- Convert session persistence to async during downloads (prevents 50-200ms UI freezes)
- Avoid unnecessary Buffer.from() copy on Uint8Array chunks (zero-copy when possible)
- Cache effective speed limit for 2s (eliminates Date object creation per chunk)
- Replace O(n) speed event shift() with pointer-based pruning
- Throttle speed event pruning to every 1.5s instead of per chunk
- Optimize refreshPackageStatus to single-loop counting (was 4 separate filter passes)
- Fix global stall watchdog race condition (re-check abort state before aborting)
- Add coalescing for async session saves (prevents write storms)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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