Python: Include reasoning messages in MESSAGES_SNAPSHOT events

python/packages/ag-ui/agent_framework_ag_ui/_agent_run.py

@@ -684,6 +684,10 @@ def _build_messages_snapshot(
             }
         )
 
+    # Add reasoning messages so frontends that reconcile state from
+    # MESSAGES_SNAPSHOT retain reasoning content after streaming ends.
+    all_messages.extend(flow.reasoning_messages)
+
     return MessagesSnapshotEvent(messages=all_messages)  # type: ignore[arg-type]
 
 
@@ -1061,7 +1065,9 @@ async def run_agent_stream(
 
     # Emit MessagesSnapshotEvent if we have tool calls or results
     # Feature #5: Suppress intermediate snapshots for predictive tools without confirmation
-    should_emit_snapshot = flow.pending_tool_calls or flow.tool_results or flow.accumulated_text
+    should_emit_snapshot = (
+        flow.pending_tool_calls or flow.tool_results or flow.accumulated_text or flow.reasoning_messages
+    )
     if should_emit_snapshot:
         # Check if we should suppress for predictive tool
         last_tool_name = None

python/packages/ag-ui/agent_framework_ag_ui/_message_adapters.py

@@ -604,6 +604,10 @@ def _filter_modified_args(
         # Handle standard tool result messages early (role="tool") to preserve provider invariants
         # This path maps AG‑UI tool messages to function_result content with the correct tool_call_id
         role_str = normalize_agui_role(msg.get("role", "user"))
+        if role_str == "reasoning":
+            # Reasoning messages are UI-only state carried in MESSAGES_SNAPSHOT.
+            # They should not be forwarded to the LLM provider.
+            continue
         if role_str == "tool":
             # Prefer explicit tool_call_id fields; fall back to backend fields only if necessary
             tool_call_id = msg.get("tool_call_id") or msg.get("toolCallId")
@@ -1020,6 +1024,11 @@ def agui_messages_to_snapshot_format(messages: list[dict[str, Any]]) -> list[dic
             elif "toolCallId" not in normalized_msg:
                 normalized_msg["toolCallId"] = ""
 
+        # Normalize encrypted_value to encryptedValue for reasoning messages
+        if normalized_msg.get("role") == "reasoning" and "encrypted_value" in normalized_msg:
+            normalized_msg["encryptedValue"] = normalized_msg["encrypted_value"]
+            del normalized_msg["encrypted_value"]
+
         result.append(normalized_msg)
 
     return result

python/packages/ag-ui/agent_framework_ag_ui/_run_common.py

@@ -126,6 +126,8 @@ class FlowState:
     tool_results: list[dict[str, Any]] = field(default_factory=list)  # pyright: ignore[reportUnknownVariableType]
     tool_calls_ended: set[str] = field(default_factory=set)  # pyright: ignore[reportUnknownVariableType]
     interrupts: list[dict[str, Any]] = field(default_factory=list)  # pyright: ignore[reportUnknownVariableType]
+    reasoning_messages: list[dict[str, Any]] = field(default_factory=list)  # pyright: ignore[reportUnknownVariableType]
+    accumulated_reasoning: dict[str, str] = field(default_factory=dict)  # pyright: ignore[reportUnknownVariableType]
 
     def get_tool_name(self, call_id: str | None) -> str | None:
         """Get tool name by call ID."""
@@ -460,7 +462,7 @@ def _emit_mcp_tool_result(
     return _emit_tool_result_common(content.call_id, raw_output, flow, predictive_handler)
 
 
-def _emit_text_reasoning(content: Content) -> list[BaseEvent]:
+def _emit_text_reasoning(content: Content, flow: FlowState | None = None) -> list[BaseEvent]:
     """Emit AG-UI reasoning events for text_reasoning content.
 
     Uses the protocol-defined reasoning event types so that AG-UI consumers
@@ -470,6 +472,10 @@ def _emit_text_reasoning(content: Content) -> list[BaseEvent]:
     ``content.protected_data`` is present it is emitted as a
     ``ReasoningEncryptedValueEvent`` so that consumers can persist encrypted
     reasoning for state continuity without conflating it with display text.
+
+    When *flow* is provided the reasoning message is persisted into
+    ``flow.reasoning_messages`` so that ``_build_messages_snapshot`` can
+    include it in the final ``MESSAGES_SNAPSHOT``.
     """
     text = content.text or ""
     if not text and content.protected_data is None:
@@ -498,6 +504,36 @@ def _emit_text_reasoning(content: Content) -> list[BaseEvent]:
 
     events.append(ReasoningEndEvent(message_id=message_id))
 
