ci: compile on scratch before assembling the runtime image

Dockerfile.runtime

@@ -0,0 +1,6 @@
+# Jenkins compiles on its scratch PVC; image assembly needs no toolchain layers.
+FROM gcr.io/distroless/static-debian12:nonroot@sha256:afa5c872c891853ca7fcf1f12c3edb23f7eeef36189728842dd51042ff57f7ab
+COPY soteria /soteria
+USER 65532:65532
+EXPOSE 8080
+ENTRYPOINT ["/soteria"]

Jenkinsfile

@@ -49,7 +49,7 @@ spec:
       resources:
         requests:
           cpu: 100m
-          memory: 1Gi
+          memory: 512Mi
         limits:
           cpu: 1500m
           memory: 2Gi
@@ -63,6 +63,19 @@ spec:
       command:
         - cat
       tty: true
+      resources:
+        requests: {cpu: 200m, memory: 512Mi}
+        limits: {cpu: 1500m, memory: 2Gi}
+      volumeMounts:
+        - name: workspace-volume
+          mountPath: /home/jenkins/agent
+    - name: ui-builder
+      image: node:22-alpine@sha256:0a7108bf6c7bf5de370ffb1a3ed6be93d405b43ff159f681a8d18c0e2bc2e402
+      command: [cat]
+      tty: true
+      resources:
+        requests: {cpu: 25m, memory: 64Mi}
+        limits: {cpu: 1000m, memory: 512Mi}
       volumeMounts:
         - name: workspace-volume
           mountPath: /home/jenkins/agent
@@ -545,6 +558,26 @@ PY
         }
       }
     }
+    stage('Build release on scratch') {
+      when {
+        expression { return params.PUBLISH_IMAGES }
+      }
+      steps {
+        container('ui-builder') {
+          sh 'cd web && npm ci && npm run build'
+        }
+        container('tester') {
+          // Reuse the tested Go cache and put compiler writes on the workspace PVC.
+          sh '''
+            set -eu
+            mkdir -p build/image internal/server/ui-dist
+            cp -R web/dist/. internal/server/ui-dist/
+            CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -p 2 -buildvcs=false -trimpath -ldflags="-s -w" -o build/image/soteria ./cmd/soteria
+            cp Dockerfile.runtime build/image/Dockerfile
+          '''
+        }
+      }
+    }
     stage('Build & push image') {
       when {
         expression { return params.PUBLISH_IMAGES }
@@ -561,11 +594,8 @@ PY
               printf '{"auths":{"registry.bstein.dev":{"auth":"%s"}}}\\n' "${auth}" > /kaniko/.docker/config.json
               trap 'rm -f /kaniko/.docker/config.json' EXIT
               /kaniko/executor \
-                --context "${WORKSPACE}" \
-                --dockerfile "${WORKSPACE}/Dockerfile" \
-                --build-arg BUILDPLATFORM=linux/arm64 \
-                --build-arg TARGETOS=linux \
-                --build-arg TARGETARCH=arm64 \
+                --context "${WORKSPACE}/build/image" \
+                --dockerfile "${WORKSPACE}/build/image/Dockerfile" \
                 --destination "registry.bstein.dev/bstein/soteria:${VERSION_TAG}" \
                 --destination registry.bstein.dev/bstein/soteria:latest
             '''

deploy/NOTES.md

@@ -14,3 +14,15 @@ RoleBindings in each backup/restore target namespace: Job creation and the
 credential-copy operations in `internal/k8s/jobs.go`. Those grants are not part
 of this Longhorn deployment. Review credential distribution before enabling
 restic; Kubernetes RBAC cannot restrict Secret creation by resource name.
+
+## CI image construction
+
+Jenkins compiles the UI and ARM64 Go binary in its `ci-scratch` workspace PVC.
+Compiler and package caches also use that PVC. The final Kaniko step receives
+only `build/image/` and `Dockerfile.runtime`, so it packages the binary without
+unpacking Node/Go toolchains or compiling on the node's runtime filesystem.
+The ordinary multistage `Dockerfile` remains available for workstation builds.
+
+Keep `CGO_ENABLED=0`, the UI embedding step and the runtime architecture aligned.
+The runtime image stays nonroot and exposes the same port and entrypoint. Image
+publication still requires all existing quality and supply-chain gates.