Python: [Feature]: Inbound chat middleware sample for an optional third-party pre-model screener

@eavanvalkenburg is already working on this.

Since Sep 10, 2026.

## Language / SDK

Python

## Summary

I would like maintainer direction before writing code.

Little Canary is a third-party inbound screener maintained by Hermes Labs, and I am affiliated with Hermes Labs. The proposed integration would remain optional and externally maintained.

The intended implementation target is existing Python chat middleware, subject to maintainer confirmation that its current pre-model and termination semantics are the supported integration seam. No framework API change is requested.

## Problem and proposed behavior

An operator may want to screen supported outbound text before it reaches a model while retaining an explicit record of whether screening occurred.

If accepted, the integration would:

- inspect supported outbound text through the current public Little Canary API, reverified immediately before implementation;
- preserve the checker’s current public result fields without renaming or inventing values;
- make degraded behavior operator-selectable, with allow/fail-open as the default;
- pass unsupported or non-text content through while marking it unscreened;
- avoid breaking Agent Framework imports when the optional dependency is absent; and
- use only the current, maintainer-approved middleware and termination contracts.

This is not proposed as a replacement for existing security wiring. It makes no claim of parity, efficacy, comprehensive safety coverage, or adoption.

## Overlap and route decision

Before filing, I was unable to complete a conclusive duplicate and owner-history check within the verification timebox. Please point me to an existing issue or integration if this overlaps prior work.

Otherwise, please select one or neither:

1. one small sample under `python/samples`;
2. an external integration maintained in Little Canary, with a documentation link from the appropriate Agent Framework security or samples page; or
3. neither.

## Tests if accepted

- A permitted result continues exactly once.
- A configured blocking result terminates through the supported middleware contract and the model is not called.
- Disabled mode makes no checker call.
- Both configured degraded behaviors are covered.
- Unsupported and non-text content passes through explicitly marked unscreened.
- Boundary-length behavior follows the reverified dependency contract rather than an invented framework limit.
- A missing optional dependency produces a clear integration error without breaking unrelated host imports.

No implementation or PR will begin until maintainers confirm the route.

**Exact wait event:** maintainer selects option 1, option 2, or neither.