ETS-backed per-expectation circuit breaker.

States: :closed → :open → :half_open → :closed.

When consecutive failures exceed the threshold, the circuit opens and rejects new episodes. After half_open_after_ms, the circuit enters :half_open — allowing one probe episode. If it succeeds, the circuit closes; if it fails, the circuit reopens.

Configuration

Set circuit_breaker on an expectation:

expect :check_health,
  circuit_breaker: %{threshold: 5, half_open_after_ms: 60_000}

ETS layout

Key: {actor_id, expectation_id} Value: %{state: atom, consecutive_failures: int, opened_at: DateTime | nil}