Cloud Run: Container failed to start and then listen on the port

Full error: "Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable."

Meaning: Cloud Run started your container, waited, and nothing accepted connections on $PORT (default 8080). The container may have crashed instantly or bound the wrong port.

Fix checklist, in order:

1. Read PORT from the environment in your code. Never hardcode 3000/5000/8000. In Node: process.env.PORT || 8080. In Python: os.environ.get("PORT", 8080). In Go: os.Getenv("PORT").
2. Bind the all-interfaces address, not YOUR_HOST. Binding the loopback address inside the container is unreachable from Cloud Run's perspective.
3. Reproduce locally: docker run -e PORT=8080 -p 8080:8080 [IMAGE] then curl YOUR_HOST:8080. If it fails locally, it is your image, not Cloud Run.
4. Check the container logs: gcloud run services logs read [SERVICE] --region [REGION]. A crash traceback here means fix the crash first.
5. Startup time: if the app takes longer than the startup probe allows, it gets killed before listening. Optimize startup or raise CPU.

Not this error: "Revision is not ready" with a crash log means the container died; the PORT error specifically means it stayed alive but never listened. Different fix.

Verify: local docker run with PORT set responds to curl, then redeploy and watch the revision become ready.

Verified 2026-09-26 on the Cloud Run troubleshooting docs, which document this exact error string and the resolution steps (run locally, check listening). The PORT env contract is documented in the deploy docs.