refactor(workbench): delete the unmounted ext-apps runtime App bridge

.changeset/remove-workbench-runtime-app-renderer.md

@@ -0,0 +1,5 @@
+---
+"agent-bundle": patch
+---
+
+Remove the unused runtime MCP App renderer from the bundled Workbench. App previews keep rendering through the server-issued sandbox frame; the package no longer ships `dist/workbench/src/mcp/APP-RENDERER-LICENSE`, and `NOTICE` and `THIRD_PARTY_NOTICES` drop the MCP Inspector `AppRenderer` attribution. (#845)

NOTICE

@@ -7,10 +7,9 @@ LICENSE file distributed with it.
 This distribution includes third-party material that is covered by its own
 license and notices, which are preserved unmodified alongside that material:
 
-  - The Agent Bundle Workbench MCP App renderer is derived from the MCP
-    Inspector project (MIT License). See THIRD_PARTY_NOTICES and
-    src/mcp/APP-RENDERER-LICENSE, which the agent-bundle package ships under
-    dist/workbench/.
+  - The Agent Bundle Workbench bundles the xterm.js terminal emulator (MIT
+    License). See THIRD_PARTY_NOTICES, which the agent-bundle package ships
+    under dist/workbench/.
 
   - The rsc-markdown-stream package (packages/rsc-markdown-stream) was
     imported from https://github.com/ScriptedAlchemy/rsc-markdown-stream at

docs/architecture/rsc-runtime-workbench.md

@@ -62,16 +62,21 @@ packages/
     tests/host-adapters.native.test.ts
     tests/host-adapters.test.ts
     tests/mcp-app-binding-service.test.ts
+    tests/mcp-app-bridge-cancellation.test.ts
     tests/mcp-app-bridge.test.ts
+    tests/mcp-app-diagnostics.test.ts
     tests/mcp-app-host-profiles.test.ts
     tests/mcp-app-metadata.test.ts
     tests/mcp-app-preview-service.test.ts
     tests/mcp-app-routes.test.ts
     tests/mcp-app-runtime-binding-service.test.ts
     tests/mcp-app-runtime-preview-service.test.ts
     tests/mcp-app-sandbox.test.ts
+    tests/mcp-apps-compile.test.ts
     tests/mcp-session-routes.test.ts
     tests/mcp-session-service.test.ts
+    tests/mcp-session-trace-publisher.test.ts
+    tests/native-host-sessions.test.ts
     tests/normalization.test.ts
     tests/playground-service.test.ts
     tests/portable-adapter.test.ts
@@ -91,21 +96,13 @@ packages/
     scripts/capture-runtime-playground.mjs
     src/main.tsx
     src/mcp/mcp-app-client.ts
-    src/mcp/mcp-app-frame.tsx
     src/mcp/mcp-app-preview.tsx
     src/mcp/mcp-page.tsx
     src/mcp/mcp-session-controller.ts
     src/mcp/mcp-session-model.ts
-    src/mcp/runtime-app-bridge.ts
-    src/mcp/runtime-consent-dialog.tsx
-    src/mcp/runtime-consent-queue.ts
-    src/mcp/runtime-mcp-handoff.ts
     src/project-client.ts
     src/runtime-client.ts
-    src/runtime-inspector.tsx
     src/runtime-model.ts
-    src/runtime-playground.tsx
-    src/runtime-stage.tsx
     src/styles.css
     tests/helpers/runtime-playground-fixture.ts
     tests/mcp-app-client.test.ts
@@ -117,21 +114,11 @@ packages/
     tests/mcp-session-controller.test.ts
     tests/mcp-session-model.test.ts
     tests/mcp-session-timeout.e2e.test.ts
-    tests/runtime-app-bridge.test.ts
+    tests/runtime-backend.test.ts
     tests/runtime-client.test.ts
-    tests/runtime-consent-dialog.test.ts
-    tests/runtime-consent-queue.test.ts
     tests/runtime-contract-compile.test.ts
-    tests/runtime-document-atoms-disposal.test.ts
-    tests/runtime-inspector.test.ts
-    tests/runtime-mcp-handoff.test.ts
+    tests/runtime-controller.test.ts
     tests/runtime-model.test.ts
-    tests/runtime-playground-capture-cleanup.test.ts
-    tests/runtime-playground-capture.test.ts
-    tests/runtime-playground-hmr.e2e.test.ts
-    tests/runtime-playground.e2e.test.ts
-    tests/runtime-playground.test.ts
-    tests/runtime-stage.test.ts
 examples/
   rsc-agent-runtime/
     package.json
@@ -144,7 +131,9 @@ examples/
     src/build/serialize-definition.ts
     src/definition.ts
     src/dev/canonical-json.ts
+    src/dev/compile-diagnostics.ts
     src/dev/definition-entry.ts
+    src/dev/durable-tree.ts
     src/dev/environment-checkpoint-store.ts
     src/dev/generation-materializer.ts
     src/dev/inspection-security.ts
@@ -171,7 +160,6 @@ examples/
     src/runtime/contracts.ts
     src/runtime/state-definition.ts
     src/runtime/state-file.ts
-    src/types/mcp-ext-apps-react.d.ts
     src/types/react-server-dom-rspack.d.ts
     src/types/styles.d.ts
     src/widget/App.tsx
@@ -186,7 +174,6 @@ examples/
     tests/host-artifacts.test.ts
     tests/host-extensions.test.tsx
     tests/http-security.test.ts
-    tests/mcp-lowering.test.tsx
     tests/mcp-transports.integration.test.ts
     tests/rsc-hook.integration.test.ts
     tests/runtime-artifact-manifest.test.ts
@@ -251,12 +238,11 @@ are never gated. `ProjectStatus.hostAdoption` exposes the adopted epoch and the
 latest evaluation, and the Overview renders it as **Host adoption** beside the
 published build, so a rejected epoch is visible rather than silently skipped.
 
