Merge pull request 'feat(frank-tts-engine): synthesize on the gfx1151 iGPU (Vulkan), CPU stays as the rollback' (#34) from feat/frank-tts-vulkan into main

The NPU path is a dead end for this payload (verdict:
report/tts-npu-spike-verdict-2026-10-19.md); the iGPU is the accelerator that
exists on this box today, and it is already shared with frank-dragoon.

- Containerfile.engine: -DGGML_VULKAN=ON, plus the three packages the door
  needs to configure — libvulkan-dev, spirv-headers, and glslc, which Ubuntu's
  glslang-tools does NOT ship (find_package(Vulkan COMPONENTS glslc REQUIRED)
  fails without it) — and libvulkan1 + mesa-vulkan-drivers (the RADV ICD) at
  runtime. No NVIDIA ICD on purpose: one Vulkan device in the enumeration is
  what makes the NAME Vulkan0 safe to write down.
- tts-engine-start.sh: QWENTTS_DEVICE -> --device, default Vulkan0. A value
  that is set but EMPTY passes no flag at all, which is the CPU rollback; that
  is why the default is written as an -v test and not with :=, because := also
  fires on an empty value and would silently undo the rollback.
- quadlet: AddDevice=/dev/dri + GroupAdd=keep-groups (a rootless container that
  drops its supplementary groups enumerates no render device). The node is not
  named: this host is hybrid, renderD128 is the NVIDIA card and renderD129 the
  amdgpu iGPU.
- env: QWENTTS_DEVICE=Vulkan0 plus the device law in the header, including the
  rollback line.
- tests: the two CPU-only assertions now assert the Vulkan shape, and a new one
  pins the rollback (empty device => no --device in argv). 451/451 green.

Measured before writing any of it: the configure in the digest-pinned base
answers "Found Vulkan: ... found components: glslc" and "Including Vulkan
backend"; gate 1 (RADV GFX1151 visible to a rootless container off this base)
is recorded in the verdict report.

dankclaw/voiceservice/Containerfile.engine

@@ -19,11 +19,14 @@
 # is recorded in the parent tree, so cloning the parent commit recursively is
 # reproducible without a second pin.
 #
-# THE BUILD LINE IS THE ONE PROVEN ON DANKCLAW, verbatim:
+# THE BUILD LINE IS THE ONE PROVEN ON DANKCLAW, verbatim — with the Vulkan door
+# open since 2026-10-19. That configure was run in this exact base image and
+# answers `Found Vulkan: /usr/lib/x86_64-linux-gnu/libvulkan.so (found version
+# "1.3.275") found components: glslc` then `Including Vulkan backend`:
 #
 #   cmake -B build -DCMAKE_BUILD_TYPE=Release -DGGML_CCACHE=OFF \
 #       -DGGML_BACKEND_DL=OFF -DGGML_CPU_ALL_VARIANTS=OFF -DGGML_OPENMP=ON \
-#       -DGGML_BLAS=OFF -DGGML_CUDA=OFF -DGGML_HIP=OFF -DGGML_VULKAN=OFF \
+#       -DGGML_BLAS=OFF -DGGML_CUDA=OFF -DGGML_HIP=OFF -DGGML_VULKAN=ON \
 #       -DGGML_METAL=OFF -DGGML_SYCL=OFF -DGGML_RPC=OFF \
 #   && cmake --build build -j 8
 #
@@ -42,8 +45,12 @@
 #     defaults it ON outside wasm/cross-compiles, i.e. -march=native for THIS
 #     host — correct while build host == run host, wrong if anyone ever builds
 #     this image elsewhere, which is why the fleet builds it on Dankclaw.
-#   CUDA/HIP/VULKAN/METAL/SYCL/RPC all OFF: this is a CPU endpoint (the trial
-#     ran on CPU; the box's GPUs belong to the text endpoints).
+#   CUDA/HIP/METAL/SYCL/RPC stay OFF, VULKAN is ON: the endpoint computes on the
+#     gfx1151 iGPU (decision and co-tenancy gates:
+#     report/tts-npu-spike-verdict-2026-10-19.md, shape in [[Frank TTS Engine]]).
+#     Nothing else is available to this image: no ROCm userland, no NVIDIA
+#     userland, no macOS, no oneAPI, and RPC would add a second process to
+#     supervise on a box that already has one engine per card.
 #
 # BUILD SHARED LIBS, RUNTIME SMALL. BUILD_SHARED_LIBS defaults ON on Linux, so
 # tts-server links libggml*.so rather than swallowing them; the runtime stage
@@ -67,9 +74,28 @@ ARG BASE_IMAGE=docker.io/library/ubuntu:24.04@sha256:68ee22004a9109b44973313b02f
 # ------------------------------------------------------------------ build
 FROM ${BASE_IMAGE} AS build
 
