From fe24e722ca6dd25f6a595d052c0e03aad62a7745 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 09:25:15 +0530
Subject: [PATCH 01/18] fix(web): allow session resume without new message
 (#4100)

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/cli/adk_web_server.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/google/adk/cli/adk_web_server.py b/src/google/adk/cli/adk_web_server.py
index b97932d042..570da8a97d 100644
--- a/src/google/adk/cli/adk_web_server.py
+++ b/src/google/adk/cli/adk_web_server.py
@@ -202,7 +202,7 @@ class RunAgentRequest(common.BaseModel):
   app_name: str
   user_id: str
   session_id: str
-  new_message: types.Content
+  new_message: Optional[types.Content] = None
   streaming: bool = False
   state_delta: Optional[dict[str, Any]] = None
   # for resume long-running functions

From 1f4f0aa049923bb2418e62eeb4b26446daae05ec Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 10:14:50 +0530
Subject: [PATCH 02/18] fix(web): adds a unit test verifying that the /run
 endpoint accepts requests for session resumption without providing new
 content.

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 0c69605349..904492a6fe 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1411,5 +1411,29 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
   assert not (tmp_path / "app" / "tmp" / "escape.yaml").exists()
 
 
+def test_agent_run_resume_without_message(test_app, create_test_session):
+  """Test that /run allows resuming a session without providing a new message."""
+  info = create_test_session
+  url = "/run"
+  # Note: 'new_message' is intentionally OMITTED here to test the fix
+  payload = {
+      "app_name": info["app_name"],
+      "user_id": info["user_id"],
+      "session_id": info["session_id"],
+      "streaming": False,
+  }
+
+  response = test_app.post(url, json=payload)
+
+  # Before your fix, this would return 422 (Validation Error)
+  # Now it should return 200 (Success)
+  assert response.status_code == 200
+  data = response.json()
+  assert isinstance(data, list)
+  # Our mock runner (dummy_run_async) returns 3 events by default
+  assert len(data) == 3
+  assert data[0]["author"] == "dummy agent"
+
+  logger.info("Agent run resume without message test passed")
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From 929fe2e98f8d53bbefc0f7da1456c2d582fd4b26 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 11:07:58 +0530
Subject: [PATCH 03/18] fix: allow agent session resumption without new message

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            |  8 +++-----
 tests/unittests/cli/test_fast_api.py | 26 +++++++++++++++-----------
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 3aaa54e257..730f489fae 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -498,11 +498,9 @@ async def _run_with_trace(
             user_id=user_id, session_id=session_id
         )
         if not invocation_id and not new_message:
-          raise ValueError(
-              'Running an agent requires either a new_message or an '
-              'invocation_id to resume a previous invocation. '
-              f'Session: {session_id}, User: {user_id}'
-          )
+          # If nothing is provided, this is a no-op resume. We return early
+          # without yielding any events.
+          return
 
         if invocation_id:
           if (
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 904492a6fe..236dccf553 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1411,11 +1411,19 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
   assert not (tmp_path / "app" / "tmp" / "escape.yaml").exists()
 
 
-def test_agent_run_resume_without_message(test_app, create_test_session):
+def test_agent_run_resume_without_message(test_app, create_test_session, monkeypatch):
   """Test that /run allows resuming a session without providing a new message."""
   info = create_test_session
   url = "/run"
-  # Note: 'new_message' is intentionally OMITTED here to test the fix
+  
+  # We simulate the NEW behavior of the real runner (returning no events)
+  async def mock_run_empty(*args, **kwargs):
+    if False: yield # Tells Python this is an async generator
+    return
+
+  # Apply the mock to the Runner class
+  monkeypatch.setattr(Runner, "run_async", mock_run_empty)
+
   payload = {
       "app_name": info["app_name"],
       "user_id": info["user_id"],
@@ -1425,15 +1433,11 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
 
   response = test_app.post(url, json=payload)
 
-  # Before your fix, this would return 422 (Validation Error)
-  # Now it should return 200 (Success)
+  # Verify the web server accepts it and the runner returns a clean empty list
   assert response.status_code == 200
-  data = response.json()
-  assert isinstance(data, list)
-  # Our mock runner (dummy_run_async) returns 3 events by default
-  assert len(data) == 3
-  assert data[0]["author"] == "dummy agent"
-
-  logger.info("Agent run resume without message test passed")
+  assert response.json() == []
+  
+  logger.info("Agent run resume without message test passed gracefully")
+  
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From 1afb89aac3e9283433b8e9a9ffb6bd3c58fb19a9 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 11:49:29 +0530
Subject: [PATCH 04/18] Style: cleanup unit test by removing unnecessary
 logging and blank lines

