[bassilkhilo-ag2]

Summary

• load_allowed() and load_tier_map() both read access.json on every _write_task call — O(N) I/O for N Slack events in a long-running daemon
• Introduce _load_access_json(): checks stat().st_mtime before re-parsing; only re-reads when the file changes
• Both helpers become thin wrappers returning [0] / [1] from the cached tuple
• The None vs set() TOFU contract is preserved (allowed = None when file absent, in the shared helper)

Tests

• tests/slack-bridge-tier-map.test.py: 5 new cache tests (same-mtime returns identical object, mtime bump invalidates, deleted file → None/{}). 19/19 pass.
• tests/slack-bridge-access.test.py: structural check updated to accept both the pre-slack-bridge: cache load_tier_map() instead of re-reading on every _write_task call [priority/low] #894 except FileNotFoundError: return None shape and the new _load_access_json() delegation shape. Still passes.

Test plan

• python3 tests/slack-bridge-tier-map.test.py → 19 passed
• python3 tests/slack-bridge-access.test.py → 1 passed

🤖 Generated with Claude Code

[VasiliyRad]

Cache logic is correct. The stat/read outside the lock is safe — a race between stat and read at best causes one extra parse on a file-changed boundary, which is harmless and self-correcting on the next call. TOFU contract preserved: allowed=None on missing file flows through correctly. Tests cover the four meaningful states (cache hit, mtime bump, file deleted). Scope is clean — only src/slack-bridge.py and its two test files.

[VasiliyRad]

Clean refactor. _load_access_json() reads + parses once per mtime tick; both load_allowed() and load_tier_map() are thin delegates now. Thread-safety via _access_cache_lock, OSError handling preserved, and the load-bearing None-vs-empty-set distinction for TOFU eligibility is intact (file-missing → None, parse-error → empty set). Tests updated to match the new shape. 3 files only, no bundled changes.

LGTM 👍