## Summary
- Add `ensure_pch()` helper to MasterServer that builds/reuses
precompiled headers via stateless workers, with preamble hash-based
staleness detection (xxh3_64bits)
- Fix `BuildPCHParams` to carry `preamble_bound` so the stateless worker
truncates content at the preamble boundary (fixes redefinition errors
when PCH included full file)
- Wire PCH into both `run_build_drain` (stateful compile path) and
`forward_stateless` (completion/signatureHelp path)
- Add PCH state cleanup on `didClose` and hash invalidation on `didSave`
## Test plan
- [x] 398 unit tests pass (including 6 new PCH tests: PreambleHash x3,
PCHWorker x2, BuildPCHRequest assertion)
- [x] 5 new integration tests pass (`test_pch.py`: diagnostics on open,
body edit recompile, no-include file, hover with PCH, completion with
PCH)
- [x] 21 existing integration tests pass unchanged
- [x] Build succeeds with 0 errors
🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Precompiled header (PCH) caching to speed compilations and reduce edit
latency
* Automatic attachment of cached PCH to compile requests, improving
hover and completion responsiveness
* Module-aware completions expanded to include available module
artifacts from other files
* **Bug Fixes**
* PCH cache cleared on file close; saving now triggers broader PCH
invalidation to prevent stale PCH use
* **Tests**
* Added unit and integration tests exercising PCH build, reuse, and
editor interactions
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
21a969af27