+# The three Vulkan build deps are not optional and not interchangeable:
+#   libvulkan-dev    vulkan/vulkan.h + the VulkanHeaders/VulkanLoader CMake
+#                    configs, i.e. what find_package(Vulkan) resolves to.
+#   glslc            ggml compiles its shaders with glslc, not glslangValidator.
+#                    Ubuntu's glslang-tools ships glslangValidator and NOT glslc,
+#                    so without this package `find_package(Vulkan COMPONENTS
+#                    glslc REQUIRED)` fails and there is no Vulkan backend.
+#                    The archive's glslc is old (2023.8): it compiles
+#                    GL_KHR_cooperative_matrix — the path ggml's quantized
+#                    matmul needs — but reports cooperative_matrix2,
+#                    integer_dot_product, bfloat16 and the micro-float
+#                    extensions as unsupported, so those shader families are
+#                    compiled out. If a Vulkan prefill ever reads as
+#                    inexplicably slow, suspect this compiler before the device;
+#                    the fix is a pinned glslang build passed as
+#                    -DVulkan_GLSLC_EXECUTABLE=<path>, not a different runtime.
+#   spirv-headers    find_package(SPIRV-Headers CONFIG REQUIRED); the distro
+#                    package ships /usr/share/cmake/SPIRV-Headers/.
 RUN apt-get update -qq \
     && apt-get install -y -qq --no-install-recommends \
         ca-certificates cmake g++ git make \
+        libvulkan-dev glslc spirv-headers \
     && rm -rf /var/lib/apt/lists/*
 
 # Checked out detached at a full SHA, then the recorded submodule. No branch
@@ -90,7 +116,7 @@ RUN cmake -B build -DCMAKE_BUILD_TYPE=Release \
         -DGGML_BLAS=OFF \
         -DGGML_CUDA=OFF \
         -DGGML_HIP=OFF \
-        -DGGML_VULKAN=OFF \
+        -DGGML_VULKAN=ON \
         -DGGML_METAL=OFF \
         -DGGML_SYCL=OFF \
         -DGGML_RPC=OFF \
@@ -102,9 +128,21 @@ FROM ${BASE_IMAGE}
 # libgomp1: the OpenMP runtime the build above links against. curl: the unit's
 # HealthCmd. ca-certificates: so that curl can speak https if anyone ever
 # points a probe at a URL with a scheme this host terminates elsewhere.
+#
+# libvulkan1 + mesa-vulkan-drivers are what make `--device Vulkan0` mean
+# anything at runtime: libvulkan1 is the loader libggml-vulkan.so dlopens, and
+# mesa-vulkan-drivers is the RADV ICD that claims the gfx1151. Loader without an
+# ICD enumerates ZERO devices, and tts-server then dies in device lookup AFTER
+# both GGUFs have been read — the journal reads as a model fault, not a missing
+# driver. Enumerated from this base on 2026-10-19 with `--device /dev/dri
+# --group-add keep-groups` plus the host's ComfyUI udev rule: "Radeon 8060S
+# Graphics (RADV GFX1151)", API 1.4.318 (the heap figure is owned by
+# [[Frank TTS Engine]]; it is the GTT-backed aperture, not the ~2 GiB DRM
+# carve-out). No NVIDIA ICD is installed on purpose: one Vulkan device in the
+# enumeration is what makes the NAME Vulkan0 safe to write down.
 RUN apt-get update -qq \
     && apt-get install -y -qq --no-install-recommends \
-        ca-certificates curl libgomp1 \
+        ca-certificates curl libgomp1 libvulkan1 mesa-vulkan-drivers \
     && rm -rf /var/lib/apt/lists/*
 
