Durable workflows

Versioned flow graphs execute event, wait, condition, and action nodes through durable jobs.

Lifecycle

Draft flows have no active event subscription.
Activation validates the acyclic graph and creates the subscription atomically.
Wait nodes schedule a stable resume job.
Every condition records its observed value and selected branch.
Replay evaluates logic but never executes external actions.

Delivery guarantees

at_most_once prefers a miss over a duplicate. at_least_once prefers a duplicate over a miss. Notifie does not claim exactly-once delivery across external providers.