🤖 refactor(stories): split Storybook helper monoliths into feature-scoped modules

[jaaydenh]

Summary

Split the monolithic mockFactory.ts (~1134 LoC) and storyHelpers.ts (~646 LoC) Storybook helper files into feature-scoped modules to reduce TurboSnap invalidation scope and improve Chromatic build efficiency.

Background

Both files were imported by 20+ story files each, meaning any edit to an unrelated helper (e.g., adding a new tool factory) would invalidate every dependent story in Chromatic's TurboSnap. This broad dependency fan-out undermined onlyChanged: true effectiveness — a single-line change in mockFactory.ts could trigger re-snapshots of 20+ stories.

Implementation

New module structure

src/browser/stories/mocks/ (from mockFactory.ts):

Module	Contents
workspaces.ts	Workspace/project factories, NOW, STABLE_TIMESTAMP
messages.ts	createUserMessage, createAssistantMessage, etc.
tools.ts	All create*Tool helpers, withHookOutput
chatHandlers.ts	Static/streaming chat handler builders
git.ts	Git status fixtures

src/browser/stories/helpers/ (from storyHelpers.ts):

Module	Contents
uiState.ts	localStorage helpers (selection, sidebar, model)
reviews.ts	Review/hunk state helpers, createReview
drafts.ts	Draft fixture/persistence
chatSetup.ts	setup*ChatStory adapters
git.ts	Git diff/executor helpers

Migration approach

1. Extracted code into 10 feature modules (pure move, no logic changes)
2. Migrated all ~35 story files + 3 test files to import from feature modules directly
3. Removed the original monolith files entirely (no compatibility shims remain)

TurboSnap impact

Previously, editing mockFactory.ts invalidated all 20 dependent stories. Now editing mocks/tools.ts only invalidates the ~15 stories that use tool factories, helpers/reviews.ts only invalidates ~3 review stories, etc.

Validation

• make typecheck ✅
• make lint ✅
• bun x storybook build --stats-json ✅
• Zero remaining imports from deleted mockFactory.ts / storyHelpers.ts

Risks

Low — pure structural refactoring with no logic changes. All exports preserved with identical signatures. The only risk is if external tooling hard-codes paths to the deleted files, but grep confirms no such references exist outside generated content strings.

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Generated with mux • Model: anthropic:claude-opus-4-6 • Thinking: xhigh • Cost: $10.78

[jaaydenh]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. More of your lovely PRs please.

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[jaaydenh]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

https://github.com/coder/mux/blob/d62b1c5534f2e98f857601eb0d635c0d5b75ea82/src/browser/stories/mockFactory.ts#L1
Keep a compatibility shim for removed story helper imports

Removing src/browser/stories/mockFactory.ts (and storyHelpers.ts) without a compatibility re-export breaks internal guidance that still imports those paths, including docs/reference/storybook.mdx and the runtime-loaded built-in skill snapshot in src/node/services/agentSkills/builtInSkillContent.generated.ts. In practice, users/agents following those instructions now hit module-resolution failures when creating stories. Please either add temporary shim files that re-export from the new modules or update+regenerate the docs/skill content in the same change.

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