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 236dccf553..650ffd11fb 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1415,10 +1415,9 @@ def test_agent_run_resume_without_message(test_app, create_test_session, monkeyp
   """Test that /run allows resuming a session without providing a new message."""
   info = create_test_session
   url = "/run"
-  
   # We simulate the NEW behavior of the real runner (returning no events)
   async def mock_run_empty(*args, **kwargs):
-    if False: yield # Tells Python this is an async generator
+    if False: yield  # Tells Python this is an async generator
     return
 
   # Apply the mock to the Runner class
@@ -1437,7 +1436,5 @@ async def mock_run_empty(*args, **kwargs):
   assert response.status_code == 200
   assert response.json() == []
   
-  logger.info("Agent run resume without message test passed gracefully")
-  
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From d10c1d319b7b43bfc8bb3244d37525f553227801 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 12:13:21 +0530
Subject: [PATCH 05/18] fix: add observability logging for no-op resume and
 cleanup tests

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            |  6 ++++++
 tests/unittests/cli/test_fast_api.py | 10 ++--------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 730f489fae..cb57b821e5 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -497,7 +497,13 @@ async def _run_with_trace(
         session = await self._get_or_create_session(
             user_id=user_id, session_id=session_id
         )
+
         if not invocation_id and not new_message:
+          logger.info(
+            'Performing no-op resume for session %s: no new_message or '
+            'invocation_id.',
+            session_id,
+          )
           # If nothing is provided, this is a no-op resume. We return early
           # without yielding any events.
           return
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 650ffd11fb..0565a04a9b 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1415,26 +1415,20 @@ def test_agent_run_resume_without_message(test_app, create_test_session, monkeyp
   """Test that /run allows resuming a session without providing a new message."""
   info = create_test_session
   url = "/run"
-  # We simulate the NEW behavior of the real runner (returning no events)
   async def mock_run_empty(*args, **kwargs):
-    if False: yield  # Tells Python this is an async generator
+    if False: yield
     return
 
-  # Apply the mock to the Runner class
   monkeypatch.setattr(Runner, "run_async", mock_run_empty)
-
   payload = {
       "app_name": info["app_name"],
       "user_id": info["user_id"],
       "session_id": info["session_id"],
       "streaming": False,
   }
-
   response = test_app.post(url, json=payload)
-
-  # Verify the web server accepts it and the runner returns a clean empty list
   assert response.status_code == 200
   assert response.json() == []
-  
+
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From 00b0f203fbb7662667196ccc51bd82a5564d9f4c Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 12:32:35 +0530
Subject: [PATCH 06/18] fix: align dummy runner logic with real runner and
 update docstring

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            |  3 +--
 tests/unittests/cli/test_fast_api.py | 15 +++++++++------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index cb57b821e5..9a871f0945 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -481,8 +481,7 @@ async def run_async(
       The events generated by the agent.
 
     Raises:
-      ValueError: If the session is not found; If both invocation_id and
-        new_message are None.
+        If both invocation_id and new_message are None, a no-op resume is performed.
     """
     run_config = run_config or RunConfig()
 
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 0565a04a9b..6e05114d38 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -132,6 +132,10 @@ async def dummy_run_async(
     run_config: Optional[RunConfig] = None,
     invocation_id: Optional[str] = None,
 ):
+  
+  if not invocation_id and not new_message:
+    return
+
   run_config = run_config or RunConfig()
   yield _event_1()
   await asyncio.sleep(0)
@@ -1411,22 +1415,21 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
   assert not (tmp_path / "app" / "tmp" / "escape.yaml").exists()
 
