Addresses the six Copilot review comments on the initial commit.
1) #6 (critical) — mcp_server.py `_get_collection` bypassed ChromaBackend
The MCP server creates its palace collection directly via
`chromadb.PersistentClient.get_or_create_collection` in `_get_collection`,
not through `ChromaBackend.get_collection`. That path was missing the
`hnsw:num_threads=1` metadata, so the primary crash surface for #974
and #965 was untouched by the original patch. Fixed by passing
`hnsw:num_threads=1` at the mcp_server create site too. Documented
in a code comment that the setting is only honored at creation
time — existing palaces created before this fix still need a
`mempalace nuke` + re-mine to gain the protection.
2) #3 — mine_global_lock over-serialized mines across unrelated palaces
Replaced the single global lock file `mine_global.lock` with a
per-palace lock keyed by `sha256(os.path.abspath(palace_path))`
(`mine_palace_<hash>.lock`). Mines against the same palace still
collapse to a single runner (the correctness boundary), but mines
against *different* palaces are now free to run in parallel.
`mine_global_lock` is kept as a backward-compatible alias for
`mine_palace_lock` so any external callers that imported the
previous name keep working.
3) #1 — hook_precompact swallowed OSError but not subprocess.TimeoutExpired
`subprocess.run(..., timeout=60)` raises `TimeoutExpired` on slow
palaces. The previous `except OSError` clause didn't catch it, so
the hook could raise and fail to emit any JSON decision — leaving
the harness without a block/passthrough signal. Fixed by catching
`(OSError, subprocess.TimeoutExpired)` together and always falling
through to the block decision so the hook reliably emits a response.
4) #2 + #4 — tests
- tests/test_hooks_cli.py: added
`test_precompact_first_two_attempts_block`,
`test_precompact_passes_through_after_cap`, and
`test_precompact_counter_is_per_session` to lock in the #955
deadlock fix.
- tests/test_palace_locks.py (new): covers `mine_palace_lock`
single-acquire, reuse-after-release, cross-process serialization
on the same palace, non-interference across different palaces,
path normalization, and the `mine_global_lock` back-compat alias.
5) #5 — known limitation, documented but not auto-fixed
Copilot suggested detecting collections missing `hnsw:num_threads=1`
and calling `collection.modify(metadata=...)` to retrofit existing
palaces. Verified against chromadb 1.5.7: `modify(metadata=...)`
replaces metadata rather than merging, and re-passing
`hnsw:space="cosine"` then raises `ValueError: Changing the
distance function of a collection once it is created is not
supported currently.` The HNSW runtime configuration
(`configuration_json`) also does not expose `num_threads` in
chromadb 1.5.x, so the flag appears to be read only at creation
time. Rather than paper over the limitation with a best-effort
`modify` that silently drops `hnsw:space`, documented in the
mcp_server comment that pre-existing palaces need a
`mempalace nuke` + re-mine to gain the protection. Fresh palaces
are always protected.
Testing
- pytest tests/test_palace_locks.py tests/test_hooks_cli.py
tests/test_backends.py tests/test_cli.py → **98 passed, 0 failed**.
- Runtime validation with two concurrent `mempalace mine` calls:
- Different palaces → both complete in parallel ✓
- Same palace → one completes, the other exits with
"another `mine` is already running against <palace> — exiting
cleanly." ✓
Felipe Truman
99b820cb42