diff --git a/.dockerignore b/.dockerignore
index af1dfc73a35..73d00fff147 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -46,3 +46,15 @@ Swabble/
 Core/
 Users/
 vendor/
+
+# Needed for building the Canvas A2UI bundle during Docker image builds.
+# Keep the rest of apps/ and vendor/ excluded to avoid a large build context.
+!apps/shared/
+!apps/shared/OpenClawKit/
+!apps/shared/OpenClawKit/Tools/
+!apps/shared/OpenClawKit/Tools/CanvasA2UI/
+!apps/shared/OpenClawKit/Tools/CanvasA2UI/**
+!vendor/a2ui/
+!vendor/a2ui/renderers/
+!vendor/a2ui/renderers/lit/
+!vendor/a2ui/renderers/lit/**
diff --git a/Dockerfile b/Dockerfile
index 237a6a238ac..716ab2099f7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,7 +24,7 @@ COPY scripts ./scripts
 RUN pnpm install --frozen-lockfile
 
 COPY . .
-RUN OPENCLAW_A2UI_SKIP_MISSING=1 pnpm build
+RUN pnpm build
 # Force pnpm for UI build (Bun may fail on ARM/Synology architectures)
 ENV OPENCLAW_PREFER_PNPM=1
 RUN pnpm ui:build
diff --git a/scripts/bundle-a2ui.sh b/scripts/bundle-a2ui.sh
index 3936858309d..aeade1b0679 100755
--- a/scripts/bundle-a2ui.sh
+++ b/scripts/bundle-a2ui.sh
@@ -14,10 +14,14 @@ A2UI_RENDERER_DIR="$ROOT_DIR/vendor/a2ui/renderers/lit"
 A2UI_APP_DIR="$ROOT_DIR/apps/shared/OpenClawKit/Tools/CanvasA2UI"
 
 # Docker builds exclude vendor/apps via .dockerignore.
-# In that environment we must keep the prebuilt bundle.
+# In that environment we can keep a prebuilt bundle only if it exists.
 if [[ ! -d "$A2UI_RENDERER_DIR" || ! -d "$A2UI_APP_DIR" ]]; then
-  echo "A2UI sources missing; keeping prebuilt bundle."
-  exit 0
+  if [[ -f "$OUTPUT_FILE" ]]; then
+    echo "A2UI sources missing; keeping prebuilt bundle."
+    exit 0
+  fi
+  echo "A2UI sources missing and no prebuilt bundle found at: $OUTPUT_FILE" >&2
+  exit 1
 fi
 
 INPUT_PATHS=(