usage-checker
Before an overnight agent batch kicks off, something has to check there is headroom left on the subscription. Claude Code only shows this inside an interactive session; usage-checker reads the same data from a shell and prints it as a single JSON object any script can parse.
Fail-closed by design: its gate mode exits non-zero when limits are too tight, so unattended runs stop cleanly instead of dying halfway through the night. Zero runtime dependencies.