diff --git a/.gitea/workflows/release.yaml b/.gitea/workflows/release.yaml
index b92c1a4..1a3b8c9 100644
--- a/.gitea/workflows/release.yaml
+++ b/.gitea/workflows/release.yaml
@@ -171,6 +171,13 @@ jobs:
           SENTRY_ORG: libnovel
           SENTRY_PROJECT: ui
 
+      - name: Upload injected build (for docker-ui)
+        uses: actions/upload-artifact@v3
+        with:
+          name: ui-build-injected
+          path: build
+          retention-days: 1
+
       - name: Create GlitchTip release
         run: sentry-cli releases new ${{ steps.ver.outputs.version }}
         env:
@@ -226,6 +233,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Download injected build (debug IDs already embedded)
+        uses: actions/download-artifact@v3
+        with:
+          name: ui-build-injected
+          path: ui/build
+
       - uses: docker/setup-buildx-action@v3
 
       - name: Log in to Docker Hub
@@ -255,6 +268,7 @@ jobs:
             BUILD_VERSION=${{ steps.meta.outputs.version }}
             BUILD_COMMIT=${{ gitea.sha }}
             BUILD_TIME=${{ gitea.event.head_commit.timestamp }}
+            PREBUILT=1
           cache-from: type=registry,ref=${{ secrets.DOCKER_USER }}/libnovel-ui:latest
           cache-to: type=inline
 
diff --git a/ui/Dockerfile b/ui/Dockerfile
index 36e29a8..8b68e67 100644
--- a/ui/Dockerfile
+++ b/ui/Dockerfile
@@ -21,7 +21,11 @@ ENV PUBLIC_BUILD_VERSION=$BUILD_VERSION
 ENV PUBLIC_BUILD_COMMIT=$BUILD_COMMIT
 ENV PUBLIC_BUILD_TIME=$BUILD_TIME
 
-RUN npm run build
+# PREBUILT=1 skips npm run build — used in CI when the build/ directory has
+# already been compiled (and debug IDs injected) by a prior job.  The caller
+# must copy the pre-built build/ into the Docker context before building.
+ARG PREBUILT=0
+RUN [ "$PREBUILT" = "1" ] || npm run build
 
 # ── Runtime image ──────────────────────────────────────────────────────────────
 # adapter-node bundles most server-side code, but packages with dynamic