Migrate WebMCP surface to document.modelContext (Promise registration, single-arg execute)

src/__tests__/context.test.tsx

@@ -14,14 +14,14 @@ function StatusDisplay() {
 }
 
 function deleteNativeModelContext() {
-  const desc = Object.getOwnPropertyDescriptor(navigator, "modelContext");
+  const desc = Object.getOwnPropertyDescriptor(document, "modelContext");
   if (desc) {
-    Object.defineProperty(navigator, "modelContext", {
+    Object.defineProperty(document, "modelContext", {
       value: undefined,
       configurable: true,
       writable: true,
     });
-    delete navigator.modelContext;
+    delete document.modelContext;
   }
 }
 
@@ -52,10 +52,11 @@ describe("WebMCPProvider availability", () => {
 
   it("available is true when native API exists", async () => {
     const native = {
-      registerTool() {},
-      unregisterTool() {},
+      registerTool() {
+        return Promise.resolve(undefined);
+      },
     };
-    Object.defineProperty(navigator, "modelContext", {
+    Object.defineProperty(document, "modelContext", {
       value: native,
       configurable: true,
       enumerable: true,
@@ -73,18 +74,19 @@ describe("WebMCPProvider availability", () => {
         expect(getByTestId("status")).toHaveTextContent("yes");
       });
       // Native API should still be the original, not replaced by polyfill
-      expect(navigator.modelContext).toBe(native);
+      expect(document.modelContext).toBe(native);
     } finally {
       deleteNativeModelContext();
     }
   });
 
-  it("available is true when native API lacks unregisterTool (Chrome 148+)", async () => {
+  it("available is true with a signal-only native API (Chrome 148+)", async () => {
     const native = {
-      registerTool() {},
-      // no unregisterTool — simulates Chrome 148+
+      registerTool() {
+        return Promise.resolve(undefined);
+      },
     };
-    Object.defineProperty(navigator, "modelContext", {
+    Object.defineProperty(document, "modelContext", {
       value: native,
       configurable: true,
       enumerable: true,
@@ -101,7 +103,7 @@ describe("WebMCPProvider availability", () => {
       await waitFor(() => {
         expect(getByTestId("status")).toHaveTextContent("yes");
       });
-      expect(navigator.modelContext).toBe(native);
+      expect(document.modelContext).toBe(native);
     } finally {
       deleteNativeModelContext();
     }
@@ -119,17 +121,20 @@ describe("polyfill lifecycle", () => {
     );
 
     await waitFor(() => {
-      expect(navigator.modelContext).toBeDefined();
+      expect(document.modelContext).toBeDefined();
     });
-    expect((navigator.modelContext as Record<string, unknown>).__isWebMCPPolyfill).toBe(true);
+    expect((document.modelContext as unknown as Record<string, unknown>).__isWebMCPPolyfill).toBe(
+      true,
+    );
   });
 
   it("does not install polyfill when native API present", async () => {
     const native = {
-      registerTool() {},
-      unregisterTool() {},
+      registerTool() {
+        return Promise.resolve(undefined);
+      },
     };
-    Object.defineProperty(navigator, "modelContext", {
+    Object.defineProperty(document, "modelContext", {
       value: native,
       configurable: true,
       enumerable: true,
@@ -144,10 +149,10 @@ describe("polyfill lifecycle", () => {
       );
 
       await waitFor(() => {
-        expect(navigator.modelContext).toBe(native);
+        expect(document.modelContext).toBe(native);
       });
       expect(
-        (navigator.modelContext as Record<string, unknown>).__isWebMCPPolyfill,
+        (document.modelContext as unknown as Record<string, unknown>).__isWebMCPPolyfill,
       ).toBeUndefined();
     } finally {
       deleteNativeModelContext();
@@ -162,19 +167,20 @@ describe("polyfill lifecycle", () => {
     );
 
     await waitFor(() => {
-      expect(navigator.modelContext).toBeDefined();
+      expect(document.modelContext).toBeDefined();
     });
 
     unmount();
-    expect(navigator.modelContext).toBeUndefined();
+    expect(document.modelContext).toBeUndefined();
   });
 
   it("does not clean up native API on unmount", async () => {
     const native = {
-      registerTool() {},
-      unregisterTool() {},
+      registerTool() {
+        return Promise.resolve(undefined);
+      },
     };
-    Object.defineProperty(navigator, "modelContext", {
+    Object.defineProperty(document, "modelContext", {
       value: native,
       configurable: true,
       enumerable: true,
@@ -189,11 +195,11 @@ describe("polyfill lifecycle", () => {
       );
 
       await waitFor(() => {
-        expect(navigator.modelContext).toBe(native);
+        expect(document.modelContext).toBe(native);
       });
 
       unmount();
-      expect(navigator.modelContext).toBe(native);
+      expect(document.modelContext).toBe(native);
     } finally {
       deleteNativeModelContext();
     }
@@ -222,12 +228,14 @@ describe("multi-provider lifecycle", () => {
 