 # Same unprivileged uid as the frank-tts façade (10000): the voice packs and the

dankclaw/voiceservice/quadlet/frank-tts-engine.container

@@ -40,12 +40,23 @@
 # speaks to the server from inside its own namespace, which is where the address
 # is valid.
 #
-# MEMORY / NO GPU. Peak RSS measured 5.7 GiB with both GGUFs resident
-# (2026-10-18 trial); no memory limit is set because the box has the room and a
-# limit would convert a busy moment into an OOM kill mid-utterance. No
-# /dev/kfd, no /dev/dri, no keep-groups: every GPU backend is compiled out of
-# the image, the endpoint is CPU-only by decision, and the GPUs on this host
-# belong to the text endpoints.
+# MEMORY / THE RENDER NODE. Host RSS stays near the 5.7 GiB the CPU trial
+# measured (weights + context resident); no memory limit is set because the box
+# has the room and a limit would convert a busy moment into an OOM kill
+# mid-utterance.
+#
+# `AddDevice=/dev/dri` + `GroupAdd=keep-groups` are what make the iGPU visible,
+# and both are required: a rootless container that drops its supplementary
+# groups has no render permission, and the Vulkan ICD then enumerates nothing —
+# this is the same ride ComfyUI takes (dankclaw/comfyui, plus the udev rule that
+# makes the nodes group-writable). The node is NOT named: this host is hybrid,
+# renderD128 is the NVIDIA card and renderD129 the amdgpu iGPU, so a node number
+# in the unit is a guess that a re-probe can invalidate, while the directory
+# hands the container every render node and the driver picks by name.
+#
+# /dev/kfd stays absent on purpose: that is the ROCm compute interface, owned by
+# the engines that use HIP. A Vulkan endpoint has no use for it, and handing a
+# container a second way onto the GPU is surface for nothing.
 #
 # THE VOICE MOUNT IS READ-ONLY AND IS FOR THE WARMER, NOT THE ENGINE. A voice
 # becomes known to the engine only through POST /v1/audio/voices, and the
@@ -98,6 +109,9 @@ Network=frank-tts-engine.network
 EnvironmentFile=/home/dank/serverAppConfigs/scripts/frank-tts-engine.env
 Volume=/home/dank/models/Qwen3-TTS-GGUF:/models:ro
 Volume=/home/dank/voices:/voices:ro
+# Render access for the iGPU (see MEMORY / THE RENDER NODE above).
+AddDevice=/dev/dri
+GroupAdd=keep-groups
 HealthCmd=curl -fsS http://127.0.0.1:8880/health
 HealthInterval=30s
 HealthTimeout=10s

dankclaw/voiceservice/tts-engine-start.sh

@@ -7,7 +7,7 @@
 # supervision, no retries, no logging of its own. PID 1 stays the server, so
 # `podman stop` and the unit's Restart=always drive it directly.
 #
-# THE FLAGS THAT ARE NOT HERE, and must stay absent:
+# THE FLAG THAT MUST STAY ABSENT:
 #
 #   --threads / -t   does not exist in this build. src/backend.h computes the
 #                    CPU thread count as std::thread::hardware_concurrency()/2
@@ -18,13 +18,19 @@
 #                    placement — pinning is deliberately not done anywhere in
 #                    this stack. See the env file header for the same warning
 #                    aimed at the operator.
-#   --device         left at its default. Every GPU backend is compiled out of
-#                    the image, so the default device pick can only land on
-#                    CPU; naming a device would add a way to be wrong.
 #
-# Everything defaults to the shape the 2026-10-18 trial measured, so an empty
-# environment still boots the decided configuration: 1.7 B talker Q4_K_M with
-# the Q8_0 tokenizer, one request at a time, on the private bridge.
+# --device IS here, but conditionally: it reaches the binary only when
+# QWENTTS_DEVICE is non-empty, and empty is the CPU rollback — the binary then
+# takes its own default device, which is CPU because the CPU backend is always
+# built. One line in scripts/frank-tts-engine.env moves the endpoint between the
+# two shapes, with no rebuild. What must never reach argv is a device NAME the
+# loader does not enumerate: that is not refused by the argument parser, it dies
+# during device lookup with the loader's own error, so the journal reads as a
+# load that failed rather than a configuration refusal.
+#
+# Everything defaults to the shape this endpoint runs: 1.7 B talker Q4_K_M with
+# the Q8_0 tokenizer, one request at a time, on the private bridge, on the
+# gfx1151 iGPU. An empty environment still boots that shape.
 set -euo pipefail
 
