diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98721f65..d6e42e6a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   loop variable that overflows for responses larger than ~2 GB. Changed to `Py_ssize_t`.
 - Fix potential `OverflowError` in `cookies.pyx`: `Cookie.max_age` and the local
   variable in `parse_cookie` were declared as C `int`; changed to `long long`.
+- Fix [#674](https://github.com/Neoteroi/BlackSheep/issues/674): OpenAPI generator
+  crashed with `AttributeError` when a handler returned `AsyncIterable[ServerSentEvent]`
+  (or any `collections.abc` async-iterable generic). `_try_get_schema_for_generic` now
+  skips types whose origin has no `__parameters__`.
 
 ## [2.6.2] - 2026-02-25 :gift:
 
diff --git a/blacksheep/server/openapi/v3.py b/blacksheep/server/openapi/v3.py
index 108087c3..892b244d 100644
--- a/blacksheep/server/openapi/v3.py
+++ b/blacksheep/server/openapi/v3.py
@@ -1017,6 +1017,11 @@ def _try_get_schema_for_generic(
                 object_type, context_type_args, schema
             )
 
+        if not hasattr(origin, "__parameters__"):
+            # e.g. AsyncIterable, AsyncGenerator, AsyncIterator — streaming types
+            # that have no meaningful OpenAPI schema representation
+            return None
+
         required: list[str] = []
         properties: dict[str, Schema | Reference] = {}
 
diff --git a/tests/test_openapi_v3.py b/tests/test_openapi_v3.py
index 08640649..ee0f2159 100644
--- a/tests/test_openapi_v3.py
+++ b/tests/test_openapi_v3.py
@@ -1,4 +1,5 @@
 import sys
+from collections.abc import AsyncGenerator, AsyncIterable, AsyncIterator
 from dataclasses import dataclass
 from datetime import date, datetime
 from enum import IntEnum
@@ -4833,3 +4834,46 @@ def create_item(data: FromJSON[CreateFooInput] | FromXML[CreateFooInput]) -> Foo
 
 
 # endregion
+
+
+# region SSE / async-generator return types
+
+
+async def test_sse_async_iterable_does_not_crash_openapi(
+    docs: OpenAPIHandler, serializer: Serializer
+):
+    """AsyncIterable[ServerSentEvent] return type must not crash the OpenAPI generator."""
+    from blacksheep.server.controllers import Controller
+    from blacksheep.server.sse import ServerSentEvent
+
+    app = get_app()
+
+    class Home(Controller):
+        @app.router.get("/events")
+        async def events(self) -> AsyncIterable[ServerSentEvent]:
+            yield ServerSentEvent({"msg": "hello"})
+
+    docs.bind_app(app)
+    await app.start()
+
+    # Must not raise
+    docs.generate_documentation(app)
+
+
+@pytest.mark.parametrize(
+    "return_type",
+    [
+        AsyncIterable[int],
+        AsyncIterator[int],
+        AsyncGenerator[int, None],
+    ],
+)
+def test_get_schema_by_type_does_not_crash_for_async_iterables(
+    docs: OpenAPIHandler, return_type
+):
+    """get_schema_by_type must not raise for async iterable generics (issue #674)."""
+    # Should not raise AttributeError
+    docs.get_schema_by_type(return_type)
+
+
+# endregion