+    # Persist reasoning into flow state for MESSAGES_SNAPSHOT.
+    # Accumulate reasoning text per message_id, similar to flow.accumulated_text,
+    # so that incremental deltas build the full reasoning string.
+    if flow is not None:
+        if text:
+            previous_text = flow.accumulated_reasoning.get(message_id, "")
+            flow.accumulated_reasoning[message_id] = previous_text + text
+        full_text = flow.accumulated_reasoning.get(message_id, text or "")
+
+        # Update existing reasoning entry for this message_id if present; otherwise append a new one.
+        existing_entry: dict[str, Any] | None = None
+        for entry in flow.reasoning_messages:
+            if isinstance(entry, dict) and entry.get("id") == message_id:
+                existing_entry = entry
+                break
+
+        if existing_entry is None:
+            reasoning_entry: dict[str, Any] = {
+                "id": message_id,
+                "role": "reasoning",
+                "content": full_text,
+            }
+            if content.protected_data is not None:
+                reasoning_entry["encryptedValue"] = content.protected_data
+            flow.reasoning_messages.append(reasoning_entry)
+        else:
+            existing_entry["content"] = full_text
+            if content.protected_data is not None:
+                existing_entry["encryptedValue"] = content.protected_data
+
     return events
 
 
@@ -527,6 +563,6 @@ def _emit_content(
     if content_type == "mcp_server_tool_result":
         return _emit_mcp_tool_result(content, flow, predictive_handler)
     if content_type == "text_reasoning":
-        return _emit_text_reasoning(content)
+        return _emit_text_reasoning(content, flow)
     logger.debug("Skipping unsupported content type in AG-UI emitter: %s", content_type)
     return []

python/packages/ag-ui/agent_framework_ag_ui/_utils.py

@@ -27,7 +27,7 @@
     "system": "system",
 }
 
-ALLOWED_AGUI_ROLES: set[str] = {"user", "assistant", "system", "tool"}
+ALLOWED_AGUI_ROLES: set[str] = {"user", "assistant", "system", "tool", "reasoning"}
 
 
 def generate_event_id() -> str:
@@ -82,7 +82,7 @@ def normalize_agui_role(raw_role: Any) -> str:
         raw_role: Raw role value from AG-UI message
 
     Returns:
-        Normalized role string (user, assistant, system, or tool)
+        Normalized role string (user, assistant, system, tool, or reasoning)
     """
     if not isinstance(raw_role, str):
         return "user"

python/packages/ag-ui/tests/ag_ui/test_message_adapters.py

@@ -1669,3 +1669,94 @@ def test_agui_fresh_approval_is_still_processed():
     assert len(approval_contents) == 1, "Fresh approval should produce function_approval_response"
     assert approval_contents[0].approved is True
     assert approval_contents[0].function_call.name == "get_datetime"
+
+
+class TestReasoningRoundTrip:
+    """Tests for reasoning message handling in inbound/outbound adapters."""
+
+    def test_reasoning_skipped_on_inbound(self):
+        """Reasoning messages from prior snapshot are not forwarded to the LLM."""
+        messages_input = [
+            {"id": "u1", "role": "user", "content": "Hello"},
+            {"id": "r1", "role": "reasoning", "content": "Thinking..."},
+            {"id": "a1", "role": "assistant", "content": "Hi there"},
+        ]
+
+        result = agui_messages_to_agent_framework(messages_input)
+
+        roles = [m.role if hasattr(m.role, "value") else str(m.role) for m in result]
+        assert "reasoning" not in roles
+        assert len(result) == 2
+
+    def test_reasoning_preserved_in_snapshot_format(self):
+        """Reasoning messages retain their role through snapshot normalization."""
+        messages_input = [
+            {"id": "u1", "role": "user", "content": "Hello"},
+            {"id": "r1", "role": "reasoning", "content": "Thinking about this..."},
+            {"id": "a1", "role": "assistant", "content": "Answer"},
+        ]
+
+        result = agui_messages_to_snapshot_format(messages_input)
+
+        reasoning_msgs = [m for m in result if m.get("role") == "reasoning"]
+        assert len(reasoning_msgs) == 1
+        assert reasoning_msgs[0]["content"] == "Thinking about this..."
+
+    def test_reasoning_with_encrypted_value_in_snapshot_format(self):
+        """Reasoning with encryptedValue passes through snapshot normalization."""
+        messages_input = [
+            {
+                "id": "r1",
+                "role": "reasoning",
+                "content": "visible",
+                "encryptedValue": "secret-data",
+            },
+        ]
+
+        result = agui_messages_to_snapshot_format(messages_input)
+
+        assert len(result) == 1
+        assert result[0]["role"] == "reasoning"
+        assert result[0]["encryptedValue"] == "secret-data"
+
+    def test_reasoning_encrypted_value_snake_case_normalized(self):
+        """Snake-case encrypted_value is normalized to encryptedValue in snapshot format."""
+        messages_input = [
+            {
+                "id": "r1",
+                "role": "reasoning",
+                "content": "visible",
+                "encrypted_value": "snake-case-data",
+            },
+        ]
+
+        result = agui_messages_to_snapshot_format(messages_input)
+
+        assert len(result) == 1
+        assert result[0]["encryptedValue"] == "snake-case-data"
+        assert "encrypted_value" not in result[0]
+
+    def test_multi_turn_with_reasoning_in_prior_snapshot(self):
+        """Second turn with reasoning from prior snapshot does not corrupt messages."""
+        messages_input = [
+            {"id": "u1", "role": "user", "content": "First question"},
+            {"id": "r1", "role": "reasoning", "content": "Prior reasoning"},
+            {"id": "a1", "role": "assistant", "content": "First answer"},
+            {"id": "u2", "role": "user", "content": "Follow-up question"},
+        ]
+
+        result = agui_messages_to_agent_framework(messages_input)
+
+        roles = [m.role if hasattr(m.role, "value") else str(m.role) for m in result]
+        # Reasoning is filtered out, other messages preserved in order
+        assert roles == ["user", "assistant", "user"]
+        # Content not corrupted
+        texts = []
+        for m in result:
+            for c in m.contents or []:
+                if hasattr(c, "text") and c.text:
+                    texts.append(c.text)
+        assert "First question" in texts
+        assert "First answer" in texts
+        assert "Follow-up question" in texts
+        assert "Prior reasoning" not in texts

