Effects, admission, and cancellation

Direct Scala operations execute immediately. Cats operations construct lazy effects: creating an effect performs no tmux I/O, and evaluating it again repeats the operation. Reusing a mutation effect is therefore a decision to repeat work, not to reuse an earlier result.

Captured values stay local¶

Captured information, relationships, and immutable collection filtering are pure reads in both facades. A subsystem accessor can also be local while its later operations perform I/O. Listing fresh state, refreshing a handle, format expansion, and mutations require execution.

Use the query concepts for local selection and the execution guide for effect boundaries. A filtered collection retains its capture; filtering does not make it current.

Bound submissions and admission¶

Cats command work crosses an interruptible blocking boundary. A concurrency limit bounds admitted calls, not the number of fibers your application may queue and not all memory used by transport workers. Use bounded traversal for a large input collection.

A wait that depends on another command must leave capacity for the command that can release it. The facade’s waiting operations reserve such capacity; respect their documented minimum rather than sharing an exhausted pool with the producer.

Ordered traversal can preserve the order of returned results while concurrent mutations reach tmux in a different order. Keep dependent mutations sequential. A Java command timeout begins after Scala admission; an effect timeout can cover waiting for admission too, while cleanup may still take additional time.

A canceled effect may have dispatched¶

Cancellation interrupts local work and waits for cleanup. It does not undo a mutation, kill a daemon-side shell job, or trigger an automatic retry. The underlying dispatch state distinguishes a command that was not sent from one whose effect is unknown.

A control acknowledgement confirms a protocol reply. Deferred work can still be running. Use a separate completion signal for the application-level task, and a separate attachment if its observation must survive command cancellation.

The execution guide describes the observer used to inspect dispatch outcomes and the exact admission rules. The complete transport programs show cleanup around both command calls and persistent control clients.