u8>)>, StoreError>>,
+    },
+    ListByPrefix {
+        prefix: Vec<u8>,
+        include_deleted: bool,
+        resp: oneshot::Sender<Result<Vec<(Vec<u8>, Vec<u8>)>, StoreError>>,
+    },
+    Put {
+        key: Vec<u8>,
+        value: Vec<u8>,
+        resp: oneshot::Sender<Result<u64, StoreActorError>>,
+    },
+    Delete {
+        key: Vec<u8>,
+        resp: oneshot::Sender<Result<u64, StoreActorError>>,
+    },
+    LogSeq {
+        resp: oneshot::Sender<u64>,
+    },
+    AppliedSeq {
+        resp: oneshot::Sender<Result<u64, StoreError>>,
+    },
+    AuthorState {
+        author: [u8; 32],
+        resp: oneshot::Sender<Result<Option<AuthorState>, StoreError>>,
+    },
+    // Sync-related commands
+    SyncState {
+        resp: oneshot::Sender<Result<SyncState, StoreError>>,
+    },
+    ReadEntriesAfter {
+        author: [u8; 32],
+        from_hash: Option<[u8; 32]>,
+        resp: oneshot::Sender<Result<Vec<SignedEntry>, StoreError>>,
+    },
+    ApplyEntry {
+        entry: SignedEntry,
+        resp: oneshot::Sender<Result<(), StoreError>>,
+    },
+    LogStats {
+        resp: oneshot::Sender<(usize, u64)>,
+    },
+    Shutdown,
+}
+
+#[derive(Debug)]
+pub enum StoreActorError {
+    Store(StoreError),
+    SigChain(SigChainError),
+}
+
+impl From<StoreError> for StoreActorError {
+    fn from(e: StoreError) -> Self {
+        StoreActorError::Store(e)
+    }
+}
+
+impl From<SigChainError> for StoreActorError {
+    fn from(e: SigChainError) -> Self {
+        StoreActorError::SigChain(e)
+    }
+}
+
+impl std::fmt::Display for StoreActorError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            StoreActorError::Store(e) => write!(f, "Store error: {}", e),
+            StoreActorError::SigChain(e) => write!(f, "SigChain error: {}", e),
+        }
+    }
+}
+
+impl std::error::Error for StoreActorError {}
+
+/// The store actor - runs in its own thread, owns Store and SigChainManager
+pub struct StoreActor {
+    store_id: Uuid,
+    store: Store,
+    chain_manager: SigChainManager,
+    node: NodeIdentity,
+    rx: mpsc::Receiver<StoreCmd>,
+    /// Broadcast sender for emitting entries after they're committed locally
+    entry_tx: broadcast::Sender<SignedEntry>,
+}
+
+impl StoreActor {
+    /// Create a new store actor (but don't start the thread yet)
+    pub fn new(
+        store_id: Uuid,
+        store: Store,
+        sigchain: SigChain,
+        node: NodeIdentity,
+        rx: mpsc::Receiver<StoreCmd>,
+        entry_tx: broadcast::Sender<SignedEntry>,
+    ) -> Self {
+        // Derive logs_dir from sigchain's log file path
+        let logs_dir = sigchain.log_path()
+            .parent()
+            .map(|p| p.to_path_buf())
+            .unwrap_or_default();
+        
+        // Create chain manager and register the local node's sigchain
+        let mut chain_manager = SigChainManager::new(&logs_dir, *store_id.as_bytes());
+        let local_author = node.public_key_bytes();
+        chain_manager.get_or_create(local_author);  // Pre-initialize local chain
+        
+        Self {
+            store_id,
+            store,
+            chain_manager,
+            node,
+            rx,
+            entry_tx,
+        }
+    }
+
+    /// Run the actor loop - processes commands until Shutdown received
+    /// Uses blocking_recv since redb is sync and we run in spawn_blocking
+    pub fn run(mut self) {
+        while let Some(cmd) = self.rx.blocking_recv() {
+            match cmd {
+                StoreCmd::Get { key, resp } => {
+                    let _ = resp.send(self.store.get(&key));
+                }
+                StoreCmd::GetHeads { key, resp } => {
+                    let _ = resp.send(self.store.get_heads(&key));
+                }
+                StoreCmd::List { include_deleted, resp } => {
+                    let _ = resp.send(self.store.list_all(include_deleted));
+                }
+                StoreCmd::ListByPrefix { prefix, include_deleted, resp } => {
+                    let _ = resp.send(self.store.list_by_prefix(&prefix, include_deleted));
+                }
+                StoreCmd::Put { key, value, resp } => {
+                    let result = self.do_put(&key, &value);
+                    let _ = resp.send(result);
+                }
+                StoreCmd::Delete { key, resp } => {
+                    let result = self.do_delete(&key);
+                    let _ = resp.send(result);
+                }
+                StoreCmd::LogSeq { resp } => {
+                    let local_author = self.node.public_key_bytes();
+                    let len = self.chain_manager.get(&local_author)
+                        .map(|c| c.len())
+                        .unwrap_or(0);
+                    let _ = resp.send(len);
+                }
+                StoreCmd::AppliedSeq { resp } => {
+                    let author = self.node.public_key_bytes();
+                    let result = self.store.author_state(&author)
+                        .map(|s| s.map(|a| a.seq).unwrap_or(0));
+                    let _ = resp.send(result);
+                }
+                StoreCmd::AuthorState { author, resp } => {
+                    let _ = resp.send(self.store.author_state(&author));
+                }
+                StoreCmd::SyncState { resp } => {
+                    let _ = resp.send(self.store.sync_state());
+                }
+                StoreCmd::ReadEntriesAfter { author, from_hash, resp } => {
+                    // Read entries from the log file for this author
+                    let result = self.do_read_entries_after(&author, from_hash);
+                    let _ = resp.send(result);
+                }
+                StoreCmd::ApplyEntry { entry, resp } => {
+                    // Use SigChainManager to append to the correct author's log
+                    if let Err(e) = self.chain_manager.append_entry(&entry) {
+                        let _ = resp.send(Err(StoreError::from(e)));
+                        continue;
+                    }
+                    
+                    // Then apply to store
+                    let result = self.store.apply_entry(&entry);
+                    let _ = resp.send(result);
+                }
+                StoreCmd::LogStats { resp } => {
+                    let _ = resp.send(self.chain_manager.log_stats());
+                }
+                StoreCmd::Shutdown => {
+                    break;
+                }
+            }
+        }
+    }
+
+    fn do_put(&mut self, key: &[u8], value: &[u8]) -> Result<u64, StoreActorError> {
+        let heads = self.store.get_heads(key)?;
+        
+        // Idempotency check (pure function)
+        if !Store::needs_put(&heads, value) {
+            let local_author = self.node.public_key_bytes();
+            return Ok(self.chain_manager.get(&local_author).map(|c| c.len()).unwrap_or(0));
+        }
+        
+        let parent_hashes: Vec<Vec<u8>> = heads.iter().map(|h| h.hash.clone()).collect();
+        self.commit_entry(parent_hashes, |b| b.put(key.to_vec(), value.to_vec()))
+    }
+
+    fn do_delete(&mut self, key: &[u8]) -> Result<u64, StoreActorError> {
+        let heads = self.store.get_heads(key)?;
+        
+        // Idempotency check (pure function)
+        if !Store::needs_delete(&heads) {
+            let local_author = self.node.public_key_bytes();
+            return Ok(self.chain_manager.get(&local_author).map(|c| c.len()).unwrap_or(0));
+        }
+        
+        let parent_hashes: Vec<Vec<u8>> = heads.iter().map(|h| h.hash.clone()).collect();
+        self.commit_entry(parent_hashes, |b| b.delete(key.to_vec()))
+    }
+
+    fn commit_entry<F>(&mut self, parent_hashes: Vec<Vec<u8>>, build: F) -> Result<u64, StoreActorError>
+    where
+        F: FnOnce(EntryBuilder) -> EntryBuilder,
+    {
+        let local_author = self.node.public_key_bytes();
+        let sigchain = self.chain_manager.get_or_create(local_author);
+        
+        let seq = sigchain.len() + 1;
+        let prev_hash = *sigchain.last_hash();
+
+        let builder = EntryBuilder::new(seq, HLC::now())
+            .store_id(self.store_id.as_bytes().to_vec())
+            .prev_hash(prev_hash.to_vec())
+            .parent_hashes(parent_hashes);
+        let entry = build(builder).sign(&self.node);
+
+        // Append to local sigchain
+        let sigchain = self.chain_manager.get_or_create(local_author);
+        sigchain.append(&entry)?;
+        self.store.apply_entry(&entry)?;
+        
+        // Broadcast the entry to listeners (for gossip)
+        let _ = self.entry_tx.send(entry.clone());
+
+        Ok(seq)
+    }
+
+    fn do_read_entries_after(
+        &self,
+        author: &[u8; 32],
+        from_hash: Option<[u8; 32]>,
+    ) -> Result<Vec<SignedEntry>, StoreError> {
+        // Build log path for this author
+        let author_hex = hex::encode(author);
+        let log_path = self.chain_manager.logs_dir().join(format!("{}.log", author_hex));
+        
+        if !log_path.exists() {
+            return Ok(Vec::new());  // No log file for this author
+        }
+        
+        // Use lattice_core's read_entries_after
+        log::read_entries_after(&log_path, from_hash)
+            .map_err(StoreError::from)
+    }
+}
+
+/// Spawn a store actor in a new thread, returns (cmd_tx, entry_tx, join_handle)
+/// Uses std::thread since redb is blocking
+pub fn spawn_store_actor(
+    store_id: Uuid,
+    store: Store,
+    sigchain: SigChain,
+    node: NodeIdentity,
+) -> (mpsc::Sender<StoreCmd>, broadcast::Sender<SignedEntry>, JoinHandle<()>) {
+    let (tx, rx) = mpsc::channel(32);
+    let (entry_tx, _entry_rx) = broadcast::channel(64);
+    let actor = StoreActor::new(store_id, store, sigchain, node, rx, entry_tx.clone());
+    let handle = thread::spawn(move || actor.run());
+    (tx, entry_tx, handle)
+}

