# MiMo-V2.6-Flash-MOPD on vLLM+r39 — the 2026-09-28 experiment (PARKED → RESOLVED)

**UPDATE 2026-09-28 ~19:30, 4 hours later — RESOLVED by the ecosystem, not by
us.** The four walls below were exactly the gap between our r39 pin (last
merge 2026-09-17) and `local-inference-lab/vllm@dev/karmic-kraken` (2026-09-22
series: MiMo aux loading, block-outermost KV layouts for mixed page sizes,
b12x non-causal attention, eagle3 language-model unwrap — plus lazy mxfp8
guards). The lane now runs `eugr/spark-vllm-b12x:latest` (the arm64 nightly
CI-built from that branch, v0.1.dev21546+g502d6cb5a) with the lab's own
`serve-mimo26-flash.sh` flag set mirrored (b12x linear/moe, block 128, BF16
KV). Boot reached the wire first try: KV pool 8.57M tokens, DFlash graphs
captured on B12X, API serving `mimo-v2.6-flash`. Our wrapper image
(`docker-images/mimo26-spark-vllm`) and its two patches are RETIRED —
upstream shipped the equivalents; delete the dir when the lane stabilizes.

Lane: `recipes/mimo26-flash-mopd-4x-vllm` + image `docker-images/mimo26-spark-vllm`
(thin FROM wrapper on `jovian-judgement:r39-glm53`, two anchor patches) —
historical, kept for the record.

**Verdict for r39: dead end.** Every layer of the vLLM DFlash path had to be
forced onto a fork that was qualified for GLM-5.3, not MiMo, and each boot
revealed one more incompatibility. None were ours to fix cleanly:

1. **EAGLE3 hook vs Omni wrapper** — MiMo-V2.6 resolves to
   `MiMoV2OmniForCausalLM` (mm wrapper); `set_eagle3_aux_hidden_state_layers`
   isinstance-checks the OUTER class and raises. Fixable (and fixed) with a
   language-model fallback patch; the protocol's own method unwraps the same
   way. Patched, works:
   `"Eagle3 interface resolved on MiMoV2FlashForCausalLM inside MiMoV2OmniForCausalLM"`,
   aux layers (1,12,24,36,48) taken from the draft config.
2. **B12X rejects non-causal attention** — DFlash's block-diffusion draft runs
   non-causal; b12x in r39 declares it unsupported. Workaround: draft on
   `TRITON_ATTN` (target keeps B12X). Works, draft loads (2.7 GB, mask
   embedding loaded).
3. **`ModelOptMxFp8LinearMethod` ImportError** — qwen3_dflash.py hard-imports
   a class r39's modelopt doesn't ship (fork predates it). Patched to a
   None-tolerant getattr (bf16 draft unaffected).
4. **KV-layout wall (fatal):** during cudagraph-memory profiling,
   `validate_kv_cache_layout` refuses: *"KV cache layout LBNHC cannot express
   this model's mixed page sizes ([131072, 163840]); set
   VLLM_KV_CACHE_LAYOUT=BLHNC"*. The hint is env-only, but BLHNC is a
   backend-declared-layout question — b12x in r39 declares LBNHC only. This
   is the architecture mismatch the whole experiment kept routing around:
   **the MiMo hybrid stack (SWA-128 + 9 GA layers, different page sizes per
   group) needs a vLLM/b12x generation qualified for it; r39 is not.**

## External intel (2026-09-28)

* `local-inference-lab/lil-catalog` MiMo DFlash entry: "implemented; runtime
  qualification unverified" — they never ran it either.
* madeby561/vllm `mimo-v26-flash-b12x-20260923-rc4`: MiMo RL + b12x + FP8 KV +
  DFlash-7, with adaptive verification — but **linux/amd64 only** (RTX 6000
  Pro). Not runnable here; its compose is a good flag corpus
  (`enable_adaptive_verification`, `kv_cache_dtype: fp8` for target+draft,
  `--max-num-scheduled-tokens 2048`, `prefill-compute-share`, `BLHNC`-class
  layouts would all apply if a Spark-native equivalent appears).
* `eugr/spark-vllm-b12x` publishes arm64 nightlies daily (latest 2026-09-28)
  — first candidate when someone asks whether MiMo landed there.

## Status now (2026-09-28 late)

1. DONE: lane switched to `eugr/spark-vllm-b12x:latest` nightly; boot is
   clean. Wrapper image + patches retired (upstream equivalents shipped).
2. Open: serial quality bench (`vllm-kk-nightly`, seed 42 hardmode+perf,
   conc 1,2, tokenizer /tmp/mimo-tok) vs sglang anchor 168/184 (91/100);
   then the d0→256K slope sweep (sglang: 77.6 → 23.5 t/s) to see whether
   b12x split-KV fixes the GA long-context cliff.
3. sglang 4x (`mimo26-flash-mopd-4x`) is the production lane in the meantime;
   the FROZEN_KV_MTP experiment is the next sglang-side lever for the
   long-context cliff.