diff --git a/backend/src/routes/documents.rs b/backend/src/routes/documents.rs
index fc7234a..d194977 100644
--- a/backend/src/routes/documents.rs
+++ b/backend/src/routes/documents.rs
@@ -4,7 +4,7 @@ use axum::extract::{Json, Multipart, Path, Query, State};
 use axum::http::StatusCode;
 use axum::response::IntoResponse;
 use chrono::{DateTime, NaiveDateTime, Utc};
-use diesel::dsl::{exists, sql};
+use diesel::dsl::{exists, not, sql};
 use diesel::{prelude::*, result::DatabaseErrorKind, select, sql_types::Text, OptionalExtension};
 use serde::{Deserialize, Serialize};
 use serde_json::{json, Value};
@@ -467,44 +467,70 @@ pub async fn list_documents(
     }
 
     if let Some(tags_param) = tags_param.as_ref() {
-        let tag_ids: Result<Vec<Uuid>, _> = tags_param
-            .split(',')
-            .map(|s| Uuid::parse_str(s.trim()))
-            .collect();
+        if tags_param.trim().eq_ignore_ascii_case("none") {
+            let docs_without_tags: Vec<Uuid> = documents::table
+                .filter(documents::tenant_id.eq(tenant_id))
+                .filter(documents::deleted_at.is_null())
+                .filter(not(exists(
+                    document_tags::table.filter(document_tags::document_id.eq(documents::id)),
+                )))
+                .select(documents::id)
+                .load(&mut conn)?;
 
-        if let Ok(ids) = tag_ids {
-            if !ids.is_empty() {
-                let mut doc_id_set: Option<HashSet<Uuid>> = None;
-                for tag_id in &ids {
-                    let docs_for_tag: Vec<Uuid> = document_tags::table
-                        .filter(document_tags::tag_id.eq(*tag_id))
-                        .select(document_tags::document_id)
-                        .load(&mut conn)?;
-                    let docs_set: HashSet<Uuid> = docs_for_tag.into_iter().collect();
-                    doc_id_set = Some(match doc_id_set {
-                        Some(existing) => existing.intersection(&docs_set).cloned().collect(),
-                        None => docs_set,
-                    });
+            let docs_set: HashSet<Uuid> = docs_without_tags.into_iter().collect();
 
-                    if let Some(ref set) = doc_id_set {
-                        if set.is_empty() {
-                            break;
+            if docs_set.is_empty() {
+                return Ok(Json(vec![]));
+            }
+
+            let new_filter = match &filter_ids {
+                Some(existing) => existing.intersection(&docs_set).copied().collect(),
+                None => docs_set,
+            };
+
+            filter_ids = Some(new_filter);
+        } else {
+            let tag_ids: Result<Vec<Uuid>, _> = tags_param
+                .split(',')
+                .map(|s| Uuid::parse_str(s.trim()))
+                .collect();
+
+            if let Ok(ids) = tag_ids {
+                if !ids.is_empty() {
+                    let mut doc_id_set: Option<HashSet<Uuid>> = None;
+                    for tag_id in &ids {
+                        let docs_for_tag: Vec<Uuid> = document_tags::table
+                            .filter(document_tags::tag_id.eq(*tag_id))
+                            .select(document_tags::document_id)
+                            .load(&mut conn)?;
+                        let docs_set: HashSet<Uuid> = docs_for_tag.into_iter().collect();
+                        doc_id_set = Some(match doc_id_set {
+                            Some(existing) => existing.intersection(&docs_set).cloned().collect(),
+                            None => docs_set,
+                        });
+
+                        if let Some(ref set) = doc_id_set {
+                            if set.is_empty() {
+                                break;
+                            }
                         }
                     }
+
+                    let matching_doc_ids: HashSet<Uuid> = doc_id_set.unwrap_or_default();
+
+                    if matching_doc_ids.is_empty() {
+                        return Ok(Json(vec![]));
+                    }
+
+                    let new_filter = match &filter_ids {
+                        Some(existing) => {
+                            existing.intersection(&matching_doc_ids).copied().collect()
+                        }
+                        None => matching_doc_ids.clone(),
+                    };
+
+                    filter_ids = Some(new_filter);
                 }
-
-                let matching_doc_ids: HashSet<Uuid> = doc_id_set.unwrap_or_default();
-
-                if matching_doc_ids.is_empty() {
-                    return Ok(Json(vec![]));
-                }
-
-                let new_filter = match &filter_ids {
-                    Some(existing) => existing.intersection(&matching_doc_ids).copied().collect(),
-                    None => matching_doc_ids.clone(),
-                };
-
-                filter_ids = Some(new_filter);
             }
         }
     }
diff --git a/backend/src/routes/folders.rs b/backend/src/routes/folders.rs
index bf590b4..dd613a2 100644
--- a/backend/src/routes/folders.rs
+++ b/backend/src/routes/folders.rs
@@ -2,7 +2,12 @@ use axum::{
     extract::{Json, Path, Query, State},
     http::StatusCode,
 };
-use diesel::{dsl::exists, prelude::*, PgConnection};
+use diesel::{
+    dsl::{exists, sql},
+    prelude::*,
+    sql_types::Text,
+    PgConnection,
+};
 use serde::{Deserialize, Serialize};
 use utoipa::{IntoParams, ToSchema};
 use uuid::Uuid;
@@ -18,8 +23,7 @@ use crate::{
 use super::documents::{hydrate_documents, DocumentResponse};
 use crate::documents::ordering::{ordering_clauses, DocumentSortField, SortDirection};
 use crate::utils::{json::deserialize_patch_field, time::to_iso};
-use diesel::dsl::sql;
-use diesel::sql_types::Text;
+use std::collections::HashMap;
 
