dankclaw: retire DSpark, use llama.cpp --spec-default (ngram-mod) preset; PARALLEL=2 trial

scripts/frank-default-large.env

@@ -11,27 +11,19 @@ PORT=7770
 # contextWindow=262144 for frank-default-large. Model is 29GB; ROCm has
 # ~70GB headroom, so 2x262k quantized KV fits. Verify at startup.
 CTX_SIZE=524288
-# Parallel slots. 2026-08-15: two concurrent 16k prose prompts (high
-# prompt-cache reuse) crashed DSpark with 'ROCm error: an illegal memory
-# access was encountered' inside per-sequence block sampling
-# (ggml_cuda_synchronize in common_speculative_impl_draft_dflash::draft,
-# status 6/ABRT, systemd restarted).  DSpark multi-slot is NOT safe on this
-# box, same class as the DFlash shared-draft-context bug.  Pinned to 1 slot
-# per user instruction; revisit after an upstream multi-slot DSpark fix.
-PARALLEL=1
-# Spec: DSpark sidecar draft (magnitudedev/Qwen3.8-27B-DSpark-GGUF Q8_0,
-# 1.36B, block_size 7, Markov confidence head).  Switched from bundled-MTP
-# 2026-08-15 at the user's request.  DSpark is the semi-autoregressive
-# extension of DFlash (DeepSeek, arXiv 2607.05147): parallel diffusion
-# backbone + sequential Markov head + confidence-scheduled verification.
-# n_max clamps to the trained block_size 7 (server warning if set higher).
-# Parallel safety FAILED on this box (see the PARALLEL=1 note above);
-# single-slot only until an upstream multi-slot DSpark fix lands.
-# DRAFT_FILE names the sidecar GGUF in MODEL_DIR (downloaded 2026-08-15,
-# sha256 b007a76b2ce57c1a3ecf36046543aebf60a763861624647d653f16d336c781d2).
-SPEC_TYPE=draft-dspark
-DRAFT_FILE=Qwen3.8-27B-DSpark-Q8_0.gguf
-SPEC_DRAFT_N_MAX=7
+# Parallel slots. 2026-08-15: DSpark multi-slot crashed the ROCm backend
+# (illegal memory access, status 6/ABRT) under two concurrent 16k prose
+# prompts, so DSpark was retired and --spec-default (ngram-mod) is used.
+# ngram-mod is draftless and passed the strict parallel test historically.
+# PARALLEL=2 is the current trial; pin to 1 if the 2x32k stream test fails.
+PARALLEL=2
+# Spec: llama.cpp --spec-default preset = ngram-mod (n_match 24, n_min 48,
+# n_max 64).  No draft model.  Switched from DSpark 2026-08-15 after the
+# DSpark multi-slot ROCm crash.  See [[qwen3.8-spec-matrix]].
+SPEC_DEFAULT=1
+SPEC_TYPE=
+DRAFT_FILE=
+SPEC_DRAFT_N_MAX=
 SPEC_DRAFT_P_MIN=
 SPEC_NGRAM_MOD_N_MIN=48
 SPEC_NGRAM_MOD_N_MAX=64

scripts/frank-default-large.service

@@ -1,5 +1,5 @@
 [Unit]
-Description=llama.cpp Qwen3.8-27B UD-Q8_K_XL + DSpark sidecar draft (frank-default-large)
+Description=llama.cpp Qwen3.8-27B UD-Q8_K_XL spec-default ngram-mod (frank-default-large)
 After=network.target
 
