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Scope Strategies

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from cqrs import ScopeStrategy

mediator = bootstrap.bootstrap(
    di_container=container,
    commands_mapper=commands_mapper,
    scope_strategy=ScopeStrategy.SEND,  # opt-in; default is NONE
)
Strategy Boundary Typical use
SEND One scope per mediator.send() / stream(), including domain events and fallback Outbox / one transaction for command + events
HANDLER Fresh scope per resolve+handle (command, event, saga step, and fallback). Always nested. Isolated UoW; parallel events
NONE (default) No framework scopes No generators; unchanged legacy resolve

Decision

I need… Use
Command, domain events, and outbox on one session SEND (Tutorial)
Fallback to start clean after the primary rolls back HANDLER
Parallel event handlers HANDLER or NONE — not SEND
No generator providers NONE (omit scope_strategy=)

Fallback

There is no fallback_shares_scope flag — the strategy is the answer.

  • SEND — fallback is another handler of the same send(). Same UoW, including a session that may need rollback() / a savepoint after a database error. Outbox rows from the primary stay in the session.
  • HANDLER — the primary scope exits with rollback first (the generator sees except, not a successful commit). Then fallback opens its own scope. Primary writes are not visible.
  • NONE — one-shot resolve, same as before scoped dependencies.

On a stream, items already yielded to the client are not cancelled; only the unit of work changes.

Where the edge cases live