diff --git a/src/renderer/components/team/editor/EditorFileTree.tsx b/src/renderer/components/team/editor/EditorFileTree.tsx
index 3172ccab..b637abe9 100644
--- a/src/renderer/components/team/editor/EditorFileTree.tsx
+++ b/src/renderer/components/team/editor/EditorFileTree.tsx
@@ -32,6 +32,7 @@ import {
   isPathPrefix,
   joinPath,
   lastSeparatorIndex,
+  normalizePathForComparison,
   splitPath,
 } from '@shared/utils/platformPath';
 import { useVirtualizer } from '@tanstack/react-virtual';
@@ -81,6 +82,17 @@ const INDENT_PX = 12;
 const MAX_DEPTH = 12;
 const AUTO_EXPAND_DELAY_MS = 500;
 
+function treePathsEqual(
+  left: string | null | undefined,
+  right: string | null | undefined
+): boolean {
+  return (
+    typeof left === 'string' &&
+    typeof right === 'string' &&
+    normalizePathForComparison(left) === normalizePathForComparison(right)
+  );
+}
+
 // =============================================================================
 // Component
 // =============================================================================
@@ -204,7 +216,7 @@ export const EditorFileTree = ({
   // Scroll to file when selectedFilePath changes (e.g. from revealFileInEditor)
   useEffect(() => {
     if (!selectedFilePath) return;
-    const idx = flatItems.findIndex((fi) => fi.node.fullPath === selectedFilePath);
+    const idx = flatItems.findIndex((fi) => treePathsEqual(fi.node.fullPath, selectedFilePath));
     if (idx >= 0) {
       virtualizer.scrollToIndex(idx, { align: 'center' });
     }
@@ -633,7 +645,7 @@ const DraggableTreeItem = React.memo(
     onRenameCancel,
   }: DraggableTreeItemProps): React.ReactElement => {
     const { node, depth, isExpanded } = item;
-    const isSelected = activeNodePath === node.fullPath;
+    const isSelected = treePathsEqual(activeNodePath, node.fullPath);
     const visualDepth = Math.min(depth, MAX_DEPTH);
     const isSensitive = node.data?.isSensitive;
 
diff --git a/src/renderer/store/slices/editorSlice.ts b/src/renderer/store/slices/editorSlice.ts
index 28f9e210..b2e0df42 100644
--- a/src/renderer/store/slices/editorSlice.ts
+++ b/src/renderer/store/slices/editorSlice.ts
@@ -19,6 +19,7 @@ import {
   isWindowsishPath,
   joinPath,
   lastSeparatorIndex,
+  normalizePathForComparison,
   splitPath,
   stripTrailingSeparators,
 } from '@shared/utils/platformPath';
@@ -42,6 +43,29 @@ function omitKey<V>(record: Record<string, V>, key: string): Record<string, V> {
   return result;
 }
 
+function editorPathsEqual(left: string, right: string): boolean {
+  return normalizePathForComparison(left) === normalizePathForComparison(right);
+}
+
+function findMatchingPathKey<V>(record: Record<string, V>, filePath: string): string | null {
+  if (filePath in record) return filePath;
+  return Object.keys(record).find((key) => editorPathsEqual(key, filePath)) ?? null;
+}
+
+function getMatchingPathMapValue<V>(map: Map<string, V>, filePath: string): V | undefined {
+  const exact = map.get(filePath);
+  if (exact !== undefined) return exact;
+  for (const [key, value] of map) {
+    if (editorPathsEqual(key, filePath)) return value;
+  }
+  return undefined;
+}
+
+function omitMatchingPathKey<V>(record: Record<string, V>, filePath: string): Record<string, V> {
+  const key = findMatchingPathKey(record, filePath);
+  return key ? omitKey(record, key) : record;
+}
+
 /**
  * Cooldown map: filePath → timestamp of last successful save.
  *
@@ -617,7 +641,7 @@ export const createEditorSlice: StateCreator<AppState, [], [], EditorSlice> = (s
     const { editorOpenTabs } = get();
 