lattice-core/src/sync_state.rs

@@ -0,0 +1,325 @@
+//! Sync state for causality tracking and reconciliation
+
+use std::collections::{HashMap, HashSet};
+
+/// Author ID type (32-byte Ed25519 public key)
+pub type Author = [u8; 32];
+
+/// Per-author sync information: seq + all head hashes.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AuthorInfo {
+    pub seq: u64,
+    pub heads: HashSet<[u8; 32]>,  // All head hashes for this author
+}
+
+impl AuthorInfo {
+    pub fn new(seq: u64, hash: [u8; 32]) -> Self {
+        let mut heads = HashSet::new();
+        heads.insert(hash);
+        Self { seq, heads }
+    }
+    
+    pub fn with_heads(seq: u64, heads: HashSet<[u8; 32]>) -> Self {
+        Self { seq, heads }
+    }
+}
+
+/// Sync state tracking per-author sequence numbers and head hashes.
+///
+/// Used during reconciliation to identify missing entries between peers.
+/// Tracks all head hashes per author to handle forks correctly.
+#[derive(Debug, Clone, Default)]
+pub struct SyncState {
+    authors: HashMap<Author, AuthorInfo>,
+}
+
+/// Describes entries needed from a peer for a specific author.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct MissingRange {
+    pub author: Author,
+    pub from_seq: u64,        // exclusive - we have up to this
+    pub from_hash: [u8; 32],  // hash to resume reading after (zero = start)
+    pub to_seq: u64,          // inclusive - peer has up to this
+}
+
+impl SyncState {
+    /// Create a new empty sync state.
+    pub fn new() -> Self {
+        Self {
+            authors: HashMap::new(),
+        }
+    }
+
+    /// Get the info for an author (returns None if not present).
+    pub fn get(&self, author: &Author) -> Option<&AuthorInfo> {
+        self.authors.get(author)
+    }
+
+    /// Get the sequence number for an author (returns 0 if not present).
+    pub fn seq(&self, author: &Author) -> u64 {
+        self.authors.get(author).map(|i| i.seq).unwrap_or(0)
+    }
+    
+    /// Get head hashes for an author (returns empty set if not present).
+    pub fn heads(&self, author: &Author) -> HashSet<[u8; 32]> {
+        self.authors.get(author).map(|i| i.heads.clone()).unwrap_or_default()
+    }
+
+    /// Set the info for an author (single hash convenience method).
+    pub fn set(&mut self, author: Author, seq: u64, hash: [u8; 32]) {
+        self.authors.insert(author, AuthorInfo::new(seq, hash));
+    }
+    
+    /// Set the info for an author with multiple heads.
+    pub fn set_heads(&mut self, author: Author, seq: u64, heads: HashSet<[u8; 32]>) {
+        self.authors.insert(author, AuthorInfo::with_heads(seq, heads));
+    }
+    
+    /// Add a head hash for an author (updates seq if higher).
+    pub fn add_head(&mut self, author: Author, seq: u64, hash: [u8; 32]) {
+        if let Some(info) = self.authors.get_mut(&author) {
+            info.heads.insert(hash);
+            if seq > info.seq {
+                info.seq = seq;
+            }
+        } else {
+            self.set(author, seq, hash);
+        }
+    }
+
+    /// Get all authors and their info.
+    pub fn authors(&self) -> &HashMap<Author, AuthorInfo> {
+        &self.authors
+    }
+
+    /// Compute what entries we're missing compared to a peer's state.
+    ///
+    /// Returns ranges of entries we need from the peer.
+    /// Compares hash sets when seq matches to detect forks.
+    pub fn diff(&self, peer: &SyncState) -> Vec<MissingRange> {
+        let mut missing = Vec::new();
+
+        for (author, peer_info) in peer.authors() {
+            let my_seq = self.seq(author);
+            let my_heads = self.heads(author);
+            
+            // We need entries if:
+            // 1. Peer's seq is higher than ours, OR
+            // 2. Peer's seq equals ours but they have heads we don't (fork)
+            let need_entries = if peer_info.seq > my_seq {
+                true
+            } else if peer_info.seq == my_seq && my_seq > 0 {
+                // Same seq - check for forks (different hashes at same seq)
+                peer_info.heads.iter().any(|h| !my_heads.contains(h))
+            } else {
+                false
+            };
+            
+            if need_entries {
+                // Request from our common ancestor (or start if we have nothing)
+                let from_hash = if my_heads.is_empty() {
+                    [0u8; 32]
+                } else {
+                    *my_heads.iter().next().unwrap()
+                };
+                
+                missing.push(MissingRange {
+                    author: *author,
+                    from_seq: my_seq,
+                    from_hash,
+                    to_seq: peer_info.seq,
+                });
+            }
+        }
+
+        missing
+    }
+
+    /// Merge another sync state into this one (union of heads, max seq).
+    pub fn merge(&mut self, other: &SyncState) {
+        for (author, info) in other.authors() {
+            if let Some(my_info) = self.authors.get_mut(author) {
+                // Union heads
+                for h in &info.heads {
+                    my_info.heads.insert(*h);
+                }
+                // Take max seq
+                if info.seq > my_info.seq {
+                    my_info.seq = info.seq;
+                }
+            } else {
+                self.authors.insert(*author, info.clone());
+            }
+        }
+    }
+
+    /// Convert to proto message for network transmission
+    pub fn to_proto(&self) -> crate::proto::SyncState {
+        let frontiers = self.authors.iter().map(|(author, info)| {
+            crate::proto::Frontier {
+                author_id: author.to_vec(),
+                max_seq: info.seq,
+                head_hashes: info.heads.iter().map(|h| h.to_vec()).collect(),
+            }
+        }).collect();
+        crate::proto::SyncState {
+            frontiers,
+            sender_hlc: None,
+        }
+    }
+
+    /// Create from proto message
+    pub fn from_proto(proto: &crate::proto::SyncState) -> Self {
+        let mut state = Self::new();
+        for frontier in &proto.frontiers {
+            if frontier.author_id.len() == 32 {
+                let mut author = [0u8; 32];
+                author.copy_from_slice(&frontier.author_id);
+                
+                let mut heads = HashSet::new();
+                for hash_bytes in &frontier.head_hashes {
+                    if hash_bytes.len() == 32 {
+                        let mut hash = [0u8; 32];
+                        hash.copy_from_slice(hash_bytes);
+                        heads.insert(hash);
+                    }
+                }
+                
+                if heads.is_empty() {
+                    // Fallback: empty hash if no heads provided
+                    heads.insert([0u8; 32]);
+                }
+                
+                state.set_heads(author, frontier.max_seq, heads);
+            }
+        }
+        state
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_diff_empty() {
+        let a = SyncState::new();
+        let b = SyncState::new();
+        assert!(a.diff(&b).is_empty());
+    }
+
+    #[test]
+    fn test_diff_peer_ahead() {
+        let mut a = SyncState::new();
+        let mut b = SyncState::new();
+        
+        let author = [1u8; 32];
+        let hash_a = [0xAA; 32];
+        let hash_b = [0xBB; 32];
+        
+        a.set(author, 5, hash_a);
+        b.set(author, 10, hash_b);
+
+        let missing = a.diff(&b);
+        assert_eq!(missing.len(), 1);
+        assert_eq!(missing[0].author, author);
+        assert_eq!(missing[0].from_seq, 5);
+        assert_eq!(missing[0].from_hash, hash_a);  // Resume after our hash
+        assert_eq!(missing[0].to_seq, 10);
+    }
+
+    #[test]
+    fn test_diff_i_am_ahead() {
+        let mut a = SyncState::new();
+        let mut b = SyncState::new();
+        
+        let author = [1u8; 32];
+        a.set(author, 10, [0xAA; 32]);
+        b.set(author, 5, [0xBB; 32]);
+
+        // I'm ahead, so I don't need anything from peer
+        let missing = a.diff(&b);
+        assert!(missing.is_empty());
+    }
+
+    #[test]
+    fn test_diff_new_author() {
+        let a = SyncState::new();
+        let mut b = SyncState::new();
+        
+        let author = [2u8; 32];
+        b.set(author, 3, [0xBB; 32]);
+
+        // Peer has author I don't have
+        let missing = a.diff(&b);
+        assert_eq!(missing.len(), 1);
+        assert_eq!(missing[0].from_seq, 0);
+        assert_eq!(missing[0].from_hash, [0u8; 32]);  // Zero hash = read from start
+        assert_eq!(missing[0].to_seq, 3);
+    }
+
+    #[test]
+    fn test_merge() {
+        let mut a = SyncState::new();
+        let mut b = SyncState::new();
+        
+        let author1 = [1u8; 32];
+        let author2 = [2u8; 32];
+        
+        a.set(author1, 10, [0xA1; 32]);
+        a.set(author2, 5, [0xA2; 32]);
+        
+        b.set(author1, 5, [0xB1; 32]);   // a is ahead
+        b.set(author2, 8, [0xB2; 32]);   // b is ahead
+
+        a.merge(&b);
+        assert_eq!(a.seq(&author1), 10);  // kept a's value
+        assert_eq!(a.seq(&author2), 8);   // took b's value
+    }
+
+    /// This test documents a known issue: SyncState tracks only ONE hash per author,
+    /// but with forks/multi-heads, there could be multiple branches.
+    /// 
+    /// Scenario:
+    /// - Author writes entry1 (hash=A)
+    /// - Two peers independently write entry2 and entry3 (both have prev=A)
+    /// - Peer1 has: entry1 -> entry2 (seq=2, hash=B)
+    /// - Peer2 has: entry1 -> entry3 (seq=2, hash=C)
+    /// - When Peer3 syncs with Peer1, SyncState says "I need entries after hash=B"
+    /// - But Peer2 only has entries after hash=A, so Peer3 never gets entry3!
+    /// 
+    #[test]
+    fn test_multihead_sync_inconsistency() {
+        // This is a conceptual test showing the problem
+        // In reality, both forks would have seq=2 but different hashes
+        // SyncState can only track one, so the other branch gets lost
+        
+        let mut peer1_state = SyncState::new();
+        let mut peer2_state = SyncState::new();
+        let new_peer_state = SyncState::new();
+        
+        let author = [1u8; 32];
+        
+        // Both peers have seq=2, but different hashes (different forks)
+        peer1_state.set(author, 2, [0xBB; 32]); // entry1 -> entry2
+        peer2_state.set(author, 2, [0xCC; 32]); // entry1 -> entry3
+        
+        // New peer syncs with peer1 first
+        let missing_from_peer1 = new_peer_state.diff(&peer1_state);
+        assert_eq!(missing_from_peer1.len(), 1);
+        assert_eq!(missing_from_peer1[0].to_seq, 2);
+        
+        // After applying peer1's entries, new peer has seq=2, hash=BB
+        let mut after_peer1 = new_peer_state.clone();
+        after_peer1.set(author, 2, [0xBB; 32]);
+        
+        // Now sync with peer2 - BUG: new peer thinks it's up to date!
+        let missing_from_peer2 = after_peer1.diff(&peer2_state);
+        
+        // This assertion FAILS - we get empty missing even though peer2 has entry3!
+        // The bug: peer2's seq=2 equals our seq=2, so we think we're in sync
+        // But peer2's hash=0xCC != our hash=0xBB - they have different entries!
+        assert!(!missing_from_peer2.is_empty(), 
+            "BUG: SyncState misses peer2's fork because seq numbers match");
+    }
+}

lattice-net/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "lattice-net"
+description = "Networking layer for Lattice using Iroh"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+lattice-core = { workspace = true }
+iroh = { workspace = true }
+iroh-gossip = { workspace = true }
+prost = { workspace = true }
+tokio = { workspace = true }
+thiserror = { workspace = true }
+tracing = { workspace = true }
+bytes = { workspace = true }
+tokio-util = { workspace = true }
+futures-util = { workspace = true }
+hex = { workspace = true }
+blake3.workspace = true
+anyhow = "1.0.100"
+futures-lite = "2.6.1"
+
+[dev-dependencies]
+tokio-test = { workspace = true }

