Frozen result summary
The representation gate required minimum aligned cosine of at least 0.99 against the matching BF16 reference, with no Top-1 or Recall@5 regression, MRR loss no worse than 0.01, and no more than two changed query ranks.
All 30 full-dimensional MLX checkpoints retained 24/24 Top-1 retrieval. The best result among Q, oQ, and oQe at each nominal bit width was:
| Family | Best Q4 | Best Q6 | Best Q8 |
|---|---|---|---|
| Qwen3 0.6B | oQ4e 0.943953 — fail | oQ6e 0.987972 — fail | oQ8e 0.998660 — pass |
| GTE-Qwen2 1.5B | oQ4e 0.977315 — fail | oQ6e 0.998114 — pass | oQ8e 0.999547 — pass |
| Qwen3 8B | oQ4e 0.983151 — fail | oQ6e 0.998220 — pass | oQ8e 0.999568 — pass |
All 54 mixed BF16/quantized query-index directions retained 24/24 Top-1. Applying a threshold calibrated once on BF16 without retuning changed decisions; the largest break was five false negatives out of 24 for Qwen3 0.6B standard-Q4 queries against the BF16 index.
The CUDA-native bitsandbytes controls are not MLX format equivalents:
| Family | CUDA format | Minimum cosine vs same-path CUDA BF16 | Top-1 | Gate |
|---|---|---|---|---|
| Qwen3 0.6B | INT8 | 0.99257 | 1.0 | pass |
| Qwen3 0.6B | NF4 | 0.90902 | 1.0 | fail |
| GTE-Qwen2 1.5B | INT8 | 0.98239 | 1.0 | fail |
| GTE-Qwen2 1.5B | NF4 | 0.89340 | 1.0 | fail |
| Qwen3 8B | INT8 | 0.99114 | 1.0 | pass |
| Qwen3 8B | NF4 | 0.97268 | 1.0 | fail |
GTE-Qwen2 1.5B is excluded from cross-runtime representation trends. Its root-packed and direct CUDA BF16 vectors diverged, and direct CUDA BF16 also diverged from local MLX BF16. Its quantized CUDA comparisons are interpreted only against the direct same-loading-path CUDA BF16 reference.
These are deterministic measurements on one frozen 24-pair smoke set. They do not establish universal embedding quality or replace broader retrieval, clustering, similarity, threshold, and batching evaluations.