The correct option is Run the env command from the container entrypoint to print all environment variables available at runtime.

For a Docker container action the entrypoint runs inside the container which means printing the environment there shows the exact variables the action can use. This approach reveals values provided by the workflow environment and default GitHub variables and any secrets that were mapped. It is the most direct way to verify whether GOOGLE_PROJECT and related variables are actually available when the action runs.

Review the env section in the action.yml to verify the variables defined for the action is incorrect because the metadata only describes defaults or expected inputs and it does not guarantee what the workflow passed at run time. Variables can be added or overridden in the workflow file or by the runner so you must check from inside the container.

Run docker inspect on the job container to view the environment configuration reported by Docker is incorrect because in GitHub Actions you do not manage the container directly and inspecting it from the host is not practical during a run. Even if you could inspect it you still might miss variables that are set or transformed by the entrypoint or shell at run time. Verifying from inside the container is authoritative.

Use Secret Manager to list the secret values and map them to the container environment is incorrect because listing secret values is not appropriate and does not reflect what the workflow actually exported. GitHub Actions injects secrets only when referenced and you should never print or enumerate secret values to debug environment presence.

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