lattice-net/src/endpoint.rs

@@ -0,0 +1,60 @@
+//! Iroh endpoint for network connectivity
+//!
+//! Creates an Iroh endpoint from the node's Ed25519 secret key,
+//! ensuring the same identity is used for both Lattice and Iroh.
+//! 
+//! Discovery: Uses both DNS (default) and mDNS (local network)
+
+use iroh::{Endpoint, endpoint::{BindError, Connection, ConnectError}};
+use iroh::discovery::mdns::MdnsDiscovery;
+pub use iroh::PublicKey;
+
+/// ALPN protocol identifier for Lattice sync
+pub const LATTICE_ALPN: &[u8] = b"lattice-sync/1";
+
+/// Wrapper around Iroh endpoint with Lattice integration
+pub struct LatticeEndpoint {
+    endpoint: Endpoint,
+}
+
+impl LatticeEndpoint {
+    /// Create a new endpoint from Ed25519 secret key bytes (from identity.key)
+    /// Enables both DNS discovery (internet) and mDNS discovery (local network)
+    pub async fn new(secret_key_bytes: [u8; 32]) -> Result<Self, BindError> {
+        let secret_key = iroh::SecretKey::from_bytes(&secret_key_bytes);
+        
+        // mDNS for local network discovery
+        let mdns = MdnsDiscovery::builder();
+        
+        let endpoint = Endpoint::builder()
+            .secret_key(secret_key)
+            .alpns(vec![
+                LATTICE_ALPN.to_vec(),
+                iroh_gossip::ALPN.to_vec(),  // Also accept gossip protocol
+            ])
+            .discovery(mdns)  // Add mDNS on top of default DNS
+            .bind()
+            .await?;
+        Ok(Self { endpoint })
+    }
+
+    /// Get the public key (same as Lattice pubkey, can be shared with peers)
+    pub fn public_key(&self) -> PublicKey {
+        self.endpoint.secret_key().public()
+    }
+
+    /// Connect to a peer by their public key
+    pub async fn connect(&self, peer: PublicKey) -> Result<Connection, ConnectError> {
+        self.endpoint.connect(peer, LATTICE_ALPN).await
+    }
+
+    /// Accept an incoming connection
+    pub async fn accept(&self) -> Option<iroh::endpoint::Incoming> {
+        self.endpoint.accept().await
+    }
+
+    /// Get the underlying endpoint
+    pub fn endpoint(&self) -> &Endpoint {
+        &self.endpoint
+    }
+}

lattice-net/src/framing.rs

@@ -0,0 +1,63 @@
+//! Message framing for Iroh streams using tokio-util LengthDelimitedCodec
+//!
+//! Provides a clean interface for sending/receiving length-prefixed PeerMessage
+//! over QUIC streams without manual buffer management.
+
+use futures_util::{SinkExt, StreamExt};
+use lattice_core::proto::PeerMessage;
+use prost::Message;
+use tokio_util::codec::{FramedRead, FramedWrite, LengthDelimitedCodec};
+
+/// Framed writer for sending PeerMessage over an Iroh SendStream
+pub struct MessageSink {
+    inner: FramedWrite<iroh::endpoint::SendStream, LengthDelimitedCodec>,
+}
+
+impl MessageSink {
+    pub fn new(stream: iroh::endpoint::SendStream) -> Self {
+        Self {
+            inner: FramedWrite::new(stream, LengthDelimitedCodec::new()),
+        }
+    }
+
+    /// Send a PeerMessage (length-prefixed)
+    pub async fn send(&mut self, msg: &PeerMessage) -> Result<(), String> {
+        let bytes = msg.encode_to_vec();
+        self.inner.send(bytes.into()).await
+            .map_err(|e| format!("Send error: {}", e))
+    }
+
+    /// Finish the stream (signal we're done sending)
+    pub async fn finish(self) -> Result<(), String> {
+        let mut stream = self.inner.into_inner();
+        let _ = stream.finish();
+        stream.stopped().await.ok();
+        Ok(())
+    }
+}
+
+/// Framed reader for receiving PeerMessage from an Iroh RecvStream
+pub struct MessageStream {
+    inner: FramedRead<iroh::endpoint::RecvStream, LengthDelimitedCodec>,
+}
+
+impl MessageStream {
+    pub fn new(stream: iroh::endpoint::RecvStream) -> Self {
+        Self {
+            inner: FramedRead::new(stream, LengthDelimitedCodec::new()),
+        }
+    }
+
+    /// Receive next PeerMessage (or None if stream closed)
+    pub async fn recv(&mut self) -> Result<Option<PeerMessage>, String> {
+        match self.inner.next().await {
+            Some(Ok(bytes)) => {
+                PeerMessage::decode(&bytes[..])
+                    .map(Some)
+                    .map_err(|e| format!("Decode error: {}", e))
+            }
+            Some(Err(e)) => Err(format!("Read error: {}", e)),
+            None => Ok(None),
+        }
+    }
+}

lattice-net/src/gossip.rs

@@ -0,0 +1,3 @@
+//! Gossip protocol for broadcasting changes
+
+// TODO: Implement gossip using iroh-gossip

lattice-net/src/lib.rs

@@ -0,0 +1,23 @@
+//! Lattice Networking
+//!
+//! Networking layer using Iroh:
+//! - **Endpoint**: Network identity and connection management
+//! - **Gossip**: Broadcasting changes across the mesh
+//! - **Unicast**: Point-to-point communication for reconciliation
+//! - **Framing**: Length-delimited message framing for QUIC streams
+//! - **Mesh**: Peer-to-peer join and sync operations
+
+pub mod endpoint;
+pub mod gossip;
+pub mod framing;
+pub mod mesh;
+
+pub use endpoint::{LatticeEndpoint, PublicKey, LATTICE_ALPN};
+pub use framing::{MessageSink, MessageStream};
+pub use lattice_core::proto::{SyncRequest, SyncResponse, SyncEntry, SyncDone, SyncState, Frontier};
+pub use mesh::{LatticeServer, SyncResult};
+
+/// Parse a PublicKey (NodeId) from hex or base32 string
+pub fn parse_node_id(s: &str) -> Result<PublicKey, String> {
+    s.parse().map_err(|e| format!("{}", e))
+}

lattice-net/src/mesh/mod.rs

@@ -0,0 +1,10 @@
+//! Mesh networking - peer-to-peer join and sync operations
+//!
+//! - **server**: LatticeServer for mesh networking (join, sync, accept loop)
+//! - **protocol**: Shared send/receive entry logic
+
+mod server;
+mod protocol;
+
+pub use server::{LatticeServer, SyncResult};
+pub use protocol::{send_missing_entries, receive_entries};

