Wire withPlanningLock into all ROADMAP.md write paths (phase add/insert/complete/remove, roadmap update-plan-progress) to prevent concurrent corruption when parallel agents modify planning files.
Extract acquireStateLock/releaseStateLock from writeStateMd and add readModifyWriteStateMd helper that holds the lock across the entire read-modify-write cycle, preventing lost updates.
Replace O(n^2) normalizeMd fence detection with single-pass O(n) pre-computed fence state array.
Warn on must_haves parse failure and stateReplaceFieldWithFallback field miss.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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