Skills M2b: Rework the core toolsets into their intended shape

code/addons/vitest/src/preset.test.ts

@@ -0,0 +1,30 @@
+import { beforeEach, describe, expect, it } from 'vitest';
+
+import { clearToolsetRegistry, getToolset } from 'storybook/open-service';
+import type { Options } from 'storybook/internal/types';
+
+import { services } from './preset.ts';
+
+const options = {
+  channel: { on: () => {}, off: () => {}, emit: () => {} },
+  presets: {
+    apply: async (key: string, fallback?: unknown) =>
+      key === 'storyIndexGenerator' ? { getIndex: async () => ({ v: 5, entries: {} }) } : fallback,
+  },
+} as unknown as Options;
+
+describe('services preset hook', () => {
+  beforeEach(() => {
+    clearToolsetRegistry();
+  });
+
+  // Consumers resolve the `test` toolset for its descriptions and schemas alone, without a dev
+  // server: `storybook ai` metadata generation applies `services` but never starts one, and a
+  // non-Vite dev server returns from `experimental_serverChannel` before it could register. Both
+  // used to hit an unregistered toolset and fail hard.
+  it('registers the test toolset without a server channel', async () => {
+    await services(undefined, options);
+
+    expect(getToolset('test').methods.run.description).toBeDefined();
+  });
+});

code/addons/vitest/src/preset.ts

@@ -9,8 +9,10 @@ import {
 } from 'storybook/internal/common';
 import {
   type StoryIndexGenerator,
+  createTestToolset,
   experimental_UniversalStore,
   experimental_getTestProviderStore,
+  registerToolset,
 } from 'storybook/internal/core-server';
 import { logger } from 'storybook/internal/node-logger';
 import { cleanPaths, oneWayHash, sanitizeError, telemetry } from 'storybook/internal/telemetry';
@@ -43,6 +45,12 @@ import { runTestRunner } from './node/boot-test-runner.ts';
 import type { CachedState, ErrorLike, StoreState } from './types.ts';
 import type { StoreEvent } from './types.ts';
 
+/**
+ * Preset marker: true exactly when this addon is enabled, since only enabled addons' presets load.
+ * addon-mcp's availability gate reads it through `presets.apply('isAddonVitestEnabled', false)`.
+ */
+export const isAddonVitestEnabled = true;
+
 type Event =
   | {
       type: 'test-discrepancy';
@@ -58,6 +66,32 @@ type Event =
       payload: StoreState['currentRun'];
     };
 
+/**
+ * Registers the public `test` toolset.
+ *
+ * This addon owns the toolset because running stories needs its channel protocol, but it must
+ * register from the `services` hook rather than `experimental_serverChannel`: consumers resolve
+ * the toolset for its descriptions and schemas alone, and the two places that do so — `storybook
+ * ai` metadata generation (which never starts a dev server) and a non-Vite dev server (where the
+ * channel hook returns early) — would otherwise ask for a toolset that was never registered and
+ * fail hard. Registering here matches the availability gate that decides whether the tool is
+ * offered at all: that gate reads the `isAddonVitestEnabled` marker this preset exports, which is
+ * true exactly when the addon is enabled — the same condition under which this hook runs. The
+ * channel is used only when a run is actually triggered.
+ */
+export const services = async (_value: void, options: Options): Promise<void> => {
+  const storyIndexGenerator =
+    await options.presets.apply<Promise<StoryIndexGenerator>>('storyIndexGenerator');
+
+  registerToolset(
+    createTestToolset({
+      channel: options.channel as Channel,
+      storyIndex: { getIndex: () => storyIndexGenerator.getIndex() },
+      a11yEnabled: await options.presets.apply('isAddonA11yEnabled', false),
+    })
+  );
+};
+
 export const experimental_serverChannel = async (channel: Channel, options: Options) => {
   const core = await options.presets.apply('core');
 

code/core/build-config.ts

@@ -206,6 +206,15 @@ const config: BuildEntries = {
         exportEntries: ['./open-service'],
         entryPoint: './src/shared/open-service/index.ts',
       },
+      {
+        // Dependency-light docs toolset surface bundled into `@storybook/mcp`'s dist (core is a
+        // dev dependency there), replacing that package's own manifest-formatter copies. Portable:
+        // its d.ts is one flat self-contained file so that consumer can inline it through standard
+        // resolution; guarded by `portable-dist.test.ts` next to the entry source.
+        exportEntries: ['./internal/toolsets-docs'],
+        entryPoint: './src/shared/open-service/toolsets/docs/public.ts',
+        portable: { external: ['valibot'] },
+      },
     ],
     runtime: [
       {

