Add Python 3.14 support (#1100)

[acul71]

This PR adds Python 3.14 support to py-libp2p.

Changes

• Added Python 3.14 to classifiers in pyproject.toml
• Updated tox.ini to include Python 3.14 in test environments (core, lint, wheel, interop)
• Updated GitHub Actions workflow to test against Python 3.14 on both Linux and Windows
• Created newsfragment for issue Add Python 3.14 support #1100

Testing

• All tests pass with make pr
• Documentation builds successfully with make docs
• Newsfragment validated and included in release notes preview

Known Issue: coincurve Dependency

Current Status: Python 3.14 CI tests are currently failing due to a build issue with coincurve==21.0.0, not with Python 3.14 itself.

Root Cause:
The error RuntimeError: Expected exactly one LICENSE file in cffi distribution, got 0 occurs during coincurve's build process when it checks for LICENSE files in the cffi distribution. This is a known compatibility issue between coincurve==21.0.0 and cffi 2.0.0 (required for Python 3.14).

Fix Status:
The fix is already merged in coincurve's master branch:

• PR Add tox and mypy #188 (merged Oct 7, 2025): Fixes the LICENSE file detection issue
• PR add typing to transport and stream_muxer #203 (merged Oct 21, 2025): Adds Python 3.14 testing support

However, the latest coincurve release is v21.0.0 (March 8, 2025), which predates these fixes. Once coincurve releases a new version (likely v21.0.1 or v22.0.0) with these fixes, we can update the dependency and Python 3.14 CI tests should pass.

References:

• coincurve PR Add tox and mypy #188: Add get_cffi_distribution_license_files() ofek/coincurve#188
• coincurve PR add typing to transport and stream_muxer #203: Test Python 3.14 ofek/coincurve#203
• coincurve Issue Propose to rename INetwork.notify #219: python 3.14 ofek/coincurve#219
• coincurve Issue disable mypy check during CI temporarily and move black --check to Makefile #208: pip install fails with coincurve-21.0.0 but works with coincurve-20.0.0 on Windows ofek/coincurve#208

Status

✅ Python 3.14 support added to codebase
✅ All configuration files updated
⏳ Waiting for coincurve release with Python 3.14 fix

Note: The PR is ready to merge from a code perspective, but CI will fail for Python 3.14 until the coincurve dependency is updated.

Closes #1100

[acul71]

Hi @pacrob @seetadev it seems that we have to wait for coincurve to release a new version...

[seetadev]

@acul71 : Thank you so much for sharing the feedback.Appreciate it.

Ccing @ofek from Coincurve team.

@ofek: Hope you are doing well.

We are planning to add python 3.14 support.
Wish if you could visit the thread above.

Looking forward to hearing your thoughts and feedback.