feat(sandbox): switch device plugin to CDI injection mode

.agents/skills/debug-openshell-cluster/SKILL.md

@@ -256,7 +256,43 @@ Look for:
 - `OOMKilled` — memory limits too low
 - `FailedMount` — volume issues
 
-### Step 8: Check DNS Resolution
+### Step 8: Check GPU Device Plugin and CDI (GPU gateways only)
+
+Skip this step for non-GPU gateways.
+
+The NVIDIA device plugin DaemonSet must be running and healthy before GPU sandboxes can be created. It uses CDI injection (`deviceListStrategy: cdi-cri`) to inject GPU devices into sandbox pods — no `runtimeClassName` is set on sandbox pods.
+
+```bash
+# DaemonSet status — numberReady must be >= 1
+openshell doctor exec -- kubectl get daemonset -n nvidia-device-plugin
+
+# Device plugin pod logs — look for "CDI" lines confirming CDI mode is active
+openshell doctor exec -- kubectl logs -n nvidia-device-plugin -l app.kubernetes.io/name=nvidia-device-plugin --tail=50
+
+# List CDI devices registered by the device plugin (requires nvidia-ctk in the cluster image).
+# Device plugin CDI entries use the vendor string "k8s.device-plugin.nvidia.com" so entries
+# will be prefixed "k8s.device-plugin.nvidia.com/gpu=". If the list is empty, CDI spec
+# generation has not completed yet.
+openshell doctor exec -- nvidia-ctk cdi list
+
+# Verify CDI spec files were generated on the node
+openshell doctor exec -- ls /var/run/cdi/
+
+# Helm install job logs for the device plugin chart
+openshell doctor exec -- kubectl -n kube-system logs -l job-name=helm-install-nvidia-device-plugin --tail=100
+
+# Confirm a GPU sandbox pod has no runtimeClassName (CDI injection, not runtime class)
+openshell doctor exec -- kubectl get pod -n openshell -o jsonpath='{range .items[*]}{.metadata.name}{" runtimeClassName="}{.spec.runtimeClassName}{"\n"}{end}'
+```
+
+Common issues:
+
+- **DaemonSet 0/N ready**: The device plugin chart may still be deploying (k3s Helm controller can take 1–2 min) or the pod is crashing. Check pod logs.
+- **`nvidia-ctk cdi list` returns no `k8s.device-plugin.nvidia.com/gpu=` entries**: CDI spec generation has not completed. The device plugin may still be starting or the `cdi-cri` strategy isn't active. Verify `deviceListStrategy: cdi-cri` is in the rendered Helm values.
+- **No CDI spec files at `/var/run/cdi/`**: Same as above — device plugin hasn't written CDI specs yet.
+- **`HEALTHCHECK_GPU_DEVICE_PLUGIN_NOT_READY` in health check logs**: Device plugin has no ready pods. Check DaemonSet events and pod logs.
+
+### Step 9: Check DNS Resolution
 
 DNS misconfiguration is a common root cause, especially on remote/Linux hosts:
 
@@ -315,6 +351,7 @@ If DNS is broken, all image pulls from the distribution registry will fail, as w
 | gRPC `UNIMPLEMENTED` for newer RPCs in push mode | Helm values still point at older pulled images instead of the pushed refs | Verify rendered `openshell-helmchart.yaml` uses the expected push refs (`server`, `sandbox`, `pki-job`) and not `:latest` |
 | Sandbox pods crash with `/opt/openshell/bin/openshell-sandbox: no such file or directory` | Supervisor binary missing from cluster image | The cluster image was built/published without the `supervisor-builder` target in `deploy/docker/Dockerfile.images`. Rebuild with `mise run docker:build:cluster` and recreate gateway. Bootstrap auto-detects via `HEALTHCHECK_MISSING_SUPERVISOR` marker |
 | `HEALTHCHECK_MISSING_SUPERVISOR` in health check logs | `/opt/openshell/bin/openshell-sandbox` not found in gateway container | Rebuild cluster image: `mise run docker:build:cluster`, then `openshell gateway destroy <name> && openshell gateway start` |
+| `nvidia-ctk cdi list` returns no `k8s.device-plugin.nvidia.com/gpu=` entries | CDI specs not yet generated by device plugin | Device plugin may still be starting; wait and retry, or check pod logs (Step 8) |
 
