implement-runtime-state-machine

name	implement-runtime-state-machine
description	Implement run, episode, step, attempt, cancellation, checkpoint, budget, or resume behavior in the durable local runtime.

Implement runtime state machine

Invariants

• committed actions are never repeated;
• attempts are append-only;
• event and projection advance atomically;
• finalization is idempotent;
• ambiguous provider outcomes remain ambiguous;
• cancellation is structured and diagnostic;
• no external call occurs inside a database transaction.

Workflow

1. Draw the transition table and list terminal/non-terminal states.
2. Define command preconditions and emitted events.
3. Implement reducer/domain transition separately from I/O.
4. Implement repository/application orchestration through ports.
5. Add injected failure points before and after each boundary.
6. Test interruption at every transition edge.
7. Test resume from every persisted non-terminal state.
8. Verify budget reservations/releases and duplicate command behavior.
9. Record event schema or migration impact.
10. Run replay test against golden event stream.

Required tests

• exhaustive transition test;
• illegal transition rejection;
• cancellation during provider call;
• crash before/after CAS and SQL commit;
• duplicate finalize;
• outcome_unknown timeout;
• hard budget stop;
• resume without duplicate action.

Do not “repair” a corrupt state by deleting evidence. Surface a diagnostic failure and preserve artifacts.