code/core/package.json

@@ -198,6 +198,11 @@
       "code": "./src/telemetry/index.ts",
       "default": "./dist/telemetry/index.js"
     },
+    "./internal/toolsets-docs": {
+      "types": "./dist/shared/open-service/toolsets/docs/public.d.ts",
+      "code": "./src/shared/open-service/toolsets/docs/public.ts",
+      "default": "./dist/shared/open-service/toolsets/docs/public.js"
+    },
     "./internal/types": {
       "types": "./dist/types/index.d.ts",
       "code": "./src/types/index.ts",
@@ -371,6 +376,7 @@
     "npmlog": "^7.0.0",
     "p-limit": "^7.2.0",
     "package-manager-detector": "^1.1.0",
+    "pathe": "^1.1.2",
     "picocolors": "^1.1.0",
     "picomatch": "^2.3.0",
     "picoquery": "^2.5.0",

code/core/src/core-server/index.ts

@@ -58,6 +58,29 @@ export {
   registerService as experimental_registerService,
 } from '../shared/open-service/server.ts';
 
+/**
+ * Toolset registration for addons that host a public toolset.
+ *
+ * Exposed from the Node entry rather than `storybook/open-service`: toolset factories reach
+ * server-only code, and that entry is built for the browser.
+ */
+export { registerToolset } from '../shared/open-service/toolset-registry.ts';
+export { createTestToolset } from '../shared/open-service/toolsets/test/definition.ts';
+export type {
+  CreateTestToolsetOptions,
+  TestToolset,
+} from '../shared/open-service/toolsets/test/definition.ts';
+export { createDocsToolset } from '../shared/open-service/toolsets/docs/definition.ts';
+export { emptyManifests } from '../shared/open-service/toolsets/docs/access.ts';
+export type { DocsAccess, ResolvedDocsEntry } from '../shared/open-service/toolsets/docs/access.ts';
+export { createServiceDocsAccess } from '../shared/open-service/toolsets/docs/access-service.ts';
+export { createManifestDocsAccess } from '../shared/open-service/toolsets/docs/access-manifest.ts';
+export { createLocalDocsAccess } from '../shared/open-service/toolsets/docs/access-local.ts';
+export { loadManifests } from './utils/manifests/manifests.ts';
+export { createStoriesToolset } from '../shared/open-service/toolsets/stories/definition.ts';
+export type { PreviewStoriesOutput } from '../shared/open-service/toolsets/stories/definition.ts';
+export { reviewToolset } from '../shared/open-service/toolsets/review/definition.ts';
+
 export { UniversalStore as experimental_UniversalStore } from '../shared/universal-store/index.ts';
 export { MockUniversalStore as experimental_MockUniversalStore } from '../shared/universal-store/mock.ts';
 export {

code/core/src/core-server/presets/common-preset.ts

@@ -19,15 +19,16 @@ import { StoryIndexGenerator } from 'storybook/internal/core-server';
 import { loadCsf } from 'storybook/internal/csf-tools';
 import { logger } from 'storybook/internal/node-logger';
 import { telemetry } from 'storybook/internal/telemetry';
-import type {
-  CoreConfig,
-  DocgenProviderDescriptor,
-  Indexer,
-  Options,
-  PresetProperty,
-  PresetPropertyFn,
-  StoryDocsProvider,
-  StorybookConfigRaw,
+import {
+  CHANGE_DETECTION_STATUS_TYPE_ID,
+  type CoreConfig,
+  type DocgenProviderDescriptor,
+  type Indexer,
+  type Options,
+  type PresetProperty,
+  type PresetPropertyFn,
+  type StoryDocsProvider,
+  type StorybookConfigRaw,
 } from 'storybook/internal/types';
 
 import { OpenServiceServicesAppliedTwiceError } from '../../server-errors.ts';
@@ -36,9 +37,14 @@ import { createDocgenWorkerClient } from '../../shared/open-service/services/doc
 import { registerModuleGraphService } from '../../shared/open-service/services/module-graph/server.ts';
 import { registerReviewService } from '../../shared/open-service/services/review/server.ts';
 import { registerStoryDocsService } from '../../shared/open-service/services/story-docs/server.ts';
+import { createLocalDocsAccess } from '../../shared/open-service/toolsets/docs/access-local.ts';
 import { registerToolset } from '../../shared/open-service/toolset-registry.ts';
-import { docsToolset } from '../../shared/open-service/toolsets/docs/definition.ts';
+import { createDocsToolset } from '../../shared/open-service/toolsets/docs/definition.ts';
 import { reviewToolset } from '../../shared/open-service/toolsets/review/definition.ts';
+import { createStoriesToolset } from '../../shared/open-service/toolsets/stories/definition.ts';
+import { GitDiffProvider } from '../change-detection/GitDiffProvider.ts';
+import { getStatusStoreByTypeId } from '../stores/status.ts';
+import { loadManifests } from '../utils/manifests/manifests.ts';
 
