feat(blender-run): --cpu runs with no GPU attached (modelling/IO jobs stay off GPU 3)

docs/fleettools/blender.md

@@ -48,6 +48,11 @@ scripts/blender-run -- --python-expr 'import bpy; print(bpy.app.version_string)'
   screen datablock's VIEW_3D area. Worked calls for every add-on:
   `scripts/blender-probes/extensions_acceptance.py`. Full notes and foot-guns: the stack README,
   section "Extensions".
+- **`--cpu`** attaches no GPU at all (no nvidia runtime), so the run never touches GPU 3. Use it
+  for modelling, add-ons and import/export, which is anything that does not render. It is proven
+  for those (the extension acceptance ran that way) and for Cycles on CPU. EEVEE and Workbench
+  are expected to fail without the GPU (untested). The container hostname is always
+  `fv-ml1-blender`.
 - **Budget:** each run is capped at 64 GB RAM and 48 CPUs, with up to the whole 96 GB of VRAM.
   Keep to about 2 concurrent renders. It is not on irv-ml1, so irv-ml1's working-set budget
   does not apply.

scripts/blender-run

@@ -2,7 +2,7 @@
 # blender-run — one-shot HEADLESS Blender on fv-ml1 GPU 3, for scripted/CLI callers (draupnir etc.).
 # The agent-driven, interactive path is scripts/blender-mcp; this is the batch path.
 #
-#   scripts/blender-run [--job DIR] [--extensions] -- <blender args after -b>
+#   scripts/blender-run [--job DIR] [--extensions] [--cpu] -- <blender args after -b>
 #   scripts/blender-run --job /mnt/smithy/draupnir/j42 -- --python render.py -- --out out.png
 #   scripts/blender-run --extensions -- --python-expr 'import bpy; print(bpy.app.version_string)'
 #
@@ -30,6 +30,12 @@
 # per distinct DIR (small files, on /tank). Without --job, the only paths Blender sees are under
 # /work (= fv-ml1:/tank/blender).
 #
+# --cpu: no GPU attached at all (no nvidia runtime), so the run never touches GPU 3. For modelling,
+# add-on work, import/export and Cycles on CPU (the 2026-09-28 extension acceptance ran this way).
+# EEVEE and Workbench render through EGL on the GPU and are expected to fail here (untested). It is
+# also the shape of the fallback if GPU 3 goes back to vLLM. Asked for by draupnir, whose design
+# stage never renders (2026-09-28).
+#
 # The container's hostname is fixed as fv-ml1-blender, so socket.gethostname() is stable across
 # runs (callers record it as provenance; draupnir, 2026-09-28). Without it, it is the container id.
 #
@@ -42,6 +48,7 @@ HOST=${BLENDER_SSH_HOST:-infra-ops@10.251.50.54}
 ENV_FILE=/opt/docker/compose/blender/.env
 JOB=""
 EXT=""
+GPU="--runtime nvidia -e NVIDIA_VISIBLE_DEVICES=3 -e NVIDIA_DRIVER_CAPABILITIES=all"
 while [ $# -gt 0 ]; do
   case "$1" in
     --job) JOB=${2:?--job needs a directory}; shift 2 ;;
@@ -51,8 +58,9 @@ while [ $# -gt 0 ]; do
       EXT="--mount type=bind,src=/tank/blender-extensions/5.2/system,dst=/blender/5.2/extensions/system,readonly \
     --mount type=bind,src=/opt/docker/conf/blender/scripts/startup/fleet_extensions.py,dst=/fleet/fleet_extensions.py,readonly"
       shift ;;
+    --cpu) GPU=""; shift ;;
     --) shift; break ;;
-    -h|--help) sed -n 2,38p "$0"; exit 0 ;;
+    -h|--help) sed -n 2,43p "$0"; exit 0 ;;
     *) echo "blender-run: unknown option $1 (blender args go after --)" >&2; exit 2 ;;
   esac
 done
@@ -79,8 +87,7 @@ PRE=""
 [ -n "$EXT" ] && PRE="--python /fleet/fleet_extensions.py"
 set +e
 ssh -n -o BatchMode=yes "$HOST" "IMG=\$(grep '^IMAGE=' $ENV_FILE | cut -d= -f2) && \
-  exec docker run --rm --name blender-run-\$\$ --hostname fv-ml1-blender --runtime nvidia \
-    -e NVIDIA_VISIBLE_DEVICES=3 -e NVIDIA_DRIVER_CAPABILITIES=all \
+  exec docker run --rm --name blender-run-\$\$ --hostname fv-ml1-blender $GPU \
     --user 1002:1003 -e HOME=/tmp -e USER=infra-ops -e LOGNAME=infra-ops --memory 64g --cpus 48 \
     -v /tank/blender:/work $EXT -w $WORKDIR --entrypoint /blender/blender \"\$IMG\" \
     -b --factory-startup --python-exit-code 1 $PRE $ARGS"