fix(python-bridge): harden sync and async execution boundaries

[yujonglee-berri]

Layer 6 of 17 in the reorganized Rust bridge stack

Scope

Adds Pythonized conversion, panic mapping, and shared sync/async execution helpers for GIL release, nested-runtime rejection, signal polling, cancellation, and safe result conversion

The helpers live in crates/python-bridge/src/execution.rs, outside routes/, with inline tests. Routes retain request assembly and tracing. Packaged bridge tests cover sync and async success, traced responses, upstream errors, concurrency, and SIGINT cancellation

Review boundary

Rebased onto the current litellm_python_bridge_modules base, preserving its shared request assembly and tracing support. Later behavior remains outside this PR

Supersedes #39263, whose record GitHub automatically marked merged when its former stacked base temporarily became a descendant during the guarded branch rewrite. The original discussion remains there; this PR is the live review head

Validation

Formatting, focused strict Clippy for core/interop/bridge, and all 264 Rust workspace tests pass. The release wheel builds and passes the packaged route tests, including traced sync/async responses and SIGINT cancellation. Ruff passes for the packaged test script

Full gateway Clippy with the server feature reports three existing collapsible_if warnings in unchanged realtime code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[greptile-apps]

Greptile Summary

The PR centralizes Python bridge route execution behind shared sync and async runtime helpers, adding GIL release, signal handling, nested-runtime rejection, panic conversion, and Python result conversion

• Migrates OCR, transcription, messages, and chat-completion routes to the shared runtime
• Adds packaged-wheel coverage for successful calls, mapped errors, concurrency, cancellation, and signal handling
• Updates PyO3 and adds the Rust dependencies required by runtime and WebSocket tests

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or independently actionable non-blocking issue identified

The shared runtime preserves route conversion and error contracts while adding bounded signal handling, panic containment, nested-runtime protection, and packaged-wheel regression coverage

Important Files Changed

Filename	Overview
litellm-rust/crates/python-bridge/src/routes/runtime.rs	Adds a well-covered shared boundary for synchronous and asynchronous route execution, panic mapping, signal polling, and result conversion
litellm-rust/crates/python-interop/src/marshal.rs	Adds reusable panic-safe Pythonization while preserving the existing pythonize-based response shape and conversion errors
litellm-rust/crates/python-bridge/src/lib.rs	Updates module initialization for free-threaded Python support and preserves WebSocket header conversion and public registration
tests/test_litellm/rust_bridge/native_route_wheel_test.py	Adds bounded loopback-only packaged-wheel tests covering route behavior, concurrency, SIGINT propagation, and upstream cancellation
.github/workflows/test-rust.yml	Runs the new native route test against the single release wheel produced by the existing workflow

_{Reviews (1): Last reviewed commit: 2b0f7e6 | Re-trigger Greptile}