[aien-spark]

Short prompts currently use a 64-row matrix kernel even when fewer rows are populated. This adds an Omega admission policy for one 32-row, four-warp shape, reusing the existing parameterized generator. The default shape, arithmetic order, instruction encodings, wait distance and ownership checks remain unchanged. All other shapes stay refused.

This is stacked on #251. It introduces no serving selection policy. The existing test setter must be called before prefill buffer sizing or tile construction.

Validation:

• The new cases fail on the parent because the generator refuses the shape. Host references and all eight simulator cases pass after the change, including tails, direct/indexed rows, both output layouts, two warp schedules and arithmetic mutants.
• Admission/refusal cases and four compiled Omega mutants pass. Pinned binding regeneration and crumb verification pass.
• The 30-token chip screen passes across four 27B matrix dimensions. Repeated full output buffers are identical. Three sampled rows per matrix match the incumbent reference contract: exact F32, at most one BF16 ulp for the SwiGLU transcendental path. All deliberate arithmetic faults are caught. The receipt is in om/prefill-shape/validation.json.

The short serving screen now passes exact128, seeded sampled32 and exact128 after sampling. First-visible latency remains around0.5 seconds; the chip timings are mixed, so no default change is proposed. See om/prefill-shape/serving-validation.json.

Full256 conversation/streaming checks, longer prompts, current-head CI and controlled performance comparisons remain pending. Keep this draft. No whole-model speed or first-token improvement is claimed. Production implementation is Omega through the pinned Bridge; Python is external verification only. Source notices are preserved and the staged diff passes whitespace checks.

[aien-spark]

Merge desk (AI), 2026-11-02. Landed on main as part of the reviewed Ribbon stack through #260 (merge 183fa4f). This head (2d7a41c) is contained in main. Closing as landed.