> ## 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-PYCB-0001: A Python callback lifetime, dispatch, concurrency, or owner declaration is invalid.

> A Python callback lifetime, dispatch, concurrency, or owner declaration is invalid.

`SIFR-PYCB-0001` belongs to the **Python-to-Sifr callbacks** diagnostic family. It means: a Python callback lifetime, dispatch, concurrency, or owner declaration is invalid.

## Why It Happens

A Python-to-Sifr callback lifetime, dispatch, or closure contract was violated.

<Info>
  Use `sifr --explain SIFR-PYCB-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-PYCB-0001`                                                                                                |
| Family                 | `PYCB`                                                                                                          |
| Severity               | Error                                                                                                           |
| Stability              | stable                                                                                                          |
| Owner                  | `sifr_lowering`                                                                                                 |
| Representative fixture | `crates/sifr_lowering/src/lower/python_interop_callback_tests.rs::callback_policy_validates_before_reservation` |

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