diff --git a/braintrust/templates/api-deployment.yaml b/braintrust/templates/api-deployment.yaml
index 4d99d1b..32aa6e4 100644
--- a/braintrust/templates/api-deployment.yaml
+++ b/braintrust/templates/api-deployment.yaml
@@ -137,8 +137,12 @@ spec:
             - name: NODE_EXTRA_CA_CERTS
               value: "/etc/braintrust/tls/ca-bundle.pem"
             {{- end }}
-          {{- if or (and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver) .Values.customTLSCABundle }}
+          {{- if or .Values.api.tmpVolume.enabled (and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver) .Values.customTLSCABundle }}
           volumeMounts:
+            {{- if .Values.api.tmpVolume.enabled }}
+            - name: tmp-volume
+              mountPath: /tmp
+            {{- end }}
             {{- if and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver }}
             - name: secrets-store-inline
               mountPath: "/mnt/secrets-store"
@@ -150,8 +154,17 @@ spec:
               readOnly: true
             {{- end }}
           {{- end }}
-      {{- if or (and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver) .Values.customTLSCABundle }}
+      {{- if or .Values.api.tmpVolume.enabled (and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver) .Values.customTLSCABundle }}
       volumes:
+        {{- if .Values.api.tmpVolume.enabled }}
+        - name: tmp-volume
+          emptyDir:
+            {{- if .Values.api.tmpVolume.sizeLimit }}
+            sizeLimit: {{ .Values.api.tmpVolume.sizeLimit | quote }}
+            {{- else }}
+            {}
+            {{- end }}
+        {{- end }}
         {{- if .Values.customTLSCABundle }}
         - name: tls-ca
           projected:
diff --git a/braintrust/templates/brainstore-reader-deployment.yaml b/braintrust/templates/brainstore-reader-deployment.yaml
index e11ef25..9ef0a5a 100644
--- a/braintrust/templates/brainstore-reader-deployment.yaml
+++ b/braintrust/templates/brainstore-reader-deployment.yaml
@@ -142,6 +142,8 @@ spec:
           volumeMounts:
             - name: cache-volume
               mountPath: {{ .Values.brainstore.reader.cacheDir }}
+            - name: tmp-volume
+              mountPath: /tmp
             {{- if and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver }}
             - name: secrets-store-inline
               mountPath: "/mnt/secrets-store"
@@ -165,8 +167,16 @@ spec:
                   requests:
                     storage: {{ required "brainstore.reader.volume.size must be set" .Values.brainstore.reader.volume.size | quote }}
           {{- else }}
-          emptyDir: {}
+          emptyDir:
+            {{- if .Values.brainstore.reader.volume.sizeLimit }}
+            sizeLimit: {{ .Values.brainstore.reader.volume.sizeLimit | quote }}
+            {{- else }}
+            {}
+            {{- end }}
           {{- end }}
+        - name: tmp-volume
+          emptyDir:
+            sizeLimit: "1Gi"
         {{- if and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver }}
         - name: secrets-store-inline
           csi:
diff --git a/braintrust/templates/brainstore-writer-deployment.yaml b/braintrust/templates/brainstore-writer-deployment.yaml
index fd2e66a..62bfb68 100644
--- a/braintrust/templates/brainstore-writer-deployment.yaml
+++ b/braintrust/templates/brainstore-writer-deployment.yaml
@@ -142,6 +142,8 @@ spec:
           volumeMounts:
             - name: cache-volume
               mountPath: {{ .Values.brainstore.writer.cacheDir }}
+            - name: tmp-volume
+              mountPath: /tmp
             {{- if and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver }}
             - name: secrets-store-inline
               mountPath: "/mnt/secrets-store"
@@ -165,8 +167,16 @@ spec:
                   requests:
                     storage: {{ required "brainstore.writer.volume.size must be set" .Values.brainstore.writer.volume.size | quote }}
           {{- else }}
-          emptyDir: {}
+          emptyDir:
+            {{- if .Values.brainstore.writer.volume.sizeLimit }}
+            sizeLimit: {{ .Values.brainstore.writer.volume.sizeLimit | quote }}
+            {{- else }}
+            {}
+            {{- end }}
           {{- end }}
+        - name: tmp-volume
+          emptyDir:
+            sizeLimit: "1Gi"
         {{- if and (eq .Values.cloud "azure") .Values.azure.enableAzureKeyVaultDriver }}
         - name: secrets-store-inline
           csi:
diff --git a/braintrust/values.yaml b/braintrust/values.yaml
index 1871595..b7b7446 100644
--- a/braintrust/values.yaml
+++ b/braintrust/values.yaml
@@ -115,11 +115,17 @@ api:
   #   runAsUser: 1000
   #   runAsGroup: 1000
   #   fsGroup: 1000
-  # Optional: Container-level security context
-  # securityContext:
-  #   capabilities:
-  #     drop:
-  #       - ALL
+  # Container-level security context (enabled for CEL policy compliance)
+  securityContext:
+    readOnlyRootFilesystem: true
+    allowPrivilegeEscalation: false
+    capabilities:
+      drop:
+        - ALL
+  # Temporary directory configuration (needed when readOnlyRootFilesystem is true)
+  tmpVolume:
+    enabled: true
+    sizeLimit: "1Gi"
   # Allow running user generated code functions (e.g. scorers/tools)
   allowCodeFunctionExecution: true
   # Brainstore backfill configuration. These defaults are fine for most cases.
@@ -229,11 +235,13 @@ brainstore:
     #   runAsUser: 1000
     #   runAsGroup: 1000
     #   fsGroup: 1000
-    # Optional: Container-level security context
-    # securityContext:
-    #   capabilities:
-    #     drop:
-    #       - ALL
+    # Container-level security context (enabled for CEL policy compliance)
+    securityContext:
+      readOnlyRootFilesystem: true
+      allowPrivilegeEscalation: false
+      capabilities:
+        drop:
+          - ALL
     cacheDir: "/mnt/tmp/brainstore"
     objectStoreCacheMemoryLimit: "1Gi"
     objectStoreCacheFileSize: "50Gi"
@@ -243,6 +251,8 @@ brainstore:
     volume:
       # Storage size for ephemeral storage requests (used with GKE Autopilot local SSDs)
       size: ""
+      # EmptyDir sizeLimit (separate from ephemeral-storage requests, required for CEL policy compliance)
+      sizeLimit: "50Gi"
     extraEnvVars: []
     nodeSelector: {}
     tolerations: []
@@ -275,11 +285,13 @@ brainstore:
     #   runAsUser: 1000
     #   runAsGroup: 1000
     #   fsGroup: 1000
-    # Optional: Container-level security context
-    # securityContext:
-    #   capabilities:
-    #     drop:
-    #       - ALL
+    # Container-level security context (enabled for CEL policy compliance)
+    securityContext:
+      readOnlyRootFilesystem: true
+      allowPrivilegeEscalation: false
+      capabilities:
+        drop:
+          - ALL
     cacheDir: "/mnt/tmp/brainstore"
     objectStoreCacheMemoryLimit: "1Gi"
     objectStoreCacheFileSize: "50Gi"
@@ -290,6 +302,8 @@ brainstore:
       # Storage size for ephemeral storage requests
       # Used with GKE Autopilot local SSDs and Azure Container Storage CSI
       size: ""
+      # EmptyDir sizeLimit (separate from ephemeral-storage requests, required for CEL policy compliance)
+      sizeLimit: "50Gi"
     extraEnvVars: []
     # Example:
     # - name: MY_ENV_VAR