diff --git a/frontend/src/desktop/tags/useDeskTagInteractions.js b/frontend/src/desktop/tags/useDeskTagInteractions.js
deleted file mode 100644
index 5c24808..0000000
--- a/frontend/src/desktop/tags/useDeskTagInteractions.js
+++ /dev/null
@@ -1,224 +0,0 @@
-import {
-  useCallback,
-  useEffect,
-  useRef,
-} from 'react';
-import {
-  isTagTransferEvent,
-  parseTagTransferPayload,
-  writeTagTransferData,
-} from '../../documents/tagTransfer';
-
-const preventAll = (event) => {
-  if (!event) return;
-  if (typeof event.preventDefault === 'function') event.preventDefault();
-  if (typeof event.stopPropagation === 'function') event.stopPropagation();
-};
-
-const createDragPreview = (node, clientX, clientY) => {
-  if (!(node instanceof HTMLElement)) {
-    return null;
-  }
-  const rect = node.getBoundingClientRect();
-  const safeClientX = Number.isFinite(clientX) ? clientX : rect.left + rect.width / 2;
-  const safeClientY = Number.isFinite(clientY) ? clientY : rect.top + rect.height / 2;
-  const offsetX = Math.min(Math.max(safeClientX - rect.left, 0), rect.width);
-  const offsetY = Math.min(Math.max(safeClientY - rect.top, 0), rect.height);
-  const clone = node.cloneNode(true);
-  clone.style.position = 'absolute';
-  clone.style.top = '-9999px';
-  clone.style.left = '-9999px';
-  clone.style.pointerEvents = 'none';
-  clone.style.opacity = '1';
-  clone.style.transform = 'none';
-  document.body.appendChild(clone);
-  return { clone, offsetX, offsetY };
-};
-
-const cleanupPreview = (previewNode) => {
-  if (previewNode && previewNode.parentNode) {
-    previewNode.parentNode.removeChild(previewNode);
-  }
-};
-
-export const useDeskTagInteractions = ({
-  onAssignTagToDocument,
-  onRemoveTagFromDocument,
-  requestCanvasFocus,
-}) => {
-  const draggingTagRef = useRef(null);
-
-  const isTagTransfer = useCallback((event) => isTagTransferEvent(event), []);
-
-  const handleTagDragEnterDoc = useCallback(
-    (event) => {
-      if (!isTagTransfer(event)) return;
-      preventAll(event);
-      event.currentTarget.classList.add('is-tag-target');
-    },
-    [isTagTransfer],
-  );
-
-  const handleTagDragOverDoc = useCallback(
-    (event, docId) => {
-      if (!isTagTransfer(event)) return;
-      preventAll(event);
-      event.currentTarget.classList.add('is-tag-target');
-
-      if (event.dataTransfer) {
-        // If dragging over source, copy (no removal). Else move (removal).
-        const isSource = draggingTagRef.current?.sourceDocId === docId;
-        event.dataTransfer.dropEffect = isSource ? 'copy' : 'move';
-      }
-    },
-    [isTagTransfer],
-  );
-
-  const handleTagDragLeaveDoc = useCallback(
-    (event) => {
-      if (!isTagTransfer(event)) return;
-      // Ignore if leaving to a child element
-      if (event.relatedTarget && event.currentTarget.contains(event.relatedTarget)) {
-        return;
-      }
-      event.currentTarget.classList.remove('is-tag-target');
-    },
-    [isTagTransfer],
-  );
-
-  const handleCanvasDragOver = useCallback(
-    (event) => {
-      if (event.dataTransfer) {
-        event.dataTransfer.dropEffect = 'move';
-      }
-    },
-    [],
-  );
-
-  const handleCanvasDrop = useCallback(
-    (event) => {
-      // Implicit removal via dragend (dropEffect='move')
-      if (event.dataTransfer) {
-        event.dataTransfer.dropEffect = 'move';
-      }
