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MiMo-V2.6-Flash-RL-NVFP4

NVFP4 weight-quantized build of XiaomiMiMo/MiMo-V2.6-Flash-RL (commit 5711b268) for NVIDIA DGX Spark / GB10 (SM121) serving with SGLang (nightly 582389ce), TP=2 across two GB10 nodes.

Preferred serve profile: EAGLE MTP, 3 steps and 4 draft tokens, advertised context 524288, multimodal on. The DFlash block-8 row is an earlier serve. It is not the preferred profile.

Quantized by r0b0tlab. Independent implementation from upstream APIs only (NVIDIA ModelOpt 7159c01d, SGLang 8ab21c8a); no third-party quantization code or configs were used.

What's inside

Component Choice
Routed experts (MoE) NVFP4 (E2M1, block 16), converted from vendor MXFP4
Attention / dense linears NVFP4 with per-tensor FP8 scales where beneficial, BF16 elsewhere
KV cache FP8 (e4m3) with calibrated per-layer scales (kv_scales.json, SGLang QuantParamSchema; identical across TP ranks)
Activations per-tensor scales, peer_headroom policy (calibration-gated, see below)
Draft weights in the checkpoint DFlash fused 5-layer KV, unchanged from base. Not the preferred serve.
Preferred serve EAGLE MTP, 3 steps, 4 draft tokens, top-k 1, draft window 4096

Non-quantized aux weights (audio tokenizer, vision tower, nextn) remain BF16: 555 tensors.

hf_quant_config.json is included for engine auto-detection (hybrid FP8+NVFP4 mode).

Quality vs vendor checkpoint (measured, same harness/hardware)

Check Vendor MXFP4 This NVFP4 Verdict
NLL, 32,768 calibration tokens 1.3360 1.3387 Δ 0.0027 (< 0.05 gate) PASS
GSM8K-200, thinking off, temp 0 0.970 0.965 Δ 0.5 pt PASS
Decode throughput, bs=8, 2×GB10 52.0–60.8 tok/s (median 56.9) 63.7–73.5 tok/s (median 69.1) +21%
Checkpoint integrity — 0 mismatched tensors across 24 shards (36,096 quantized linears) PASS

GSM8K harness: chat endpoint, enable_thinking: false, temperature 0, 512 max tokens, #### <answer> extraction.

Provenance / method (summary)

  1. Calibration: 512×512 rows from internal corpus (NLL 1.5317 post-cal). Per-layer activation-scale policy peer_headroom selected by runtime-style QDQ scoring (nvfp4_act_relmse); gate: chosen ≤1.10× best candidate per layer (worst observed 1.056).
  2. Conversion: MXFP4 routed experts → NVFP4 (E2M1/block-16, FP8 block scales), adapted from ModelOpt DeepSeek example APIs. Output verified bit-exact where expected: 0 non-exact blocks among 9.46B/9.46B compared.
  3. KV scales: per-layer min/max calibration → kv_cache.scaling_factor[tp_rank][layer_idx]; both ranks identical by construction.
  4. Serving: the preferred profile is EAGLE MTP, 3 steps and 4 draft tokens, on SGLang nightly 582389ce. The earlier FINAL3-500k serve was DFlash block 8, with --tp-size 2 --ep-size 2 --moe-runner-backend marlin --mem-fraction-static 0.90, --context-length 524288, --tool-call-parser mimo, and SWA ratio 0.02. It skips allocating unused NVFP4 *_blockscale_swizzled tensors on the Marlin path.

The package ghcr.io/r0b0tlab/sglang-mimo26-env is public. Preferred tag 20260922-582389ce-mtp-mm (digest sha256:84857252a1a9b4196702154ae38eb3cfafdf4cd832795eba18ac2772f8a83f1e). The FINAL3-500k serve used parent 20260922-582389ce-marlin-skip (digest sha256:42737e9dfd3731072c8fd3d65d479ba03381e0e0cb5e171cbab632a8bddeb507). Tag 20260922-582389ce is torchcodec only and does not contain the Marlin skip. Not on Docker Hub.

