🤖 perf: improve Review panel performance and fix UI flashes #946
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- Migrate MarkdownComponents.tsx to use highlightCode() from worker client - Delete shikiHighlighter.ts, inline fallback into highlightWorkerClient.ts - Move MAX_DIFF_SIZE_BYTES to highlightDiffChunk.ts (only consumer) - All highlighting now shares LRU cache and worker (or fallback)
Combine two CRC32 hashes with different seeds to create a 64-bit key, reducing collision probability for the LRU cache.
Web Crypto API is built-in and hardware-accelerated, no external deps needed.
Replaces manual message ID tracking, pending request maps, and postMessage/onmessage boilerplate with Comlink's proxy-based RPC. - Worker exposes API via Comlink.expose() - Client wraps worker via Comlink.wrap() - Exceptions propagate naturally - ~30 lines removed
Reset hasLoadedOnce and hunks when workspace changes to prevent showing stale 'No changes found' message from previous workspace.
Replace independent state variables (isLoadingHunks, hasLoadedOnce,
error, hunks, truncationWarning) with a single DiffState union:
type DiffState =
| { status: 'loading' }
| { status: 'loaded'; hunks: DiffHunk[]; truncationWarning: string | null }
| { status: 'error'; message: string }
This makes invalid states unrepresentable - it's now impossible to
show 'No changes found' while loading because the type system
enforces that hunks only exist in the 'loaded' state.
Add workspaceId to DiffState to distinguish between: - Refreshing same workspace: show stale data while loading (no flash) - Switching workspaces: show loading indicator (no stale data) The state machine now correctly handles: 1. Initial load → 'loading' → 'loaded' 2. Refresh (same workspace) → 'refreshing' (keeps hunks visible) → 'loaded' 3. Workspace switch → 'loading' (clears stale hunks) → 'loaded'
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Instead of tracking workspaceId in state and checking it everywhere,
use React's key prop to force remount when workspace changes.
This is simpler and more reliable:
- Component unmounts, clearing all state
- New instance mounts with fresh { status: 'loading' }
- No stale data from previous workspace can leak through
Simplifies DiffState by removing workspaceId from the union.
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Also adds worker name for DevTools visibility. TODO: For 20k+ line diffs, the main thread bottleneck is likely DOM rendering (thousands of HunkViewer components), not highlighting. Consider adding virtualization (@tanstack/react-virtual) to only render visible hunks.
- Change main-thread fallback to use dynamic import() so shiki isn't bundled with the main thread code path - Add ESLint rule to enforce shiki is only imported in highlightWorker.ts - Type-only imports are allowed (erased at compile time) This ensures the 9.7MB @shikijs/langs package is only loaded in the web worker, not blocking the main thread during app startup.
ammario
approved these changes
Dec 8, 2025
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Summary
Performance improvements and UI polish for the Review panel when viewing large diffs.
Manually verified: Much better performance when viewing large diffs (~3000+ lines).
Performance
UI Flash Fixes
Refactoring
shikiHighlighter.ts, consolidated intohighlightWorkerClient.tsbuildGitDiffCommandtosrc/common/utils/git/diffParser.tsRIGHT_SIDEBAR_TAB_KEY, etc.)State Machine
loading→loadedloaded→refreshing→loadedloaded{ws1}→loading→loaded{ws2}Testing
make typecheck✓make static-check✓bun test src/browser/utils/highlighting/highlightDiffChunk.test.ts— 18 passGenerated with
mux