 
-def test_agent_run_resume_without_message(test_app, create_test_session, monkeypatch):
+def test_agent_run_resume_without_message(test_app, create_test_session):
   """Test that /run allows resuming a session without providing a new message."""
   info = create_test_session
   url = "/run"
-  async def mock_run_empty(*args, **kwargs):
-    if False: yield
-    return
-
-  monkeypatch.setattr(Runner, "run_async", mock_run_empty)
+  # We no longer mock the runner. This tests the real logic in runners.py
   payload = {
       "app_name": info["app_name"],
       "user_id": info["user_id"],
       "session_id": info["session_id"],
       "streaming": False,
   }
+
   response = test_app.post(url, json=payload)
+
+  # Verify the web server and real runner work together to return success
   assert response.status_code == 200
   assert response.json() == []
 

From 29879319f073c83e0da18dd547ee707956b9a8b2 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 17 Jan 2026 12:38:16 +0530
Subject: [PATCH 07/18] docs: remove misleading comment in unit test per bot
 feedback

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            | 2 +-
 tests/unittests/cli/test_fast_api.py | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 9a871f0945..f9e5b4eb0d 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -481,7 +481,7 @@ async def run_async(
       The events generated by the agent.
 
     Raises:
-        If both invocation_id and new_message are None, a no-op resume is performed.
+      ValueError: If the session is not found and auto-creation is disabled.
     """
     run_config = run_config or RunConfig()
 
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 6e05114d38..34bb72b363 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1419,7 +1419,6 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
   """Test that /run allows resuming a session without providing a new message."""
   info = create_test_session
   url = "/run"
-  # We no longer mock the runner. This tests the real logic in runners.py
   payload = {
       "app_name": info["app_name"],
       "user_id": info["user_id"],
@@ -1429,7 +1428,7 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
 
   response = test_app.post(url, json=payload)
 
-  # Verify the web server and real runner work together to return success
+  # Verify the web server and dummy runner work together to return success
   assert response.status_code == 200
   assert response.json() == []
 

From c2511c597df6641de7a03bb561cf60aa91eacae8 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 18 Jan 2026 22:11:21 +0530
Subject: [PATCH 08/18] fix: handle state_delta warning in no-op resume and
 cleanup dummy runner

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            | 12 +++++++++---
 tests/unittests/cli/test_fast_api.py |  2 ++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index f9e5b4eb0d..0b11f5285a 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -498,10 +498,16 @@ async def _run_with_trace(
         )
 
         if not invocation_id and not new_message:
+          if state_delta:
+            logger.warning(
+                'state_delta provided without new_message or invocation_id for '
+                'session %s. The state_delta will be ignored.',
+                session_id,
+            )
           logger.info(
-            'Performing no-op resume for session %s: no new_message or '
-            'invocation_id.',
-            session_id,
+              'Performing no-op resume for session %s: no new_message or '
+              'invocation_id.',
+              session_id,
           )
           # If nothing is provided, this is a no-op resume. We return early
           # without yielding any events.
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 34bb72b363..c0ade12b3a 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -134,6 +134,8 @@ async def dummy_run_async(
 ):
   
   if not invocation_id and not new_message:
+    if state_delta:
+      logger.warning("state_delta ignored in no-op resume")
     return
 
   run_config = run_config or RunConfig()

From ac9f90447cbc39d463f16e45b059b4eae4fe47e9 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Wed, 21 Jan 2026 19:21:53 +0530
Subject: [PATCH 09/18] fix: the formatting

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index c0ade12b3a..1abd14e2ad 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -132,7 +132,7 @@ async def dummy_run_async(
     run_config: Optional[RunConfig] = None,
     invocation_id: Optional[str] = None,
 ):
-  
+
   if not invocation_id and not new_message:
     if state_delta:
       logger.warning("state_delta ignored in no-op resume")
@@ -1434,5 +1434,6 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
   assert response.status_code == 200
   assert response.json() == []
 
+
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From 1fdf7efd15f070c82937671093e6383ad9d9b304 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sat, 24 Jan 2026 23:16:50 +0530
Subject: [PATCH 10/18] fix: finalize session resumption logic and test
 coverage

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            |  3 ++-
 tests/unittests/cli/test_fast_api.py | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 0b11f5285a..8a0203bbb9 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -481,7 +481,8 @@ async def run_async(
       The events generated by the agent.
 
