Addon-Vitest: Add channel API to programmatically trigger test runs

[JReinhold]

Works on storybookjs/mcp#138

Companion PR: storybookjs/mcp#131

What I did

Added a new programmatic trigger to addon-vitest, which allows external actors (like addon-mcp) to trigger a test run and get results back via events on the channel.

To support this, I had to make additional modifications:

1. Add the channel to the options, so that any preset property (like experimental_devServer) automatically has access to the channel and can do stuff with it.
2. Replaced the flow for how addon-vitest gets the index on the server.

Previously, it would fetch the index.json when necessary; however, it wouldn't know which origin/url to fetch from. To know that, the manager would send the origin to the server (indexUrl) on startup, because the client does know where to fetch the index from. If this sounds bad, it's because it was, but it was a good compromise at the time.

But not anymore, because now you can trigger tests without even opening the manager UI once, which would leave indexUrl undefined, and crash the test run. So now it does the more clear thing, which is possible as of recently, but wasn't before. Now addon-vitest gets the index directly from StoryIndexGenerator on the server, and subscribes to changes to the index, so that when tests are triggered, the index is already available and up-to-date.

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

1. Have a react-vite Storybook with addon-mcp installed from Add testing toolset mcp#131
2. Start the dev server and configure the MCP server for your agent
3. Prompt your agent with "Run tests for the Button component stories using the Storybook MCP testing tool. Use the run-story-tests tool and report which stories passed or failed."
4. See that it runs tests and reports results back. See that in the Storybook UI, you can see the statuses too in the sidebar/testing widget, because they are all connected.

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

• 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-33206-sha-06900f2a. Try it out in a new sandbox by running npx storybook@0.0.0-pr-33206-sha-06900f2a sandbox or in an existing project with npx storybook@0.0.0-pr-33206-sha-06900f2a upgrade.

More information

Published version	0.0.0-pr-33206-sha-06900f2a
Triggered by	@JReinhold
Repository	storybookjs/storybook
Branch	jeppe/addon-vitest-trigger-api
Commit	06900f2a
Datetime	Fri Feb 6 12:53:21 UTC 2026 (1770382401)
Workflow run	21751255283

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=33206

Summary by CodeRabbit

• New Features

  • Programmatic Vitest test-run API with trigger/response flow, optional config override, and new run/result types
  • A11y addon exposes an opt-in preset and a runtime flag; per-run a11y statuses and reports are surfaced
  • In-memory story index for faster lookup and focused-run filtering

• Refactor

  • Standardized accessibility type names
  • Streamlined channel plumbing across server, build, and presets

• Tests

  • New tests for selective/focused test triggering and result handling

[nx-cloud]

View your CI Pipeline Execution ↗ for commit a3aad16

Command	Status	Duration	Result
nx run-many -t compile,check,knip,test,pretty-d...	❌ Failed	1m 6s	View ↗

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☁️ Nx Cloud last updated this comment at 2026-02-19 19:14:14 UTC

[storybook-bot]

Failed to publish canary version of this pull request, triggered by @JReinhold. See the failed workflow run at: https://github.com/storybookjs/storybook/actions/runs/19732250010

[storybook-bot]

Failed to publish canary version of this pull request, triggered by @JReinhold. See the failed workflow run at: https://github.com/storybookjs/storybook/actions/runs/21150762531

[storybook-bot]

Failed to publish canary version of this pull request, triggered by @JReinhold. See the failed workflow run at: https://github.com/storybookjs/storybook/actions/runs/21150973271

[storybook-bot]

Failed to publish canary version of this pull request, triggered by @JReinhold. See the failed workflow run at: https://github.com/storybookjs/storybook/actions/runs/21151373423