> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sifr.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# SIFR-RUST-ASYNC-0001: Rust async interop contract is invalid.

> Rust async interop contract is invalid.

`SIFR-RUST-ASYNC-0001` belongs to the **Rust async interop** diagnostic family. It means: rust async interop contract is invalid.

## Why It Happens

A Rust async, blocking, or runtime-affinity bridge rule was violated.

<Info>
  Use `sifr --explain SIFR-RUST-ASYNC-0001` locally to see the renderer's exact message template and any machine-applicable suggestions for the compiler version you are running.
</Info>

## Details

| Field                  | Value                                                                                                                           |
| ---------------------- | ------------------------------------------------------------------------------------------------------------------------------- |
| Code                   | `SIFR-RUST-ASYNC-0001`                                                                                                          |
| Family                 | `RUST-ASYNC`                                                                                                                    |
| Severity               | Error                                                                                                                           |
| Stability              | stable                                                                                                                          |
| Owner                  | `sifr_driver::build::rust_interop`                                                                                              |
| Representative fixture | `crates/sifr_driver/src/build/rust_interop_async_contract_tests.rs::package_rust_interop_async_requires_send_future_by_default` |

See the [Error Codes index](/diagnostics/error-codes) for the complete catalog.