# Phase 0 Spike Report — Needle 2 prescreen & RustFS storage

> Date: 2026-08-16. Evidence from live testing in isolated environments
> (`/tmp/opencode/needle-spike`, ephemeral `rustfs/rustfs:latest` container).
> Gates the Phase 1 (extraction refactor) and Phase 2 (prescreen stage) plans.

## Spike 1: cactus-needle (Needle 2) for RU contract prescreen — **NOT VIABLE**

### What was verified

- `cactus-needle==2.0.5` is real (Cactus Compute, Apache-2.0, first release
  2026-08-10). Installs cleanly on Python 3.13. The spec's claims hold:
  14MB engine (fetched once from HF, cached offline), `needle.extract(text,
  PydanticModel)`, calibrated `confidence` on responses, `.cact` LoRA
  fine-tuning pipeline. Note: PyPI package name is **`cactus-needle`**
  (`import needle`); bare `needle` on PyPI is an unrelated dead 2017 CSS
  testing tool.
- Engine session RAM measured at 37.8MB (simple schema) to 119.7MB (larger
  schema) — fine for a 256M container. Python deps pull the JAX/Flax/optax
  stack (~200MB+ image impact) because fine-tuning support ships in the core
  dependency list.

### Results (base weights, `buffer_size` default)

| Case | Result |
|---|---|
| EN invoice (README example) | Perfect extraction, `confidence=0.9484` |
| EN off-topic sentence | Correctly refused: empty call `[]`, `confidence=0.7427` |
| RU contract, 2.5K chars | **Total hallucination**: parties → "Supplier"/"Supplier", amount → 12.0 USD (real: 1 234 567,80 RUB), dates → 2024 defaults. `confidence=0.0` |
| RU contract, 43K chars | Same failure mode, different hallucinations. `confidence=0.0` |
| RU garbage text | **Not refused** — fabricated "Party A/Party B/150 USD". `confidence=0.0` |

### Verdict

The base model is **English-centric; it does not understand Russian**. The
calibrated confidence head behaves correctly (0.0 = "I can't read this"), so a
naive deployment would have been *safe* (100% → manual_review) but useless.

Fine-tuning cannot rescue this for v1:

1. Calibrated confidence is **disabled on tuned weights** (reports `None`) —
   and the spec's entire routing design hinges on confidence gating.
2. The model failed even trivial verbatim copy tasks (could not copy
   «ООО «Ромашка»» from adjacent text) — this is tokenizer/training coverage,
   not prompt tuning.
3. Building a RU legal extraction dataset + LoRA pipeline is its own project.

### Plan adjustment (Phase 2)

- `worker-prescreen` ships with a **deterministic regex+pydantic extractor**
  instead of Needle: RU/BY contract boilerplate is highly templated
  («договор поставки», «именуемое в дальнейшем», «сумма договора составляет
  N рублей», «неустойка», «арбитражный суд», DD.MM.YYYY ranges). Zero marginal
  cost, no hallucination, p95 ≈ ms. Absence of a match = `None` →
  `manual_review`, which matches the routing philosophy.
- `confidence_score` is redefined as a deterministic **field-coverage score**
  (fraction of target fields extracted), not model calibration. Router
  thresholds operate on coverage.
- `needle_client.py` / `model_weights` / `NEEDLE_*` env are dropped from the
  plan; keep `prescreen_results.extractor_version` for future engine swaps.
- Optional fast-follow (not v1): small-LLM prescreen via the existing
  `core/llm` port for fields regex missed.
- Revisit Needle only if/when a multilingual or RU-tuned base ships with
  calibration intact.

## Spike 2: RustFS as MinIO alternative — **VIABLE, but stay on MinIO for now**

Tested with the project's own `MinioStorage` adapter (minio SDK) against
`rustfs/rustfs:latest`, single node, named volume.

| Check | Result |
|---|---|
| Health (`/minio/health/live`) | 200 — MinIO-compatible probe works |
| bucket create/exists, put/get/stat/delete | OK (incl. Cyrillic UTF-8 payloads) |
| `set/get/delete_bucket_lifecycle` (ILM config API) | OK — rule round-trips |
| **ILM expiration behavior** (`RUSTFS_ILM_DEBUG_DAY_SECS=2`, rule days=1) | **Object under `users/` purged in ~10s; control object outside prefix untouched** |
| Perf (4KB put+get ×20) | ~2.0ms/op |
| Docker ergonomics | Runs as UID 10001 — bind mounts must be chowned; named volumes are the easy path |

### Verdict

The critical blocker (152-ФЗ TTL purge via ILM) **works in practice** — the
"Under Testing" label upstream refers to CI gating, not absence. Remaining
reasons to keep MinIO as the default for production:

1. Project is weeks old (1.0.0-rc era); lifecycle, distributed mode, and KMS
   are all still marked "Under Testing" upstream.
2. **SSE migration trap**: objects written by MinIO with SSE-S3/KMS/C are not
   readable by RustFS — a later migration requires re-putting objects through
   the app (we run SSE-S3=off in dev, on in prod per `S3_SERVER_SIDE_ENCRYPTION`).
3. No operational history; MinIO is battle-tested for this exact compose setup.

Because everything S3-shaped is already behind `core/s3/port.py`, switching
later is a compose + env change, not a code change. Action item: revisit when
RustFS marks Lifecycle + KMS GA (tracked in ARCHITECTURE notes, not code).

## Phase gate outcomes

- **Phase 1 (extraction refactor): GO** — unchanged.
- **Phase 2 (prescreen stage): GO with amendments** — regex extractor instead
  of Needle; coverage-based confidence; no needle deps/env; conservative
  routing (`PRESCREEN_AUTO_APPROVE=false` default) as already planned.
- **Storage: no change** — MinIO stays; RustFS is a credible fast-follow.