Concurrency and parallelism

Tier	API	Use
Native thread	spawn, join	Independent or blocking tasks
Work-stealing pool	fork-task, fib.parallel	Chunked CPU work and nested parallel calls
Stackless	async, await, block-on	Suspended computations

fib.parallel adds with-tasks, fork, pmap, pfor, preduce and pscan. A scope waits for its children. Ordered reductions use input-derived chunks, so changing worker count does not choose a different default reduction tree (ADR 0021). FIB_THREADS sets the pool size. Mark OS-blocking sections in pool tasks with blocking; cancellation is still planned. Use atoms for shared updates. Cell captures and other non-Send data cannot cross threads. Exclusive tiles use fib.view.tiles; ordinary views cannot escape their scope.

(ns main)
(defun main () -> i64
  (let ((task (spawn (fn () (+ 20 22)))))
    (do (println (join task)) 0)))

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