.agents/memory/2026-02-27-predictor-bug-fix-reject-mismatched-candidate-feat.md

2026-02-27 Session Notes

Predictor Bug Fix: Reject Mismatched candidate_features

Nicholai implemented a fix to eliminate silent data corruption in packages/predictor/src/main.rs (line 79). The code previously silently replaced mismatched candidate_features vectors with all-zero values when their length didn't match candidate_ids. This masked upstream bugs and degraded ranking quality without signaling the problem.

The fix changed the logic to:

1. If candidate_features is empty → zero-fill (correct, feature not provided)
2. If length matches candidate_ids → use as-is (correct, provided correctly)
3. If provided but length mismatches → return explicit error (fixed from silent zero-fill)

This brings consistency with how candidate_embeddings and candidate_texts already handle the same scenario (returning explicit length-mismatch errors). The change was applied via Edit tool and preserves the empty-features fallback behavior while fixing the dangerous silent-corruption case.