Implement OIDC support for Gateway

README.md

@@ -8,13 +8,14 @@ A toolkit for building LLM-powered applications and agent loops.
 uv add ai
 ```
 
-AI Gateway usage works with the base package. Direct providers that use an
-OpenAI-compatible or Anthropic-compatible adapter load the corresponding
-official SDK lazily and require optional extras:
+AI Gateway API-key usage works with the base package. Direct providers that
+use an OpenAI-compatible or Anthropic-compatible adapter load the corresponding
+official SDK lazily. Vercel OIDC for AI Gateway also uses an optional extra:
 
 ```bash
 uv add "ai[openai]"      # OpenAI-compatible providers
 uv add "ai[anthropic]"   # Anthropic-compatible providers
+uv add "ai[vercel]"      # Vercel OIDC for AI Gateway
 ```
 
 ```python

examples/fastapi-vite/backend/main.py

@@ -2,8 +2,9 @@
 
 from __future__ import annotations
 
+import importlib
 import sys
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Protocol, cast
 
 import agent as agent_
 import fastapi
@@ -17,11 +18,67 @@
 if TYPE_CHECKING:
     from collections.abc import AsyncGenerator
 
+    import starlette.types
+
+
+class _VercelHeaders(Protocol):
+    def set_headers(self, headers: dict[str, str] | None) -> None: ...
+
+
+class VercelOIDCHeadersMiddleware:
+    def __init__(self, app: starlette.types.ASGIApp) -> None:
+        self.app = app
+
+    async def __call__(
+        self,
+        scope: starlette.types.Scope,
+        receive: starlette.types.Receive,
+        send: starlette.types.Send,
+    ) -> None:
+        headers = _vercel_headers()
+        if scope.get("type") != "http" or headers is None:
+            await self.app(scope, receive, send)
+            return
+
+        headers.set_headers(_scope_headers(scope))
+        try:
+            await self.app(scope, receive, send)
+        finally:
+            headers.set_headers(None)
+
+
+def _vercel_headers() -> _VercelHeaders | None:
+    try:
+        return cast(
+            "_VercelHeaders",
+            importlib.import_module("vercel.headers"),
+        )
+    except ModuleNotFoundError as exc:
+        if exc.name not in {"vercel", "vercel.headers"}:
+            raise
+        return None
+
+
+def _scope_headers(scope: starlette.types.Scope) -> dict[str, str]:
+    return {
+        _header_text(key): _header_text(value)
+        for key, value in scope.get("headers", [])
+    }
+
+
+def _header_text(value: object) -> str:
+    if isinstance(value, bytes | bytearray):
+        return bytes(value).decode("latin1")
+    return str(value)
+
+
 app = fastapi.FastAPI(
     title="py-ai-fastapi-chat",
     description="Chat demo using Python Vercel AI SDK",
 )
 
+app.add_middleware(VercelOIDCHeadersMiddleware)
+
 app.add_middleware(
     fastapi.middleware.cors.CORSMiddleware,
     allow_origins=["*"],

examples/fastapi-vite/e2e-test/run.sh

@@ -38,7 +38,7 @@ trap cleanup EXIT
 echo "Starting backend on :$BACKEND_PORT..."
 (
     cd "$ROOT/backend"
-    uv run --frozen --with-editable ~/src/py-ai/ fastapi dev main.py --port "$BACKEND_PORT"
+    uv run --frozen --with-editable "$ROOT/../.." fastapi dev main.py --port "$BACKEND_PORT"
 ) > "$LOGS/backend.log" 2>&1 &
 BACKEND_PID=$!
 

pyproject.toml

@@ -38,6 +38,9 @@ dependencies = [
 anthropic = ["anthropic>=0.83.0"]
 mcp = ["mcp>=1.18.0"]
 openai = ["openai>=2.14.0"]
+vercel = [
+    "vercel>=0.5.9",
+]
 
 [build-system]
 requires = ["hatchling", "uv-dynamic-versioning>=0.7.0"]

src/ai/providers/ai_gateway/client/__init__.py

@@ -1,6 +1,6 @@
 """Async client for the AI Gateway provider protocol."""
 
 from . import errors
-from ._client import GatewayClient, ModelType
+from ._client import AuthMethod, GatewayClient, ModelType
 
-__all__ = ["GatewayClient", "ModelType", "errors"]
+__all__ = ["AuthMethod", "GatewayClient", "ModelType", "errors"]