     // Unmount first provider — polyfill should still be alive
     result1.unmount();
-    expect(navigator.modelContext).toBeDefined();
-    expect((navigator.modelContext as Record<string, unknown>).__isWebMCPPolyfill).toBe(true);
+    expect(document.modelContext).toBeDefined();
+    expect((document.modelContext as unknown as Record<string, unknown>).__isWebMCPPolyfill).toBe(
+      true,
+    );
 
     // Unmount second provider — now polyfill should be cleaned up
     result2.unmount();
-    expect(navigator.modelContext).toBeUndefined();
+    expect(document.modelContext).toBeUndefined();
   });
 });
 
@@ -308,6 +316,6 @@ describe("Strict Mode", () => {
     });
 
     unmount();
-    expect(navigator.modelContext).toBeUndefined();
+    expect(document.modelContext).toBeUndefined();
   });
 });

src/__tests__/smoke.test.tsx

@@ -86,7 +86,7 @@ describe("smoke: SSR + client mount availability", () => {
 // ─── Tool registration lifecycle ──────────────────────────────────
 
 describe("smoke: tool registration lifecycle", () => {
-  it("tool visible in listTools after mount, unregisterTool called on unmount", async () => {
+  it("tool visible in listTools after mount, removed on unmount", async () => {
     const { unmount } = render(
       <WebMCPProvider name="smoke" version="1.0">
         <SmokeToolComponent
@@ -107,21 +107,17 @@ describe("smoke: tool registration lifecycle", () => {
     expect(tools[0].name).toBe("smoke_greet");
     expect(tools[0].description).toBe("Smoke test greeter");
 
-    // Spy before unmount — provider cleanup removes the polyfill
-    const mc = navigator.modelContext;
-    expect(mc).toBeDefined();
-    const spy = vi.spyOn(mc as NonNullable<typeof mc>, "unregisterTool");
-
     unmount();
 
-    expect(spy).toHaveBeenCalledWith("smoke_greet");
+    // Provider cleanup removes the polyfill, so the tool is gone.
+    await waitFor(() => expect(navigator.modelContextTesting?.listTools() ?? []).toHaveLength(0));
   });
 });
 
 // ─── StrictMode safety ────────────────────────────────────────────
 
 describe("smoke: StrictMode safety", () => {
-  it("one tool registered after double-mount, clean unregister on real unmount", async () => {
+  it("one tool registered after double-mount, removed on real unmount", async () => {
     const { unmount } = render(
       <StrictMode>
         <WebMCPProvider name="smoke" version="1.0">
@@ -143,14 +139,9 @@ describe("smoke: StrictMode safety", () => {
     expect(tools).toHaveLength(1);
     expect(tools[0].name).toBe("strict_tool");
 
-    const mc = navigator.modelContext;
-    expect(mc).toBeDefined();
-    const spy = vi.spyOn(mc as NonNullable<typeof mc>, "unregisterTool");
-
     unmount();
 
-    expect(spy).toHaveBeenCalledTimes(1);
-    expect(spy).toHaveBeenCalledWith("strict_tool");
+    await waitFor(() => expect(navigator.modelContextTesting?.listTools() ?? []).toHaveLength(0));
   });
 });
 

src/context.tsx

@@ -30,15 +30,15 @@ function WebMCPProvider({ name, version, children }: WebMCPProviderProps) {
 
   useEffect(() => {
     const hasNativeApi =
-      !!navigator.modelContext && !("__isWebMCPPolyfill" in navigator.modelContext);
+      !!document.modelContext && !("__isWebMCPPolyfill" in document.modelContext);
 
     if (!hasNativeApi) {
       installPolyfill();
       usesPolyfillRef.current = true;
       polyfillConsumerCount++;
     }
 
-    setAvailable(!!navigator.modelContext);
+    setAvailable(!!document.modelContext);
 
     return () => {
       if (usesPolyfillRef.current) {