Replace httpx and httpx-sse with httpx2 (#2972)

Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

tests/interaction/transports/test_hosting_http.py

@@ -9,7 +9,7 @@ travels on -- that the SDK client never exposes. Transport-agnostic behaviour is
 import anyio
 import pytest
 from anyio.lowlevel import checkpoint
-from httpx_sse import ServerSentEvent, aconnect_sse
+from httpx2 import ServerSentEvent
 from inline_snapshot import snapshot
 from mcp_types import (
     CLIENT_CAPABILITIES_META_KEY,
@@ -260,7 +260,7 @@ async def test_a_second_standalone_get_stream_on_the_same_session_returns_409()
     async with mounted_app(_server()) as (http, _):
         session_id = await initialize_via_http(http)
 
-        async with aconnect_sse(http, "GET", "/mcp", headers=base_headers(session_id=session_id)) as first:
+        async with http.sse("/mcp", headers=base_headers(session_id=session_id)) as first:
             assert first.response.status_code == 200
             # The standalone-stream writer registers its key as its first action, then parks
             # awaiting messages; one yield to the loop lets that registration complete before the
@@ -296,10 +296,10 @@ async def test_messages_are_routed_to_exactly_one_stream() -> None:
         get_events: list[ServerSentEvent] = []
 
         async def read_standalone_stream() -> None:
-            async with aconnect_sse(http, "GET", "/mcp", headers=base_headers(session_id=session_id)) as get:
+            async with http.sse("/mcp", headers=base_headers(session_id=session_id)) as get:
                 assert get.response.status_code == 200
                 standalone_ready.set()
-                async for event in get.aiter_sse():
+                async for event in get:
                     get_events.append(event)
                     seen_on_standalone.set()
 
@@ -312,16 +312,15 @@ async def test_messages_are_routed_to_exactly_one_stream() -> None:
 
                 params = CallToolRequestParams(name="narrate", arguments={})
                 body = JSONRPCRequest(jsonrpc="2.0", id=5, method="tools/call", params=params.model_dump())
-                async with aconnect_sse(
-                    http,
-                    "POST",
+                async with http.sse(
                     "/mcp",
+                    method="POST",
                     json=body.model_dump(by_alias=True, exclude_none=True),
                     headers=base_headers(session_id=session_id),
                 ) as post:
                     assert post.response.status_code == 200
                     # The POST stream iterator ends when the server closes the stream after the response.
-                    post_events = [event async for event in post.aiter_sse()]
+                    post_events = [event async for event in post]
 
                 await seen_on_standalone.wait()
                 tg.cancel_scope.cancel()
@@ -360,11 +359,14 @@ async def test_origin_validation_rejects_disallowed_origins_when_enabled() -> No
             "/mcp", json=initialize_body(), headers=base_headers() | {"origin": "http://evil.example"}
         )
         bad_host = await http.post("/mcp", json=initialize_body(), headers=base_headers() | {"host": "evil.example"})
-        async with aconnect_sse(
-            http, "POST", "/mcp", json=initialize_body(), headers=base_headers() | {"origin": "http://127.0.0.1:8000"}
+        async with http.sse(
+            "/mcp",
+            method="POST",
+            json=initialize_body(),
+            headers=base_headers() | {"origin": "http://127.0.0.1:8000"},
         ) as ok:
             assert ok.response.status_code == 200
-            assert [event async for event in ok.aiter_sse()]
+            assert [event async for event in ok]
 
     assert (bad_origin.status_code, bad_origin.text) == snapshot((403, "Invalid Origin header"))
     assert (bad_host.status_code, bad_host.text) == snapshot((421, "Invalid Host header"))
@@ -372,10 +374,10 @@ async def test_origin_validation_rejects_disallowed_origins_when_enabled() -> No
     async with mounted_app(
         Server("unguarded"), transport_security=TransportSecuritySettings(enable_dns_rebinding_protection=False)
     ) as (http, _):
-        async with aconnect_sse(
-            http, "POST", "/mcp", json=initialize_body(), headers=base_headers() | {"origin": "http://evil.example"}
+        async with http.sse(
+            "/mcp", method="POST", json=initialize_body(), headers=base_headers() | {"origin": "http://evil.example"}
         ) as unguarded:
             status = unguarded.response.status_code
-            assert [event async for event in unguarded.aiter_sse()]
+            assert [event async for event in unguarded]
 
     assert status == 200