-      preventAll(event);
-    },
-    [],
-  );
-
-  const handleTagDropOnDoc = useCallback(
-    (event, doc) => {
-      if (!doc) {
-        return;
-      }
-      if (!isTagTransfer(event)) {
-        return;
-      }
-      preventAll(event);
-      event.currentTarget.classList.remove('is-tag-target');
-
-      // Add to target
-      const payload = parseTagTransferPayload(event);
-
-      setTimeout(() => {
-        if (!payload || !payload.id) {
-          return;
-        }
-
-        if (payload.sourceDocId === doc.id) {
-          return;
-        }
-
-        requestCanvasFocus?.();
-
-        if (onAssignTagToDocument) {
-          onAssignTagToDocument(doc.id, payload.id);
-        }
-      }, 0);
-    },
-    [isTagTransfer, onAssignTagToDocument, requestCanvasFocus],
-  );
-
-  const handleDocTagDragStart = useCallback(
-    (event, doc, tag) => {
-      console.log('[Tag] handleDocTagDragStart', { docId: doc?.id, tagId: tag?.id });
-      if (!event?.dataTransfer || !doc || !tag) {
-        return;
-      }
-      event.dataTransfer.effectAllowed = 'copyMove';
-      writeTagTransferData(event.dataTransfer, tag, doc.id);
-
-      const pointerX = event.clientX;
-      const pointerY = event.clientY;
-      const { clone, offsetX, offsetY } = createDragPreview(event.currentTarget, pointerX, pointerY) || {};
-      if (clone) {
-        event.dataTransfer.setDragImage(clone, offsetX || 0, offsetY || 0);
-      }
-
-      const element = event.currentTarget instanceof HTMLElement ? event.currentTarget : null;
-      if (element) {
-        element.classList.add('is-drag-hidden');
-      }
-
-      draggingTagRef.current = {
-        element,
-        previewClone: clone,
-        sourceDocId: doc.id,
-        tagId: tag.id,
-        initialX: pointerX,
-        initialY: pointerY,
-        distance: 0,
-      };
-    },
-    [],
-  );
-
-  const handleDocTagDragEnd = useCallback(
-    (event) => {
-      console.log('[Tag] handleDocTagDragEnd', { dropEffect: event?.dataTransfer?.dropEffect });
-      const dropEffect = event?.dataTransfer?.dropEffect;
-
-      setTimeout(() => {
-        const state = draggingTagRef.current;
-        if (state) {
-          const element = state.element;
-          if (element) {
-            element.classList.remove('is-drag-hidden');
-          }
-          cleanupPreview(state.previewClone);
-
-          // Remove if move operation completed
-          if (dropEffect === 'move') {
-            if (onRemoveTagFromDocument && state.sourceDocId && state.tagId) {
-              onRemoveTagFromDocument(state.sourceDocId, state.tagId);
-            }
-          }
-        }
-        draggingTagRef.current = null;
-      }, 0);
-    },
-    [onRemoveTagFromDocument],
-  );
-
-  useEffect(() => {
-    return () => {
-      if (draggingTagRef.current && draggingTagRef.current.previewClone) {
-        cleanupPreview(draggingTagRef.current.previewClone);
-      }
-      draggingTagRef.current = null;
-    };
-  }, []);
-
-  return {
-    handleTagDragEnterDoc,
-    handleTagDragOverDoc,
-    handleTagDragLeaveDoc,
-    handleTagDropOnDoc,
-    handleDocTagDragStart,
-    handleDocTagDragEnd,
-    handleCanvasDragOver,
-    handleCanvasDrop,
-  };
-};
-
-export default useDeskTagInteractions;
diff --git a/frontend/src/desktop/tags/useDeskTagInteractions.ts b/frontend/src/desktop/tags/useDeskTagInteractions.ts