 #[derive(Deserialize, ToSchema)]
 pub struct CreateFolderRequest {
@@ -48,6 +52,18 @@ pub struct FolderContentsResponse {
     pub documents: Vec<DocumentResponse>,
 }
 
+#[derive(Clone, Serialize, ToSchema)]
+pub struct FolderTreeNode {
+    pub id: Uuid,
+    pub name: String,
+    #[schema(nullable)]
+    pub parent_id: Option<Uuid>,
+    pub created_at: String,
+    pub updated_at: String,
+    #[serde(default)]
+    pub children: Vec<FolderTreeNode>,
+}
+
 #[derive(Deserialize, IntoParams, ToSchema)]
 #[into_params(parameter_in = Query)]
 pub struct FolderContentsQuery {
@@ -418,6 +434,74 @@ pub async fn list_folder_contents(
     }))
 }
 
+#[utoipa::path(
+    get,
+    path = "/api/folders/tree",
+    responses((status = 200, description = "Folder hierarchy", body = [FolderTreeNode])),
+    tag = "Folders"
+)]
+pub async fn list_folder_tree(
+    TenantScopedConn {
+        mut conn,
+        tenant_id,
+        ..
+    }: TenantScopedConn,
+) -> AppResult<Json<Vec<FolderTreeNode>>> {
+    let folders: Vec<Folder> = folders::table
+        .filter(folders::tenant_id.eq(tenant_id))
+        .order(sql::<Text>("name COLLATE \"unicode_ci\" ASC"))
+        .load(&mut conn)?;
+
+    let mut node_map: HashMap<Uuid, FolderTreeNode> = HashMap::with_capacity(folders.len());
+    let mut children_map: HashMap<Uuid, Vec<Uuid>> = HashMap::new();
+    let mut roots: Vec<Uuid> = Vec::new();
+
+    for folder in folders {
+        let id = folder.id;
+        let parent_id = folder.parent_id;
+        let node = FolderTreeNode {
+            id,
+            name: folder.name,
+            parent_id,
+            created_at: to_iso(folder.created_at),
+            updated_at: to_iso(folder.updated_at),
+            children: Vec::new(),
+        };
+
+        if let Some(parent) = parent_id {
+            children_map.entry(parent).or_default().push(id);
+        } else {
+            roots.push(id);
+        }
+
+        node_map.insert(id, node);
+    }
+
+    fn build_node(
+        id: Uuid,
+        nodes: &HashMap<Uuid, FolderTreeNode>,
+        child_map: &HashMap<Uuid, Vec<Uuid>>,
+    ) -> FolderTreeNode {
+        let mut node = nodes.get(&id).cloned().expect("folder node must exist");
+
+        if let Some(children) = child_map.get(&id) {
+            node.children = children
+                .iter()
+                .map(|child_id| build_node(*child_id, nodes, child_map))
+                .collect();
+        }
+
+        node
+    }
+
+    let tree = roots
+        .iter()
+        .map(|root_id| build_node(*root_id, &node_map, &children_map))
+        .collect();
+
+    Ok(Json(tree))
+}
+
 #[utoipa::path(
     delete,
     path = "/api/folders/{id}",
@@ -639,6 +723,7 @@ pub(super) fn gather_descendant_folder_ids(
         crate::routes::folders::ensure_folder_path,
         crate::routes::folders::get_folder,
         crate::routes::folders::list_folder_contents,
+        crate::routes::folders::list_folder_tree,
         crate::routes::folders::delete_folder,
         crate::routes::folders::update_folder
     ),
@@ -649,6 +734,7 @@ pub(super) fn gather_descendant_folder_ids(
         crate::routes::folders::FolderInfo,
         crate::routes::folders::FolderContentsQuery,
         crate::routes::folders::FolderContentsResponse,
+        crate::routes::folders::FolderTreeNode,
         crate::routes::folders::UpdateFolderRequest
     ))
 )]
diff --git a/backend/src/routes/mod.rs b/backend/src/routes/mod.rs
index f6c8379..b79bb48 100644
--- a/backend/src/routes/mod.rs
+++ b/backend/src/routes/mod.rs
@@ -223,6 +223,11 @@ pub fn create_router(state: AppState) -> Router<()> {
             post(folders::ensure_folder_path)