 # The binary path. Overridable for one reason: the bats seam runs a stub
@@ -60,13 +66,33 @@ set -euo pipefail
 : "${QWENTTS_LANG:=auto}"
 
 # One request at a time. The server-side queue is a serialised FIFO at this
-# setting, which is what keeps the measured per-voice timings true; batching
-# on a CPU build splits the same cores between two syntheses and the warm RTF
-# margin (0.55-0.67 against real time 1.0) disappears. The engine's own
-# default is also 1; it is written here because it is a decision, not an
-# accident.
+# setting, which is what keeps the per-voice timings predictable. A second
+# concurrent synthesis shares the device with the first — and on this box that
+# device is also carrying frank-dragoon — so it buys no throughput and it
+# doubles the wait for the caller behind it. The engine's own default is also 1;
+# written here because it is a decision, not an accident.
 : "${QWENTTS_MAX_BATCH:=1}"
 
+# The compute device, NAMED and not numbered: `Vulkan0` is how ggml enumerates
+# the gfx1151 iGPU on this host. An index would follow whatever order the
+# loader's device list returns; a name says which device this endpoint means.
+# The container sees exactly one Vulkan device because the image carries the
+# Mesa ICD and no NVIDIA one, so the 3090 is not in the enumeration at all.
+#
+# EMPTY IS THE CPU ROLLBACK: a value that is set but EMPTY passes no `--device`,
+# the binary picks its own default, and the CPU backend is always built — which
+# is why moving this endpoint between the iGPU and the CPU is one line in
+# scripts/frank-tts-engine.env and not a rebuild.
+#
+# That is also why the default below is NOT `${QWENTTS_DEVICE:=Vulkan0}`: `:=`
+# fires on a set-but-empty variable as well as an unset one, so the rollback line
+# `QWENTTS_DEVICE=` would be rewritten back to Vulkan0 and the endpoint would sit
+# on the shared GPU with no way out short of a rebuild. Only UNSET takes the
+# default.
+if [[ ! -v QWENTTS_DEVICE ]]; then
+    QWENTTS_DEVICE=Vulkan0
+fi
+
 # Fail loudly BEFORE binding, so the journal says which artifact is missing
 # instead of the unit reporting a container that starts and dies. This is the
 # self-healing path: Restart=always re-runs it every RestartSec, and the same
@@ -79,11 +105,20 @@ for artifact in "$QWENTTS_MODEL" "$QWENTTS_CODEC"; do
     fi
 done
 
-exec "$QWENTTS_BIN" \
-    --model "$QWENTTS_MODEL" \
-    --codec "$QWENTTS_CODEC" \
-    --alias "$QWENTTS_ALIAS" \
-    --host "$QWENTTS_HOST" \
-    --port "$QWENTTS_PORT" \
-    --lang "$QWENTTS_LANG" \
+ARGS=(
+    --model "$QWENTTS_MODEL"
+    --codec "$QWENTTS_CODEC"
+    --alias "$QWENTTS_ALIAS"
+    --host "$QWENTTS_HOST"
+    --port "$QWENTTS_PORT"
+    --lang "$QWENTTS_LANG"
     --max-batch "$QWENTTS_MAX_BATCH"
+)
+
+# Only when a device is named. An empty QWENTTS_DEVICE has to produce NO flag,
+# because "the rollback shape" is argv identical to the pre-iGPU endpoint.
+if [[ -n "$QWENTTS_DEVICE" ]]; then
+    ARGS+=(--device "$QWENTTS_DEVICE")
+fi
+
+exec "$QWENTTS_BIN" "${ARGS[@]}"