 import * as pathe from 'pathe';
 import { isAbsolute, join } from 'pathe';
@@ -50,7 +56,7 @@ import { initCreateNewStoryChannel } from '../server-channel/create-new-story-ch
 import { initFileSearchChannel } from '../server-channel/file-search-channel.ts';
 import { initGhostStoriesChannel } from '../server-channel/ghost-stories-channel.ts';
 import { initOpenInEditorChannel } from '../server-channel/open-in-editor-channel.ts';
-import { isReviewFeatureEnabled } from '../../shared/review/features.ts';
+import { isReviewExplicitlyEnabled, isReviewFeatureEnabled } from '../../shared/review/features.ts';
 import { initReviewChannel } from '../server-channel/review-channel.ts';
 import { initTelemetryChannel } from '../server-channel/telemetry-channel.ts';
 import { initializeChecklist } from '../utils/checklist.ts';
@@ -367,13 +373,31 @@ export const services = async (_value: void, options: Options): Promise<void> =>
     presets: options.presets,
   });
 
-  // Toolsets register imperatively alongside their services: addons contribute both from their own
-  // `services` hook. The stories and test toolsets join once their boot-time dependencies are wired
-  // (stories factory; test moves to addon-vitest).
-  registerToolset(docsToolset);
-
   const features = await options.presets.apply('features');
 
+  // Toolsets register imperatively alongside their services: addons contribute both from their own
+  // `services` hook. The test toolset registers from addon-vitest, which owns the channel it needs.
+  const storyIndex = { getIndex: () => storyIndexGenerator.getIndex() };
+  const gitDiffProvider = new GitDiffProvider(process.cwd());
+
+  registerToolset(
+    createStoriesToolset({
+      storyIndex,
+      git: {
+        getRepoRoot: () => gitDiffProvider.getRepoRoot(),
+        getChangedFiles: () => gitDiffProvider.getChangedFiles(),
+      },
+      changeStatuses: {
+        getAll: () => getStatusStoreByTypeId(CHANGE_DETECTION_STATUS_TYPE_ID).getAll(),
+      },
+      // The explicit opt-in gate, not `isReviewFeatureEnabled`: with the flag unset the review
+      // infrastructure below still registers (the `storybook ai` CLI channel enables the tool per
+      // request), but direct MCP clients never see `display-review`, so the stories prose must
+      // not point at it.
+      reviewEnabled: isReviewExplicitlyEnabled(features),
+    })
+  );
+
   if (isReviewFeatureEnabled(features)) {
     registerReviewService({
       getIndex: () => storyIndexGenerator.getIndex(),
@@ -410,12 +434,27 @@ export const services = async (_value: void, options: Options): Promise<void> =>
       });
     }
 
+    // Story-docs registers whenever this block runs, docgen only when a worker is available, so
+    // docgen registered ⇒ story-docs registered. `createLocalDocsAccess` requires both before
+    // reading from the services and degrades to the manifests otherwise, so reordering or gating
+    // these registrations cannot make the docs toolset throw — only fall back.
     registerStoryDocsService({
       getIndex: () => storyIndexGenerator.getIndex(),
       storyDocsProvider,
       workingDir: process.cwd(),
     });
   }
+
+  registerToolset(
+    createDocsToolset({
+      // Registration-based selection between the docgen services and the inline manifests, shared
+      // with addon-mcp's composed local source so both read this Storybook the same way.
+      docsAccess: createLocalDocsAccess({
+        storyIndex,
+        getManifests: () => loadManifests(options.presets),
+      }),
+    })
+  );
 };
 
 // Store the promise (not the result) to prevent race conditions.

code/core/src/core-server/utils/manifests/manifests.ts

@@ -70,6 +70,18 @@ function mergeServicePayloads(
   );
 }
 
+/**
+ * Whether the dev server should 404 `manifests/components.json` and `manifests/docs.json` because
+ * docgen-server mode owns that data.
+ *
+ * Deliberately flag-based, while the docs toolset's engine selection (`createLocalDocsAccess`) is
+ * registration-based. The two can disagree: with the flag on but the docgen services unregistered
+ * (manager-only build, no docgen worker), the toolset falls back to reading the inline manifests
+ * while this route keeps 404ing them — so a composing parent Storybook fetching manifests over
+ * HTTP sees nothing even though the local MCP tools still serve docs. Accepted for now: switching
+ * this gate to registration would change composition behavior that only the live-fixture suites
+ * cover, so it is deferred to its own change.
+ */
 function isDocgenServerManifestMode(features: {
   experimentalDocgenServer?: boolean;
   componentsManifest?: boolean;
@@ -123,6 +135,16 @@ async function getManifests(
   );
 }
 
+/**
+ * Loads the live manifests, the same way the dev-server manifest routes do.
+ *
+ * Exposed for the docs toolset, which reads manifest data in-process instead of fetching its own
+ * server over loopback HTTP.
+ */
+export async function loadManifests(presets: Presets) {
+  return getManifests(presets, await getManifestEntries(presets), { watch: true });
+}
+
 /**
  * Resolves the docgen `meta` for the components HTML debugger.
  *