                 .layer(RequireCapabilitiesLayer::all([ApiCapability::FoldersWrite])),
         )
+        .route(
+            "/tree",
+            get(folders::list_folder_tree)
+                .layer(RequireCapabilitiesLayer::all([ApiCapability::FoldersRead])),
+        )
         .route(
             "/:id",
             get(folders::get_folder)
diff --git a/backend/tests/documents_flow.rs b/backend/tests/documents_flow.rs
index 67c10ab..031999d 100644
--- a/backend/tests/documents_flow.rs
+++ b/backend/tests/documents_flow.rs
@@ -605,6 +605,81 @@ async fn upload_skips_existing_when_requested() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn filter_documents_without_tags() -> Result<()> {
+    let _lock = acquire_db_lock().await;
+    let app = TestApp::new().await?;
+
+    let password = "tagfilter";
+    app.insert_user("tagfilter", password, "admin").await?;
+    let token = app.login_token("tagfilter", password).await?;
+
+    // Create a tag and upload a document that uses it.
+    let tag_payload = CreateTagPayload {
+        label: "with-tag",
+        color: None,
+    };
+    let tag_resp = app
+        .post_json("/api/tags", &tag_payload, Some(&token))
+        .await?;
+    assert!(tag_resp.status().is_success());
+    let tag_body = body_to_vec(tag_resp.into_body()).await?;
+    let tag: TagResponse = serde_json::from_slice(&tag_body)?;
+
+    let tag_json = format!("[\"{}\"]", tag.id);
+    let tagged_upload = app
+        .upload_document_with_extras(
+            "/api/documents",
+            "with-tag.txt",
+            "text/plain",
+            b"tagged",
+            None,
+            UploadExtras {
+                title: Some("With Tag"),
+                metadata_json: None,
+                tag_ids_json: Some(tag_json.as_str()),
+                correspondents_json: None,
+                issued_at: None,
+                skip_existing: None,
+            },
+            &token,
+        )
+        .await?;
+    assert!(tagged_upload.status().is_success());
+
+    let untagged_upload = app
+        .upload_document(
+            "/api/documents",
+            "without-tag.txt",
+            "text/plain",
+            b"untagged",
+            None,
+            &token,
+        )
+        .await?;
+    assert!(untagged_upload.status().is_success());
+    let untagged_body = body_to_vec(untagged_upload.into_body()).await?;
+    let untagged_detail: DocumentDetail = serde_json::from_slice(&untagged_body)?;
+
+    // Sanity: both documents appear in the default listing.
+    let all_resp = app.get("/api/documents", Some(&token)).await?;
+    assert_eq!(all_resp.status(), StatusCode::OK);
+    let all_body = body_to_vec(all_resp.into_body()).await?;
+    let all_docs: Vec<DocumentListItem> = serde_json::from_slice(&all_body)?;
+    assert_eq!(all_docs.len(), 2);
+
+    // Filter for documents without tags.
+    let none_resp = app.get("/api/documents?tags=none", Some(&token)).await?;
+    assert_eq!(none_resp.status(), StatusCode::OK);
+    let none_body = body_to_vec(none_resp.into_body()).await?;
+    let none_docs: Vec<DocumentListItem> = serde_json::from_slice(&none_body)?;
+    assert_eq!(none_docs.len(), 1);
+    assert_eq!(none_docs[0].id, untagged_detail.document.id);
+
+    app.cleanup().await?;
+    Ok(())
+}
+
 #[tokio::test]
 async fn bulk_move_documents_to_folder() -> Result<()> {
     let _lock = acquire_db_lock().await;
diff --git a/backend/tests/folders_flow.rs b/backend/tests/folders_flow.rs
index 12d487b..d26a160 100644
--- a/backend/tests/folders_flow.rs
+++ b/backend/tests/folders_flow.rs
@@ -32,6 +32,12 @@ struct DocSummary {
     id: Uuid,
 }
 
