[Feature] Support Python 3.14 in Free-threaded mode without the Global Interpreter Lock (GIL)

[whybeyoung]

Checklist

• 1. If the issue you raised is not a feature but a question, please raise a discussion at https://github.com/sgl-project/sglang/discussions/new/choose Otherwise, it will be closed.
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Motivation

Background Information
Python 3.14, the latest stable version of the Python programming language, was officially released on October 7, 2025 (local time). Compared with its predecessor Python 3.13, it brings notable enhancements in both functionality and performance.

Key features of Python 3.14 include:
Python 3.14 supports running in a free-threaded mode without the Global Interpreter Lock (GIL)—a capability that helps improve the parallel performance of multi-threaded programs on multi-core CPUs.

Related resources

• uvloop 0.22.0 MagicStack/uvloop#692
• Support Python 3.14 Kludex/uvicorn#2723
• Python 3.14 support for PyTorch pytorch/pytorch#156856
• flashinfer 0.4.0 does not support python 3.13 or higher #11568