diff --git a/dankclaw/udev/98-halogen-npu-access.rules b/dankclaw/udev/98-halogen-npu-access.rules
new file mode 100644
index 0000000..cc093ec
--- /dev/null
+++ b/dankclaw/udev/98-halogen-npu-access.rules
@@ -0,0 +1,26 @@
+# /etc/udev/rules.d/98-halogen-npu-access.rules
+#
+# Why the NPU node is world-writable: `frank-dragoon` runs rootless podman under a
+# unit with `User=dank`, and the container's user namespace maps exactly one uid and
+# one gid (dank). `/dev/accel/accel0` is `root:render 0660`, so inside the container
+# the node reads `nobody:nogroup` and the engine dies with its own diagnosis:
+#
+#   halogen npu: /dev/accel/accel0 is here, but this process cannot open it
+#     (crw-rw---- nobody:nogroup).
+#
+# `--group-add keep-groups` is the vendor's advice and it does NOT work in this
+# shape: measured 2026-10-19 from the host as a `dank` shell that was already in
+# `render`, with and without the flag, the node still read `nobody:nogroup` and the
+# open was refused — an unmapped gid cannot be granted to a process inside a
+# namespace that does not map it. Same conclusion `99-comfyui-gpu-access.rules`
+# reached for `/dev/kfd` from the systemd-user-spawn direction: the mode is the only
+# spawn-context-independent door short of running the stack rootful.
+#
+# Blast radius: any process in this host's single uid domain (every rootless
+# container here shares it) can submit to the XDNA2 NPU. The NPU holds no user data
+# and no privileged context — the same trade already accepted for the GPU compute
+# nodes beside it. Installed by `deploy-remote.sh` when the NPU lane is armed and left
+# in place afterwards — the mode costs nothing while the lane is idle. `serve-frank-dragoon.sh`
+# refuses to arm the lane on a node that is not other-accessible, so a host that lost this
+# file fails loudly at boot instead of crash-looping.
+KERNEL=="accel[0-9]*", SUBSYSTEM=="accel", MODE="0666"
diff --git a/scripts/deploy-remote.sh b/scripts/deploy-remote.sh
index de2ed5a..10a0709 100755
--- a/scripts/deploy-remote.sh
+++ b/scripts/deploy-remote.sh
@@ -1452,6 +1452,20 @@ deploy_llm_dragoon() {
             echo "ERROR: NPU node $LLM_DRAGOON_DEV_ACCEL absent — amdxdna is not bound (is iommu=pt still on the boot line?)" >&2
             return 1
         fi
+        # Access, not existence: a rootless container cannot open a root:render
+        # 0660 node (its namespace maps one uid/gid, and keep-groups cannot grant
+        # an unmapped gid — measured 2026-10-19). Install the mode rule, re-trigger
+        # the node, then PROVE the node is other-accessible before the restart.
+        run_privileged install -m 0644 dankclaw/udev/98-halogen-npu-access.rules \
+            /etc/udev/rules.d/98-halogen-npu-access.rules
+        run_privileged udevadm control --reload-rules
+        run_privileged udevadm trigger --sysname-match="$(basename "$LLM_DRAGOON_DEV_ACCEL")"
+        # (`-o FILE` is not "other-writable" — it means "exists", and `-o` is also
+        # the OR operator inside test), so the bit is read straight off the mode.
+        if [[ $(( 8#$(stat -c '%a' "$LLM_DRAGOON_DEV_ACCEL") & 8#2 )) -eq 0 ]]; then
+            echo "ERROR: $LLM_DRAGOON_DEV_ACCEL is still $(stat -c '%a %U:%G' "$LLM_DRAGOON_DEV_ACCEL") after installing the access rule — the lane cannot open it rootless" >&2
+            return 1
+        fi
         for xl in libxrt_coreutil.so.2 libxrt_core.so.2 libxrt_driver_xdna.so.2; do
             if [[ ! -e "$LLM_DRAGOON_XRT_DIR/$xl" ]]; then
                 echo "ERROR: XRT NPU library $LLM_DRAGOON_XRT_DIR/$xl absent (Ubuntu libxrt2 + libxrt-npu2)" >&2
diff --git a/scripts/serve-frank-dragoon.sh b/scripts/serve-frank-dragoon.sh
index 24f6c82..cb5e6c9 100755
--- a/scripts/serve-frank-dragoon.sh
+++ b/scripts/serve-frank-dragoon.sh
@@ -165,6 +165,18 @@ if [ -n "$NPU_MODELS" ]; then
         echo "frank-dragoon: $DEV_ACCEL missing — the NPU lane needs the amdxdna node (is iommu=pt still on the boot line?)" >&2
         exit 1
     fi
+    # Existence is not access. This endpoint runs rootless, so the container's
+    # namespace maps exactly one uid/gid (dank) and a root:render 0660 node reads
+    # `nobody:nogroup` inside it — the engine then dies naming the node itself
+    # (measured 2026-10-19). --group-add keep-groups cannot help: an unmapped gid
+    # cannot be granted into a namespace that does not map it, verified with and
+    # without the flag from a shell already in `render`. The door is the udev mode.
+    # NB: `[ -o FILE ]` is NOT "other-writable" — it means "exists", and `-o` is
+    # also the OR operator inside test — so the permission bit is read directly.
+    if [ $(( 8#$(stat -c '%a' "$DEV_ACCEL") & 8#2 )) -eq 0 ]; then
+        echo "frank-dragoon: $DEV_ACCEL is $(stat -c '%a %U:%G' "$DEV_ACCEL") — a rootless container cannot open it; install dankclaw/udev/98-halogen-npu-access.rules and re-trigger udev (sudo udevadm control --reload-rules && sudo udevadm trigger --sysname-match=accel0)" >&2
+        exit 1
+    fi
     for M in ${NPU_MODELS//,/ }; do
         if [ ! -d "$NPU_DIR/$M" ]; then
             echo "frank-dragoon: NPU model $M not staged in $NPU_DIR;" >&2
diff --git a/serverAppConfigs-docs/LLM/frank-dragoon.md b/serverAppConfigs-docs/LLM/frank-dragoon.md
index 1c4c6f6..cde7abd 100644
--- a/serverAppConfigs-docs/LLM/frank-dragoon.md
+++ b/serverAppConfigs-docs/LLM/frank-dragoon.md
@@ -240,8 +240,15 @@ precondition that surfaces as an engine crash-loop is a gate that was never writ
 box as of 2026-10-19; the endpoint still runs with the lane **off** until that day's mount fix merges, and the first
 armed boot's evidence lands here with it:
 
