## Summary
`reindex_embeddings` crashed with `ModuleNotFoundError: No module named 'networkx'` when Unstructured hit spreadsheet files via `partition/xlsx.py`. Reindex clears Chroma first, so a mid-run crash leaves an empty/partial vector store.
### True fix
Depend on **`unstructured[xlsx]==0.18.21`** (not bare `unstructured`). That extra pulls the required spreadsheet partition deps: `networkx`, `msoffcrypto-tool`, `xlrd` (plus openpyxl/pandas already present).
### Resilience
Also catch per-document ingest failures so one corrupt/unsupported file cannot abort a full rebuild after Chroma was cleared. Successful files still ingest; failures are logged.
## Test plan
- [x] CI / unit tests on this PR
- [ ] Merge + redeploy image to all hosts
- [ ] On each host: `docker compose -p chat_backend_prod exec web bash -lc 'cd /app/llm_be && SKIP_RAG_INIT=1 uv run python manage.py reindex_embeddings'`
- [ ] Confirm non-zero chunk count and no `networkx` / `msoffcrypto` / `xlrd` import errors
## Ops workaround (running containers only, until deploy)
```bash
uv pip install 'unstructured[xlsx]==0.18.21'
cd /app/llm_be && SKIP_RAG_INIT=1 uv run python manage.py reindex_embeddings
```Reviewed-on: #66
## Summary
- Closes Phases 1–3 of [#62](#62) (Phase 4 eval harness left for a follow-up).
- **Accuracy:** Retrieval is decided every turn (`GroundingDecider`, fails open). `FAST` no longer skips search — it only selects `OLLAMA_MODEL_FAST`. Search failures surface an explicit error instead of hallucinating from parametric memory.
- **Search:** Pluggable `services/search/` with **SearxNG primary** + DDGS failover, ranking/dedupe/rumour filtering, numbered dated source blocks, citations persisted on `Prompt.citations` and emitted as `{"v":1,"type":"citations",...}` after stream end.
- **Models:** Role-scoped `OLLAMA_MODEL_THINKING` / `_FAST` / `_UTILITY` / `OLLAMA_EMBED_MODEL=nomic-embed-text`, configurable `num_ctx`, real model name on `PromptMetric`, `reindex_embeddings` management command + loud embedding-dimension mismatch.
## SearxNG (ops)
See README **SearxNG** section. Short version: run `searxng/searxng` on the GPU host, enable `json` in `settings.yml`, set `SEARXNG_BASE_URL=http://10.0.0.128:8080` in prod/beta secrets, open `:8080` on the LAN firewall like Ollama.
## Test plan
- [x] `SKIP_RAG_INIT=1 python manage.py test chat_backend.tests` — 442 OK (6 skipped)
- [ ] Deploy beta with updated secrets (`OLLAMA_MODEL_*`, `OLLAMA_EMBED_MODEL=nomic-embed-text`, `SEARXNG_BASE_URL`)
- [ ] After embed change: `python manage.py reindex_embeddings`
- [ ] Verify `did Taylor Swift get married` in FAST and THINKING returns grounded answer with citations frame
- [ ] Kill SearxNG and confirm factual turns return search_unavailable (not Joe Alwyn hallucination); non-factual chat still worksReviewed-on: #65
westfarn