lattice-net/src/mesh/protocol.rs

@@ -0,0 +1,86 @@
+//! Protocol - shared logic for bidirectional sync entry exchange
+
+use crate::{MessageSink, MessageStream};
+use lattice_core::{StoreHandle, CausalEntryIter};
+use lattice_core::proto::{peer_message, PeerMessage, SignedEntry};
+use lattice_core::sync_state::SyncState;
+use prost::Message;
+use std::collections::VecDeque;
+
+/// Send entries that peer is missing based on state diff.
+/// Returns (entries_sent, optional_error).
+pub async fn send_missing_entries(
+    sink: &mut MessageSink,
+    store: &StoreHandle,
+    my_state: &SyncState,
+    peer_state: &SyncState,
+) -> Result<u64, String> {
+    let missing = peer_state.diff(my_state);
+    
+    // Build queues for each author's entries
+    let mut author_entries: Vec<VecDeque<SignedEntry>> = Vec::new();
+    for range in missing {
+        let from_hash = if range.from_hash == [0u8; 32] { None } else { Some(range.from_hash) };
+        let entries = store.read_entries_after(&range.author, from_hash).await
+            .map_err(|e| format!("Failed to read entries: {}", e))?;
+        if !entries.is_empty() {
+            author_entries.push(entries.into());
+        }
+    }
+    
+    // Stream entries in HLC (causal) order
+    let mut entries_sent = 0u64;
+    for entry in CausalEntryIter::new(author_entries) {
+        let sync_msg = PeerMessage {
+            message: Some(peer_message::Message::SyncEntry(lattice_core::proto::SyncEntry {
+                signed_entry: entry.encode_to_vec(),
+                hash: vec![],
+            })),
+        };
+        sink.send(&sync_msg).await?;
+        entries_sent += 1;
+    }
+    
+    // Send SyncDone
+    let done = PeerMessage {
+        message: Some(peer_message::Message::SyncDone(lattice_core::proto::SyncDone {
+            entries_sent,
+        })),
+    };
+    sink.send(&done).await?;
+    
+    Ok(entries_sent)
+}
+
+/// Receive and apply entries until SyncDone is received.
+/// Returns (entries_applied, entries_reported_by_peer).
+pub async fn receive_entries(
+    stream: &mut MessageStream,
+    store: &StoreHandle,
+) -> Result<(u64, u64), String> {
+    let mut entries_applied = 0u64;
+    let mut entries_reported = 0u64;
+    
+    loop {
+        match stream.recv().await {
+            Ok(Some(msg)) => match msg.message {
+                Some(peer_message::Message::SyncEntry(entry)) => {
+                    if let Ok(signed) = SignedEntry::decode(&entry.signed_entry[..]) {
+                        if store.apply_entry(signed).await.is_ok() {
+                            entries_applied += 1;
+                        }
+                    }
+                }
+                Some(peer_message::Message::SyncDone(done)) => {
+                    entries_reported = done.entries_sent;
+                    break;
+                }
+                _ => {}
+            }
+            Ok(None) => break,
+            Err(_) => break,
+        }
+    }
+    
+    Ok((entries_applied, entries_reported))
+}