     Raises:
-      ValueError: If the session is not found and auto-creation is disabled.
+      None: if both invocation_id and new_message are None, a no-op resume
+        is performed.
     """
     run_config = run_config or RunConfig()
 
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 1abd14e2ad..bd8d1879a6 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1434,6 +1434,27 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
   assert response.status_code == 200
   assert response.json() == []
 
+def test_agent_run_resume_without_message_with_state_delta(
+    test_app, create_test_session, caplog
+):
+  """Test that /run with no message ignores state_delta and logs a warning."""
+  info = create_test_session
+  url = "/run"
+  payload = {
+      "app_name": info["app_name"],
+      "user_id": info["user_id"],
+      "session_id": info["session_id"],
+      "streaming": False,
+      "state_delta": {"some_key": "some_value"},
+  }
+
+  caplog.set_level(logging.WARNING)
+  response = test_app.post(url, json=payload)
+
+  assert response.status_code == 200
+  assert response.json() == []
+  # Verifies the warning you added to runners.py
+  assert "state_delta ignored in no-op resume" in caplog.text
 
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From 5af99c7a0e5be4202c5300c831fb3551a1c09f4b Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 00:31:27 +0530
Subject: [PATCH 11/18] fix: align mock warning with production and update
 docstring

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 src/google/adk/runners.py            |  3 +--
 tests/unittests/cli/test_fast_api.py | 12 ++++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index 8a0203bbb9..057df62563 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -481,8 +481,7 @@ async def run_async(
       The events generated by the agent.
 
     Raises:
-      None: if both invocation_id and new_message are None, a no-op resume
-        is performed.
+      ValueError: If the session is not found and `auto_create_session` is False.
     """
     run_config = run_config or RunConfig()
 
diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index bd8d1879a6..70ddc0a4d0 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -135,7 +135,11 @@ async def dummy_run_async(
 
   if not invocation_id and not new_message:
     if state_delta:
-      logger.warning("state_delta ignored in no-op resume")
+      logger.warning(
+          "state_delta provided without new_message or invocation_id for "
+          "session %s. The state_delta will be ignored.",
+          session_id,
+      )
     return
 
   run_config = run_config or RunConfig()
@@ -1434,6 +1438,7 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
   assert response.status_code == 200
   assert response.json() == []
 
+
 def test_agent_run_resume_without_message_with_state_delta(
     test_app, create_test_session, caplog
 ):
@@ -1454,7 +1459,10 @@ def test_agent_run_resume_without_message_with_state_delta(
   assert response.status_code == 200
   assert response.json() == []
   # Verifies the warning you added to runners.py
-  assert "state_delta ignored in no-op resume" in caplog.text
+  assert (
+      "state_delta provided without new_message or invocation_id" in caplog.text
+  )
+
 
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])

From e3ed2692cd177e5ed9d63b2613a5eca91acc26aa Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 00:40:08 +0530
Subject: [PATCH 12/18] test: improve robustness of no-op resume warning
 assertion

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 70ddc0a4d0..9321ba8b1e 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1458,9 +1458,13 @@ def test_agent_run_resume_without_message_with_state_delta(
 
   assert response.status_code == 200
   assert response.json() == []
-  # Verifies the warning you added to runners.py
+
+  # Robust log verification as requested by the code review
+  assert len(caplog.records) == 1
+  assert caplog.records[0].levelname == "WARNING"
   assert (
-      "state_delta provided without new_message or invocation_id" in caplog.text
+      "state_delta provided without new_message or invocation_id"
+      in caplog.records[0].message
   )
 
 

From d8d340148607d8172f1777e6f3ef72d117a8b4ac Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 00:46:08 +0530
Subject: [PATCH 13/18] test: improve robustness of no-op resume warning
 assertion

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 9321ba8b1e..b636ec4c9e 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -140,6 +140,11 @@ async def dummy_run_async(
           "session %s. The state_delta will be ignored.",
           session_id,
       )
+    logger.info(
+        "Performing no-op resume for session %s: no new_message or "
+        "invocation_id.",
+        session_id,
+    )
     return
 
   run_config = run_config or RunConfig()

From c5ac29afb5ed9e38b0c29de423a9c848c4789d81 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 01:42:27 +0530
Subject: [PATCH 14/18] fix: implement graceful session resumption and separate
 test concerns

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 14 +++--------
 tests/unittests/test_runners.py      | 37 +++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index b636ec4c9e..dd453022d5 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1445,9 +1445,9 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
 
 
 def test_agent_run_resume_without_message_with_state_delta(
-    test_app, create_test_session, caplog
+    test_app, create_test_session
 ):
-  """Test that /run with no message ignores state_delta and logs a warning."""
+  """Test that /run with no message accepts the request even with state_delta."""
   info = create_test_session
   url = "/run"
   payload = {
@@ -1458,20 +1458,12 @@ def test_agent_run_resume_without_message_with_state_delta(
       "state_delta": {"some_key": "some_value"},
   }
 
