Abstract chat simulation backends

[SakshiKekre]

Summary

• Add a model backend registry for the compiled UK engine and the Python policyengine-uk package
• Route chat tool execution through the selected backend
• Add a frontend model selector backed by GET /chat/backends
• Load local repo-root .env for backend dev and make conversation persistence best-effort when no DB is configured

Verification

• PYTHONPATH=backend .venv/bin/python -m pytest backend/tests/test_agent_tools.py -k "ModelBackends or Compute or ExecuteTool"
• PYTHONPATH=backend .venv/bin/python -m pytest backend/tests/test_api.py -k "ChatBackends"
• .venv/bin/python -m py_compile backend/main.py backend/agent_tools.py backend/model_backends.py backend/routes/chatbot.py backend/tests/test_agent_tools.py backend/tests/test_api.py
• npm run build

[vercel]

@SakshiKekre is attempting to deploy a commit to the PolicyEngine Team on Vercel.

A member of the Team first needs to authorize it.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
policyengine-uk-chat	Ready	Preview, Comment	Apr 29, 2026 6:29am