diff --git a/.env.example b/.env.example
index 60ef3e7..5b3237c 100644
--- a/.env.example
+++ b/.env.example
@@ -33,6 +33,11 @@ STATION_SWITCH_ENABLED=0
 # --- Vision ---
 # Internal address of the vision worker. Never exposed outside tmflow-net.
 VISION_WORKER_URL=http://vision:8100
+# The pinned VisionSuite commit, stamped into the vision image at build time
+# (Dockerfile.vision ARG). Required: `docker compose build vision` fails
+# immediately without it. Set with:
+#   VISION_ENGINE_VERSION=$(git -C vendor/visionsuite rev-parse HEAD)
+VISION_ENGINE_VERSION=
 
 # --- File Storage ---
 # Resolved against the project root in src/backend/config.py.
diff --git a/Dockerfile.vision b/Dockerfile.vision
index d44d00a..7e29cb1 100644
--- a/Dockerfile.vision
+++ b/Dockerfile.vision
@@ -24,6 +24,14 @@ COPY src/vision_worker/ ./src/vision_worker/
 #   VISION_ENGINE_VERSION=$(git -C vendor/visionsuite rev-parse HEAD) \
 #     docker compose build vision
 ARG VISION_ENGINE_VERSION
+# I4: a build without the commit must fail now, at build time - not later, at
+# every request including /health, with a container Docker still reports as
+# healthy because no healthcheck existed to say otherwise.
+RUN test -n "$VISION_ENGINE_VERSION" || { \
+        echo "VISION_ENGINE_VERSION is required. Build with:"; \
+        echo '  VISION_ENGINE_VERSION=$(git -C vendor/visionsuite rev-parse HEAD) docker compose build vision'; \
+        exit 1; \
+    }
 ENV VISION_ENGINE_VERSION=${VISION_ENGINE_VERSION}
 
 EXPOSE 8100
diff --git a/docker-compose.dev.yml b/docker-compose.dev.yml
index 46b54f6..8eb1b35 100644
--- a/docker-compose.dev.yml
+++ b/docker-compose.dev.yml
@@ -50,6 +50,12 @@ services:
         VISION_ENGINE_VERSION: ${VISION_ENGINE_VERSION:-}
     container_name: tmflow-vision
     restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python3", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8100/health', timeout=5)"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 20s
     networks:
       - tmflow-net
 
diff --git a/docker-compose.yml b/docker-compose.yml
index b3ead40..57d5c71 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -59,6 +59,12 @@ services:
         VISION_ENGINE_VERSION: ${VISION_ENGINE_VERSION:-}
     container_name: tmflow-vision
     restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python3", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8100/health', timeout=5)"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 20s
     networks:
       - tmflow-net