Record bounded Medium DFlash2 feasibility test and VRAM limit

experiments/dflash2-medium-20260920/README.md

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+# DFlash2 Medium-only feasibility probe, 2026-09-20
+
+User requested one quick indication of whether deeper tests are worthwhile.
+No new Qwen baseline run. Reference: `benchmarks/athena-qwen38-reference-20260920/`.
+
+Target: existing Pure IQ4_XS, exact existing llama.cpp image b29c606. Runtime
+help advertises draft-dflash; libllama contains build_dflash2_conv and
+build_dflash2_selector. No rebuild, driver or kernel changes.
+
+Draft: incoai/Qwen3.8-27B-DFlash2-GGUF, revision
+`51962825493a48b846b40126d35c799ac4093ad0`, Q4_K_M, 1,143,006,816 bytes.
+SHA256: `1a25c56858e1ebe93f2718ac1d49d1151f9323325c1bbfd6209370f4db131ebd`.
+Source: https://huggingface.co/incoai/Qwen3.8-27B-DFlash2-GGUF
+Runtime source inspected:
+https://github.com/ggml-org/llama.cpp/blob/b29c606/common/speculative.cpp
+
+## Scope
+
+160000 shared context, two configured slots, **one sequential request at a time**.
+Pure target split 80:20, draft entirely on CUDA0/5080, q4_0 KV for target and
+draft, microbatch128, draft7, batch2048, text only/no projector, cache RAM0.
+TTS remains resident on 3060. These are changes from production Medium's
+85:15/MTP3/ub512/vision/cache RAM32768. The test is not full Medium equivalence.
+Maximum context is allocated, not validated by a full-length input in this quick
+probe. No concurrency, vision or broad quality validation is claimed.
+
+Two existing decode prompts (German/code,768 output-token cap) and one frozen
+4196-input-token retrieval/prefill prompt (512 output-token cap), plus health
+smoke. Sampling matches the frozen requests: temp1/top-p.95/top-k20/min-p0,
+seed42 (code43), no reasoning. Save all responses, timings and GPU samples.
+
+The saved dual-GPU Pure/MTP reference is a useful orientation, but uses 262144
+context and one slot. The single-GPU reference uses 32768 context/ub512/MTP3.
+Any ratios are whole-configuration comparisons, not isolated DFlash speedups.
+Same seed under speculative sampling does not guarantee identical output text.
+
+## Safety / restoration
+
+Adapted from the prior bounded isolated harness. No changes to production
+container arguments or images. Supervisor drains and stops router/controller/
+Medium only and restores the same containers in finally. Ten-minute child limit;
+read-only models,26GiB container RAM limit without extra swap, no privileges,
+no core files. At least512MiB free per used GPU required before inference;
+85C temperature and3GiB host RAM limits monitored. A failed case is not retried
+with increasingly aggressive settings. No automated invocation on repo checkout.
+
+Commands, case configuration and results are archived here. Scripts have fixed
+Athena paths; do not run them as generic unit tests or rerun without a concrete
+benchmark task. This probe does not prove quality equivalence even if responses
+look reasonable; that requires subsequent verification.
+
+## Observed outcome
+
+Target loaded; draft allocation of1079.61MiB onCUDA0 failed with CUDA malloc
+OOM. No benchmark inference executed. Supervisor restored original production;
+health/smoke/kernel checks passed. No performance or quality conclusion can be
+drawn. See results/ and restore-verification.json.