scripts/frank-tts-engine.env

@@ -27,6 +27,16 @@
 # below stop describing the process you are running. Nothing in this fleet
 # pins this container; that is a decision, not an oversight.
 #
+# THE DEVICE LAW (since the 2026-10-19 Vulkan cutover). Synthesis computes on
+# the gfx1151 iGPU — the SAME card frank-dragoon serves. It is a shared device,
+# never a dedicated one, so two numbers matter and neither is what `rocm-smi`
+# prints first: the memory the container may use is the RADV heap inside the
+# GTT-backed aperture (the ~2 GiB DRM carve-out is not the working set), and the
+# timing that matters is dragoon's, measured WITH a synthesis in flight. The
+# rollback is one line: set QWENTTS_DEVICE empty, and the entrypoint passes no
+# --device at all — the pre-iGPU CPU shape, no rebuild, no restart of anything
+# else on the box.
+#
 # THE REGISTRY LAW (why the unit has an ExecStartPost at all). Registrations live
 # in memory only, so a restart loses them, and re-registration alone does NOT warm
 # a voice — the warm pass has to synthesize something. Without it the façade
@@ -103,6 +113,17 @@ QWENTTS_LANG=auto
 # round-trip outside it) is what absorbs the queue.
 QWENTTS_MAX_BATCH=1
 
+# The compute device, by ggml device NAME. `Vulkan0` is the gfx1151 iGPU: the
+# image carries the Mesa (RADV) ICD and no NVIDIA ICD, so this container's
+# Vulkan enumeration has exactly one entry and it is the iGPU. The unit hands
+# the container /dev/dri and keeps the render group; on this hybrid host the
+# iGPU's render node is renderD129 and renderD128 is the NVIDIA card, which is
+# why the unit passes the directory and lets the driver resolve the node.
+#
+# ROLLBACK: an empty value means no --device flag at all — the CPU shape this
+# endpoint shipped with until 2026-10-19. One line, no rebuild.
+QWENTTS_DEVICE=Vulkan0
+
 # --- the boot warmer (dankclaw/voiceservice/tts-engine-warm.sh) --------------
 # These three are read by the warm hook, not by tts-server. They live here
 # because the hook is exec-ed into this container and therefore inherits this

serverAppConfigs-docs/LLM/LLM Performance Diagnosis.md

@@ -1,9 +1,9 @@
 ---
 type: reference
 title: LLM Performance Diagnosis
-description: "Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and profiler attribution."
+description: "Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and step-shape attribution."
 tags: [performance, profiling, moe, pcie, prefix-cache, routing, telemetry]
-timestamp: 2026-10-05T00:00:00-07:00
+timestamp: 2026-10-19T00:00:00-07:00
 ---
 
 # LLM Performance Diagnosis
@@ -213,9 +213,75 @@ function directly with synthetic bodies (stdlib-only policy module)
 conversation identity is the FIRST N KiB of prompt — a shorter tested prefix
 hashes differently per turn and pinning silently never happens.
 