Campaign scripts, evidence, and logs: https://github.com/r0b0tlab/mimo26-nvfp4-sm121

r0b0bench systems, FINAL3-500k (2026-09-26)

One r0b0bench run --profile systems on the 2×GB10 TP=2 serve. Advertised max_model_len 524288. Think-off (enable_thinking=false, thinking=false). Harness 1.0.0rc2. All seven lanes passed. Infrastructure errors 0. invalid_for_publish false.

Ledger: mimo26-nvfp4-final3-500k-systems-20260925

Lane Result
Canary PASS, 5/5, including the tool-call check
BFCL multi-turn 114/200 (0.570)
BFCL AST multiple 71/200, parallel 101/200, parallel_multiple 39/200, micro 211/600 (0.352)
Latency TTFT 254 ms, inter-token 159 ms
Concurrency aggregate c1 50.2, c2 66.0, c4 91.6, c6 159.6 tok/s
Throughput C1 decode median 15.48 tok/s. Prefill median 16,535 tok/s at 22,771 prompt tokens
NIAH 3/3 exact at depths 131008, 262016, 471628

The 15.48 tok/s figure is single-stream chat decode. It is not the bs=8 aggregate in the table above (median 69.1 tok/s).

Disclosures:

  • Seven multi-turn rows were regenerated after 1200s client timeouts. This invocation scored the repaired 200-row file and did not regenerate the other 193.
  • The package lane summary had pointed all three AST categories at the parallel_multiple file and reported micro 0.195. The numbers above are the official score-file headers from the same run.
  • Q200v2 text-180 was kept from the earlier FINAL3 serve, not remeasured on the MTP boot. Think-off, workers 1, max tokens 8192, 180/180 stopped, longest completion 5844. GSM8K 78/80, HumanEval 38/40, IFEval 35/40. Independent review of the 20 hard_reasoning answers is 17/20. Failures: hard-04 answered 19208/715, while the 4x4 Hilbert determinant is 1/6048000; hard-12 claimed every graph of minimum degree 2 has a cycle, which is false for an infinite 2-regular graph; hard-16 did not give the uniform-lift height 1/(2π). Total 168/180. Not a core-subset quality claim.
  • On that same FINAL3 boot, the serial quality run produced 51,977 completion tokens in 2,254.2 seconds, 23.06 client tok/s including prefill. A separate 1024-token harness on that boot, truncated at the token cap, measured concurrency-1 aggregate 27.25 and 26.02 tok/s (per-request decode 27.51 and 26.25) and concurrency-2 aggregate 32.39 and 34.08 tok/s. That harness is not the quality-run rate and not the MTP systems throughput.
  • Memory on the Q200 boot: weights 84.436 GB, KV cache 6.575 GB, startup available 9.166 GB, full-token pool 1,044,581, SWA pool 20,891. Graph reservations were target-verify 1.495 GB and draft-decode 0.134 GB; prefill, decode, and draft-extend graphs were 0. KV is the calibrated FP8 pool. Host available at admission was 4.84 GiB and 8.71 GiB, above a 4 GiB floor.

Systems, MTP-500k-mm, 2026-09-27

Think-off. Advertised context 524288. EAGLE, 3 steps, 4 draft tokens, top-k 1, draft window 4096, --mem-fraction-static 0.90. Multimodal pins: mimo reasoning parser, mimo tool parser, Triton vision attention, torchvision. Draft-extend CUDA graphs on. One full systems profile. Not a core-subset quality claim.

Lane Result
Canary 5/5
BFCL-MT 117/200 (0.585)
BFCL-AST multiple 70/200
BFCL-AST parallel 103/200
BFCL-AST parallel_multiple 42/200
BFCL-AST micro 215/600 (0.358)
Latency, mean TTFT 276.5 ms, ITL 139.6 ms, end-to-end 4.12 s
Concurrency, aggregate tok/s 26.7 / 43.5 / 66.6 / 93.2 at 1, 2, 4, 6
Throughput decode median 17.31 tok/s; prefill median 17,941 tok/s at 22,771 prompt tokens
NIAH 3/3 exact at 131008, 262016, and 471628

A separate 1024-token harness on the same boot, not the systems c1 number above, measured decode 24.1 / 23.6 / 15.6 tok/s on short code, medium code, and prose.