python/packages/ag-ui/tests/ag_ui/test_run.py

@@ -1346,3 +1346,158 @@ def test_routes_text_reasoning(self):
 
         assert len(events) == 5
         assert isinstance(events[0], ReasoningStartEvent)
+
+
+class TestReasoningInSnapshot:
+    """Tests for reasoning message inclusion in MESSAGES_SNAPSHOT."""
+
+    def test_reasoning_persisted_to_flow_state(self):
+        """_emit_text_reasoning with flow persists reasoning into flow.reasoning_messages."""
+        flow = FlowState()
+        content = Content.from_text_reasoning(
+            id="reason_persist",
+            text="Let me think step by step.",
+        )
+
+        _emit_text_reasoning(content, flow)
+
+        assert len(flow.reasoning_messages) == 1
+        assert flow.reasoning_messages[0]["id"] == "reason_persist"
+        assert flow.reasoning_messages[0]["role"] == "reasoning"
+        assert flow.reasoning_messages[0]["content"] == "Let me think step by step."
+        assert "encryptedValue" not in flow.reasoning_messages[0]
+
+    def test_reasoning_with_encrypted_value_persisted(self):
+        """Reasoning with protected_data preserves encryptedValue in flow state."""
+        flow = FlowState()
+        content = Content.from_text_reasoning(
+            id="reason_enc",
+            text="visible reasoning",
+            protected_data="encrypted-data-123",
+        )
+
+        _emit_text_reasoning(content, flow)
+
+        assert len(flow.reasoning_messages) == 1
+        assert flow.reasoning_messages[0]["encryptedValue"] == "encrypted-data-123"
+
+    def test_snapshot_includes_reasoning(self):
+        """_build_messages_snapshot includes reasoning messages from flow state."""
+        from agent_framework_ag_ui._agent_run import _build_messages_snapshot
+
+        flow = FlowState()
+        flow.accumulated_text = "Here is my answer."
+        flow.reasoning_messages = [
+            {"id": "r1", "role": "reasoning", "content": "Thinking..."},
+        ]
+
+        snapshot = _build_messages_snapshot(flow, [])
+
+        roles = [m.get("role") if isinstance(m, dict) else getattr(m, "role", None) for m in snapshot.messages]
+        assert "reasoning" in roles
+
+    def test_snapshot_preserves_reasoning_encrypted_value(self):
+        """Snapshot reasoning with encryptedValue is preserved end-to-end."""
+        from agent_framework_ag_ui._agent_run import _build_messages_snapshot
+
+        flow = FlowState()
+        content = Content.from_text_reasoning(
+            id="reason_e2e",
+            text="visible",
+            protected_data="secret-data",
+        )
+        _emit_text_reasoning(content, flow)
+
+        text_content = Content.from_text("Final answer.")
+        _emit_text(text_content, flow)
+
+        snapshot = _build_messages_snapshot(flow, [])
+
+        reasoning_msgs = [
+            m
+            for m in snapshot.messages
+            if (m.get("role") if isinstance(m, dict) else getattr(m, "role", None)) == "reasoning"
+        ]
+        assert len(reasoning_msgs) == 1
+        msg = reasoning_msgs[0]
+        if isinstance(msg, dict):
+            assert msg["content"] == "visible"
+            assert msg["encryptedValue"] == "secret-data"
+
+    def test_emit_content_routes_reasoning_with_flow(self):
+        """_emit_content passes flow to _emit_text_reasoning for persistence."""
+        flow = FlowState()
+        content = Content.from_text_reasoning(text="routed reasoning")
+
+        _emit_content(content, flow)
+
+        assert len(flow.reasoning_messages) == 1
+        assert flow.reasoning_messages[0]["content"] == "routed reasoning"
