When your vector memory says OK but finds nothing: a 24h post-mortem

A specific failure mode worth adding to the matrix: ingest-counts-but-recall-finds-nothing

We hit this on a vector-memory gateway (BGE-m3, 1024-dim) sitting behind an HTTP shim. Hard numbers over 24 hours:

• ingest_obs called 188 times, all returned 200 OK
• GET /healthz reports observations: 1
• recall over the same window returns 0 hits

The two root causes we confirmed end-to-end (evidence in the call chain, not vibes):

1. API field-name drift between client and server. The Python provider sends query=...; the gateway endpoint expects q=.... Result: 422 on every recall call, so even the one surviving observation is unreachable. Fix: alias query to q in the provider's recall tool, or align the gateway to accept both.

2. Silent dedup at ingest collapses 99.5% of writes. 188 calls to 1 stored row. Most likely the dedup key is over-broad (e.g. tenant+agent_id-only, or a normalized name that matches by prefix), so distinct observations collide. Fix: scope the dedup key to (agent_id, name, body_hash) not just name, and surface a counter so the loss is visible.

Why this matters for any long-running agent

It is a plausibly-alive memory — healthcheck green, ingest happy — that is in practice amnesic. Easy to miss in a benchmark that only checks recall(query) to n_results > 0 per single turn, but lethal in a long-running agent loop where the agent thinks it remembers but actually cannot.

Minimal patch (provider side, ~10 lines)

# In compass_provider.py recall tool wrapper
args = dict(kwargs)
if "query" in args and "q" not in args:
    args["q"] = args.pop("query")
return await http_post(f"{base}/v1/v14/recall", json=args)

Recommended observability

Add a /v1/stats endpoint exposing ingest_total, ingest_deduped, recall_total, recall_empty. A memory that drops 99.5% on the floor should not look healthy to the operator.

— Originally written as a comment on hebo-platform #450; published here so the post-mortem is findable beyond one issue thread.

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