LFM2.5 2.6B ยท Calibrated GPTQ MXFP4

An activation-calibrated, native-format MXFP4 conversion of LiquidAI/LFM2.5-2.6B. This is not a naive round-to-nearest repack: its 166 quantized linear layers were solved sequentially with activation Hessians and native E8M0 scale search.

Status: ready for MLX deployment and integrity-verified. AIME25, IFBench, LiveCodeBench v6, and every locally runnable BFCL v4 category have complete, receipted results. Multi-IF is being rerun with final-answer-only response handling and is not reported as a final score.

At a glance

Property Value
Value format MXFP4 E2M1
Scale format E8M0, one scale per 32 weights
Solver Sequential GPTQ with native-scale search and non-regression fallback
Quantized layers 166 linear layers
Preserved precision Tied embedding/output head in BF16
Calibration 128 ร— 1,024-token disjoint windows; 131,072 tokens total
Damping 0.01
Packed biases None

Held-out quality check

WikiText-2 test, fingerprint a46124b21ac53738, using 32 ร— 512-token predictions:

Checkpoint Perplexity Relative to BF16
BF16 source 48.3791 baseline
Native MXFP4 RTN 55.3957 +14.50%
GPTQ MXFP4 48.4551 +0.157%

GPTQ reduces perplexity by 12.529% versus the matched native MXFP4 RTN control while remaining within 0.157% of BF16 on this check.

Completed benchmark results

Completed benchmark results

Benchmark Scope GPTQ MXFP4 Liquid published reference
AIME25 30 problems ร— 4 samples 26.67% 51.87%
IFBench 300 examples 47.33% 59.17%
BFCL v4 20 runnable categories; 4,906 scored examples 43.06% 56.88%
LiveCodeBench v6 1,055 problems 51.47% 59.41%

AIME25 and IFBench use the pinned Liquid OpenBench harness, temperature 0.6, 32,768 maximum output tokens, and matched local seed 42. Liquid did not publish its seed. IFBench evaluates the visible answer after the model's </think> boundary; the corrected scorer was checked by reproducing the original raw score exactly before applying that boundary. The BFCL score is the official partial-overall produced by the pinned BFCL harness; web_search_base and web_search_no_snippet are excluded because they require unavailable SerpAPI credentials. The Liquid BFCL reference includes those categories, so it is context rather than an exact matched control.

Runtime

The checkpoint uses native MLX block-scaled tensors and runs with current MLX and mlx-lm on Apple Silicon.

mlx_lm.generate \
  --model RESMP-DEV/LFM2.5-2.6B-GPTQ-MXFP4-calibrated \
  --prompt "Explain why calibrated quantization can outperform naive RTN."

For the CUDA quality campaign, the calibrated tensors were exactly dequantized, restored to Hugging Face LFM2 convolution layout, stored as BF16, and served by vLLM 0.26.0. This evaluates the calibrated checkpoint values under BF16 CUDA accumulation; it is not native packed-MXFP throughput or bit-identical MLX accumulation. A throughput smoke test on one RTX PRO 6000 Blackwell measured 1,410.6 aggregate output tokens/second at eight concurrent 64-token requests.

Reproducibility and integrity

  • Base-model revision: 403f92a2c4d78f2505f874b8b1b713cc0c9b9ae8
  • Calibration snapshot: private prerelease commit 2604ec2a4df3756c155648451364cd49c9dbb189; all eight non-card/config artifacts, including both weight shards and the tokenizer, are byte-identical to the public revision above
  • Calibration seed: 17
  • Calibration token SHA-256: b685dd74f7732611b78696f108ba50acbccb8905cb4f72ce1b49575b1b85858f
  • Layer-set SHA-256: cf1654096a8d86bb4dbaf37412adc6992a3767fe6b9114a788764ea4d98b2a65
  • model.safetensors SHA-256: a57eda09de8c9531007c2858d32086dd0cd641cc7bb94e02a3c746d8cc793329

Fresh loading and generation succeeded. All packed weights and scales were independently compared byte-for-byte with the CUDA calibration receipt. See GPTQ_RECEIPT.md for the compact provenance record.

Evaluation scope

Complete: AIME25, IFBench, LiveCodeBench v6, and the 20 locally available BFCL v4 categories. Re-evaluation in progress: Multi-IF with final-answer-only response handling. IFStruct and the remaining Liquid release rows are not yet complete. Disclosure- or credential-gated rows remain separate rather than being approximated silently.

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