`mcp_server._get_collection` bypassed `ChromaBackend.get_collection`
and called `client.get_collection` / `client.create_collection` without
`embedding_function=`. ChromaDB 1.x does not persist the EF identity
with the collection, so the MCP server's reopen silently bound
chromadb's built-in `DefaultEmbeddingFunction` while the miner / Stop
hook ingest path bound `mempalace.embedding.get_embedding_function()`.
On bleeding-edge interpreters (python 3.14 + chromadb 1.5.x on Apple
Silicon, per #1299) the default EF's lazy ONNX provider selection could
SIGSEGV the host process on first `col.add()`, killing the MCP stdio
server and leaving every subsequent tool call returning
`Connection closed` until Claude Code was relaunched. Reads worked
because `col.get(ids=...)` and metadata fetches don't invoke the EF;
the auto-ingest path worked because mining routes through the backend
abstraction. Diary writes were the consistent failure surface.
Resolve the EF up front (matching `ChromaBackend._resolve_embedding_function`)
and pass it into both reopen branches. Falls back to the chromadb default
only if `mempalace.embedding.get_embedding_function` itself raises.
Regression test patches the chromadb client class to capture
`embedding_function=` on every `get_collection` / `create_collection`
call from `_get_collection(create=True)` and `_get_collection()`, and
fails if any call omits it.
Follow-up to #1262 / #1289 (which fixed the metadata-mismatch SIGSEGV
path); this addresses the EF-mismatch SIGSEGV path on the same surface.
Igor Lins e Silva
ac6c2b6af6