Core: Add experimentalReview feature flag and make the features type augmentable

[yannbf]

What I did

Two related changes to make the agentic review feature properly opt-in:

1. Extracted the inline features type on StorybookConfigRaw into an exported StorybookFeatures interface (code/core/src/types/modules/core-common.ts). Addons can now declare their own feature flags via TypeScript module augmentation instead of forcing users to @ts-expect-error unknown flags in main.ts:

   declare module 'storybook/internal/types' {
     interface StorybookFeatures {
       myAddonFeature?: boolean;
     }
   }

   Verified against the production d.ts bundle: the interface survives the rollup un-renamed, augmentation merges, and a config using an augmented flag typechecks (and fails without the augmentation).

2. Declared features.experimentalReview in core (default false) and gated the review feature on it. The review feature (manager UI layer + server review channel) previously mounted unconditionally; the only gate lived in the external @storybook/addon-mcp. Core now gates both sides on experimentalReview && changeDetection (mirroring the addon's availability check) via a shared isReviewFeatureEnabled helper:

   • server: initReviewChannel in common-preset.ts only runs when enabled
   • manager: ReviewPersistentLayer (App.tsx) and ReviewToolbarHeader (Preview.tsx) only mount when enabled, read from global.FEATURES

   The internal Storybook (code/.storybook/main.ts) enables the flag since it registers @storybook/addon-mcp and uses the review workflow. Docs entry added to main-config-features.mdx.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

Caution

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

1. cd code && yarn storybook:ui — the internal Storybook has experimentalReview: true, so the review workflow should behave exactly as before (push a review via addon-mcp's display-review; the review notification/summary appears).
2. Remove experimentalReview: true from code/.storybook/main.ts and restart — the review layer no longer mounts (no review notification/summary, review routes render as plain stories) and the server does not respond to review channel events.
3. Type check: in a sandbox main.ts, features: { experimentalReview: true } typechecks without @ts-expect-error. Adding an unknown flag still errors, unless an addon augments StorybookFeatures with it (see example above).

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Declare whether manual QA will be needed for this PR during the next release, through qa:needed or qa:skip

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added an opt-in review feature setting to Storybook configuration.
  • Review-related UI and server behavior now only appear when the feature is enabled.
• Documentation
  • Added setup examples showing how to turn on the new review feature in different configuration styles.
  • Updated configuration docs to include the new option and its requirements.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds an experimentalReview feature flag and isReviewFeatureEnabled helper that gates review-related server channel initialization and manager UI rendering (ReviewPersistentLayer, review collection story detection). Introduces a StorybookFeatures type, enables the flag in internal Storybook config, and adds documentation and example snippets.

Changes

Experimental review feature flag

Layer / File(s)	Summary
StorybookFeatures type and isReviewFeatureEnabled utility code/core/src/types/modules/core-common.ts, code/core/src/shared/review/features.ts, code/core/src/shared/review/index.ts	Adds exported StorybookFeatures interface consolidating feature flags and isReviewFeatureEnabled, which checks experimentalReview and changeDetection flags; re-exported from the review module.
Server-side review channel gating code/core/src/core-server/presets/common-preset.ts	Adds experimentalReview: false default to the features preset and conditionally initializes the review server channel using isReviewFeatureEnabled.
Manager UI review flag gating code/core/src/manager/App.tsx, code/core/src/manager/components/preview/Preview.tsx	Conditionally renders ReviewPersistentLayer via slotOverlay and gates isReviewCollectionStory based on isReviewFeatureEnabled(global.FEATURES).
Documentation and Storybook config for experimentalReview code/.storybook/main.ts, docs/api/main-config/main-config-features.mdx, docs/_snippets/main-config-features-experimental-review.md	Enables experimentalReview in internal Storybook config, documents the new option, and adds example configuration snippets.

Estimated code review effort: 2 (Simple) | ~12 minutes

Sequence Diagram(s)

sequenceDiagram
  participant AppTsx as App.tsx
  participant PreviewTsx as Preview.tsx
  participant CommonPreset as common-preset.ts
  participant Features as isReviewFeatureEnabled

  AppTsx->>Features: isReviewFeatureEnabled(global.FEATURES)
  Features-->>AppTsx: boolean
  AppTsx->>AppTsx: render ReviewPersistentLayer or undefined

  PreviewTsx->>Features: isReviewFeatureEnabled(global.FEATURES)
  Features-->>PreviewTsx: boolean
  PreviewTsx->>PreviewTsx: combine with route check for isReviewCollectionStory

  CommonPreset->>Features: isReviewFeatureEnabled(resolved features)
  Features-->>CommonPreset: boolean
  CommonPreset->>CommonPreset: initReviewChannel(channel) only if enabled

Loading

Possibly related PRs

• storybookjs/storybook#35223: Both PRs modify the review server-channel initialization in common-preset.ts, adding gating around initReviewChannel.
• storybookjs/storybook#35233: Both PRs modify the same code/core/src/shared/review/index.ts public review export surface.
• storybookjs/storybook#35351: Both PRs touch the same manager review UI wiring in App.tsx and Preview.tsx.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@code/core/src/types/modules/core-common.ts`:
- Around line 472-638: `StorybookFeatures` is missing the `babelRemoveBugfixes`
flag even though `common-preset.ts` still emits it, causing excess-property
checking on `StorybookConfigRaw['features']`. Add `babelRemoveBugfixes` to the
`StorybookFeatures` interface in `core-common.ts` with the appropriate boolean
type and default/temporary docs if needed, so the preset and config types stay
aligned.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: fb842f32-3ae6-4029-81a2-ffa572aba2bd

📥 Commits

Reviewing files that changed from the base of the PR and between fac05a5 and 423e2f2.

📒 Files selected for processing (9)

• code/.storybook/main.ts
• code/core/src/core-server/presets/common-preset.ts
• code/core/src/manager/App.tsx
• code/core/src/manager/components/preview/Preview.tsx
• code/core/src/shared/review/features.ts
• code/core/src/shared/review/index.ts
• code/core/src/types/modules/core-common.ts
• docs/_snippets/main-config-features-experimental-review.md
• docs/api/main-config/main-config-features.mdx

[storybook-app-bot]

Package Benchmarks

^{Commit: 423e2f2, ran on 6 July 2026 at 16:23:37 UTC}

The following packages have significant changes to their size or dependencies:

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