Extensions can replace the sidebar with custom React components

[benvinegar]

Extensions can now contribute a custom sidebar view via hunk.registerSidebarView(), replacing the built-in file-navigation pane with their own React component. This enables extensions to provide alternative navigation UIs while maintaining full integration with Hunk's review model and theme system.

Key changes

• Extension API: Added registerSidebarView() method to HunkExtensionAPI, accepting a view with an id and React component. New types: ExtensionSidebarView, ExtensionSidebarViewProps, ExtensionSidebarActions, and ExtensionSidebarTheme define the public contract.

• Host React serving: Introduced hostRuntimeModules.ts to serve Hunk's own React instance to extension files at import time. Extensions outside the app bundle (user config or repo-local) now receive the host's React, hooks dispatcher, and JSX runtime through virtual modules (hunk-host:react, etc.), ensuring hooks work correctly and preventing dispatcher conflicts. The mechanism transpiles extension source and rewrites host-owned specifiers before Bun's loader would resolve them.

• Sidebar rendering: New ExtensionSidebarPane component wraps extension-contributed views in an error boundary, projects the active theme onto a curated public token slice, and guards all navigation actions. Failures are reported as warnings naming the extension, and the built-in sidebar takes over as fallback.

• Registry and resolution: Extended ExtensionRegistry to collect sidebar views; resolveExtensionSidebarView() picks the first registration (load order wins) and reports later ones as skipped. App now conditionally renders the extension sidebar or built-in pane based on registry state.

• Integration: App.tsx coordinates sidebar selection and passes filtered file views, theme tokens, and guarded action callbacks to the component. Selection changes from extension actions fire the same selection_changed lifecycle event as the built-in sidebar.

Notable implementation details

• Extension files are transpiled with JSX automatic runtime enabled and host specifiers rewritten before import, so JSX lowering emits imports that pass through the rewrite and resolve to virtual modules.

• The sidebar component receives frozen, read-only file views and a curated theme object to prevent accidental review-model corruption.

• Actions (selectFile, selectHunk, notify) are guarded: failures inside them emit warnings instead of propagating into the component, keeping the session stable.

• Error boundary isolation is keyed by extension and view id, so a reloaded registry gets a fresh chance to render.

• Comprehensive tests cover the host module serving (including JSX transpilation and helper module resolution), extension registration and rollback on factory failure, and live PTY integration with hooks and actions.

https://claude.ai/code/session_01JML2m7oy2sUbFftN7QoHhi

[vercel]

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Project	Deployment	Actions	Updated (UTC)
hunk-web	Ready	Preview	Jul 27, 2026 5:38pm

[greptile-apps]

Greptile Summary

Adds extension-provided React sidebar views and the host-runtime infrastructure needed to render them.

• Extends the public extension API and registry with sidebar view registration, props, actions, and theme tokens.
• Rewrites extension imports to host-served React, JSX, OpenTUI, and extension API virtual modules.
• Conditionally renders extension sidebars with guarded navigation, error isolation, and a built-in fallback.
• Adds unit and integration coverage plus extension authoring documentation.

Confidence Score: 3/5

The PR should not merge until invalid hunk selections are rejected and failed sidebar boundaries reliably reset after extension reloads.

The new action path can store a hunk index that has no corresponding hunk, and a sidebar that once threw remains permanently replaced by the fallback when corrected code reloads under the same identifiers.

Files Needing Attention: src/ui/App.tsx; src/ui/components/panes/ExtensionSidebarPane.tsx

Important Files Changed

Filename	Overview
src/extensions/hostRuntimeModules.ts	Adds scoped Bun plugins that transpile extension sources and redirect host-owned runtime imports.
src/ui/components/panes/ExtensionSidebarPane.tsx	Adds extension rendering, error isolation, and action guards, but selectHunk permits invalid upper-bound and non-finite indices.
src/ui/App.tsx	Integrates the extension sidebar, but its stable identifier-only key prevents a failed boundary from resetting after same-id reloads.
src/extension-api/types.ts	Defines the import-free public sidebar component, action, file, and theme contracts.
src/extensions/runExtension.ts	Validates, registers, and rolls back sidebar contributions with extension factory state.

Sequence Diagram

sequenceDiagram
  participant E as Extension
  participant R as Extension registry
  participant A as App
  participant P as ExtensionSidebarPane
  participant C as Review controller
  E->>R: registerSidebarView(view)
  A->>R: resolve first sidebar view
  A->>P: render files, theme, selection, actions
  P->>C: selectFile / selectHunk
  C-->>A: update review selection
  A-->>E: emit selection_changed
  alt Component render throws
    P-->>A: report warning
    A->>A: render built-in sidebar fallback
  end

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Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
src/ui/App.tsx:1257
**Failed boundary survives reload**

When a sidebar throws and its extension is reloaded with the same extension and view IDs, this unchanged key preserves the error boundary's failed state, causing the corrected component to remain unmounted and the built-in fallback to stay active for the rest of the session.

### Issue 2 of 2
src/ui/components/panes/ExtensionSidebarPane.tsx:142-147
**Invalid hunk indices reach controller**

When an extension passes an index beyond the file's hunk count or a non-finite number, this guard forwards the invalid value to `review.selectHunk`, causing selection state to reference no hunk while reveal scrolling and `selection_changed` proceed with that invalid index.

_{Reviews (1): Last reviewed commit: "feat(extensions): custom sidebar views v..." | Re-trigger Greptile}