upstream-watch 10-17: eugr/spark-vllm-b12x nightly (vLLM 0.1.dev21830, 10-15, 391 archs) checked — NO MuseSpark, NO Step5 (only MuseGlimmer + Step3 family). Confirms SGLang #44530 series is earliest path for Muse-816B. Bonus: b12x has DSpark speculators (Glm53DSpark, Qwen3OmniDSpark, K3DSpark, Gemma4DSpark)

specs/tech-architecture/upstream-watch-2026-10-17.md

@@ -118,6 +118,21 @@ SGLang (latest release **v0.5.21**, 2026-10-02):
 - SGLang DOES have `bailing_moe_v3.py` (Ling/BailingMoeV3) — a real alternative
   engine to A/B our Ling fp8/fp4 serve against vLLM (not a blocker, an option).
 
+### eugr/spark-vllm-b12x nightly checked — still no MuseSpark / Step5
+Pulled the digest-pinned b12x image (`sha256:03a95654…`) and dumped its registry:
+it is a **nightly vLLM `0.1.dev21830+g8244d1c44` built 2026-10-15** (ahead of
+v0.31.0), **391 archs**. Yet:
+- **MUSE**: only `MuseGlimmer*` — **no `MuseSparkForConditionalGeneration`**.
+- **STEP**: `Step1`, `Step3Text`, `Step3p5`, `StepVL`, `Step3VL`, `Step3p7`,
+  `Step3p5MTP` — **no `Step5ForConditionalGeneration`**.
+So Muse-816B and Step-5 are unsupported across vLLM stable, vLLM main, the b12x
+nightly, AND SGLang — the b12x build is not ahead on these archs. Confirms the
+SGLang #44530 series is the earliest path for Muse-816B.
+- Useful find in the b12x nightly: DSpark speculators `Glm53DSparkForCausalLM`,
+  `Qwen3DSparkModel`, `Qwen3OmniDSparkModel`, `K3DSparkModel`, `Gemma4DSparkModel`,
+  `DSparkV41DraftModel` — a DSpark spec-decode path for GLM-5.3 (and others)
+  available in the b12x image; candidate for our kindling/GLM lanes.
+
 ## Ling-3.1-flash fp8→fp4 (our own converter — in progress)
 No official 3.1-flash fp4 exists (inclusionAI has fp4 only for 3.0). We wrote a
 converter (fp8-block routed experts → MXFP4, "even" scale mode, byte-exact vs