new file mode 100644
index 0000000..9e58fca
--- /dev/null
+++ b/frontend/src/desktop/tags/useDeskTagInteractions.ts
@@ -0,0 +1,243 @@
+import {
+    useCallback,
+    useEffect,
+    useRef,
+} from 'react';
+import React from 'react';
+import {
+    isTagTransferEvent,
+    parseTagTransferPayload,
+    writeTagTransferData,
+} from '../../documents/tagTransfer';
+import type { Identifier } from '../../types/identifiers';
+import type { Document, DocumentTag } from '../../types/documents';
+
+const preventAll = (event?: React.SyntheticEvent | Event | null) => {
+    if (!event) return;
+    if (typeof event.preventDefault === 'function') event.preventDefault();
+    if (typeof event.stopPropagation === 'function') event.stopPropagation();
+};
+
+const createDragPreview = (node: EventTarget | null, clientX: number, clientY: number) => {
+    if (!(node instanceof HTMLElement)) {
+        return null;
+    }
+    const rect = node.getBoundingClientRect();
+    const safeClientX = Number.isFinite(clientX) ? clientX : rect.left + rect.width / 2;
+    const safeClientY = Number.isFinite(clientY) ? clientY : rect.top + rect.height / 2;
+    const offsetX = Math.min(Math.max(safeClientX - rect.left, 0), rect.width);
+    const offsetY = Math.min(Math.max(safeClientY - rect.top, 0), rect.height);
+    const clone = node.cloneNode(true) as HTMLElement;
+    clone.style.position = 'absolute';
+    clone.style.top = '-9999px';
+    clone.style.left = '-9999px';
+    clone.style.pointerEvents = 'none';
+    clone.style.opacity = '1';
+    clone.style.transform = 'none';
+    document.body.appendChild(clone);
+    return { clone, offsetX, offsetY };
+};
+
+const cleanupPreview = (previewNode: HTMLElement | null) => {
+    if (previewNode && previewNode.parentNode) {
+        previewNode.parentNode.removeChild(previewNode);
+    }
+};
+
+interface UseDeskTagInteractionsArgs {
+    onAssignTagToDocument?: (docId: Identifier, tagId: Identifier) => void;
+    onRemoveTagFromDocument?: (docId: Identifier, tagId: Identifier) => void;
+    requestCanvasFocus?: () => void;
+}
+
+interface DraggingTagState {
+    element: HTMLElement | null;
+    previewClone: HTMLElement | null;
+    sourceDocId: Identifier;
+    tagId: Identifier;
+    initialX: number;
+    initialY: number;
+    distance: number;
+}
+
+export const useDeskTagInteractions = ({
+    onAssignTagToDocument,
+    onRemoveTagFromDocument,
+    requestCanvasFocus,
+}: UseDeskTagInteractionsArgs) => {
+    const draggingTagRef = useRef<DraggingTagState | null>(null);
+
+    const isTagTransfer = useCallback((event: React.DragEvent) => isTagTransferEvent(event), []);
+
+    const handleTagDragEnterDoc = useCallback(
+        (event: React.DragEvent<HTMLDivElement>, _docId: Identifier) => {
+            if (!isTagTransfer(event)) return;
+            preventAll(event);
+            event.currentTarget.classList.add('is-tag-target');
+        },
+        [isTagTransfer],
+    );
+
+    const handleTagDragOverDoc = useCallback(
+        (event: React.DragEvent<HTMLDivElement>, docId: Identifier) => {
+            if (!isTagTransfer(event)) return;
+            preventAll(event);
+            event.currentTarget.classList.add('is-tag-target');
+
+            if (event.dataTransfer) {
+                // If dragging over source, copy (no removal). Else move (removal).
