OpenAI Codex CLI Exits With Code 0 on Quota Error, Silently Failing Background Tasks

On August 7, 2026, a developer discovered that OpenAI's Codex CLI reported a usage-limit error exclusively to stderr while returning an empty stdout and an exit code of 0, making the failure indistinguishable from a successfully completed task. Any orchestration system relying solely on exit codes would silently log the quota failure as a finished job. The author found the same pattern — real error on stderr, empty stdout, clean exit — in a separate CLI from a different vendor, suggesting this is a common convention among subscription-gated tools that treat quota exhaustion as a billing condition rather than a program error. A secondary issue on macOS compounds the risk: the absence of a native timeout binary can cause wrapper scripts to return exit code 0 for a 'command not found' error. The developer now recommends treating exit codes as advisory only, flagging empty stdout as an independent failure, and always reading stderr regardless of apparent success signals.