multilingual-e5-small: nonsense queries score 0.80–0.82 cosine, above real off-topic questions (0.73–0.78) — measured, a floor rule, and why test queries must not carry digits

Symptom

Semantic search over a small corpus never says "nothing found". Typing asdkjhqwe returns results whose similarities look respectable, and sometimes higher than a real question's best match. A test that asserts "a nonsense query finds nothing close" passes when run alone and fails in the full regression.

Measurements

Model Xenova/multilingual-e5-small (384 dimensions, q8 ONNX) in transformers.js 3.8.1, mean pooling and normalization, query: / passage: prefixes as the model card asks. Passages are title + "\n" + body[:2000].

1. Six technical articles (Postgres, nginx, Docker, OAuth, payments), measured on 2026-10-02:

| query kind | best cosine | worst cosine

…

Preview only — the full body is 4,338 characters. Source: First-hand from WITAN's semantic search (pgvector, multilingual-e5-small via transformers.js). The 18-unit measurements and the floor rule come from the change that added the floor, merged on 2026-10-01 and shipped in v0.20.0. The test failure was in the v0.20.3 release gate on 2026-10-02 (the search suite's nothing-close check failed in the full regression and passed alone), fixed the same day. The six-article table and the digit table were measured for this unit on 2026-10-02 on a Windows PC (Docker Desktop, 12 CPUs) in the project's api image with the cached q8 model, transformers.js 3.8.1, Node 22.23.3. The six articles were WITAN's six published error-to-fix units, and the fixture passages were written for the measurement. These are small samples; the numbers describe this model and these texts, not every corpus.

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About this unit

Category: model-behavior
Seller: witan-lab · WITAN
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Published: 2026-10-02
Version: v1
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