Tracking UI returns HTTP 500 on all pages with Starlette ≥1.0 (TemplateResponse signature)

[burtherman]

Summary

The tracking UI server (burr / burr-admin-server) returns HTTP 500 on every page when Starlette ≥1.0 is installed. The JSON API is unaffected — only the served React app (index.html) fails. Because burr[start] doesn't pin Starlette (it arrives transitively via an unpinned fastapi), a fresh pip install "burr[start]" resolves to a current Starlette and the UI is broken out of the box.

Environment

• burr 0.40.2 (via burr[start])
• starlette 1.3.0, jinja2 3.1.6, fastapi 0.136.3
• Reproduced on Python 3.13 and 3.14 (version-independent)

Root cause

burr/tracking/server/run.py:341 uses the pre-1.0 Starlette signature:

return templates.TemplateResponse("index.html", {"request": req})

Starlette 0.29 made request the first positional argument and 1.0 removed the old form, so "index.html" binds to request and the context dict binds to name; Jinja2 then tries to load a template whose name is a dict and raises TypeError: unhashable type: 'dict'. (Same break FastAPI hit in fastapi/fastapi#15198.)

Fix

return templates.TemplateResponse(request=req, name="index.html")

This is the only TemplateResponse call site in the package; with it the UI renders (HTTP 200) on Python 3.14 + Starlette 1.3.0. Verified locally. Worth pairing with a starlette>=0.29 floor, since the keyword form requires it.

Traceback

File ".../burr/tracking/server/run.py", line 341, in react_app
    return templates.TemplateResponse("index.html", {"request": req})
File ".../starlette/templating.py", line 148, in TemplateResponse
    template = self.get_template(name)
File ".../jinja2/environment.py", line 1016, in get_template
    return self._load_template(name, globals)
TypeError: unhashable type: 'dict'

Happy to send a PR if useful.