Demo UI fails to run due to pypika build failure

The issue is a build failure for pypika 0.48.9 with Python 3.14, due to an AttributeError about ast.Str. Check the project's dependency chain: crewai>=0.95.0 -> chromadb>=1.1.0, <1.2.dev0 -> pypika>=0.48.9. Look at the pyproject.toml or requirements.txt in the a2a-samples repository. Investigate if pypika has a newer version compatible with Python 3.14, or if a dependency constraint needs to be updated. Running uv run main.py reproduces the error.

What happened?

Steps to reproduce

1. Clone a2a-samples
2. Follow instructions in Demo's README.md
3. uv run main.py fails with the log output below

Environment config

==> sw_vers
ProductName:		macOS
ProductVersion:		26.0.1
BuildVersion:		25A362

==> python3 --version
Python 3.14.0

==> uv --version
uv 0.9.2 (141369ce7 2025-10-10)

Relevant log output

==> uv run main.py
Using CPython 3.14.0 interpreter at: /opt/homebrew/opt/python@3.14/bin/python3.14
Creating virtual environment at: /Users/dmt/Dev/a2a-samples/.venv
  × Failed to build `pypika==0.48.9`
  ├─▶ The build backend returned an error
  ╰─▶ Call to `setuptools.build_meta:__legacy__.build_wheel` failed (exit status: 1)

      [stderr]
      Traceback (most recent call last):
        File "<string>", line 14, in <module>
          requires = get_requires_for_build({})
        File "/Users/dmt/.cache/uv/builds-v0/.tmpw28aR2/lib/python3.14/site-packages/setuptools/build_meta.py", line
      331, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=[])
                 ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/Users/dmt/.cache/uv/builds-v0/.tmpw28aR2/lib/python3.14/site-packages/setuptools/build_meta.py", line
      301, in _get_build_requires
          self.run_setup()
          ~~~~~~~~~~~~~~^^
        File "/Users/dmt/.cache/uv/builds-v0/.tmpw28aR2/lib/python3.14/site-packages/setuptools/build_meta.py", line
      512, in run_setup
          super().run_setup(setup_script=setup_script)
          ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/Users/dmt/.cache/uv/builds-v0/.tmpw28aR2/lib/python3.14/site-packages/setuptools/build_meta.py", line
      317, in run_setup
          exec(code, locals())
          ~~~~^^^^^^^^^^^^^^^^
        File "<string>", line 38, in <module>
        File "<string>", line 20, in version
      AttributeError: module 'ast' has no attribute 'Str'

      hint: This usually indicates a problem with the package or the build environment.
  help: `pypika` (v0.48.9) was included because `a2a-samples-image-gen` (v0.1.0) depends on `crewai>=0.95.0` (v0.95.0)
        which depends on `chromadb>=1.1.0, <1.2.dev0` (v1.1.1) which depends on `pypika>=0.48.9`

Code of Conduct

• I agree to follow this project's Code of Conduct