Interface PaymentRouterOptions

On by default; pass false to disable outage memory entirely.

Fallback candidate chain; defaults to the service's registration order.

Observability: called once per failed/skipped candidate and once for the winner (error absent). Exceptions it throws are swallowed — routing always wins over observability, so never rely on this hook for control flow.

Observability: fired when a PSP's circuit opens (starts being skipped) or closes (a response proved it alive). A failed half-open probe restarts the cooldown without re-firing "opened" — the circuit never closed in between. Exception-isolated like onAttempt.

First matching rule wins. No match -> defaultChain.

Decides whether a failed candidate cascades to the next one. Default: transient PSP-side trouble only (err.retryable, psp_unavailable, rate_limited, processing_error). Business rejections (invalid_request, card_declined, …) abort the cascade — retrying them elsewhere would produce surprise duplicate sessions for a request that is simply wrong. The circuit breaker counts exactly the failures this predicate cascades on, so a custom predicate also redefines what the breaker treats as transient (anything else closes the circuit as proof of life).