+
+    def test_reasoning_without_flow_does_not_error(self):
+        """Calling _emit_text_reasoning without flow still works (backward compat)."""
+        content = Content.from_text_reasoning(text="no flow")
+
+        events = _emit_text_reasoning(content)
+
+        assert len(events) == 5
+        assert isinstance(events[0], ReasoningStartEvent)
+
+    def test_snapshot_reasoning_ordering(self):
+        """Reasoning messages appear after assistant text in snapshot."""
+        from agent_framework_ag_ui._agent_run import _build_messages_snapshot
+
+        flow = FlowState()
+        reasoning_content = Content.from_text_reasoning(id="r1", text="Thinking...")
+        _emit_text_reasoning(reasoning_content, flow)
+
+        text_content = Content.from_text("Answer")
+        _emit_text(text_content, flow)
+
+        snapshot = _build_messages_snapshot(flow, [{"id": "u1", "role": "user", "content": "Hi"}])
+
+        # user -> assistant text -> reasoning
+        assert len(snapshot.messages) == 3
+        roles = [m.get("role") if isinstance(m, dict) else getattr(m, "role", None) for m in snapshot.messages]
+        assert roles == ["user", "assistant", "reasoning"]
+
+    def test_reasoning_accumulates_incremental_deltas(self):
+        """Multiple reasoning deltas with the same id accumulate into one entry."""
+        flow = FlowState()
+        content1 = Content.from_text_reasoning(id="reason_inc", text="First ")
+        content2 = Content.from_text_reasoning(id="reason_inc", text="second ")
+        content3 = Content.from_text_reasoning(id="reason_inc", text="third.")
+
+        _emit_text_reasoning(content1, flow)
+        _emit_text_reasoning(content2, flow)
+        _emit_text_reasoning(content3, flow)
+
+        assert len(flow.reasoning_messages) == 1
+        assert flow.reasoning_messages[0]["id"] == "reason_inc"
+        assert flow.reasoning_messages[0]["content"] == "First second third."
+
+    def test_reasoning_accumulates_distinct_message_ids(self):
+        """Reasoning entries with different ids are stored separately."""
+        flow = FlowState()
+        content_a = Content.from_text_reasoning(id="a", text="alpha")
+        content_b = Content.from_text_reasoning(id="b", text="beta")
+
+        _emit_text_reasoning(content_a, flow)
+        _emit_text_reasoning(content_b, flow)
+
+        assert len(flow.reasoning_messages) == 2
+        assert flow.reasoning_messages[0]["content"] == "alpha"
+        assert flow.reasoning_messages[1]["content"] == "beta"
+
+    def test_reasoning_encrypted_value_updated_on_later_delta(self):
+        """encryptedValue is set even when it arrives with a later delta."""
+        flow = FlowState()
+        content1 = Content.from_text_reasoning(id="enc_late", text="part1 ")
+        content2 = Content.from_text_reasoning(id="enc_late", text="part2", protected_data="encrypted-payload")
+
+        _emit_text_reasoning(content1, flow)
+        _emit_text_reasoning(content2, flow)
+
+        assert len(flow.reasoning_messages) == 1
+        assert flow.reasoning_messages[0]["content"] == "part1 part2"
+        assert flow.reasoning_messages[0]["encryptedValue"] == "encrypted-payload"

python/packages/ag-ui/tests/ag_ui/test_utils.py

@@ -450,6 +450,7 @@ def test_normalize_agui_role_valid():
     assert normalize_agui_role("assistant") == "assistant"
     assert normalize_agui_role("system") == "system"
     assert normalize_agui_role("tool") == "tool"
+    assert normalize_agui_role("reasoning") == "reasoning"
 
 
 def test_normalize_agui_role_invalid():