First G1+ piece. Standalone vectord service with in-memory HNSW
indexes keyed by string IDs and optional opaque JSON metadata.
Wraps github.com/coder/hnsw v0.6.1 (pure Go, no cgo). New port
:3215 with /v1/vectors/* routed through gateway.
API:
POST /v1/vectors/index create
GET /v1/vectors/index list
GET /v1/vectors/index/{name} get info
DELETE /v1/vectors/index/{name}
POST /v1/vectors/index/{name}/add (batch)
POST /v1/vectors/index/{name}/search
Acceptance smoke 7/7 PASS — including recall=1 on inserted vector
w-042 (cosine distance 5.96e-8, float32 precision noise), 200-
vector batch round-trip, dim mismatch → 400, missing index → 404,
duplicate create → 409.
Two upstream library quirks worked around in the wrapper:
1. coder/hnsw.Add panics with "node not added" on re-adding an
existing key (length-invariant fires because internal
delete+re-add doesn't change Len). Pre-Delete fixes for n>1.
2. Delete of the LAST node leaves layers[0] non-empty but
entryless; next Add SIGSEGVs in Dims(). Workaround: when
re-adding to a 1-node graph, recreate the underlying graph
fresh via resetGraphLocked().
Cross-lineage scrum on shipped code:
- Opus 4.7 (opencode): 0 BLOCK + 4 WARN + 3 INFO
- Kimi K2-0905 (openrouter): 2 BLOCK + 2 WARN + 1 INFO
- Qwen3-coder (openrouter): "No BLOCKs" (4 tokens)
Fixed (4 real + 2 cleanup):
O-W1: Lookup returned the raw []float32 from coder/hnsw — caller
mutation would corrupt index. Now copies before return.
O-W3: NaN/Inf vectors poison HNSW (distance comparisons return
false for both < and >, breaking heap invariants). Zero-norm
under cosine produces NaN. Now validated at Add time.
K-B1: Re-adding with nil metadata silently cleared the existing
entry — JSON-omitted "metadata" field deserializes as nil,
making upsert non-idempotent. Now nil = "leave alone"; explicit
{} or Delete to clear.
O-W4: Batch Add with mid-batch failure left items 0..N-1
committed and item N rejected. Now pre-validates all IDs+dims
before any Add.
O-I1: jsonItoa hand-roll replaced with strconv.Itoa — no
measured allocation win.
O-I2: distanceFn re-resolved per Search → use stored i.g.Distance.
Dismissed (2 false positives):
K-B2 "MaxBytesReader applied after full read" — false, applied
BEFORE Decode in decodeJSON
K-W1 "Search distances under read lock might see invalidated
slices from concurrent Add" — false, RWMutex serializes
write-lock during Add against read-lock during Search
Deferred (3): HTTP server timeouts (consistent G0 punt),
Content-Type validation (internal service behind gateway), Lookup
dim assertion (in-memory state can't drift).
The K-B1 finding is worth pausing on: nil metadata on re-add is
the kind of API ergonomics bug only a code-reading reviewer
catches — smoke would never detect it because the smoke always
sends explicit metadata. Three lines changed in Add; the resulting
API matches what callers actually expect.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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