diff --git a/python/packages/ag-ui/agent_framework_ag_ui/_agent_run.py b/python/packages/ag-ui/agent_framework_ag_ui/_agent_run.py
index 330a66dc10..4daef8e76e 100644
--- a/python/packages/ag-ui/agent_framework_ag_ui/_agent_run.py
+++ b/python/packages/ag-ui/agent_framework_ag_ui/_agent_run.py
@@ -790,9 +790,9 @@ async def run_agent_stream(
     # Create session (with service session support)
     if config.use_service_session:
         supplied_thread_id = input_data.get("thread_id") or input_data.get("threadId")
-        session = AgentSession(service_session_id=supplied_thread_id)
+        session = AgentSession(session_id=thread_id, service_session_id=supplied_thread_id)
     else:
-        session = AgentSession()
+        session = AgentSession(session_id=thread_id)
 
     # Inject metadata for AG-UI orchestration (Feature #2: Azure-safe truncation)
     base_metadata: dict[str, Any] = {
diff --git a/python/packages/ag-ui/tests/ag_ui/conftest.py b/python/packages/ag-ui/tests/ag_ui/conftest.py
index 744196dbdf..64ac8e9d66 100644
--- a/python/packages/ag-ui/tests/ag_ui/conftest.py
+++ b/python/packages/ag-ui/tests/ag_ui/conftest.py
@@ -183,6 +183,7 @@ def __init__(
         self.client = client or SimpleNamespace(function_invocation_configuration=None)
         self.messages_received: list[Any] = []
         self.tools_received: list[Any] | None = None
+        self.last_session: AgentSession | None = None
 
     @overload
     def run(
@@ -216,6 +217,7 @@ def run(
 
             async def _stream() -> AsyncIterator[AgentResponseUpdate]:
                 self.messages_received = [] if messages is None else list(messages)  # type: ignore[arg-type]
+                self.last_session = session
                 self.tools_received = kwargs.get("tools")
                 for update in self.updates:
                     yield update
diff --git a/python/packages/ag-ui/tests/ag_ui/test_run.py b/python/packages/ag-ui/tests/ag_ui/test_run.py
index 392f0cd723..70af4c064a 100644
--- a/python/packages/ag-ui/tests/ag_ui/test_run.py
+++ b/python/packages/ag-ui/tests/ag_ui/test_run.py
@@ -1640,3 +1640,115 @@ def test_reasoning_distinct_ids_close_previous_block(self):
         # close: MsgEnd(block2) + End(block2)
         assert isinstance(close[0], ReasoningMessageEndEvent)
         assert close[0].message_id == "block2"
+
+
+async def test_session_id_matches_thread_id():
+    """Session created by run_agent_stream uses the client thread_id as session_id."""
+    from conftest import StubAgent
+
+    from agent_framework_ag_ui import AgentFrameworkAgent
+
+    stub = StubAgent()
+    agent = AgentFrameworkAgent(agent=stub)
+
+    payload = {
+        "thread_id": "my-thread-123",
+        "run_id": "run-1",
+        "messages": [{"role": "user", "content": "Hello"}],
+    }
+
+    _ = [event async for event in agent.run(payload)]
+
+    assert stub.last_session is not None
+    assert stub.last_session.session_id == "my-thread-123"
+
+
+async def test_session_id_matches_camel_case_thread_id():
+    """Session uses threadId (camelCase) as session_id when snake_case is absent."""
+    from conftest import StubAgent
+
+    from agent_framework_ag_ui import AgentFrameworkAgent
+
+    stub = StubAgent()
+    agent = AgentFrameworkAgent(agent=stub)
+
+    payload = {
+        "threadId": "camel-thread-456",
+        "run_id": "run-2",
+        "messages": [{"role": "user", "content": "Hello"}],
+    }
+
+    _ = [event async for event in agent.run(payload)]
+
+    assert stub.last_session is not None
+    assert stub.last_session.session_id == "camel-thread-456"
+
+
+async def test_session_id_matches_thread_id_with_service_session():
+    """Session uses thread_id as session_id even when use_service_session is enabled."""
+    from conftest import StubAgent
+
+    from agent_framework_ag_ui import AgentFrameworkAgent
+
+    stub = StubAgent()
+    agent = AgentFrameworkAgent(agent=stub, use_service_session=True)
+
+    payload = {
+        "thread_id": "service-thread-789",
+        "run_id": "run-3",
+        "messages": [{"role": "user", "content": "Hello"}],
+    }
+
+    _ = [event async for event in agent.run(payload)]
+
+    assert stub.last_session is not None
+    assert stub.last_session.session_id == "service-thread-789"
+    assert stub.last_session.service_session_id == "service-thread-789"
+
+
+async def test_session_id_generated_when_no_thread_id():
+    """Session gets a generated UUID as session_id when no thread_id is provided."""
+    import uuid
+
+    from conftest import StubAgent
+
+    from agent_framework_ag_ui import AgentFrameworkAgent
+
+    stub = StubAgent()
+    agent = AgentFrameworkAgent(agent=stub)
+
+    payload = {
+        "run_id": "run-4",
+        "messages": [{"role": "user", "content": "Hello"}],
+    }
+
+    _ = [event async for event in agent.run(payload)]
+
+    assert stub.last_session is not None
+    # Should be a valid UUID (auto-generated)
+    uuid.UUID(stub.last_session.session_id)
+
+
+async def test_service_session_no_thread_id_generates_uuid():
+    """With use_service_session=True and no thread_id, session_id is a UUID and service_session_id is None."""
+    import uuid
+
+    from conftest import StubAgent
+
+    from agent_framework_ag_ui import AgentFrameworkAgent
+
+    stub = StubAgent()
+    agent = AgentFrameworkAgent(agent=stub, use_service_session=True)
+
+    payload = {
+        "run_id": "run-5",
+        "messages": [{"role": "user", "content": "Hello"}],
+    }
+
+    _ = [event async for event in agent.run(payload)]
+
+    assert stub.last_session is not None
+    # session_id should be a valid auto-generated UUID
+    uuid.UUID(stub.last_session.session_id)
+    # service_session_id should be None since no thread_id was supplied
+    assert stub.last_session.service_session_id is None
diff --git a/python/samples/02-agents/conversations/file_history_provider.py b/python/samples/02-agents/conversations/file_history_provider.py
index 04a87f8224..20735ffd17 100644
--- a/python/samples/02-agents/conversations/file_history_provider.py
+++ b/python/samples/02-agents/conversations/file_history_provider.py
@@ -21,7 +21,7 @@
 from pydantic import Field
 
 try:
-    import orjson
+    import orjson  # pyright: ignore[reportMissingImports]
 except ImportError:
     orjson = None
 
diff --git a/python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py b/python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py
index 70c5d7e8e8..693501b0f9 100644
--- a/python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py
+++ b/python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py
@@ -22,7 +22,7 @@
 from pydantic import Field
 
 try:
-    import orjson
+    import orjson  # pyright: ignore[reportMissingImports]
 except ImportError:
     orjson = None