(plan) system review and break down plans

tasks/M2.1-embeddings-client.md

@@ -0,0 +1,86 @@
+# M2.1 — Embeddings client
+
+| Field | Value |
+|---|---|
+| Phase | M2 — Projections |
+| Size | S — under 1 day |
+| Status | ⬜ Not started |
+| Flags | — |
+| Spec | inlined below |
+| Blocks | M1.1 |
+
+## Goal
+
+Turn text into 768-dim vectors, batched, against the gateway's TEI endpoint.
+
+## Facts (inlined — no spec read needed)
+
+```
+POST /v1/embeddings
+{"model":"nomic-ai/nomic-embed-text-v2-moe","input":["..."]}
+-> {"object":"list","data":[{"embedding":[...768 floats...]}],"usage":{...}}
+```
+
+**768 dimensions**, probed and confirmed. It is the `vector(768)` in the schema
+and in the HNSW index; a model swap is a schema migration, not a config change.
+
+**Batch limit is 32.** Verified: 1200 inputs returned
+`{"message":"batch size 1200 > maximum allowed batch size 32","code":413}`.
+Chunk the input list accordingly.
+
+This route currently has **no auth** — no `konghq.com/plugins` annotation, so
+`model-key-auth` never attaches. Send the `apikey` header anyway: the route
+should be fixed, and a client that only works while auth is broken breaks when
+it is fixed.
+
+Bodies here are large (many texts × long strings) and the Kong buffer is 16m, so
+batching also keeps requests well inside it.
+
+## Steps
+
+1. `EmbeddingsClient::embed(texts: &[String]) -> Result<Vec<Vec<f32>>>` in `mem-llm`.
+2. Split into batches of ≤32, preserving input order in the output.
+3. Assert every returned vector is exactly 768 long; a mismatch is an error
+   naming the model, not a silent pad or truncate.
+4. Reuse M1.1's client config: `apikey` header, retry on 5xx only, generous
+   timeout.
+5. `embed_one` convenience wrapper.
+
+## Acceptance
+
+- 100 texts return 100 vectors in input order.
+- Every vector is 768-dim.
+- A dimension mismatch errors loudly.
+
+## Verify
+
+**Harness:** `wiremock` offline, one `#[ignore]` live test.
+
+**Integration test** — `tests/it_embeddings.rs`:
+1. `a1_batches_at_32` — 100 inputs produce exactly 4 requests.
+2. `a2_order_preserved` — mock returns identifiable vectors; assert output order
+   matches input order across batch boundaries.
+3. `a3_dimension_asserted` — mock returns a 512-dim vector; assert an error
+   naming the model.
+4. `a4_apikey_sent` — assert the header is present even though the route does not
+   require it.
+5. `a5_live_dims` — `#[ignore]`; real gateway, assert 768.
+
+**Command:** `cargo test -p mem-llm embeddings` (add `-- --ignored` for a5)
+
+**False pass:**
+- Testing with ≤32 inputs. The batching path never runs and order-across-batches
+  — the thing most likely to be wrong — is never exercised.
+- Trusting the response order within a batch without asserting it. Assertion 2
+  must use distinguishable vectors, not a length check.
+
+## Traps
+
+- Hardcoding 768 in three places. Put it in one constant that the schema
+  migration also references, so a model change is one edit and one migration.
+- Assuming no auth is needed because it currently works without a key. That route
+  is missing its plugin annotation, which is a bug scheduled to be fixed.
+
+---
+
+Background: [DESIGN.md](../DESIGN.md) — Verified facts, pgvector