---

name: x07-concurrency description: Canonical deterministic concurrency patterns in X07 (defasync + task.* + chan.bytes.*), including the determinism constraints. metadata: short-description: Deterministic async patterns version: 0.1.0 kind: docs

x07-concurrency

In deterministic solve-* worlds, X07 concurrency is deterministic and virtual (no OS threads); blocking points are explicit.

In OS worlds (run-os*), use subprocess spawning for multi-core parallelism. In run-os-sandboxed, process spawning must be enabled by policy (start from x07 policy init --template worker-parallel when needed).

Canonical patterns

• Use defasync + task.* + chan.bytes.* for deterministic concurrency.
• Avoid implicit sources of nondeterminism (OS clocks, random, network) in solve worlds.
• Keep scheduling decisions explicit and data-driven (inputs → outputs), so runs are replayable.

For the built-in reference guide, use x07 guide and search for defasync / task. / chan.bytes..