Rust Async Conventions

Apply these conventions in async Rust projects. These rules are written for any coding agent, including Claude Code, Codex, Cursor, and Copilot.

Async Fundamentals

• An async fn returns a Future; it does nothing until awaited or driven by an executor.
• Do not call an async function without awaiting or spawning it.
• Use .await, not block_on, inside async contexts.
• Use async move blocks when a future must own captured values and outlive the current scope.

Lifetimes in Async

• A future returned by an async fn borrows its non-'static arguments.
• Await such futures while their borrowed arguments remain valid.
• When lifetime issues arise, move owned arguments into an async block.
• Futures passed to tokio::spawn or similar APIs must be 'static; move owned data in or use Arc.

Send and Sync