docs: Qwen3.8 spec-matrix benchmark page; add matrix tools; final env n_max=5

Recording the 54-config matrix, the realistic-prompt correction (n_max=5 not
10), the ubatch findings (256 is the safe/fast point), and the premature-stop
sampling-variance investigation.

docs/index.md

@@ -52,6 +52,7 @@ MTP-ONLY draft, port 7770]
 - [[Running Qwen3.6 35B A3B FP8 on Dankserver]] — MoE model (35B total, 3B active) on RTX 3090
 - [[Running Qwen3.6 27B FP8 on Dankclaw]] — Dense model (27B) on Strix Halo APU
 - [[frank-default-large-benchmark]] — backend/spec benchmark; chose MTP sidecar (2026-08-14) over DFlash (parallel premature-EOS bug)
+- [[qwen3.8-spec-matrix]] — Qwen3.8-27B UD-Q8_K_XL bundled-MTP spec matrix; winner draft-mtp n_max=5
 - [[frank-default-small-benchmark]] — ncmoe and batch/ubatch sweep that drove the Dankserver state
 - [[dankserver-vram-growth]] — VRAM/RAM growth investigation behind the recurring cuBLAS crash on frank-default-small
 - [[Dankclaw Improvements]] — researched enhancements: self-hosted agentic tools, runtime tuning, server/OS settings

docs/qwen3.8-spec-matrix.md

@@ -0,0 +1,86 @@
+# Qwen3.8-27B UD-Q8_K_XL Speculative-Decoding Matrix
+
+This page records the speculative-decoding benchmark and the production
+tuning for the unsloth Qwen3.8-27B `UD-Q8_K_XL` service on Dankclaw
+(`frank-default-large`).
+
+## Result (applied)
+
+- Model: `Qwen3.8-27B-UD-Q8_K_XL.gguf` (29.29 GiB, bundled MTP).
+- Spec: `draft-mtp`, `--spec-draft-n-max 5`, no `--spec-draft-p-min`.
+- Batch 8192 / ubatch 256, parallel 2, ctx 524288 (262144 per slot).
+- Realistic-prompt generation: ~13.3 t/s single, ~8 t/s per slot under
+  2 concurrent streams. No premature stop.
+
+## How MTP works on Qwen3.8
+
+The unsloth `UD-*` GGUFs keep the MTP (Multi-Token Prediction) head inside
+the model file. llama.cpp b10411+ auto-detects it and creates the draft
+context from the target model. Do not pass `--spec-draft-model`.
+
+The stock llama.cpp build must be b10411 or newer. The 2026-08-14 rebuild
+on Dankclaw is b10433 (`9b05354ec`) with `GGML_HIP` + `gfx1151` + Vulkan.
+
+## Benchmark Method
+
+The matrix ran 54 configurations: 3 spec types (`draft-mtp,ngram-mod`,
+`draft-mtp`, `ngram-mod`) x `--spec-draft-n-max` 2..10 x
+`--spec-draft-p-min` {off, 0.8}. Each config loaded `llama-server`,
+then ran 3 generations. The tool is `scripts/spec-matrix-bench.sh`;
+analysis is `scripts/analyze-spec-matrix.py`.
+
+## Matrix Caveat: Benchmark Prompt
+
+The matrix used a repetitive 1100-token prompt
+(`scripts/bench_live.sh` style). MTP drafts that repeated sentence almost
+perfectly, which inflated the numbers for long drafts. The matrix reported
+`draft-mtp` n_max=10 at ~30 t/s. A realistic story prompt gave very
+different results:
+
+| n_max | median t/s (realistic) |
+| ----- | ----------------------- |
+| 4 | 12.5 |
+| 5 | 13.3 (peak) |
+| 6 | 10.6 |
+| 7 | 10.1 |
+| 10 | 8.6 |
+| none (baseline) | 7.2 |
+
+Long drafts collapse to ~18% acceptance on real writing. n_max=5 balances
+acceptance against draft cost.
+
+## Premature Stop Investigation
+
+Two failure patterns appeared during early production tests:
+
+1. Speed collapse. `ubatch >= 512` reduced MTP acceptance to ~25% and
+   generation to ~9 t/s. `ubatch 128` with `batch >= 2048` triggered a
+   premature instant-EOS under 2 concurrent slots. `ubatch 256` avoids
+   both: ~30 t/s single, concurrent-safe.
+2. Apparent premature-EOS. The repetitive benchmark prompt with `temp 1.0`
+   sometimes stops after 1-2 tokens because the model legitimately emits an
+   EOS on a wall of repeated text. This is sampling variance, not a
+   corruption bug. Realistic prompts never stop early.
+
+## Production Configuration
+
+`scripts/frank-default-large.env`:
+
+```ini
+SPEC_TYPE=draft-mtp
+SPEC_DRAFT_N_MAX=5
+SPEC_DRAFT_P_MIN=
+BATCH_SIZE=8192
+UBATCH_SIZE=256
+CTX_SIZE=524288
+PARALLEL=2
+```
+
+Window: 524288 total / 2 = 262144 per slot, matching the pi
+`models.json` contextWindow for `frank-default-large`.
+
+## See Also
+
+- [[frank-default-large-benchmark]]
+- [[ling-3.0-flash-trial]]
+- [[deployment]]