+## 9. Decode cadence under a prefill (the step-shape census)
+
+"Decode turns to sludge the moment a long prompt arrives, then recovers" is not a
+link or a gather story — on a chunked-prefill engine the unit of interference is
+**the step**. A step that carries a prefill chunk takes the chunk's time, and every
+decode row sharing that step waits that long for its next token. Chunk size is
+`min(remaining, --checkpoint-interval, --max-num-batched-tokens)`, so on a hybrid
+model the interval caps it before the budget does.
+
+Census it without touching the model — the engine's own counters (`/stats`,
+`/metrics`, cumulative since boot):
+
+```
+decode-only step = step_ns_decode / steps_decode
+shared step      = (step_ns - step_ns_decode) / (steps_prefill + steps_mixed)
+```
+
+Then bucket a day of `decode_tokens_per_second` by `prefill_tokens_per_second`
+(Prometheus `query_range`, step 120 s) and **check the lag**: correlate decode with
+prefill at lag 0 and again at 2-14 minutes. Lag-0-only ⇒ step-time contention, the
+chunk is holding the device. A lagged tail ⇒ residency churn — the prefill's working
+set evicted something decode needs (expert slab, KV) and decode pays after the
+prefill is over. `preemptions` separates the third shape: a preempted-and-recomputed
+sequence stops producing entirely and then re-prefills from token 0, which is a
+stall, not sludge.
+
+Knobs, in the order worth trying them (radiance GUIDE §4.5):
+
+- `--prefill-interleave N` — after a chunk step taken beside decoders, the next N
+  steps carry decode rows only and admit nothing. Decoders keep their cadence; the
+  prompt pays that in TTFT. Counts as `engine_steps_held_total`.
+- `--busy-prefill-chunk MODE` — the chunk's share of a step that has other work:
+  `auto` (default) reserves a row plus the draft window per decode row behind it and
+  an eighth of the budget per waiting prefill/request, `off` lets the chunk take the
+  whole step (admission never runs while it does), `N` pins the share. Never under
+  the prefill stager's smallest pass — the startup line names it, and below it every
+  routed layer reads its pooled experts synchronously, which costs the prefill far
+  more than sharing saves. Counts as `engine_prefill_chunks_capped_total`.
+- `--max-num-batched-tokens` — the blunt rung, and the only one older pins have. The
+  vendor's curve on a 48-layer MoE at 200k on two cards: chunk 512 → 1750 t/s, 1024
+  → 2200, 2048 → 2706 (a 185k prompt: 138 s against 91 s), so halving the stall
+  costs ~19 % of prefill. Raising it past the interval buys nothing and loses expert
+  residency to the arena.
+- `--prefill-span N` — the inverse trade: a *lone* prefill carries N intervals a step
+  while every shared step is planned at a smaller shared budget, which on an
+  expert-tiered box lends that arena back to the expert slab. Vendor TP2
+  expert-tiered TTFT deltas vs a plain 2048 budget: −6.1 % at 2k, +2.3 % at 18k,
+  +49.1 % at 250k — long prompts only.
+
+Two traps. **The arena/slab coupling makes a shared step doubly expensive on an
+expert-tiered shape**: the full-plan arena takes VRAM the resident expert slab would
+have had (320 MiB/card at TP2 for a 4096 budget), so the decode rows inside that step
+also read experts over the link — a smaller shared budget helps twice. And **re-check
+`prefix_hit_rate` / `prefix_evictions` after any chunk change**: the arena and the KV
+pool are the same memory, and the failure looks like turn two taking as long as turn
+one.
+
+Availability is a version question, not a config question: `--busy-prefill-chunk` and
+`--prefill-interleave` are absent from older pins — prove it on the running container
+(`podman exec <c> <binary> --help | grep -iE "prefill|chunk"`), never from the vendored
+tree, and check the source clone's depth before dating a flag from `git log -S`
+(a `--depth 1` clone reports its own tip for every search).
+
+Run on: [[frank-archon]] (radiance 1.0.13, TP2 `expert_tiered`, budget 2048 = interval
+2048) — the measured census and the verdict for this fleet's shape are that page's.
+
 ## Related
 
 -  the window discipline and usage-counter law
 - [[PCIe Link and Atomics]] — link probing and the streaming-vs-compute ceiling
 - [[RDNA4 MoE Expert Offload VRAM Budget]] — the plan behind duty-cycle terms
--  the compile fix for the pointwise-glue bound
+- [[frank-archon]] — the endpoint where §9's step-shape census was run

serverAppConfigs-docs/LLM/frank-archon.md

@@ -239,6 +239,29 @@ vllm-radiance era (this table opens on 09-26; the era page claims 10-10).
 - **MNBT 2048.** 2560 collapses decode to 2.6-7.7 t/s (MTP resonance); the w4 file tier streams
   in place only at MNBT ≤ 2048 and the activation arena scales with the chunk (32768 → 33.3
   GiB, refused).
+- **Decode pays for the chunk it shares a step with.** Census of the live engine
+  (radiance 1.0.13, `/stats` + `/metrics`, cumulative over the 2026-10-15 boot):
+  1,435,585 decode-only steps at **18.7 ms** each against 127,991 prefill+mixed steps
+  at **317 ms** — 60 % of engine wall-clock spent inside 8 % of the steps, because the
+  chunk is `min(remaining, checkpoint interval 2048, MNBT 2048)` = 2048 rows and every
+  decode row in that step waits the whole chunk. Day of Prometheus (120 s step, 721
+  samples): `decode_tokens_per_second` median **13.3 t/s** in the 56 % of samples where
+  `prefill_tokens_per_second` ≥ 1000, against 106-240 t/s in the light-prefill buckets;
+  bucketed by mean step time it is 128.7 t/s at 0.02-0.05 s steps and 12.0 t/s at
+  0.15-0.4 s. The stall is **during**, not after — decode in windows 2-14 min after a
+  busy-prefill window sits at the idle baseline (58-64 vs 77-85 t/s, the residual
+  confounded by co-scheduling), so no lingering expert-residency penalty at 2-minute
+  resolution, and `preemptions: 0` rules out preempt-and-re-prefill. Method:
+  [[LLM Performance Diagnosis]] §9.
+- **The knobs for it are not in this pin.** `--busy-prefill-chunk` and
+  `--prefill-interleave` (radiance GUIDE §4.5 — a shared chunk's cap, and N decode-only
+  steps after each chunk) are absent from 1.0.13: proven on the running container
+  (`podman exec frank-archon radiance --help` prints no `prefill`/`chunk` flag), and the
+  2026-10-18 source tree carries both. The only crank this pin has is MNBT, and that is
+  an arm and not an edit: the vendor prices a 1024 chunk at −19 % prefill to halve the
+  stall, and this page's own MNBT law already knows 2560 collapses decode (MTP
+  resonance). An image bump is gated by the 1.2.0 numerics dead end below, so any try
+  re-scores draft acceptance before it is trusted.
 - **Slots cost KV and rows, never speed.** `--max-num-seqs` carries no radiance constraint: it
   adds 110 MiB of recurrent state per slot and declares the fused TP all-reduce over `seqs ×
   (1 + spec)` rows, and `wht6` is bit-exact up to 25 rows (single-sequence decode and any step