 ## Full Diagnostic Dump
 
@@ -368,4 +405,9 @@ openshell doctor exec -- ls -la /opt/openshell/bin/openshell-sandbox
 
 echo "=== DNS Configuration ==="
 openshell doctor exec -- cat /etc/rancher/k3s/resolv.conf
+
+# GPU gateways only
+echo "=== GPU Device Plugin ==="
+openshell doctor exec -- kubectl get daemonset -n nvidia-device-plugin
+openshell doctor exec -- nvidia-ctk cdi list
 ```

architecture/gateway-single-node.md

@@ -300,7 +300,7 @@ GPU support is part of the single-node gateway bootstrap path rather than a sepa
 - When enabled, the cluster container is created with Docker `DeviceRequests`, which is the API equivalent of `docker run --gpus all`.
 - `deploy/docker/Dockerfile.images` installs NVIDIA Container Toolkit packages in a dedicated Ubuntu stage and copies the runtime binaries, config, and `libnvidia-container` shared libraries into the final Ubuntu-based cluster image.
 - `deploy/docker/cluster-entrypoint.sh` checks `GPU_ENABLED=true` and copies GPU-only manifests from `/opt/openshell/gpu-manifests/` into k3s's manifests directory.
-- `deploy/kube/gpu-manifests/nvidia-device-plugin-helmchart.yaml` installs the NVIDIA device plugin chart, currently pinned to `0.18.2`. NFD and GFD are disabled; the device plugin's default `nodeAffinity` (which requires `feature.node.kubernetes.io/pci-10de.present=true` or `nvidia.com/gpu.present=true` from NFD/GFD) is overridden to empty so the DaemonSet schedules on the single-node cluster without requiring those labels.
+- `deploy/kube/gpu-manifests/nvidia-device-plugin-helmchart.yaml` installs the NVIDIA device plugin chart, currently pinned to `0.18.2`. NFD and GFD are disabled; the device plugin's default `nodeAffinity` (which requires `feature.node.kubernetes.io/pci-10de.present=true` or `nvidia.com/gpu.present=true` from NFD/GFD) is overridden to empty so the DaemonSet schedules on the single-node cluster without requiring those labels. The chart is configured with `deviceListStrategy: cdi-cri` so the device plugin injects devices via direct CDI device requests in the CRI.
 - k3s auto-detects `nvidia-container-runtime` on `PATH`, registers the `nvidia` containerd runtime, and creates the `nvidia` `RuntimeClass` automatically.
 - The OpenShell Helm chart grants the gateway service account cluster-scoped read access to `node.k8s.io/runtimeclasses` and core `nodes` so GPU sandbox admission can verify both the `nvidia` `RuntimeClass` and allocatable GPU capacity before creating a sandbox.
 
@@ -311,10 +311,12 @@ Host GPU drivers & NVIDIA Container Toolkit
     └─ Docker: --gpus all (DeviceRequests in bollard API)
         └─ k3s/containerd: nvidia-container-runtime on PATH -> auto-detected
             └─ k8s: nvidia-device-plugin DaemonSet advertises nvidia.com/gpu
-                └─ Pods: request nvidia.com/gpu in resource limits
+                └─ Pods: request nvidia.com/gpu in resource limits (CDI injection — no runtimeClassName needed)
 ```
 
-The expected smoke test is a plain pod requesting `nvidia.com/gpu: 1` with `runtimeClassName: nvidia` and running `nvidia-smi`.
+Device injection uses CDI (`deviceListStrategy: cdi-cri`): the device plugin injects devices via direct CDI device requests in the CRI. Sandbox pods only need `nvidia.com/gpu: 1` in their resource limits — no `runtimeClassName` field is set on GPU pods.
+
+The expected smoke test is a plain pod requesting `nvidia.com/gpu: 1` (without `runtimeClassName`) and running `nvidia-smi`.
 
