Monthly summary for 2025-09 (canonical/multipass): Stability and reliability improvements focused on concurrent writes to write_json. Key achievements include implementing an interprocess file lock to synchronize per-file write_json operations across threads and processes, adding a robust retry with backoff (and jitter) to handle transient access conflicts, and introducing logging to diagnose file access issues. This work reduces intermittent 'Could not commit transactional file' errors, especially on Windows, and improves cross-platform safety of the JSON persistence layer. No new features were shipped this month; the primary delivery was a bug fix that enhances data integrity and operational stability for multipass workflows. The commit [5b1c7eb41562175fa334289e210a4cd22bd6f5ce] ([json-utils] implement file lock for write_json function (#4294)) captures the changes. Impact: more reliable VM lifecycle operations, fewer user-facing failures, and better observability. Technologies/skills demonstrated: Python concurrency, interprocess locking, retry/backoff with jitter, logging/diagnostics, cross-platform considerations.