lattice-net/src/mesh/server.rs

@@ -0,0 +1,575 @@
+//! Server - LatticeServer for mesh networking
+
+use crate::{MessageSink, MessageStream, LatticeEndpoint, parse_node_id, LATTICE_ALPN};
+use lattice_core::{Node, NodeError, NodeEvent, PeerStatus, Uuid, StoreHandle};
+use iroh::endpoint::Connection;
+use iroh::protocol::{Router, ProtocolHandler, AcceptError};
+use iroh_gossip::Gossip;
+use std::sync::Arc;
+use std::collections::HashMap;
+use tokio::sync::RwLock;
+use futures_util::StreamExt;
+use lattice_core::proto::{PeerMessage, peer_message, JoinRequest, JoinResponse, SignedEntry};
+use prost::Message;
+use super::protocol;
+
+/// Result of a sync operation with a peer
+pub struct SyncResult {
+    pub entries_applied: u64,
+    pub entries_sent_by_peer: u64,
+}
+
+/// LatticeServer wraps Node + Endpoint + Gossip and provides mesh networking methods.
+/// Uses Router to handle incoming connections for both sync and gossip protocols.
+pub struct LatticeServer {
+    node: Arc<Node>,
+    endpoint: LatticeEndpoint,
+    gossip: Gossip,
+    #[allow(dead_code)]
+    router: Router,
+    /// Gossip senders per store topic
+    gossip_senders: Arc<RwLock<HashMap<Uuid, iroh_gossip::api::GossipSender>>>,
+}
+
+/// Protocol handler for lattice sync connections
+struct SyncProtocol {
+    node: Arc<Node>,
+}
+
+impl std::fmt::Debug for SyncProtocol {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SyncProtocol").finish()
+    }
+}
+
+
+impl ProtocolHandler for SyncProtocol {
+    fn accept(&self, conn: Connection) -> impl std::future::Future<Output = Result<(), AcceptError>> + Send {
+        let node = self.node.clone();
+        Box::pin(async move {
+            if let Err(e) = handle_connection(node, conn).await {
+                eprintln!("[Accept] Error: {}", e);
+                // Log error but return Ok - protocol handled the connection
+            }
+            Ok(())
+        })
+    }
+}
+
+impl LatticeServer {
+    /// Create a new LatticeServer from just a Node (creates endpoint internally).
+    pub async fn new_from_node(node: Arc<Node>) -> Result<Self, String> {
+        let endpoint = LatticeEndpoint::new(node.secret_key_bytes()).await
+            .map_err(|e| format!("Failed to create endpoint: {}", e))?;
+        Self::new(node, endpoint).await
+    }
+    
+    /// Create a new LatticeServer with existing endpoint.
+    pub async fn new(node: Arc<Node>, endpoint: LatticeEndpoint) -> Result<Self, String> {
+        // Create gossip instance
+        let gossip = Gossip::builder().spawn(endpoint.endpoint().clone());
+        
+        // Create sync protocol handler
+        let sync_protocol = SyncProtocol { node: node.clone() };
+        
+        // Create router to handle both protocols
+        let router = Router::builder(endpoint.endpoint().clone())
+            .accept(LATTICE_ALPN, sync_protocol)
+            .accept(iroh_gossip::ALPN, gossip.clone())
+            .spawn();
+        
+        let server = Self { 
+            node, 
+            endpoint,
+            gossip,
+            router,
+            gossip_senders: Arc::new(RwLock::new(HashMap::new())),
+        };
+        server.spawn_node_event_listener();
+        
+        // If root store is already open, start gossip for it  
+        if let Some(store) = (*server.node.root_store().await).clone() {
+            println!("[Gossip] Root store already open, starting gossip...");
+            server.join_gossip_topic(store.id()).await?;
+            server.spawn_entry_forward_loop(store);
+        }
+        
+        Ok(server)
+    }
+    
+    /// Spawn a listener for Node events (auto-starts gossip when root store is activated)
+    fn spawn_node_event_listener(&self) {
+        let mut event_rx = self.node.subscribe_events();
+        let gossip_senders = self.gossip_senders.clone();
+        let gossip = self.gossip.clone();
+        let node = self.node.clone();
+        
+        tokio::spawn(async move {
+            while let Ok(event) = event_rx.recv().await {
+                match event {
+                    NodeEvent::RootStoreActivated(store) => {
+                        println!("[Gossip] Root store activated: {}, starting gossip...", store.id());
+                        
+                        let store_id = store.id();
+                        
+                        // Get bootstrap peers from node's peer list
+                        let bootstrap_peers: Vec<iroh::PublicKey> = match node.list_peers().await {
+                            Ok(peers) => {
+                                peers.iter()
+                                    .filter(|p| p.status == PeerStatus::Active)
+                                    .filter_map(|p| parse_node_id(&p.pubkey).ok())
+                                    .collect()
+                            }
+                            Err(e) => {
+                                eprintln!("[Gossip] Failed to list peers: {}, using empty list", e);
+                                Vec::new()
+                            }
+                        };
+                        println!("[Gossip] Bootstrap peers: {}", bootstrap_peers.len());
+                        
+                        // Topic ID from hash of "lattice/{store_id}" for namespacing
+                        let topic_bytes = blake3::hash(format!("lattice/{}", store_id).as_bytes());
+                        let topic_id = iroh_gossip::TopicId::from_bytes(*topic_bytes.as_bytes());
+                        
+                        // Use subscribe (non-blocking) - peers will connect when they sync
+                        // subscribe_and_join would block waiting for peers we can't reach yet
+                        match gossip.subscribe(topic_id, bootstrap_peers).await {
+                            Ok(sub) => {
+                                let (sender, receiver) = sub.split();
+                                
+                                // Store sender
+                                gossip_senders.write().await.insert(store_id, sender);
+                                
+                                // Spawn receive loop
+                                let store_recv = store.clone();
+                                tokio::spawn(async move {
+                                    let mut receiver = receiver;
+                                    println!("[Gossip] Receive loop started for topic {:?}", topic_id);
+                                    
+                                    while let Some(event) = futures_util::StreamExt::next(&mut receiver).await {
+                                        match event {
+                                            Ok(iroh_gossip::api::Event::Received(msg)) => {
+                                                println!("[Gossip] Received {} bytes", msg.content.len());
+                                                if let Ok(entry) = SignedEntry::decode(&msg.content[..]) {
+                                                    if let Err(e) = store_recv.apply_entry(entry).await {
+                                                        eprintln!("[Gossip] Failed to apply entry: {}", e);
+                                                    } else {
+                                                        println!("[Gossip] Applied entry successfully");
+                                                    }
+                                                }
+                                            }
+                                            Ok(other) => {
+                                                println!("[Gossip] Event: {:?}", other);
+                                            }
+                                            Err(e) => {
+                                                eprintln!("[Gossip] Error: {}", e);
+                                            }
+                                        }
+                                    }
+                                });
+                                
+                                // Spawn entry forward loop
+                                let gossip_senders = gossip_senders.clone();
+                                let mut entry_rx = store.subscribe_entries();
+                                tokio::spawn(async move {
+                                    println!("[Gossip] Entry forward loop started for store {}", store_id);