-The RSC result tree is not the MCP App document. A current preview moves through
-`McpAppPreview`, `SecureAppRenderer`, the official App renderer, the
-generation-bound bridge, and the runtime client-surface proxy to an opaque-origin
-App iframe. The direct frame, bridge, handoff, proxy, message-limit, binding,
-preview-service, routes, mounted-page, and real-browser tests retained above
-are the single lifecycle boundary for that binding.
+The RSC result tree is not the MCP App document. An App route preview moves
+through `McpAppPreview`, which mounts the server-issued sandbox proxy iframe and
+drives it with the frame relay (`web-host/browser/frame-relay.ts`) over the
+Workbench App routes. The frame-relay, preview, routes, mounted-page, and
+real-browser tests retained above are the lifecycle boundary for that binding.
 
 Portable is the baseline. ChatGPT/OpenAI and Claude Workbench profiles are local
 compatibility simulations, not vendor certification. Native terminal evidence

packages/agent-bundle/README.md

@@ -1139,8 +1139,7 @@ harness.
   and Codex selections are refused when it is configured.
 - Raw HTML, JSX/MDX, and Mermaid in Skill Markdown are inert in the workbench renderer.
 
-Third-party notices, including the MIT license and provenance of the MCP App renderer derived from
-the MCP Inspector's `AppRenderer`, ship in the published package.
+Third-party notices for material bundled into the workbench ship in the published package.
 
