---

title: Enforce time limits in the worker and again from the controller status: accepted tags:

• decision
• runner
• scheduler

origin: kind: agent recorded_at: '2026-10-29T16:05:48.302Z' id: ADR-runner-two-level-time-limits type: adr --- ## Context

A mutated clause can loop forever or backtrack exponentially. call_with_time_limit/2 in the worker is not enough on its own: code under test can catch time_limit_exceeded and keep looping, and a blocking read on the worker pipe would hang the controller with it.

Decision

Each mutant gets timeout_factor times its covering tests' dry-run time plus timeout_ms, enforced by the worker. The controller enforces a hard limit 10 seconds later, reads worker pipes without blocking, and kills and replaces a worker that misses it.

Consequences

A runaway mutant is always settled as timeout and the pool keeps going. Timeouts are not retried, because a timeout already counts as detected.