+                                    while let Ok(entry) = entry_rx.recv().await {
+                                        let senders = gossip_senders.read().await;
+                                        if let Some(sender) = senders.get(&store_id) {
+                                            let bytes = entry.encode_to_vec();
+                                            println!("[Gossip] Broadcasting {} bytes", bytes.len());
+                                            let _ = sender.broadcast(bytes.into()).await;
+                                        }
+                                    }
+                                });
+                                
+                                println!("[Gossip] Gossip started for store {}", store_id);
+                            }
+                            Err(e) => {
+                                eprintln!("[Gossip] Failed to subscribe to topic: {}", e);
+                            }
+                        }
+                    }
+                }
+            }
+        });
+    }
+    
+    /// Start gossip for a store (call after store is opened)
+    pub async fn start_gossip_for_store(&self, store: StoreHandle) -> Result<(), String> {
+        println!("[Gossip] Starting gossip for store {}", store.id());
+        self.join_gossip_topic(store.id()).await?;
+        self.spawn_entry_forward_loop(store);
+        Ok(())
+    }
+    
+    /// Spawn a loop that forwards local store entry broadcasts to gossip
+    fn spawn_entry_forward_loop(&self, store: StoreHandle) {
+        let store_id = store.id();
+        let gossip_senders = self.gossip_senders.clone();
+        let mut entry_rx = store.subscribe_entries();
+        
+        println!("[Gossip] Starting entry forward loop for store {}", store_id);
+        
+        tokio::spawn(async move {
+            while let Ok(entry) = entry_rx.recv().await {
+                println!("[Gossip] Received local entry, forwarding to gossip...");
+                // Forward to gossip sender
+                let senders = gossip_senders.read().await;
+                if let Some(sender) = senders.get(&store_id) {
+                    let bytes = entry.encode_to_vec();
+                    println!("[Gossip] Broadcasting {} bytes to topic {}", bytes.len(), store_id);
+                    if let Err(e) = sender.broadcast(bytes.into()).await {
+                        eprintln!("[Gossip] Failed to broadcast entry: {}", e);
+                    } else {
+                        println!("[Gossip] Broadcast successful");
+                    }
+                } else {
+                    eprintln!("[Gossip] No gossip sender for store {}", store_id);
+                }
+            }
+            println!("[Gossip] Entry forward loop ended for store {}", store_id);
+        });
+    }
+    
+    /// Access the underlying node
+    pub fn node(&self) -> &Node {
+        &self.node
+    }
+    
+    /// Access the underlying endpoint
+    pub fn endpoint(&self) -> &LatticeEndpoint {
+        &self.endpoint
+    }
+
+    
+    /// Join gossip topic for a store (subscribes and spawns receive loop)
+    pub async fn join_gossip_topic(&self, store_id: Uuid) -> Result<(), String> {
+        // Get active peers to bootstrap gossip
+        let peers = self.node.list_peers().await
+            .map_err(|e| format!("Failed to list peers: {}", e))?;
+        
+        let bootstrap_peers: Vec<iroh::PublicKey> = peers.iter()
+            .filter(|p| p.status == PeerStatus::Active)
+            .filter_map(|p| parse_node_id(&p.pubkey).ok())
+            .collect();
+        
+        println!("[Gossip] Joining topic {} with {} bootstrap peers", store_id, bootstrap_peers.len());
+        
+        // Topic ID from store UUID bytes (padded to 32 bytes)
+        // Topic ID from hash of "lattice/{store_id}" for namespacing
+        let topic_bytes = blake3::hash(format!("lattice/{}", store_id).as_bytes());
+        let topic_id = iroh_gossip::TopicId::from_bytes(*topic_bytes.as_bytes());
+        
+        // Subscribe to topic
+        let (sender, mut receiver) = self.gossip.subscribe(topic_id, bootstrap_peers).await
+            .map_err(|e| format!("Failed to subscribe to gossip topic: {}", e))?
+            .split();
+        
+        // Store sender for broadcasting
+        {
+            let mut senders = self.gossip_senders.write().await;
+            senders.insert(store_id, sender);
+        }
+        
+        // Spawn receive loop
+        let node = self.node.clone();
+        let topic = topic_id;
+        tokio::spawn(async move {
+            // StreamExt imported at module level
+            println!("[Gossip] Receive loop started for topic {:?}", topic);
+            
+            while let Some(event) = receiver.next().await {
+                match event {
+                    Ok(iroh_gossip::api::Event::Received(message)) => {
+                        println!("[Gossip] Received gossip message: {} bytes", message.content.len());
+                        // Decode SignedEntry and apply
+                        match SignedEntry::decode(&message.content[..]) {
+                            Ok(entry) => {
+                                println!("[Gossip] Decoded entry, applying...");
+                                // Find store and apply entry
+                                if let Some(store) = (*node.root_store().await).clone() {
+                                    if let Err(e) = store.apply_entry(entry.into()).await {
+                                        eprintln!("[Gossip] Failed to apply entry: {}", e);
+                                    } else {
+                                        println!("[Gossip] Entry applied successfully");
+                                    }
+                                } else {
+                                    eprintln!("[Gossip] No root store to apply entry to");
+                                }
+                            }
+                            Err(e) => eprintln!("[Gossip] Failed to decode entry: {}", e),
+                        }
+                    }
+                    Ok(other) => {
+                        println!("[Gossip] Other event: {:?}", other);
+                    }
+                    Err(e) => eprintln!("[Gossip] Receive error: {}", e),
+                }
+            }
+            println!("[Gossip] Receive loop ended for topic");
+        });
+        
+        Ok(())
+    }
+    
+    /// Broadcast an entry to all gossip subscribers for a store
+    pub async fn broadcast_entry(&self, store_id: Uuid, entry: &SignedEntry) -> Result<(), String> {
+        let senders = self.gossip_senders.read().await;
+        if let Some(sender) = senders.get(&store_id) {
+            let bytes = entry.encode_to_vec();
+            sender.broadcast(bytes.into()).await
+                .map_err(|e| format!("Gossip broadcast failed: {}", e))?;
+        }
+        Ok(())
+    }
+    
+    /// Join an existing mesh by connecting to a peer.
+    pub async fn join_mesh(&self, peer_id: iroh::PublicKey) -> Result<StoreHandle, NodeError> {
+        let conn = self.endpoint.connect(peer_id).await
+            .map_err(|e| NodeError::Actor(format!("Connection failed: {}", e)))?;
+        
+        let (send, recv) = conn.open_bi().await
+            .map_err(|e| NodeError::Actor(format!("Failed to open stream: {}", e)))?;
+        
+        let mut sink = MessageSink::new(send);
+        let mut stream = MessageStream::new(recv);
+        
+        // Send JoinRequest
+        let req = PeerMessage {
+            message: Some(peer_message::Message::JoinRequest(JoinRequest {
+                node_pubkey: self.node.node_id().to_vec(),
+            })),
+        };
+        sink.send(&req).await.map_err(|e| NodeError::Actor(e))?;
+        sink.finish().await.map_err(|e| NodeError::Actor(e))?;
+        
+        // Receive JoinResponse
+        let msg = stream.recv().await
+            .map_err(|e| NodeError::Actor(e))?
+            .ok_or_else(|| NodeError::Actor("Peer closed stream".to_string()))?;
+        
+        match msg.message {
+            Some(peer_message::Message::JoinResponse(resp)) => {
+                let store_uuid = lattice_core::Uuid::from_slice(&resp.store_uuid)
+                    .map_err(|_| NodeError::Actor("Invalid UUID from peer".to_string()))?;
