Platform

A limit that fits how you actually work.

Caps are read by the guard on every tool call. Everything is off until you switch it on, and every limit is a number you set — or one of four presets sized from this machine's own median session and median day.

Oversized read hold

A read with no offset or limit, on a file whose size implies more than the threshold, pauses and asks. A paged or searched read goes straight through.

Three budgets

A session budget, a daily one, and a tighter unattended one. The meter is the session's own transcript, parsed incrementally from a stored offset.

Unattended means nobody is there

Mockingbyrd's heartbeat is stale, so there is no one to ask. That work gets the tighter cap, because a loop at 3am is what empties a budget.

This layer fails open, on purpose

Any error inside the cap logic — an unreadable policy, a half-written transcript, a corrupt tally — lets the call through. The checks above it, for originals and destructive verbs, stay fail-closed.

That asymmetry is deliberate and it is the design's most important line. A safety control that fails open is not a control. A cost control that fails closed stops your work because a JSON file was half-written, and a cost control that stops your work gets uninstalled by the end of the week.

A cap that trips says what it is about

It uses the same ask-and-wait protocol as a doctrine block — the hook writes a request, the app raises the prompt, you answer — and the prompt says in as many words that this one is about cost rather than safety. Confusing the two teaches people to dismiss both.

Presets, measured rather than invented

Off, careful, everyday and lean are derived from your own transcripts: the median session and the median day on this machine. A limit copied from someone else's working pattern is a limit you will spend a week fighting.

What is deliberately not built

  • No OpenTelemetry receiver and no adapters for agents beyond Claude Code and Codex.
  • No remediation scripts and no alerting.
  • No way for Mockingbyrd to change an agent's effort level.