Vitest Addon: Add support for Preact

[yannbf]

Closes #

What I did

This PR enables Preact in the testing feature of Storybook

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

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

Initialize Storybook in a Preact project, then make sure tests can be run using the testing widget.

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 PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

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

Summary by CodeRabbit

• New Features

  • Added support for Preact paired with Vite.
  • Preact+Vite project templates now include Vitest integration by default.

• Documentation

  • Updated Vitest addon docs to list Preact as a supported renderer and framework option.

• Chores

  • Increased parallelism for Vitest integration jobs in CI to speed up test runs.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit f557f7f

Command	Status	Duration	Result
nx run-many -t build --parallel=3	✅ Succeeded	44s	View ↗

---

☁️ Nx Cloud last updated this comment at 2025-11-05 16:09:16 UTC

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 7785262

Command	Status	Duration	Result
nx run-many -t build -c production --parallel=3	✅ Succeeded	11s	View ↗

---

☁️ Nx Cloud last updated this comment at 2025-11-04 17:06:56 UTC

[coderabbitai]

📝 Walkthrough

Walkthrough

Registered '@storybook/preact-vite' as a supported framework for the Vitest addon, removed vitest-integration from preact-vite sandbox template skip tasks, updated Vitest addon docs to list Preact, and increased vitest-integration CircleCI parallelism in workflow configs.

Changes

Cohort / File(s)	Summary
Vitest addon framework registration code/addons/vitest/src/constants.ts	Added @storybook/preact-vite to the SUPPORTED_FRAMEWORKS array.
Sandbox template configuration code/lib/cli-storybook/src/sandbox-templates.ts	Removed vitest-integration from skipTasks for the preact-vite default-js and default-ts templates (now ['e2e-tests','bench']).
Vitest addon documentation docs/writing-tests/integrations/vitest-addon.mdx	Added Preact to the renderer/support lists and included preact-vite in example framework lists.
CI parallelism adjustments .circleci/config.yml, .circleci/src/workflows/daily.yml, .circleci/src/workflows/merged.yml	Increased vitest-integration job parallelism: daily workflow from 11→13, merged workflow from 6→7.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Notes for reviewer:

• Verify constants update doesn't require downstream mapping elsewhere.
• Confirm sandbox template change aligns with test coverage expectations for preact-vite.
• Check docs formatting and example correctness.
• Ensure CircleCI parallelism values comply with CI quota/policy.

Possibly related PRs

• Nextjs: Add Next v16 support #32791 — Edits the same CircleCI vitest-integration parallelism entries in .circleci/src/workflows/*, likely related to CI concurrency adjustments.

---

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 7785262 and f557f7f.

📒 Files selected for processing (3)

• .circleci/config.yml (2 hunks)
• .circleci/src/workflows/daily.yml (1 hunks)
• .circleci/src/workflows/merged.yml (1 hunks)

🧰 Additional context used

🧠 Learnings (3)

📓 Common learnings

Learnt from: CR
Repo: storybookjs/storybook PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-10-13T13:33:14.659Z
Learning: Applies to test-storybooks/** : Maintain test Storybook configurations under `test-storybooks/` for E2E and visual testing scenarios

📚 Learning: 2025-09-17T08:11:04.287Z

Learnt from: CR
Repo: storybookjs/storybook PR: 0
File: .cursorrules:0-0
Timestamp: 2025-09-17T08:11:04.287Z
Learning: Use Vitest as the test runner for this repository

Applied to files:

• .circleci/src/workflows/merged.yml
• .circleci/src/workflows/daily.yml
• .circleci/config.yml

📚 Learning: 2025-10-13T13:33:14.659Z

Learnt from: CR
Repo: storybookjs/storybook PR: 0
File: .github/copilot-instructions.md:0-0
Timestamp: 2025-10-13T13:33:14.659Z
Learning: Applies to test-storybooks/** : Maintain test Storybook configurations under `test-storybooks/` for E2E and visual testing scenarios

Applied to files:

• .circleci/src/workflows/merged.yml
• .circleci/src/workflows/daily.yml
• .circleci/config.yml

🔇 Additional comments (4)

.circleci/config.yml (2)

1014-1014: Parallelism increase for daily vitest-integration job is reasonable.

Increasing parallelism from 11 to 13 aligns with adding Preact support, which expands the test matrix. Ensure the CI runner has sufficient capacity for 13 parallel tasks.

---

1109-1109: Parallelism increase for merged vitest-integration job is reasonable.

Increasing parallelism from 6 to 7 for the post-merge validation workflow maintains proportional testing coverage. This change is consistent with the daily workflow update.

.circleci/src/workflows/merged.yml (1)

57-57: Parallelism increase aligns with Preact support expansion.

Increasing vitest-integration parallelism from 6 to 7 in the merged workflow accommodates the additional Preact template testing. This is consistent with the daily workflow update and supports the PR's Preact integration goal.

.circleci/src/workflows/daily.yml (1)

57-57: Parallelism increase supports comprehensive daily testing with Preact.

Increasing vitest-integration parallelism from 11 to 13 in the daily workflow accommodates expanded test coverage, including the new Preact framework. This is the most comprehensive testing cadence, so the increase is appropriate.

Warning

Review ran into problems

🔥 Problems

Git: Failed to clone repository. Please run the @coderabbitai full review command to re-trigger a full review. If the issue persists, set path_filters to include or exclude specific files.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[kylegach]

Docs are good; thanks!