-1. `--device /dev/accel/accel0` plus `--group-add keep-groups` (the pattern ComfyUI uses for `/dev/kfd`; `dank` is
-   already in `render`).
+1. `--device /dev/accel/accel0` **and** a node the container's namespace can open. `/dev/accel/accel0` is
+   `root:render 0660` and a rootless namespace maps exactly one uid/gid, so the engine's own first words are
+   *"this process cannot open it (crw-rw---- nobody:nogroup)"*. `--group-add keep-groups` — the vendor's advice and
+   the ComfyUI pattern for `/dev/kfd` — is **dead in this shape**: measured 2026-10-19 from a `dank` shell already
+   in `render`, with and without the flag the node stayed `nobody:nogroup` and the open was refused; an unmapped
+   gid cannot be granted across a namespace that does not map it. The door is the udev mode
+   (`dankclaw/udev/98-halogen-npu-access.rules`, installed and re-triggered by the deployer, `0666` like the GPU
+   compute nodes beside it); the serve script refuses any node that is not other-accessible, so the fault cannot
+   return as a crash-loop.
 2. The host's XRT reachable inside: there is **no `/opt/xilinx/xrt`** here — distro packages put the three files the
    container needs (`libxrt_coreutil.so.2`, `libxrt_core.so.2`, `libxrt_driver_xdna.so.2`) in
    `/usr/lib/x86_64-linux-gnu`, where all three exist.
diff --git a/tests/frank_dragoon_unit.bats b/tests/frank_dragoon_unit.bats
index d66555f..6f542f9 100755
--- a/tests/frank_dragoon_unit.bats
+++ b/tests/frank_dragoon_unit.bats
@@ -30,6 +30,7 @@ setup() {
     HOST_UNIT="$ROOT/dankclaw/host/halogen-fabric-clock"
     HOST_SERVICE="$ROOT/dankclaw/host/halogen-fabric-clock.service"
     NPU_FETCH="$ROOT/scripts/download-frank-dragoon-npu.sh"
+    NPU_RULE="$ROOT/dankclaw/udev/98-halogen-npu-access.rules"
     BUILD="$ROOT/scripts/build-rocmfpx.sh"
     TEST_TMP="$(mktemp -d)"
     touch "$TEST_TMP/empty.env"
@@ -418,7 +419,10 @@ $(cat "$TEST_TMP/serve.log")"
 # refused BY NAME instead of surfacing as an engine crash-loop.
 
 npu_fixture() {
+    # 0666 like the installed node: a rootless container's namespace cannot open
+    # the stock root:render 0660 mode, and the serve gate checks exactly that.
     touch "$TEST_TMP/accel0"
+    chmod 666 "$TEST_TMP/accel0"
     mkdir -p "$TEST_TMP/xrt"
     for l in libxrt_coreutil.so.2 libxrt_core.so.2 libxrt_driver_xdna.so.2; do
         touch "$TEST_TMP/xrt/$l"
@@ -526,6 +530,32 @@ $(cat "$TEST_TMP/serve.log")"
     [[ "$output" == *"iommu=pt"* ]]
 }
 
+@test "the lane refuses an NPU node the container namespace could not open, and names the rule" {
+    # Stock Debian mode is root:render 0660. The engine's own first words on such
+    # a node are "this process cannot open it (crw-rw---- nobody:nogroup)" and no
+    # flag fixes a mode an unmapped gid cannot cross (keep-groups measured dead
+    # 2026-10-19), so the unit refuses instead of crash-looping 189 times.
+    podman_stub
+    good_env
+    npu_fixture
+    chmod 660 "$TEST_TMP/accel0"
+    run_with_log
+    [ "$status" -ne 0 ]
+    [[ "$output" == *"$TEST_TMP/accel0 is 660"* ]]
+    [[ "$output" == *"98-halogen-npu-access.rules"* ]]
+    [[ "$output" != *"--device"* ]]
+}
+
+@test "the NPU access rule is the accel counterpart of the GPU compute rule" {
+    [ -f "$NPU_RULE" ]
+    grep -qE '^KERNEL=="accel\[0-9\]\*", SUBSYSTEM=="accel", MODE="0666"$' "$NPU_RULE"
+    # The deployer installs the rule and re-triggers the node BEFORE it trusts
+    # the mode, so a machine that never had it self-heals instead of refusing.
+    grep -qE '98-halogen-npu-access\.rules' "$DEPLOYER"
+    grep -qE 'udevadm control --reload-rules' "$DEPLOYER"
+    grep -qE 'udevadm trigger --sysname-match=' "$DEPLOYER"
+}
+
 @test "the lane refuses when an XRT NPU library is missing" {
     podman_stub
     good_env