+                const isSource = draggingTagRef.current?.sourceDocId === docId;
+                event.dataTransfer.dropEffect = isSource ? 'copy' : 'move';
+            }
+        },
+        [isTagTransfer],
+    );
+
+    const handleTagDragLeaveDoc = useCallback(
+        (event: React.DragEvent<HTMLDivElement>, _docId: Identifier) => {
+            if (!isTagTransfer(event)) return;
+            // Ignore if leaving to a child element
+            if (event.relatedTarget && event.currentTarget.contains(event.relatedTarget as Node)) {
+                return;
+            }
+            event.currentTarget.classList.remove('is-tag-target');
+        },
+        [isTagTransfer],
+    );
+
+    const handleCanvasDragOver = useCallback(
+        (event: React.DragEvent<HTMLDivElement>) => {
+            if (event.dataTransfer) {
+                event.dataTransfer.dropEffect = 'move';
+            }
+        },
+        [],
+    );
+
+    const handleCanvasDrop = useCallback(
+        (event: React.DragEvent<HTMLDivElement>) => {
+            // Implicit removal via dragend (dropEffect='move')
+            if (event.dataTransfer) {
+                event.dataTransfer.dropEffect = 'move';
+            }
+            preventAll(event);
+        },
+        [],
+    );
+
+    const handleTagDropOnDoc = useCallback(
+        (event: React.DragEvent<HTMLDivElement>, doc: Document) => {
+            if (!doc || !doc.id) {
+                return;
+            }
+            if (!isTagTransfer(event)) {
+                return;
+            }
+            preventAll(event);
+            event.currentTarget.classList.remove('is-tag-target');
+
+            // Add to target
+            const payload = parseTagTransferPayload(event);
+
+            setTimeout(() => {
+                if (!payload || !payload.id) {
+                    return;
+                }
+
+                if (payload.sourceDocId === doc.id) {
+                    return;
+                }
+
+                requestCanvasFocus?.();
+
+                if (onAssignTagToDocument && doc.id) {
+                    onAssignTagToDocument(doc.id, payload.id);
+                }
+            }, 0);
+        },
+        [isTagTransfer, onAssignTagToDocument, requestCanvasFocus],
+    );
+
+    const handleDocTagDragStart = useCallback(
+        (event: React.DragEvent<HTMLElement>, doc: Document, tag: DocumentTag) => {
+            console.log('[Tag] handleDocTagDragStart', { docId: doc?.id, tagId: tag?.id });
+            if (!event?.dataTransfer || !doc?.id || !tag?.id) {
+                return;
+            }
+            event.dataTransfer.effectAllowed = 'copyMove';
+            writeTagTransferData(event.dataTransfer, tag, doc.id);
+
+            const pointerX = event.clientX;
+            const pointerY = event.clientY;
+            const { clone, offsetX, offsetY } = createDragPreview(event.currentTarget, pointerX, pointerY) || {};
+            if (clone) {
+                event.dataTransfer.setDragImage(clone, offsetX || 0, offsetY || 0);
+            }
+
+            const element = event.currentTarget instanceof HTMLElement ? event.currentTarget : null;
+            if (element) {
+                element.classList.add('is-drag-hidden');
+            }
+
+            draggingTagRef.current = {
+                element,
+                previewClone: clone || null,
+                sourceDocId: doc.id,
+                tagId: tag.id,
+                initialX: pointerX,
+                initialY: pointerY,
+                distance: 0,
+            };
+        },
+        [],
+    );
+
+    const handleDocTagDragEnd = useCallback(
+        (event: React.DragEvent<HTMLElement>) => {
+            console.log('[Tag] handleDocTagDragEnd', { dropEffect: event?.dataTransfer?.dropEffect });
+            const dropEffect = event?.dataTransfer?.dropEffect;
+
+            setTimeout(() => {
+                const state = draggingTagRef.current;
+                if (state) {
+                    const element = state.element;
+                    if (element) {
+                        element.classList.remove('is-drag-hidden');
+                    }
+                    cleanupPreview(state.previewClone);
+
+                    // Remove if move operation completed
+                    if (dropEffect === 'move') {
+                        if (onRemoveTagFromDocument && state.sourceDocId && state.tagId) {
+                            onRemoveTagFromDocument(state.sourceDocId, state.tagId);
+                        }
+                    }
+                }
+                draggingTagRef.current = null;
+            }, 0);
+        },
+        [onRemoveTagFromDocument],
+    );
+
+    useEffect(() => {
+        return () => {
+            if (draggingTagRef.current && draggingTagRef.current.previewClone) {
+                cleanupPreview(draggingTagRef.current.previewClone);
+            }
+            draggingTagRef.current = null;
+        };
+    }, []);
+
+    return {
+        handleTagDragEnterDoc,
+        handleTagDragOverDoc,
+        handleTagDragLeaveDoc,
+        handleTagDropOnDoc,
+        handleDocTagDragStart,
+        handleDocTagDragEnd,
+        handleCanvasDragOver,
+        handleCanvasDrop,
+    };
+};
+
+export default useDeskTagInteractions;