 ## Remote Image Transfer
 

crates/openshell-server/src/sandbox/mod.rs

@@ -888,12 +888,7 @@ fn sandbox_template_to_k8s(
     }
 
     let mut spec = serde_json::Map::new();
-    if gpu {
-        spec.insert(
-            "runtimeClassName".to_string(),
-            serde_json::json!(GPU_RUNTIME_CLASS_NAME),
-        );
-    } else if !template.runtime_class_name.is_empty() {
+    if !template.runtime_class_name.is_empty() {
         spec.insert(
             "runtimeClassName".to_string(),
             serde_json::json!(template.runtime_class_name),
@@ -1030,13 +1025,6 @@ fn inject_pod_template(
         return pod_template;
     };
 
-    if gpu {
-        spec.insert(
-            "runtimeClassName".to_string(),
-            serde_json::json!(GPU_RUNTIME_CLASS_NAME),
-        );
-    }
-
     // Add hostAliases so sandbox pods can reach the Docker host.
     if !host_gateway_ip.is_empty() {
         spec.insert(
@@ -1828,6 +1816,41 @@ mod tests {
         }
     }
 
+    #[test]
+    fn gpu_inject_pod_template_does_not_set_runtime_class() {
+        let pod_template = serde_json::json!({
+            "spec": {
+                "containers": [{"name": "agent"}]
+            }
+        });
+
+        let result = inject_pod_template(
+            pod_template,
+            &SandboxTemplate::default(),
+            true,
+            "openshell/sandbox:latest",
+            "",
+            "sandbox-id",
+            "sandbox-name",
+            "https://gateway.example.com",
+            "0.0.0.0:2222",
+            "secret",
+            300,
+            &std::collections::HashMap::new(),
+            "",
+            "",
+        );
+
+        assert!(
+            result["spec"]["runtimeClassName"].is_null(),
+            "GPU pods using CDI injection must not have runtimeClassName set"
+        );
+        assert_eq!(
+            result["spec"]["containers"][0]["resources"]["limits"][GPU_RESOURCE_NAME],
+            serde_json::json!(GPU_RESOURCE_QUANTITY)
+        );
+    }
+
     #[test]
     fn gpu_sandbox_adds_runtime_class_and_gpu_limit() {
         let pod_template = sandbox_template_to_k8s(
@@ -1848,7 +1871,7 @@ mod tests {
 
         assert_eq!(
             pod_template["spec"]["runtimeClassName"],
-            serde_json::json!(GPU_RUNTIME_CLASS_NAME)
+            serde_json::Value::Null
         );
         assert_eq!(
             pod_template["spec"]["containers"][0]["resources"]["limits"][GPU_RESOURCE_NAME],
@@ -1954,7 +1977,7 @@ mod tests {
 
         assert_eq!(
             pod_template["spec"]["runtimeClassName"],
-            serde_json::json!(GPU_RUNTIME_CLASS_NAME)
+            serde_json::Value::Null
         );
         assert_eq!(
             pod_template["spec"]["containers"][0]["resources"]["limits"][GPU_RESOURCE_NAME],

deploy/kube/gpu-manifests/nvidia-device-plugin-helmchart.yaml

@@ -12,6 +12,10 @@
 # (which requires nvidia.com/gpu.present=true) is overridden to empty
 # so it schedules on any node without requiring NFD/GFD labels.
 #
+# CDI injection mode: the device plugin uses deviceListStrategy=cdi-cri so that
+# devices are injected via CDI hooks before container start. Sandbox pods only
+# need the nvidia.com/gpu resource request — no runtimeClassName is required.
+#
 # k3s auto-detects nvidia-container-runtime on PATH and registers the "nvidia"
 # RuntimeClass automatically, so no manual RuntimeClass manifest is needed.
 
@@ -28,6 +32,10 @@ spec:
   createNamespace: true
   valuesContent: |-
     runtimeClassName: nvidia
+    deviceListStrategy: cdi-cri
+    cdi:
+      nvidiaHookPath: /usr/bin/nvidia-cdi-hook
+    nvidiaDriverRoot: "/"
     gfd:
       enabled: false
     nfd: