Cli: Install MCP when upgrade is ran by agent

[huang-julien]

Closes #

What I did

This PR add addon-mcp upgrade/installation when upgrade command is run through AI.

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

verify upgrade command from AI correctly installs addon-mcp or update it

Tested with Claude OK.

Caution

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

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.

🦋 Canary release

This pull request has been released as version 0.0.0-pr-35215-sha-cf433ce6. Try it out in a new sandbox by running npx storybook@0.0.0-pr-35215-sha-cf433ce6 sandbox or in an existing project with npx storybook@0.0.0-pr-35215-sha-cf433ce6 upgrade.

More information

Published version	0.0.0-pr-35215-sha-cf433ce6
Triggered by	@huang-julien
Repository	storybookjs/storybook
Branch	feat/addon-mcp-agent-upgrade
Commit	cf433ce6
Datetime	Thu Jun 18 15:29:08 UTC 2026 (1781796548)
Workflow run	27770466961

To request a new release of this pull request, mention the @storybookjs/core team.

core team members can create a new canary release here or locally with gh workflow run --repo storybookjs/storybook publish.yml --field pr=35215

Summary by CodeRabbit

• New Features

  • Enhanced Storybook upgrades to automatically ensure the MCP support addon (@storybook/addon-mcp) is present when an AI-powered agent is detected, installing or refreshing it as needed.

• Tests

  • Added a Vitest suite covering the upgrade automation flow, including agent-detection scenarios and verification that addon installation is skipped in dry-run mode.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a770b986-9784-46b1-8749-800e9144a076

📥 Commits

Reviewing files that changed from the base of the PR and between cf433ce and 84cf052.

📒 Files selected for processing (1)

• code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.test.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.test.ts

---

📝 Walkthrough

Walkthrough

Adds a new addonMcp automigration fix that detects AI coding agents during storybook upgrade, checks whether @storybook/addon-mcp is already configured, and installs or updates it via the shared add() helper. The fix is registered in allFixes, and a Vitest suite covers all check and run scenarios.

Changes

addonMcp automigration fix

Layer / File(s)	Summary
addonMcp fix: contract, check, prompt, run, and registration code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.ts, code/lib/cli-storybook/src/automigrate/fixes/index.ts	Defines AddonMcpOptions (agentName, isInstalled), implements check using detectAgent and addon list inspection, prompt generating a user message, and run calling add() with skipInstall/skipPostinstall/yes flags while respecting dryRun. Registers addonMcp in the exported allFixes array.
check and run phase tests code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.test.ts	Mocks detectAgent and a package manager; asserts check returns null when no agent is detected, returns { agentName, isInstalled: false } when addon is absent, and isInstalled: true for both string and object addon config forms. Verifies add is called with correct flags for install and force-update, and is not called in dryRun mode.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

---

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[coderabbitai]

Actionable comments posted: 3

🤖 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/lib/cli-storybook/src/automigrate/fixes/addon-mcp.test.ts`:
- Line 10: The `vi.mock()` calls for mocking the add module and another module
are missing the required `spy: true` option. Update both `vi.mock()`
declarations to include the `spy: true` option in their configuration objects to
ensure the original implementation is preserved for unmocked exports, as per the
Vitest mocking guidelines. Find the mock declarations around lines 10 and 13
where the add module is being mocked and apply the same `spy: true`
configuration to both calls.
- Around line 38-82: The mock implementations for detectAgent are currently set
inline within each test case in the check phase describe block. Move the
detectAgent.mockReturnValue() calls from inside each test (in "returns null when
no AI agent is detected", "returns isInstalled: false when an agent is detected
and addon-mcp is missing", "returns isInstalled: true when addon-mcp is already
configured", and "detects addon-mcp when configured as an object") into
appropriate beforeEach blocks. Create separate beforeEach blocks before each
test or group tests by their shared mock behavior, so that mock setups are
declared before the test runs rather than inline within the test case.
- Around line 1-14: The test file is missing mocks for dependencies that the
addonMcp module uses. You need to add vi.mock() calls for the modules that
export getAddonNames and logger, following the same pattern as the existing
vi.hoisted() mock for detectAgent. Once the mocks are declared, implement the
mock behaviors in the beforeEach hook using vi.fn() to create spy functions for
getAddonNames and logger. This ensures that when addonMcp accesses these
dependencies during testing, it receives controlled mock implementations rather
than the actual modules.

🪄 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: 17b54268-80f9-469b-9391-7cc98b833e23

📥 Commits

Reviewing files that changed from the base of the PR and between 1688451 and cf433ce.

📒 Files selected for processing (3)

• code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.test.ts
• code/lib/cli-storybook/src/automigrate/fixes/addon-mcp.ts
• code/lib/cli-storybook/src/automigrate/fixes/index.ts

[storybook-app-bot]

Package Benchmarks

^{Commit: 84cf052, ran on 19 June 2026 at 10:02:24 UTC}

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

storybook

	Before	After	Difference
Dependency count	72	72	0
Self size	21.12 MB	21.08 MB	🎉 -47 KB 🎉
Dependency size	36.42 MB	36.42 MB	0 B
Bundle Size Analyzer	Link	Link

@storybook/cli

	Before	After	Difference
Dependency count	204	204	0
Self size	820 KB	804 KB	🎉 -16 KB 🎉
Dependency size	91.48 MB	91.42 MB	🎉 -56 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/codemod

	Before	After	Difference
Dependency count	197	197	0
Self size	32 KB	32 KB	🚨 +36 B 🚨
Dependency size	89.96 MB	89.91 MB	🎉 -47 KB 🎉
Bundle Size Analyzer	Link	Link

create-storybook

	Before	After	Difference
Dependency count	73	73	0
Self size	1.09 MB	1.08 MB	🎉 -10 KB 🎉
Dependency size	57.55 MB	57.50 MB	🎉 -47 KB 🎉
Bundle Size Analyzer	node	node