+#[derive(Deserialize)]
+struct FolderTreeNodeResponse {
+    name: String,
+    children: Vec<FolderTreeNodeResponse>,
+}
+
 #[derive(Serialize)]
 struct CreateFolder<'a> {
     name: &'a str,
@@ -144,6 +150,71 @@ async fn folder_move_and_delete_flow() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn folder_tree_lists_hierarchy() -> Result<()> {
+    let _lock = acquire_db_lock().await;
+    let app = TestApp::new().await?;
+
+    let password = "folderpass";
+    app.insert_user("folder-tree", password, "admin").await?;
+    let token = app.login_token("folder-tree", password).await?;
+
+    let alpha_resp = app
+        .post_json(
+            "/api/folders",
+            &CreateFolder {
+                name: "Alpha",
+                parent_id: None,
+            },
+            Some(&token),
+        )
+        .await?;
+    assert_eq!(alpha_resp.status(), StatusCode::CREATED);
+    let alpha_body = body_to_vec(alpha_resp.into_body()).await?;
+    let alpha: FolderResponse = serde_json::from_slice(&alpha_body)?;
+
+    let archive_resp = app
+        .post_json(
+            "/api/folders",
+            &CreateFolder {
+                name: "Archive",
+                parent_id: Some(alpha.folder.id),
+            },
+            Some(&token),
+        )
+        .await?;
+    assert_eq!(archive_resp.status(), StatusCode::CREATED);
+
+    let beta_resp = app
+        .post_json(
+            "/api/folders",
+            &CreateFolder {
+                name: "Beta",
+                parent_id: None,
+            },
+            Some(&token),
+        )
+        .await?;
+    assert_eq!(beta_resp.status(), StatusCode::CREATED);
+
+    let tree_resp = app.get("/api/folders/tree", Some(&token)).await?;
+    assert_eq!(tree_resp.status(), StatusCode::OK);
+    let tree_body = body_to_vec(tree_resp.into_body()).await?;
+    let tree: Vec<FolderTreeNodeResponse> = serde_json::from_slice(&tree_body)?;
+
+    assert_eq!(tree.len(), 2);
+    assert_eq!(tree[0].name, "Alpha");
+    assert_eq!(tree[0].children.len(), 1);
+    assert_eq!(tree[0].children[0].name, "Archive");
+    assert!(tree[0].children[0].children.is_empty());
+
+    assert_eq!(tree[1].name, "Beta");
+    assert!(tree[1].children.is_empty());
+
+    app.cleanup().await?;
+    Ok(())
+}
+
 #[tokio::test]
 async fn update_folder_parent_to_root() -> Result<()> {
     let _lock = acquire_db_lock().await;