+                
+                let handle = self.node.complete_join(store_uuid).await?;
+                
+                // Sync with peer to get initial data
+                println!("[Join] Syncing with peer to get initial data...");
+                if let Ok(result) = self.sync_with_peer(&handle, peer_id).await {
+                    println!("[Join] Initial sync complete: {} entries", result.entries_applied);
+                }
+                
+                Ok(handle)
+            }
+            _ => Err(NodeError::Actor("Unexpected response".to_string())),
+        }
+    }
+    
+    /// Sync with a specific peer.
+    pub async fn sync_with_peer(&self, store: &StoreHandle, peer_id: iroh::PublicKey) -> Result<SyncResult, NodeError> {
+        let conn = self.endpoint.connect(peer_id).await
+            .map_err(|e| NodeError::Actor(format!("Connection failed: {}", e)))?;
+        
+        let (send, recv) = conn.open_bi().await
+            .map_err(|e| NodeError::Actor(format!("Failed to open stream: {}", e)))?;
+        
+        let mut sink = MessageSink::new(send);
+        let mut stream = MessageStream::new(recv);
+        
+        let my_state = store.sync_state().await?;
+        
+        // Send SyncRequest
+        let req = PeerMessage {
+            message: Some(peer_message::Message::SyncRequest(lattice_core::proto::SyncRequest {
+                store_id: store.id().as_bytes().to_vec(),
+                state: Some(my_state.to_proto()),
+                full_sync: false,
+            })),
+        };
+        sink.send(&req).await.map_err(|e| NodeError::Actor(e))?;
+        
+        // Receive SyncResponse
+        let resp_msg = stream.recv().await.map_err(|e| NodeError::Actor(e))?
+            .ok_or_else(|| NodeError::Actor("Peer closed stream".to_string()))?;
+        
+        let peer_state = match resp_msg.message {
+            Some(peer_message::Message::SyncResponse(resp)) => {
+                resp.state.map(|s| lattice_core::sync_state::SyncState::from_proto(&s))
+                    .unwrap_or_default()
+            }
+            _ => return Err(NodeError::Actor("Expected SyncResponse".to_string())),
+        };
+        
+        // Exchange entries
+        let _entries_sent = protocol::send_missing_entries(&mut sink, store, &my_state, &peer_state).await
+            .map_err(|e| NodeError::Actor(e))?;
+        
+        let (entries_applied, entries_sent_by_peer) = protocol::receive_entries(&mut stream, store).await
+            .map_err(|e| NodeError::Actor(e))?;
+        
+        sink.finish().await.map_err(|e| NodeError::Actor(e))?;
+        
+        Ok(SyncResult { entries_applied, entries_sent_by_peer })
+    }
+    
+    /// Sync with all active peers.
+    pub async fn sync_all(&self, store: &StoreHandle) -> Result<Vec<SyncResult>, NodeError> {
+        let peers = self.node.list_peers().await?;
+        let mut results = Vec::new();
+        let my_pubkey = self.endpoint.public_key();
+        
+        for peer in peers {
+            if peer.status != PeerStatus::Active {
+                continue;
+            }
+            
+            let peer_id = match parse_node_id(&peer.pubkey) {
+                Ok(id) => id,
+                Err(e) => {
+                    eprintln!("[Sync] Failed to parse peer {}: {}", peer.pubkey, e);
+                    continue;
+                }
+            };
+            
+            // Skip self
+            if peer_id == my_pubkey {
+                continue;
+            }
+            
+            println!("[Sync] Syncing with {}...", peer_id.fmt_short());
+            match self.sync_with_peer(store, peer_id).await {
+                Ok(result) => {
+                    println!("[Sync] Applied {} entries", result.entries_applied);
+                    results.push(result);
+                }
+                Err(e) => eprintln!("[Sync] Failed: {}", e),
+            }
+        }
+        
+        Ok(results)
+    }
+}
+
+// --- Connection handling ---
+// --- Connection handling ---
+
+/// Handle a single incoming connection
+async fn handle_connection(
+    node: Arc<Node>,
+    conn: Connection,
+) -> Result<(), String> {
+    let remote_id = conn.remote_id();
+    let remote_hex = hex::encode(remote_id.as_bytes());
+    println!("\n[Incoming] {} (ALPN: {})", remote_id.fmt_short(), String::from_utf8_lossy(conn.alpn()));
+    
+    // Parse remote pubkey
+    let remote_pubkey: [u8; 32] = hex::decode(&remote_hex)
+        .map_err(|_| "Invalid pubkey hex")?
+        .try_into()
+        .map_err(|_| "Invalid pubkey length")?;
+    
+    let (send, recv) = conn.accept_bi().await
+        .map_err(|e| format!("Accept stream error: {}", e))?;
+    
+    let sink = MessageSink::new(send);
+    let mut stream = MessageStream::new(recv);
+    
+    // Read first message to determine request type
+    let msg = stream.recv().await?
+        .ok_or_else(|| "Peer closed stream".to_string())?;
+    
+    match msg.message {
+        Some(peer_message::Message::JoinRequest(req)) => {
+            handle_join_request(&node, &remote_pubkey, req, sink).await
+        }
+        Some(peer_message::Message::SyncRequest(req)) => {
+            handle_sync_request(&node, &remote_pubkey, req, sink, stream).await
+        }
+        _ => Err("Unexpected message type".to_string()),
+    }
+}
+
+/// Handle a join request from an invited peer
+async fn handle_join_request(
+    node: &Node,
+    remote_pubkey: &[u8; 32],
+    req: lattice_core::proto::JoinRequest,
+    mut sink: MessageSink,
+) -> Result<(), String> {
+    println!("[Join] Got JoinRequest from {}", hex::encode(&req.node_pubkey));
+    
+    // Accept the join - verifies invited, sets active, returns store ID
+    let acceptance = node.accept_join(remote_pubkey).await
+        .map_err(|e| e.to_string())?;
+    
+    let resp = PeerMessage {
+        message: Some(peer_message::Message::JoinResponse(JoinResponse {
+            store_uuid: acceptance.store_id.as_bytes().to_vec(),
+            inviter_pubkey: vec![],
+        })),
+    };
+    sink.send(&resp).await?;
+    sink.finish().await?;
+    
+    println!("[Join] Sent JoinResponse, peer now active");
+    Ok(())
+}
+
+/// Handle a sync request - bidirectional exchange of entries
+async fn handle_sync_request(
+    node: &Node,
+    remote_pubkey: &[u8; 32],
+    peer_request: lattice_core::proto::SyncRequest,
+    mut sink: MessageSink,
+    mut stream: MessageStream,
+) -> Result<(), String> {
+    // Verify peer is active (allowed to sync)
+    node.verify_peer_status(remote_pubkey, &[PeerStatus::Active]).await
+        .map_err(|e| e.to_string())?;
+    println!("[Sync] Verified peer as active");
+    
+    // Parse store_id from request
+    let store_id = Uuid::from_slice(&peer_request.store_id)
+        .map_err(|_| format!("Invalid store_id in SyncRequest: {} bytes, expected 16", peer_request.store_id.len()))?;
+    
+    println!("[Sync] Received SyncRequest for store {}", store_id);
+    
+    // Open the requested store (uses cache if available)
+    let (store, _info) = node.open_store(store_id).await
+        .map_err(|e| format!("Failed to open store {}: {}", store_id, e))?;
+    
+    println!("[Sync] Received SyncRequest");
+    
+    // Get our sync state
+    let my_state = store.sync_state().await
+        .map_err(|e| format!("Failed to get sync state: {}", e))?;
+    
+    // 1. Send our sync state as response
+    let resp = PeerMessage {
+        message: Some(peer_message::Message::SyncResponse(lattice_core::proto::SyncResponse {
+            store_id: store.id().as_bytes().to_vec(),
+            state: Some(my_state.to_proto()),
+        })),
+    };
+    sink.send(&resp).await?;
+    
+    // 2. Send entries peer is missing
+    let peer_state = peer_request.state
+        .map(|s| lattice_core::sync_state::SyncState::from_proto(&s))
+        .unwrap_or_default();
+    
+    let entries_sent = protocol::send_missing_entries(&mut sink, &store, &my_state, &peer_state).await?;
+    println!("[Sync] Sent {} entries, now receiving from peer...", entries_sent);
+    
+    // 3. Receive entries from requester (bidirectional)
+    let (entries_applied, _) = protocol::receive_entries(&mut stream, &store).await?;
+    
+    sink.finish().await?;
+    
+    println!("[Sync] Applied {} entries from peer", entries_applied);
+    Ok(())
+}
+