 ## License
 

packages/agent-bundle/src/dev/mcp-apps/mcp-app-routes.ts

@@ -30,7 +30,7 @@ import { runtimeAppMessageLimits } from '../runtime-app-message-limits.ts';
 // A force-close DELETE that lands after an accepted graceful close must stay
 // idempotent (200, not 404), so this window has to dominate the frame relay's
 // force-close budget — clients may fall back as late as their closeTimeoutMs,
-// which mcp-app-frame.tsx caps at 30s.
+// which web-host/browser/frame-relay.ts caps at 30s.
 const gracefulCloseReceiptTimeoutMs = 35_000;
 
 interface CreateRoute {

packages/agent-bundle/src/dev/workbench-assets.ts

@@ -39,9 +39,9 @@ const packageRoot = basename(import.meta.dirname) === 'dist'
 
 const defaultRoot = (): string => resolve(packageRoot, 'dist', 'workbench');
 
-// The Workbench build copies its attribution files into the asset tree without
-// an extension (`THIRD_PARTY_NOTICES`, `src/mcp/APP-RENDERER-LICENSE`). Those
-// conventional names are plain text a browser should render; every other
+// The Workbench build copies its attribution file into the asset tree without
+// an extension (`THIRD_PARTY_NOTICES`). Such conventional license and notice
+// names are plain text a browser should render; every other
 // extensionless file keeps the binary fallback.
 const noticeFileName = /^(?:[a-z0-9]+[-_])*(?:licen[cs]e|notices?|copying)$/iu;
 

packages/agent-bundle/tests/dev-workbench-packaging.test.ts

@@ -14,7 +14,6 @@ const execFile = promisify(executeFile);
 const workspaceRoot = process.cwd();
 const packageRoot = join(workspaceRoot, 'packages', 'agent-bundle');
 const workbenchRoot = join(workspaceRoot, 'packages', 'workbench');
-const appRendererLicense = join('src', 'mcp', 'APP-RENDERER-LICENSE');
 let built: Promise<void> | undefined;
 
 const buildPackage = async (): Promise<void> => {
@@ -27,17 +26,16 @@ describe.sequential('workbench package build', () => {
 const hashedWorkbenchBundle = (kind: 'css' | 'js'): RegExp =>
   kind === 'css' ? /^index\.[a-f0-9]{8}\.css$/u : /^index\.[a-f0-9]{8}\.js$/u;
 
-it('copies content-hashed prebuilt workbench assets and the exact app-renderer license into the package distribution', async () => {
+it('copies content-hashed prebuilt workbench assets and third-party notices into the package distribution', async () => {
   await buildPackage();
 
   await expect(access(join(packageRoot, 'dist', 'workbench', 'index.html'))).resolves.toBeUndefined();
   const jsRoot = join(packageRoot, 'dist', 'workbench', 'static', 'js');
   const hashedJs = (await readdir(jsRoot)).find((name) => hashedWorkbenchBundle('js').test(name));
   if (hashedJs === undefined) throw new Error('Expected a content-hashed workbench index.js.');
   await expect(readFile(join(jsRoot, hashedJs), 'utf8')).resolves.toContain('Workbench navigation');
-  await expect(readFile(join(packageRoot, 'dist', 'workbench', 'THIRD_PARTY_NOTICES'), 'utf8')).resolves.toContain('MCP Inspector');
-  await expect(readFile(join(packageRoot, 'dist', 'workbench', appRendererLicense), 'utf8')).resolves.toBe(
-    await readFile(join(workbenchRoot, appRendererLicense), 'utf8'),
+  await expect(readFile(join(packageRoot, 'dist', 'workbench', 'THIRD_PARTY_NOTICES'), 'utf8')).resolves.toBe(
+    await readFile(join(workbenchRoot, 'THIRD_PARTY_NOTICES'), 'utf8'),
   );
 }, 60_000);
 
@@ -76,7 +74,6 @@ it('serves prebuilt workbench assets from an installed tarball without the repos
     const listing = await execFile('tar', ['-tf', tarball]);
     expect(listing.stdout).toContain('package/dist/workbench/index.html');
     expect(listing.stdout).toContain('package/dist/workbench/THIRD_PARTY_NOTICES');
-    expect(listing.stdout).toContain('package/dist/workbench/src/mcp/APP-RENDERER-LICENSE');
     expect(listing.stdout).not.toMatch(/package\/dist\/workbench\/.*\.map$/mu);
     expect(listing.stdout).toMatch(/package\/dist\/workbench\/static\/js\/index\.[a-f0-9]{8}\.js$/mu);
     expect(listing.stdout).toMatch(/package\/dist\/workbench\/static\/css\/index\.[a-f0-9]{8}\.css$/mu);