serverAppConfigs-docs/LLM/index.md

@@ -35,7 +35,7 @@ the endpoint's **Eras** table, and the numbers a retired era measured are gone.
 | [[GGUF Compatibility]] | Answering whether an engine loads a GGUF from the file header alone, and pinning a fork build that can. |
 | [[Heterogeneous Split Triage]] | Triage before splitting across unequal accelerators: link characterisation, real bottleneck, what placement never buys. |
 | [[Llama Cpp Serving Sizing]] | Measurement-first sizing for llama.cpp shapes: slot pools against a headroom band, per-device accounting, prompt cache. |
-| [[LLM Performance Diagnosis]] | Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and profiler attribution. |
+| [[LLM Performance Diagnosis]] |  Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and step-shape attribution. |
 | [[Model Swap and Rollback]] | The model-swap discipline: fit preflight, fetch verification, build and flag checks, live validation, three-pin revert. |
 | [[PCIe Link and Atomics]] | Link probing, the streaming-versus-compute ceiling arithmetic, and the atomics wall that decides multi-GPU collectives. |
 | [[Quantization by Hardware Architecture]] | This page maps LLM quantization formats to the GPU and CPU architectures that support them. |

serverAppConfigs-docs/index.md

@@ -154,7 +154,7 @@ is a locator: one row, one clause, no numbers.
 | [[GGUF Compatibility]] | Answering whether an engine loads a GGUF from the file header alone, and pinning a fork build that can. |
 | [[Heterogeneous Split Triage]] | Triage before splitting across unequal accelerators: link characterisation, real bottleneck, what placement never buys. |
 | [[Llama Cpp Serving Sizing]] | Measurement-first sizing for llama.cpp shapes: slot pools against a headroom band, per-device accounting, prompt cache. |
-| [[LLM Performance Diagnosis]] | Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and profiler attribution. |
+| [[LLM Performance Diagnosis]] | Probing why a served model is slow: the flat-depth probe, offload duty-cycle arithmetic, and step-shape attribution. |
 | [[Model Swap and Rollback]] | The model-swap discipline: fit preflight, fetch verification, build and flag checks, live validation, three-pin revert. |
 | [[PCIe Link and Atomics]] | Link probing, the streaming-versus-compute ceiling arithmetic, and the atomics wall that decides multi-GPU collectives. |
 | [[Quantization by Hardware Architecture]] | This page maps LLM quantization formats to the GPU and CPU architectures that support them. |

tests/frank_tts_engine.bats

@@ -331,13 +331,40 @@ FAKE
     [ "$(argv --port)" = "8880" ]
     [ "$(argv --lang)" = "auto" ]
     [ "$(argv --max-batch)" = "1" ]
-    # The two flags that must never appear: there is no thread count to set (it
-    # comes from hardware_concurrency()/2), and naming a device on an image with
-    # every GPU backend compiled out is only a new way to be wrong.
-    ! grep -qx -- '--device' "$ARGS_FILE"
+    # The device the env names has to reach argv BY NAME: the image ships the
+    # Mesa ICD and no NVIDIA one, so Vulkan0 is the gfx1151 and cannot drift onto
+    # another card the way an index would.
+    [ "$(argv --device)" = "Vulkan0" ]
+    # The flag that must never appear: there is no thread count to set in this
+    # build (it comes from hardware_concurrency()/2), so naming one would only
+    # disagree with what the binary sized its pools from.
     ! grep -qE -- '^--?t$|^--threads$' "$ARGS_FILE"
 }
 