-  caplog.set_level(logging.WARNING)
   response = test_app.post(url, json=payload)
 
+  # Only verify the HTTP layer (FastAPI accepts the request)
   assert response.status_code == 200
   assert response.json() == []
 
-  # Robust log verification as requested by the code review
-  assert len(caplog.records) == 1
-  assert caplog.records[0].levelname == "WARNING"
-  assert (
-      "state_delta provided without new_message or invocation_id"
-      in caplog.records[0].message
-  )
-
 
 if __name__ == "__main__":
   pytest.main(["-xvs", __file__])
diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index 62b8d7334b..a9a0a4bce8 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -11,13 +11,14 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import importlib
+import logging
 from pathlib import Path
 import sys
 import textwrap
 from typing import AsyncGenerator
 from typing import Optional
+from unittest import mock
 from unittest.mock import AsyncMock
 
 from google.adk.agents.base_agent import BaseAgent
@@ -1321,5 +1322,39 @@ def test_infer_agent_origin_detects_mismatch_for_user_agent(
     assert "actual_name" in runner._app_name_alignment_hint
 
 
+@pytest.mark.asyncio
+async def test_run_async_no_op_resume_logging(caplog):
+  """Verifies that the actual Runner logic logs a warning when state_delta is ignored."""
+  from google.adk.runners import Runner
+
+  # 1. Setup dependencies
+  mock_agent = mock.MagicMock()
+  mock_agent.name = "test_agent"
+
+  # Added app_name="test_app" to satisfy validation
+  runner = Runner(
+      app_name="test_app",
+      agent=mock_agent,
+      session_service=mock.AsyncMock(),
+  )
+
+  # 2. Capture logs while running the actual logic in runners.py
+  with caplog.at_level(logging.WARNING):
+    # Call run_async without message or invocation_id, but WITH state_delta
+    async for _ in runner.run_async(
+        user_id="user",
+        session_id="session",
+        new_message=None,
+        state_delta={"test": 1},
+    ):
+      pass
+
+  # 3. This verifies the REAL warning logic in src/google/adk/runners.py
+  assert any(
+      "state_delta provided without new_message" in r.message
+      for r in caplog.records
+  )
+
+
 if __name__ == "__main__":
   pytest.main([__file__])

From a397ea3a54fbacc4fa0a4bd9b9a9f111c42b848c Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 02:06:36 +0530
Subject: [PATCH 15/18] refactor: use targeted mocks for session resumption
 tests per bot feedback

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index dd453022d5..b01b249d75 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1426,8 +1426,19 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
   assert not (tmp_path / "app" / "tmp" / "escape.yaml").exists()
 
 
-def test_agent_run_resume_without_message(test_app, create_test_session):
+async def _noop_run_async(*args, **kwargs):
+  """A mock that does nothing and yields no events for no-op resume tests."""
+  if False:
+    yield
+
+
+def test_agent_run_resume_without_message(
+    test_app, create_test_session, monkeypatch
+):
   """Test that /run allows resuming a session without providing a new message."""
+  # Override the global mock with a specific no-op mock for this test
+  monkeypatch.setattr("google.adk.runners.Runner.run_async", _noop_run_async)
+
   info = create_test_session
   url = "/run"
   payload = {
@@ -1439,15 +1450,18 @@ def test_agent_run_resume_without_message(test_app, create_test_session):
 
   response = test_app.post(url, json=payload)
 
-  # Verify the web server and dummy runner work together to return success
+  # Verify the web server handles the empty message and returns success
   assert response.status_code == 200
   assert response.json() == []
 
 
 def test_agent_run_resume_without_message_with_state_delta(
-    test_app, create_test_session
+    test_app, create_test_session, monkeypatch
 ):
   """Test that /run with no message accepts the request even with state_delta."""
+  # Override the global mock with a specific no-op mock for this test
+  monkeypatch.setattr("google.adk.runners.Runner.run_async", _noop_run_async)
+
   info = create_test_session
   url = "/run"
   payload = {

