diff --git a/deploy/helm/sie-cluster/README.md b/deploy/helm/sie-cluster/README.md
index 9ff8048ae..1999d9513 100644
--- a/deploy/helm/sie-cluster/README.md
+++ b/deploy/helm/sie-cluster/README.md
@@ -572,6 +572,32 @@ autoscaling:
   cooldownPeriod: 600  # 10 min before scale-down
 ```
 
+### Worker init containers and volumes
+
+`workers.common.extraInitContainers` adds init containers to every worker pod,
+run before the worker starts. `workers.common.extraVolumes` adds volumes for
+them. Both are standard Kubernetes lists and are not rendered on remote lanes.
+Init containers can also mount the worker's `shm` and `model-cache` volumes, plus
+`sie-ipc` and `kernel-cache` when those features are on. Extra volume names
+must not reuse a chart worker volume name (`shm`, `model-cache`, `sie-ipc`,
+`upstreams`, `equivalence`, `kernel-cache`); the render fails if they do.
+
+```yaml
+workers:
+  common:
+    extraInitContainers:
+      - name: wait-for-dependency
+        image: busybox:1.37.0
+        command: ["sh", "-c", "until wget -q -O /dev/null http://my-dependency/readyz; do sleep 2; done"]
+        volumeMounts:
+          - name: extra-config
+            mountPath: /etc/extra
+    extraVolumes:
+      - name: extra-config
+        configMap:
+          name: my-extra-config
+```
+
 ### Multi-GPU Worker Shapes
 
 Req6 separates the Kubernetes allocation shape from the worker execution shape.
diff --git a/deploy/helm/sie-cluster/templates/worker-statefulset.yaml b/deploy/helm/sie-cluster/templates/worker-statefulset.yaml
index 2dfc87d12..1ab944cd7 100644
--- a/deploy/helm/sie-cluster/templates/worker-statefulset.yaml
+++ b/deploy/helm/sie-cluster/templates/worker-statefulset.yaml
@@ -55,6 +55,11 @@ fast at render time.
 {{- end -}}
 {{- include "sie-cluster.env.assertNoReserved" (dict "path" "workers.common.extraEnv" "entries" $root.Values.workers.common.extraEnv "reserved" $reservedWorkerEnv) -}}
 {{- include "sie-cluster.env.assertNoReserved" (dict "path" "workers.common.workerSidecar.extraEnv" "entries" $root.Values.workers.common.workerSidecar.extraEnv "reserved" $reservedSidecarEnv) -}}
+{{- range $volume := (default (list) $root.Values.workers.common.extraVolumes) -}}
+{{- if has $volume.name (list "shm" "model-cache" "sie-ipc" "upstreams" "equivalence" "kernel-cache") -}}
+{{- fail (printf "workers.common.extraVolumes: %q is a chart-owned worker volume name" $volume.name) -}}
+{{- end -}}
+{{- end -}}
 {{- range $poolName, $pool := .Values.workers.pools }}
 {{- if $pool.enabled }}
 {{- if not $pool.bundles }}
@@ -295,6 +300,10 @@ spec:
         fsGroup: 1000
         runAsUser: 1000
         runAsGroup: 1000
+      {{- with (and (not $remoteLane) $root.Values.workers.common.extraInitContainers) }}
+      initContainers:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
       containers:
         {{- range $workerIndex := $workerIndexes }}
         {{- $workerSocket := "/var/run/sie/ipc.sock" }}
@@ -883,6 +892,9 @@ spec:
             name: {{ $evidenceConfigMap | quote }}
         {{- end }}
         {{- end }}
+        {{- with (and (not $remoteLane) $root.Values.workers.common.extraVolumes) }}
+        {{- toYaml . | nindent 8 }}
+        {{- end }}
 {{- end }}
 {{- end }}
 {{- end }}
diff --git a/deploy/helm/sie-cluster/values.yaml b/deploy/helm/sie-cluster/values.yaml
index b72af4176..5c8b979a0 100644
--- a/deploy/helm/sie-cluster/values.yaml
+++ b/deploy/helm/sie-cluster/values.yaml
@@ -698,6 +698,25 @@ workers:
     # scope. The sidecar additionally reserves its health/capacity identity.
     extraEnv: []
 
+    # -- Extra init containers for worker pods (standard Kubernetes container
+    # list), run before the worker starts. Not rendered on remote lanes. They
+    # can mount `extraVolumes`, `shm`, `model-cache`, and `sie-ipc` /
+    # `kernel-cache` when enabled:
+    #
+    #   - name: wait-for-dependency
+    #     image: busybox:1.37.0
+    #     command: ["sh", "-c", "until wget -q -O /dev/null http://my-dependency/readyz; do sleep 2; done"]
+    #     volumeMounts:
+    #       - name: extra-config
+    #         mountPath: /etc/extra
+    extraInitContainers: []
+
+    # -- Extra volumes for worker pods (standard Kubernetes volume list), e.g.