The measured process used the parent image with the loader and draft-extend window-index files bind-mounted. Preferred tag ghcr.io/r0b0tlab/sglang-mimo26-env:20260922-582389ce-mtp-mm (sha256:84857252a1a9b4196702154ae38eb3cfafdf4cd832795eba18ac2772f8a83f1e) is public and copies those same three files. It was not the process that served this suite. Q200 was not remeasured on this serve.

Ledger: https://github.com/r0b0tlab/r0b0bench/blob/b35bb28ca058e74eca5642a732c0d791481a7f36/results/entries/mimo26-nvfp4-mtp-500k-mm-systems-20260927.json

Max-performance review + Q200v2 protocol, 2026-09-30

A 12-cell one-variable-per-boot ladder tested every remaining serve-flag lever (speculative geometry, kernel fusions, NCCL tuning, KV splits, chunk size, scheduler conservativeness, stream interval, torch.compile) against the preferred MTP-500k-mm-graph serve. No cell won on all c1 lanes; the preferred profile is confirmed optimal for this build. torch.compile fails at capture on this driver/kernel pair (triton illegal memory access) — do not retry.

Q200v2 protocol on that serve, think-off (2026-09-30):

Measure Result
GSM8K-200 192/200 (0.960), 0 truncations, 0 transport errors
Concurrency aggregate c1 21.6 · c2 38.0 · c4 47.7 · c8 69.2 tok/s
Per-stream decode 21.9 / 19.4 / 12.4 / 9.0 tok/s (TTFT 0.57–1.48 s)
Spec accept length 3.38–3.47 at every level
Per-request e2e p50 23.5 tok/s over 200 answers (mean 209 tokens)
Load telemetry 26 W mean, 47–56 °C, GPU util ~79%, host MemAvailable ≥ 10.9 GiB

Evidence and the full cell table live in the campaign repo: results/maxperf/ (FINAL-VERDICT.json, MORNING-REPORT.md, 12 CELL-*.json), results/e2e/FINAL3-concurrency.json, results/q200/FINAL3-nothink.jsonl.

Known limits

  • NVFP4 KV cache is not supported by SGLang 582389ce for this model's hybrid-SWA pool (torch.zeros(Float4_e2m1fn_x2) → NotImplemented); FP8 KV + calibrated scales ships instead. Evidence in the campaign repo (results/nvfp4_kv_verdict.md).
  • moe_runner=auto selects triton on this build, which cannot consume MiMo's packed MXFP4 experts; marlin is required (and is the native SM121 path).
  • The published FINAL3-500k and MTP-500k-mm serves both advertise max_model_len 524288, not the base model's 1,048,576. NIAH above is at 25/50/90 of that advertised length.

Credits

  • Base model: XiaomiMiMo/MiMo-V2.6-Flash-RL, MIT. XiaomiMiMo is the base-model author.
  • Quantization: r0b0tlab, using NVIDIA Model Optimizer public APIs at 7159c01d. No third-party quantization code or configs were copied.
  • Serving: SGLang, Apache-2.0, nightly 582389ce, with FlashInfer 0.6.18, PyTorch 2.13.0+cu130, and Marlin MoE kernels as shipped in that nightly.
  • Preferred speculation: SGLang's EAGLE implementation. DFlash weights remain in the checkpoint for the earlier lane.
  • modelopt_quant.py in the runtime image is adapted from the vLLM project, Apache-2.0.
  • Systems harness: r0b0bench, MIT. BFCL scores use the Berkeley Function-Calling Leaderboard tasks.

License

Base model is MIT (XiaomiMiMo). This quantization is provided under the same MIT license. XiaomiMiMo is credited as the base-model author; r0b0tlab claims only the quantization deltas described above. Campaign repo: MIT for original work, Apache-2.0 retained on upstream patch files. See https://github.com/r0b0tlab/mimo26-nvfp4-sm121

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