proto/lattice.proto

@@ -0,0 +1,143 @@
+syntax = "proto3";
+
+package lattice;
+
+// 1. The Wrapper (What flies over the wire)
+message SignedEntry {
+  // The serialized bytes of the 'Entry' message.
+  // We keep this as raw bytes so the signature verification is stable.
+  bytes entry_bytes = 1;
+  
+  // Ed25519 Signature of 'entry_bytes'
+  bytes signature = 2;
+  
+  // Public Key of the author (32 bytes)
+  bytes author_id = 3;
+}
+
+// 2. The Log Entry (The Atomic Unit)
+message Entry {
+  // Versioning allows us to change the format radically later if needed
+  uint32 version = 1;
+
+  // Store this entry belongs to (16-byte UUID)
+  bytes store_id = 6;
+
+  // Ordering Metadata
+  bytes prev_hash = 2;   // Link to previous sigchain entry (32 bytes)
+  uint64 seq = 3;        // Monotonic sequence number
+  HLC timestamp = 4;     // Hybrid Logical Clock
+
+  // DAG ancestry: hashes of entries this supersedes (separate from sigchain)
+  repeated bytes parent_hashes = 7;
+
+  // The Batch of Operations
+  repeated Operation ops = 5;
+}
+
+// HeadInfo: a tip/head in the DAG for a key
+message HeadInfo {
+  bytes value = 1;       // The value at this head
+  uint64 hlc = 2;        // Combined HLC for ordering (wall_time_ms << 16 | counter)
+  bytes author = 3;      // Author's public key (32 bytes)
+  bytes hash = 4;        // Hash of the SignedEntry that created this head
+  bool tombstone = 5;    // True if this head represents a delete
+}
+
+// HeadList: wrapper for storing multiple heads per key in state.db
+message HeadList {
+  repeated HeadInfo heads = 1;
+}
+
+// AuthorState: tracks last applied entry per author for replay optimization
+message AuthorState {
+  uint64 seq = 1;        // Last applied seq for this author's sigchain
+  bytes hash = 2;        // Hash of last applied entry
+  uint64 log_offset = 3; // Byte offset in log file for fast resume
+}
+
+// Hybrid Logical Clock
+message HLC {
+  uint64 wall_time = 1;  // Unix timestamp (ms)
+  uint32 counter = 2;    // Logical counter for same-ms ordering
+}
+
+// 3. The Operation (The Change)
+message Operation {
+  // "oneof" is how Protobuf handles Rust Enums
+  oneof op_type {
+    PutOp put = 1;
+    DeleteOp delete = 2;
+    // Future: MergeOp merge = 3;
+  }
+}
+
+message PutOp {
+  bytes key = 1;
+  bytes value = 2;
+}
+
+message DeleteOp {
+  bytes key = 1;
+}
+
+// 4. The Sync Handshake (Vector Clocks)
+message SyncState {
+  repeated Frontier frontiers = 1;
+  HLC sender_hlc = 2;  // Sender's current clock (for peer time awareness)
+}
+
+message Frontier {
+  bytes author_id = 1;  // Ed25519 public key (32 bytes)
+  uint64 max_seq = 2;   // Highest sequence number seen from this author
+  repeated bytes head_hashes = 3;  // All head hashes for this author
+}
+
+// 5. Log File Record (wrapper for storage)
+message LogRecord {
+  bytes hash = 1;         // BLAKE3 hash of entry_bytes (32 bytes)
+  bytes entry_bytes = 2;  // Serialized SignedEntry
+}
+
+// 6. Join Protocol Messages (new node joining existing mesh)
+message JoinRequest {
+  bytes node_pubkey = 1;  // Joining node's public key (32 bytes)
+}
+
+message JoinResponse {
+  bytes store_uuid = 1;   // Root store UUID (16 bytes) for new node to create
+  bytes inviter_pubkey = 2;  // Inviter's public key for verification
+}
+
+// 7. Sync Protocol Messages (bidirectional sync after join)
+message SyncRequest {
+  bytes store_id = 1;     // Store UUID to sync (16 bytes)
+  SyncState state = 2;    // Sender's sync state (for incremental sync)
+  bool full_sync = 3;     // If true, request all entries (for join)
+}
+
+message SyncResponse {
+  bytes store_id = 1;     // Store UUID being synced (16 bytes)
+  SyncState state = 2;    // Responder's sync state
+}
+
+message SyncEntry {
+  bytes signed_entry = 1; // Serialized SignedEntry
+  bytes hash = 2;         // Hash for verification
+}
+
+message SyncDone {
+  uint64 entries_sent = 1;
+}
+
+// 8. Peer Message Wrapper (for proper message type discrimination)
+message PeerMessage {
+  oneof message {
+    JoinRequest join_request = 1;
+    JoinResponse join_response = 2;
+    SyncRequest sync_request = 3;
+    SyncResponse sync_response = 4;
+    SyncEntry sync_entry = 5;
+    SyncDone sync_done = 6;
+  }
+}