packages/agent-bundle/tests/license-metadata.test.ts

@@ -34,7 +34,6 @@ it('ships the canonical Apache License 2.0 text and a NOTICE naming the copyrigh
   expect(createHash('sha256').update(license).digest('hex')).toBe(canonicalApache2Sha256);
   expect(notice.startsWith('agent-bundle\nCopyright 2026 ')).toBe(true);
   expect(notice).toContain('THIRD_PARTY_NOTICES');
-  expect(notice).toContain('src/mcp/APP-RENDERER-LICENSE');
 });
 
 it('declares Apache-2.0 on every first-party workspace package', async () => {

packages/agent-bundle/tests/rsc-runtime-topology-script.test.ts

@@ -25,11 +25,9 @@ const expectedTree = `packages/
     tests/playground-service.test.ts
     tests/runtime-provider.test.ts
   workbench/
-    src/mcp/runtime-app-bridge.ts
     src/mcp/runtime-consent-dialog.tsx
     src/mcp/runtime-consent-queue.ts
     src/runtime-model.ts
-    tests/runtime-app-bridge.test.ts
     tests/runtime-consent-dialog.test.ts
     tests/runtime-consent-queue.test.ts
 examples/
@@ -70,11 +68,9 @@ describe('rsc runtime topology script', () => {
         'packages/agent-bundle/tests/normalization.test.ts',
         'packages/agent-bundle/tests/playground-service.test.ts',
         'packages/agent-bundle/tests/runtime-provider.test.ts',
-        'packages/workbench/src/mcp/runtime-app-bridge.ts',
         'packages/workbench/src/mcp/runtime-consent-dialog.tsx',
         'packages/workbench/src/mcp/runtime-consent-queue.ts',
         'packages/workbench/src/runtime-model.ts',
-        'packages/workbench/tests/runtime-app-bridge.test.ts',
         'packages/workbench/tests/runtime-consent-dialog.test.ts',
         'packages/workbench/tests/runtime-consent-queue.test.ts',
         'examples/rsc-agent-runtime/src/dev/provider.ts',

packages/workbench/THIRD_PARTY_NOTICES

@@ -1,14 +1,3 @@
-Agent Bundle workbench includes an MCP App renderer derived from the MCP
-Inspector project's AppRenderer component:
-
-  MCP Inspector 2.2.0
-  https://github.com/modelcontextprotocol/inspector
-  commit 672f9f41c548487a468b9e7007d2f9de14da5a69
-  MIT License
-
-The derived code is src/mcp/app-renderer.tsx. The MIT license text is in
-src/mcp/APP-RENDERER-LICENSE.
-
 Agent Bundle workbench bundles the xterm.js terminal emulator and its fit
 addon for the Host sessions pane (src/sessions/terminal.tsx):
 

packages/workbench/package.json

@@ -15,7 +15,6 @@
   "dependencies": {
     "@effect/atom-react": "4.0.0-rc.112",
     "@modelcontextprotocol/client": "2.0.0",
-    "@modelcontextprotocol/ext-apps": "2.0.0",
     "@xterm/addon-fit": "0.11.0",
     "@xterm/xterm": "6.0.0",
     "effect": "4.0.0-rc.112",

packages/workbench/rsbuild.config.ts

@@ -27,7 +27,6 @@ export const createWorkbenchConfig = (
     overrideBrowserslist: ['chrome >= 120'],
     copy: [
       { from: resolve(import.meta.dirname, 'THIRD_PARTY_NOTICES'), to: 'THIRD_PARTY_NOTICES', toType: 'file' },
-      { from: resolve(sourceRoot, 'mcp', 'APP-RENDERER-LICENSE'), to: 'src/mcp/APP-RENDERER-LICENSE', toType: 'file' },
     ],
     distPath: {
       root: 'dist',