From 222cd2d7f2fe62170154654a264f46762543ba94 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 02:20:17 +0530
Subject: [PATCH 16/18] refactor: remove logic duplication in global mock per
 bot feedback

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index b01b249d75..9baf95035c 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -132,21 +132,7 @@ async def dummy_run_async(
     run_config: Optional[RunConfig] = None,
     invocation_id: Optional[str] = None,
 ):
-
-  if not invocation_id and not new_message:
-    if state_delta:
-      logger.warning(
-          "state_delta provided without new_message or invocation_id for "
-          "session %s. The state_delta will be ignored.",
-          session_id,
-      )
-    logger.info(
-        "Performing no-op resume for session %s: no new_message or "
-        "invocation_id.",
-        session_id,
-    )
-    return
-
+  
   run_config = run_config or RunConfig()
   yield _event_1()
   await asyncio.sleep(0)

From 1faac6f27f354bc81df819fa58d6bf7297049e22 Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 02:31:04 +0530
Subject: [PATCH 17/18] refactor: use parameterized tests for session
 resumption scenarios

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 39 +++++++++-------------------
 1 file changed, 12 insertions(+), 27 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index 9baf95035c..df940bea35 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -132,7 +132,7 @@ async def dummy_run_async(
     run_config: Optional[RunConfig] = None,
     invocation_id: Optional[str] = None,
 ):
-  
+
   run_config = run_config or RunConfig()
   yield _event_1()
   await asyncio.sleep(0)
@@ -1418,8 +1418,16 @@ async def _noop_run_async(*args, **kwargs):
     yield
 
 
+@pytest.mark.parametrize(
+    "extra_payload",
+    [
+        {},
+        {"state_delta": {"some_key": "some_value"}},
+    ],
+    ids=["no_state_delta", "with_state_delta"],
+)
 def test_agent_run_resume_without_message(
-    test_app, create_test_session, monkeypatch
+    test_app, create_test_session, monkeypatch, extra_payload
 ):
   """Test that /run allows resuming a session without providing a new message."""
   # Override the global mock with a specific no-op mock for this test
@@ -1432,35 +1440,12 @@ def test_agent_run_resume_without_message(
       "user_id": info["user_id"],
       "session_id": info["session_id"],
       "streaming": False,
+      **extra_payload,
   }
 
   response = test_app.post(url, json=payload)
 
-  # Verify the web server handles the empty message and returns success
-  assert response.status_code == 200
-  assert response.json() == []
-
-
-def test_agent_run_resume_without_message_with_state_delta(
-    test_app, create_test_session, monkeypatch
-):
-  """Test that /run with no message accepts the request even with state_delta."""
-  # Override the global mock with a specific no-op mock for this test
-  monkeypatch.setattr("google.adk.runners.Runner.run_async", _noop_run_async)
-
-  info = create_test_session
-  url = "/run"
-  payload = {
-      "app_name": info["app_name"],
-      "user_id": info["user_id"],
-      "session_id": info["session_id"],
-      "streaming": False,
-      "state_delta": {"some_key": "some_value"},
-  }
-
-  response = test_app.post(url, json=payload)
-
-  # Only verify the HTTP layer (FastAPI accepts the request)
+  # Verify the web server handles the request and returns success
   assert response.status_code == 200
   assert response.json() == []
 

From 74bb3dbd7f2712170b3db50ee37263f6ac9982ef Mon Sep 17 00:00:00 2001
From: Akshat Kumar <akshat230405@gmail.com>
Date: Sun, 25 Jan 2026 02:36:15 +0530
Subject: [PATCH 18/18] style: use explicit empty loop for async generator mock
 per bot feedback

Signed-off-by: Akshat Kumar <akshat230405@gmail.com>
---
 tests/unittests/cli/test_fast_api.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/unittests/cli/test_fast_api.py b/tests/unittests/cli/test_fast_api.py
index df940bea35..58e4307c13 100755
--- a/tests/unittests/cli/test_fast_api.py
+++ b/tests/unittests/cli/test_fast_api.py
@@ -1414,8 +1414,8 @@ def test_builder_save_rejects_traversal(builder_test_client, tmp_path):
 
 async def _noop_run_async(*args, **kwargs):
   """A mock that does nothing and yields no events for no-op resume tests."""
-  if False:
-    yield
+  for item in []:
+    yield item
 
 
 @pytest.mark.parametrize(