Structured concurrency

AGL 0.5 owns concurrent work as a scope. Ordinary parallel, ordered parallel map, and race join their children before leaving the statement. race sends cooperative cancellation to losers.

let summaries = parallel map document in documents max_concurrency 4 fail_fast {
  let summary = summarize(document);
};

let answer = race {
  let primary = ask_primary(question);
  let backup = ask_backup(question);
};

parallel map preserves input ordering regardless of completion order. fail_fast stops scheduling later chunks after a failure; collect_all completes the dataset and aggregates failures. Direct task calls keep cancellation and durable identity unambiguous in 0.5.

Task/tool declarations can share a scheduler contract with concurrency_group api concurrency_limit 4 rate_limit 10. Pipeline budget { concurrency: ... } still caps a local scope, while named groups coordinate calls across scopes.