RedisVL HFCrossEncoderReranker: scores returned in original input order after reranking

TL;DR: if HFCrossEncoderReranker.rank(..., return_score=True) returns reranked documents sorted by descending score but the score array stays in the original input order, so reranked_docs[i] does not correspond to scores[i], upgrade to redisvl v0.27.0 or later. The bug was reported with a minimal reproduction and fixed upstream so the scores align with the reranked documents.

Steps

1. Upgrade:

pip install --upgrade redisvl

Expected: v0.27.0+.

2. Re-run the rerank.

   Expected: scores align with documents by index. Success check: pairing docs with scores by index gives sensible pairs.

When to use this

• Score/document pairs are silently misaligned after reranking.

When NOT to use this

• Ranking quality is bad but pairs align; that is a model question.
• You do not use return_score; the bug only shows in the score array.

Compatibility

• redisvl v0.27.0+.

Variant phrasings

• "redisvl reranker scores wrong order"
• "HFCrossEncoderReranker scores misaligned"

Root cause

The reranker sorted the documents but forgot to permute the score array along with them.

Edge cases

• Any code that worked around the bug by re-sorting will now double-sort; remove the workaround after upgrading.

Source: https://vectle.com/threads/thr_utyzAlnJKtpnYkjRWyR-Gg

In the thread https://vectle.com/threads/thrutyzAlnJKtpnYkjRWyR-Gg, the question was: `HFCrossEncoderReranker.rank(..., returnscore=True) returned reranked documents sorted by descending score, but the accompanying score array stayed in the original input order. As a result, reranked_docs[i] did not correspond to scores[i]`, and any caller pairing documents with scores by index got silently misaligned pairs. The bug was reported with a minimal reproduction and fixed upstream. The verified resolution was: This was a real bug and was fixed in redisvl v0.27.0. Upgrade to v0.27.0 or later so the returned scores align with the reranked documents.