+@test "an empty device value is the CPU rollback: no --device reaches argv" {
+    # The same entrypoint with one key cleared, which is the rollback the env
+    # header documents. A script-level default that survived an explicitly empty
+    # value would leave the endpoint on the iGPU with no way back except a
+    # rebuild.
+    cat > "$TEST_TMP/fake-tts-server" <<'FAKE'
+#!/usr/bin/env bash
+printf '%s\n' "$@" > "$ARGS_FILE"
+FAKE
+    chmod +x "$TEST_TMP/fake-tts-server"
+    mkdir -p "$TEST_TMP/models"
+    : > "$TEST_TMP/models/$TALKER"
+    : > "$TEST_TMP/models/$CODEC"
+    export QWENTTS_MODEL="$TEST_TMP/models/$TALKER"
+    export QWENTTS_CODEC="$TEST_TMP/models/$CODEC"
+    export QWENTTS_BIN="$TEST_TMP/fake-tts-server"
+    export ARGS_FILE="$TEST_TMP/argv.txt"
+    export QWENTTS_DEVICE=""
+
+    run bash "$START"
+    [ "$status" -eq 0 ] || { echo "$output"; false; }
+    ! grep -qx -- '--device' "$ARGS_FILE"
+}
+
 @test "missing weights are a refusal that names the fetcher, before the port is bound" {
     cat > "$TEST_TMP/fake-tts-server" <<'FAKE'
 #!/usr/bin/env bash
@@ -627,17 +654,23 @@ PY
 @test "the image build is the pinned commit with the proven cmake line" {
     # GGML_BLAS=OFF is forced by the host (libopenblas.so.0 present, no dev
     # headers) and upstream's own Dockerfile passes it ON, so this file is not a
-    # copy of upstream on purpose. -j 8 and the OFF-for-every-GPU-backend list
-    # are what the 2026-10-18 trial ran.
+    # copy of upstream on purpose. -j 8 is what the 2026-10-18 trial ran;
+    # GGML_VULKAN=ON is the 2026-10-19 iGPU cutover, and the two greps below are
+    # the packages that door needs at build time and at run time.
     grep -qE '^ARG QWENTTS_COMMIT=[0-9a-f]{40}$' "$CF"
     grep -qF '5916bf7c79dbb4e66fc059cdc507a79a23a28bb4' "$CF"
     grep -qE 'git -C /src checkout --detach' "$CF"
     grep -qE 'submodule update --init' "$CF"   # ggml is a submodule; without it the build cannot configure
     for flag in -DGGML_CCACHE=OFF -DGGML_BACKEND_DL=OFF -DGGML_CPU_ALL_VARIANTS=OFF \
                 -DGGML_OPENMP=ON -DGGML_BLAS=OFF -DGGML_CUDA=OFF -DGGML_HIP=OFF \
-                -DGGML_VULKAN=OFF -DGGML_METAL=OFF -DGGML_SYCL=OFF -DGGML_RPC=OFF; do
+                -DGGML_VULKAN=ON -DGGML_METAL=OFF -DGGML_SYCL=OFF -DGGML_RPC=OFF; do
         grep -qF -- "$flag" "$CF" || { echo "build line lost $flag"; false; }
     done
+    # glslc is not in glslang-tools on this distro, and the configure fails
+    # without it; an image with the loader and no RADV ICD enumerates zero
+    # devices and dies in device lookup after the weights load.
+    grep -qE 'libvulkan-dev glslc spirv-headers' "$CF"
+    grep -qE 'libvulkan1 mesa-vulkan-drivers' "$CF"
     grep -qE 'cmake --build build -j 8' "$CF"
     # OpenMP on means the runtime stage needs the OpenMP runtime, and the probe
     # runs as /bin/sh -c, so the runtime stage needs curl.