 [Service]

scripts/serve-llama-frank-large.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
-# Serve unsloth Qwen3.8-27B UD-Q8_K_XL on dankclaw with a DSpark
-# sidecar draft model (draft-dspark). ROCm backend.
+# Serve unsloth Qwen3.8-27B UD-Q8_K_XL on dankclaw with llama.cpp's
+# --spec-default preset (ngram-mod). ROCm backend.
 # Runtime: llama.cpp llama-server (>= b10411).
 #
 # Tunables come from frank-default-large.env in this directory unless the
@@ -25,7 +25,7 @@ fi
 : "${PORT:=7770}"
 : "${CTX_SIZE:=262144}"   # Qwen3.8 native context (env may raise for parallel≥2)
 : "${PARALLEL:=2}"
-: "${SPEC_TYPE:=draft-mtp}"
+: "${SPEC_DEFAULT:=0}"   # 1: use --spec-default (ngram-mod preset) instead of --spec-type
 : "${SPEC_DRAFT_N_MAX:=10}"
 : "${SPEC_NGRAM_MOD_N_MIN:=48}"
 : "${SPEC_NGRAM_MOD_N_MAX:=64}"
@@ -52,29 +52,37 @@ if [[ ! -f "$MODEL" ]]; then
     exit 1
 fi
 
-# Draft-model flag applies only when a separate draft file is provided.
-# Qwen3.8-UD bundles MTP in-model; leave DRAFT_FILE empty for bundled MTP,
-# or set it to a DSpark/DFlash sidecar GGUF for a dedicated draft.
+# Spec flags.  --spec-default is a preset that enables ngram-mod
+# (n_match=24, n_min=48, n_max=64) and takes no draft model.  The explicit
+# --spec-type / draft-model path is used when SPEC_DEFAULT is 0.
 SPEC_ARGS=()
-if [[ -n "$DRAFT_FILE" ]]; then
-    if [[ ! -f "$DRAFT" ]]; then
-        echo "missing required file: $DRAFT" >&2
+if [[ "${SPEC_DEFAULT}" == "1" ]]; then
+    SPEC_ARGS+=(--spec-default)
+else
+    if [[ -z "${SPEC_TYPE:-}" ]]; then
+        echo "SPEC_TYPE must be set when SPEC_DEFAULT=0" >&2
         exit 1
     fi
-    SPEC_ARGS+=(--spec-draft-model "$DRAFT")
-fi
-if [[ -n "${SPEC_DRAFT_P_MIN:-}" ]]; then
-    SPEC_ARGS+=(--spec-draft-p-min "$SPEC_DRAFT_P_MIN")
+    SPEC_ARGS+=(--spec-type "$SPEC_TYPE")
+    if [[ -n "$DRAFT_FILE" ]]; then
+        if [[ ! -f "$DRAFT" ]]; then
+            echo "missing required file: $DRAFT" >&2
+            exit 1
+        fi
+        SPEC_ARGS+=(--spec-draft-model "$DRAFT")
+    fi
+    if [[ -n "${SPEC_DRAFT_P_MIN:-}" ]]; then
+        SPEC_ARGS+=(--spec-draft-p-min "$SPEC_DRAFT_P_MIN")
+    fi
+    SPEC_ARGS+=(--spec-draft-n-max "$SPEC_DRAFT_N_MAX")
+    SPEC_ARGS+=(--spec-ngram-mod-n-min "$SPEC_NGRAM_MOD_N_MIN")
+    SPEC_ARGS+=(--spec-ngram-mod-n-max "$SPEC_NGRAM_MOD_N_MAX")
+    SPEC_ARGS+=(--spec-ngram-mod-n-match "$SPEC_NGRAM_MOD_N_MATCH")
 fi
 
 exec "$LLAMA_SERVER" \
     --model "$MODEL" \
     "${SPEC_ARGS[@]}" \
-    --spec-type "$SPEC_TYPE" \
-    --spec-draft-n-max "$SPEC_DRAFT_N_MAX" \
-    --spec-ngram-mod-n-min "$SPEC_NGRAM_MOD_N_MIN" \
-    --spec-ngram-mod-n-max "$SPEC_NGRAM_MOD_N_MAX" \
-    --spec-ngram-mod-n-match "$SPEC_NGRAM_MOD_N_MATCH" \
     --device "$DEVICE" \
     --gpu-layers "$N_GPU_LAYERS" \
     --fit off \