     // Dedup: if file already open, just activate it
-    const existing = editorOpenTabs.find((t) => t.filePath === filePath);
+    const existing = editorOpenTabs.find((t) => editorPathsEqual(t.filePath, filePath));
     if (existing) {
       set({ editorActiveTabId: existing.id });
       return;
@@ -1216,26 +1240,27 @@ export const createEditorSlice: StateCreator<AppState, [], [], EditorSlice> = (s
       }, 2000);
     }
     const { editorOpenTabs, editorProjectPath, editorSaving } = get();
+    const openTab = editorOpenTabs.find((tab) => editorPathsEqual(tab.filePath, event.path));
+    const canonicalEventPath = openTab?.filePath ?? event.path;
 
     // Ignore watcher events for files we are currently saving (our own write)
-    if (editorSaving[event.path]) return;
+    if (findMatchingPathKey(editorSaving, event.path)) return;
 
     // Ignore watcher events within cooldown after save
     // (covers race: save completes → editorSaving cleared → watcher fires late)
-    const lastSaveTime = recentSaveTimestamps.get(event.path);
+    const lastSaveTime = getMatchingPathMapValue(recentSaveTimestamps, event.path);
     if (lastSaveTime && Date.now() - lastSaveTime < SAVE_COOLDOWN_MS) return;
 
     // Ignore watcher events within cooldown after move
-    const lastMoveTime = recentMoveTimestamps.get(event.path);
+    const lastMoveTime = getMatchingPathMapValue(recentMoveTimestamps, event.path);
     if (lastMoveTime && Date.now() - lastMoveTime < MOVE_COOLDOWN_MS) return;
 
     // Track changes for open files
-    const isOpenFile = editorOpenTabs.some((t) => t.filePath === event.path);
-    if (isOpenFile || event.type === 'delete') {
+    if (openTab || event.type === 'delete') {
       set((s) => ({
         editorExternalChanges: {
           ...s.editorExternalChanges,
-          [event.path]: event.type,
+          [canonicalEventPath]: event.type,
         },
       }));
     }
@@ -1267,7 +1292,7 @@ export const createEditorSlice: StateCreator<AppState, [], [], EditorSlice> = (s
 
   clearExternalChange: (filePath: string) => {
     set((s) => ({
-      editorExternalChanges: omitKey(s.editorExternalChanges, filePath),
+      editorExternalChanges: omitMatchingPathKey(s.editorExternalChanges, filePath),
     }));
   },
 
diff --git a/test/renderer/store/editorSlice.test.ts b/test/renderer/store/editorSlice.test.ts
index eac85169..b008d099 100644
--- a/test/renderer/store/editorSlice.test.ts
+++ b/test/renderer/store/editorSlice.test.ts
@@ -295,6 +295,16 @@ describe('editorSlice', () => {
       expect(state.editorActiveTabId).toBe('/project/src/index.ts');
     });
 
+    it('deduplicates Windows tabs across drive case and separator differences', () => {
+      store.getState().openFile('C:\\Repo\\src\\index.ts');
+      store.getState().openFile('c:/repo/src/index.ts');
+
+      const state = store.getState();
+      expect(state.editorOpenTabs).toHaveLength(1);
+      expect(state.editorOpenTabs[0].filePath).toBe('C:\\Repo\\src\\index.ts');
+      expect(state.editorActiveTabId).toBe('C:\\Repo\\src\\index.ts');
+    });
+
     it('detects language from file extension', () => {
       store.getState().openFile('/project/data.json');
 
@@ -531,6 +541,31 @@ describe('editorSlice', () => {
     });
   });
 
+  describe('handleExternalFileChange', () => {
+    it('keys Windows watcher changes to the open tab path across separator differences', () => {
+      vi.useFakeTimers();
+      try {
+        store.getState().openFile('C:\\Repo\\src\\index.ts');
+
+        store.getState().handleExternalFileChange({
+          type: 'change',
+          path: 'c:/repo/src/index.ts',
+        });
+
+        expect(store.getState().editorExternalChanges).toEqual({
+          'C:\\Repo\\src\\index.ts': 'change',
+        });
+
+        store.getState().clearExternalChange('c:/repo/src/index.ts');
+
+        expect(store.getState().editorExternalChanges).toEqual({});
+      } finally {
+        vi.runOnlyPendingTimers();
+        vi.useRealTimers();
+      }
+    });
+  });
+
   describe('closeEditor resets all state including Group 2+3', () => {
     it('resets tabs, dirty, saving, errors', () => {
       store.setState({