+    # for `extraInitContainers`. Not rendered on remote lanes. Names must not
+    # clash with the chart's worker volumes (shm, model-cache, sie-ipc,
+    # upstreams, equivalence, kernel-cache).
+    extraVolumes: []
+
     # -- Shared model cold-start/ready timeout in seconds. The chart renders
     # this into both containers as SIE_MODEL_READY_TIMEOUT_S: the adapter worker
     # uses it as an SGLang startup-health timeout fallback, and the Rust
diff --git a/tools/ci/tests/test_helm_render.py b/tools/ci/tests/test_helm_render.py
index e8210cb99..c7b9fd22d 100644
--- a/tools/ci/tests/test_helm_render.py
+++ b/tools/ci/tests/test_helm_render.py
@@ -3996,3 +3996,58 @@ def test_worker_auth_off_preserves_existing_image_compatibility(tmp_path: Path,
     assert "SIE_AUTH_TOKEN" not in env
     assert WORKER_AUTH_TEST_JOB not in hook_jobs(docs)
     assert worker_auth_requirements(docs) == {}
+
+
+EXTRA_INIT_CONTAINER = {
+    "name": "wait-for-dependency",
+    "image": "busybox:1.37.0",
+    "command": ["true"],
+    "volumeMounts": [{"name": "extra-config", "mountPath": "/etc/extra"}],
+}
+EXTRA_VOLUME = {"name": "extra-config", "configMap": {"name": "my-extra-config"}}
+
+
+def extra_init_values(**common: object) -> dict:
+    return {"workers": {"common": common, "pools": {"l4": {"enabled": True}}}}
+
+
+def test_workers_render_no_init_containers_by_default(tmp_path: Path) -> None:
+    for statefulset in worker_statefulsets(tmp_path, L4_POOL):
+        pod = statefulset["spec"]["template"]["spec"]
+        assert "initContainers" not in pod
+        assert "extra-config" not in {volume["name"] for volume in pod["volumes"]}
+
+
+def test_extra_init_containers_and_volumes_reach_every_worker(tmp_path: Path) -> None:
+    values = extra_init_values(extraInitContainers=[EXTRA_INIT_CONTAINER], extraVolumes=[EXTRA_VOLUME])
+    statefulsets = worker_statefulsets(tmp_path, values)
+    assert statefulsets
+    for statefulset in statefulsets:
+        pod = statefulset["spec"]["template"]["spec"]
+        assert pod["initContainers"] == [EXTRA_INIT_CONTAINER]
+        volumes = {volume["name"]: volume for volume in pod["volumes"]}
+        assert volumes["extra-config"] == EXTRA_VOLUME
+        assert pod["containers"][0]["name"] == "worker"
+
+
+def test_extra_init_containers_and_volumes_skip_remote_lanes(tmp_path: Path) -> None:
+    values = remote_pool_values(l4={"enabled": True})
+    values["workers"]["common"] = {"extraInitContainers": [EXTRA_INIT_CONTAINER], "extraVolumes": [EXTRA_VOLUME]}
+    pods = {
+        doc["metadata"]["name"]: doc["spec"]["template"]["spec"]
+        for doc in rendered_documents(tmp_path, values)
+        if doc["kind"] == "StatefulSet" and "-worker-" in doc["metadata"]["name"]
+    }
+    remote = pods.pop(REMOTE_WORKER[1])
+    assert "initContainers" not in remote
+    assert "extra-config" not in {volume["name"] for volume in remote["volumes"]}
+    assert pods
+    for pod in pods.values():
+        assert pod["initContainers"] == [EXTRA_INIT_CONTAINER]
+
+
+@pytest.mark.parametrize("name", ["shm", "model-cache", "sie-ipc", "upstreams", "equivalence", "kernel-cache"])
+def test_extra_volumes_cannot_reuse_a_chart_worker_volume_name(tmp_path: Path, name: str) -> None:
+    result = render_workers(tmp_path, extra_init_values(extraVolumes=[{"name": name, "emptyDir": {}}]))
+    assert result.returncode != 0
+    assert f'workers.common.extraVolumes: "{name}" is a chart-owned worker volume name' in result.stderr