Jordan Ritter 973b4e460e fix(sdk-python): loosen FastAPI version ceiling from ^0.115.0 to >=0.115.0,<1.0.0 (#3261) ...

## Problem

The Poetry caret constraint `^0.115.0` in `sdk-python/pyproject.toml`
resolves to `>=0.115.0,<0.116.0` for 0.x versions (per [PEP 440 / Poetry
docs](https://python-poetry.org/docs/dependency-specification/#caret-requirements)).
This blocks installation alongside any FastAPI release since **0.116.0
(June 2025)**.

Current stable FastAPI is **0.129.0** — 14 minor versions ahead of the
ceiling.

## Impact

- Cannot `pip install copilotkit` in any project using FastAPI >=0.116.0
- Multiple users blocked (see #2771 comments)
- Our production project has **~90 tests bypassed** with
`COPILOTKIT_AVAILABLE = False` guards because of this

## Fix

```diff
- fastapi = "^0.115.0"
+ fastapi = ">=0.115.0,<1.0.0"
```

This allows all current and future 0.x FastAPI releases while still
capping at the upcoming 1.0 major version boundary, which may introduce
breaking changes.

## Testing

- The SDK uses standard FastAPI features (routing, dependency injection,
middleware) that have been stable across all 0.11x–0.12x releases
- No FastAPI APIs used by the SDK were deprecated or removed in
0.116.0–0.129.0
- `ag-ui-langgraph` (also in deps) uses `>=0.115.0` without an upper
bound, so this change aligns the two constraints

## Note on `ag-ui-langgraph`

`ag-ui-langgraph[fastapi]` also depends on FastAPI. Its constraint is
already `>=0.115.0` (no ceiling), so this change to `copilotkit` is the
only fix needed.

Fixes #2771

2026-03-06 14:39:52 -04:00

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