diff --git a/docs/performance-optimization.md b/docs/performance-optimization.md
index 3b66b71..5021926 100644
--- a/docs/performance-optimization.md
+++ b/docs/performance-optimization.md
@@ -41,6 +41,8 @@ CommunityMap.jsx ── createOverlayRenderer(canvas) ─┬─ worker mode:
 
 Both modes call the same `drawOverlayFrame()`, so the output is identical. Main-thread mode is used when `Worker`, `OffscreenCanvas` or `transferControlToOffscreen` is missing. If the worker fails after control was transferred, the canvas cannot be reused, so `CommunityMap` remounts a fresh canvas and forces main-thread mode.
 
+React StrictMode replays effect setup and cleanup in development. Because a transferred canvas cannot be transferred again, `CommunityMap` retains the renderer across that synchronous replay and defers teardown by one microtask; a real unmount still destroys it, while a replacement canvas gets a new renderer.
+
 Usage: pass `overlays` (an array of `{ id, x, y, kind }` in map viewBox units, `1140 x 540`) and optionally `onRenderStats`. With no `overlays` prop, no canvas is rendered and behaviour is unchanged.
 
 ### Frame rate
diff --git a/src/components/CommunityMap.jsx b/src/components/CommunityMap.jsx
index 48d4c8b..a39fac6 100644
--- a/src/components/CommunityMap.jsx
+++ b/src/components/CommunityMap.jsx
@@ -13,6 +13,8 @@ const MAP_HEIGHT = 540;
 export default function CommunityMap({ overlays, onRenderStats }) {
   const canvasRef = useRef(null);
   const rendererRef = useRef(null);
+  const rendererCanvasRef = useRef(null);
+  const rendererGenerationRef = useRef(0);
   const statsRef = useRef(onRenderStats);
   statsRef.current = onRenderStats;
   // A canvas whose control was transferred can't be reused; bump the key to
@@ -57,21 +59,43 @@ export default function CommunityMap({ overlays, onRenderStats }) {
   useEffect(() => {
     const canvas = canvasRef.current;
     if (!hasOverlay || !canvas) return undefined;
-    const renderer = createOverlayRenderer(canvas, {
-      width: MAP_WIDTH,
-      height: MAP_HEIGHT,
-      dpr: Math.min(window.devicePixelRatio || 1, 2),
-      forceMainThread: forceMain,
-      onStats: (s) => statsRef.current?.(s),
-      onError: () => {
+    let renderer = rendererRef.current;
+    if (rendererCanvasRef.current !== canvas) {
+      if (renderer) renderer.destroy();
+      rendererRef.current = null;
+      rendererCanvasRef.current = null;
+      try {
+        renderer = createOverlayRenderer(canvas, {
+          width: MAP_WIDTH,
+          height: MAP_HEIGHT,
+          dpr: Math.min(window.devicePixelRatio || 1, 2),
+          forceMainThread: forceMain,
+          onStats: (s) => statsRef.current?.(s),
+          onError: () => {
+            setForceMain(true);
+            setMountKey((k) => k + 1);
+          },
+        });
+      } catch (error) {
+        if (forceMain) throw error;
+        console.error("[CommunityMap] Offscreen worker setup failed; retrying on the main thread.", error);
         setForceMain(true);
         setMountKey((k) => k + 1);
-      },
-    });
-    rendererRef.current = renderer;
+        return undefined;
+      }
+      rendererRef.current = renderer;
+      rendererCanvasRef.current = canvas;
+    }
+    const generation = ++rendererGenerationRef.current;
     return () => {
-      renderer.destroy();
-      rendererRef.current = null;
+      queueMicrotask(() => {
+        if (rendererGenerationRef.current !== generation) return;
+        if (rendererRef.current === renderer) {
+          renderer.destroy();
+          rendererRef.current = null;
+          rendererCanvasRef.current = null;
+        }
+      });
     };
   }, [hasOverlay, mountKey, forceMain]);
 
diff --git a/test/community-map-overlay.test.jsx b/test/community-map-overlay.test.jsx
index 58a1ba6..4891432 100644
--- a/test/community-map-overlay.test.jsx
+++ b/test/community-map-overlay.test.jsx
@@ -1,4 +1,5 @@
 // @vitest-environment jsdom
+import { StrictMode } from 'react';
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { render, screen, act, cleanup } from '@testing-library/react';
 
@@ -12,8 +13,11 @@ import CommunityMap from '../src/components/CommunityMap.jsx';
 const overlays = [{ id: 'a', x: 10, y: 20, kind: 'pending' }];
 
 describe('CommunityMap canvas overlay', () => {
-  beforeEach(() => {
+  beforeEach(async () => {
     cleanup();
+    await act(async () => {
+      await Promise.resolve();
+    });
     vi.clearAllMocks();
   });
 
@@ -66,9 +70,48 @@ describe('CommunityMap canvas overlay', () => {
     expect(screen.getByTestId('map-overlay-canvas')).not.toBe(firstCanvas);
   });
 
-  it('destroys the renderer on unmount', () => {
+  it('retries on a fresh main-thread canvas when worker initialization throws', () => {
+    const error = new DOMException('Canvas was already transferred', 'InvalidStateError');
+    const consoleError = vi.spyOn(console, 'error').mockImplementation(() => {});
+    createOverlayRenderer.mockImplementationOnce(() => {
+      throw error;
+    });
+
+    render(<CommunityMap overlays={overlays} />);
+
+    expect(createOverlayRenderer).toHaveBeenCalledTimes(2);
+    expect(createOverlayRenderer.mock.calls[1][1].forceMainThread).toBe(true);
+    expect(screen.getByTestId('map-overlay-canvas')).toBeTruthy();
+    expect(consoleError).toHaveBeenCalledWith(
+      '[CommunityMap] Offscreen worker setup failed; retrying on the main thread.',
+      error,
+    );
+    consoleError.mockRestore();
+  });
+
+  it('does not transfer the same canvas twice during StrictMode effect replay', async () => {
+    const { unmount } = render(
+      <StrictMode>
+        <CommunityMap overlays={overlays} />
+      </StrictMode>,
+    );
+
+    expect(createOverlayRenderer).toHaveBeenCalledTimes(1);
+    expect(renderer.destroy).not.toHaveBeenCalled();
+
+    unmount();
+    await act(async () => {
+      await Promise.resolve();
+    });
+    expect(renderer.destroy).toHaveBeenCalledTimes(1);
+  });
+
+  it('destroys the renderer on unmount', async () => {
     const { unmount } = render(<CommunityMap overlays={overlays} />);
     unmount();
+    await act(async () => {
+      await Promise.resolve();
+    });
     expect(renderer.destroy).toHaveBeenCalledTimes(1);
   });