diff --git a/libs/langchain/langchain/schema/runnable/base.py b/libs/langchain/langchain/schema/runnable/base.py
index 9d45d86551f..558495173bc 100644
--- a/libs/langchain/langchain/schema/runnable/base.py
+++ b/libs/langchain/langchain/schema/runnable/base.py
@@ -2100,7 +2100,7 @@ class RunnableGenerator(Runnable[Input, Output]):
             params = inspect.signature(func).parameters
             first_param = next(iter(params.values()), None)
             if first_param and first_param.annotation != inspect.Parameter.empty:
-                return first_param.annotation
+                return getattr(first_param.annotation, "__args__", (Any,))[0]
             else:
                 return Any
         except ValueError:
@@ -2112,7 +2112,7 @@ class RunnableGenerator(Runnable[Input, Output]):
         try:
             sig = inspect.signature(func)
             return (
-                sig.return_annotation
+                getattr(sig.return_annotation, "__args__", (Any,))[0]
                 if sig.return_annotation != inspect.Signature.empty
                 else Any
             )
@@ -2162,7 +2162,7 @@ class RunnableGenerator(Runnable[Input, Output]):
                 final += output
         return final
 
-    async def atransform(
+    def atransform(
         self,
         input: AsyncIterator[Input],
         config: Optional[RunnableConfig] = None,
@@ -2175,7 +2175,7 @@ class RunnableGenerator(Runnable[Input, Output]):
             input, self._atransform, config, **kwargs
         )
 
-    async def astream(
+    def astream(
         self,
         input: Input,
         config: Optional[RunnableConfig] = None,
diff --git a/libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py b/libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py
index b72144102a5..316a9ecad66 100644
--- a/libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py
+++ b/libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py
@@ -1,7 +1,18 @@
 import sys
 from operator import itemgetter
-from typing import Any, Dict, List, Optional, Sequence, Union, cast
+from typing import (
+    Any,
+    AsyncIterator,
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Union,
+    cast,
+)
 from uuid import UUID
+from langchain.schema.runnable.base import RunnableGenerator
 
 import pytest
 from freezegun import freeze_time
@@ -2809,3 +2820,81 @@ async def test_tool_from_runnable() -> None:
         "title": "PromptInput",
         "type": "object",
     }
+
+
+@pytest.mark.asyncio
+async def test_runnable_gen() -> None:
+    """Test that a generator can be used as a runnable."""
+
+    def gen(input: Iterator[Any]) -> Iterator[int]:
+        yield 1
+        yield 2
+        yield 3
+
+    runnable = RunnableGenerator(gen)
+
+    assert runnable.input_schema.schema() == {"title": "RunnableGeneratorInput"}
+    assert runnable.output_schema.schema() == {
+        "title": "RunnableGeneratorOutput",
+        "type": "integer",
+    }
+
+    assert runnable.invoke(None) == 6
+    assert list(runnable.stream(None)) == [1, 2, 3]
+    assert runnable.batch([None, None]) == [6, 6]
+
+    async def agen(input: AsyncIterator[Any]) -> AsyncIterator[int]:
+        yield 1
+        yield 2
+        yield 3
+
+    arunnable = RunnableGenerator(agen)
+
+    assert await arunnable.ainvoke(None) == 6
+    assert [p async for p in arunnable.astream(None)] == [1, 2, 3]
+    assert await arunnable.abatch([None, None]) == [6, 6]
+
+
+@pytest.mark.asyncio
+async def test_runnable_gen_transform() -> None:
+    """Test that a generator can be used as a runnable."""
+
+    def gen_indexes(length_iter: Iterator[int]) -> Iterator[int]:
+        for i in range(next(length_iter)):
+            yield i
+
+    async def agen_indexes(length_iter: AsyncIterator[int]) -> AsyncIterator[int]:
+        async for length in length_iter:
+            for i in range(length):
+                yield i
+
+    def plus_one(input: Iterator[int]) -> Iterator[int]:
+        for i in input:
+            yield i + 1
+
+    async def aplus_one(input: AsyncIterator[int]) -> AsyncIterator[int]:
+        async for i in input:
+            yield i + 1
+
+    chain = RunnableGenerator(gen_indexes, agen_indexes) | plus_one
+    achain = RunnableGenerator(gen_indexes, agen_indexes) | aplus_one
+
+    assert chain.input_schema.schema() == {
+        "title": "RunnableGeneratorInput",
+        "type": "integer",
+    }
+    assert chain.output_schema.schema() == {
+        "title": "RunnableGeneratorOutput",
+        "type": "integer",
+    }
+    assert achain.input_schema.schema() == {
+        "title": "RunnableGeneratorInput",
+        "type": "integer",
+    }
+    assert achain.output_schema.schema() == {
+        "title": "RunnableGeneratorOutput",
+        "type": "integer",
+    }
+
+    assert list(chain.stream(3)) == [1, 2, 3]
+    assert [p async for p in achain.astream(4)] == [1, 2, 3, 4]