Fix ag_ui message toolcall order to support Anthropic requirements

Fixes #2327

Author: ChuckJonas

pydantic_ai_slim/pydantic_ai/ag_ui.py

@@ -477,7 +477,6 @@ async def _handle_tool_result_event(
                 if isinstance(item, BaseEvent):  # pragma: no branch
                     yield item
 
-
 def _messages_from_ag_ui(messages: list[Message]) -> list[ModelMessage]:
     """Convert a AG-UI history to a Pydantic AI one."""
     result: list[ModelMessage] = []
@@ -486,7 +485,23 @@ def _messages_from_ag_ui(messages: list[Message]) -> list[ModelMessage]:
         if isinstance(msg, UserMessage):
             result.append(ModelRequest(parts=[UserPromptPart(content=msg.content)]))
         elif isinstance(msg, AssistantMessage):
-            if msg.tool_calls:
+            if msg.tool_calls and msg.content:
+                # When both content and tool_calls exist, combine them in the correct order:
+                # text content first, then tool calls (preserving original assistant behavior)
+                for tool_call in msg.tool_calls:
+                    tool_calls[tool_call.id] = tool_call.function.name
+
+                parts = [TextPart(content=msg.content)]
+                parts.extend([
+                    ToolCallPart(
+                        tool_name=tool_call.function.name,
+                        tool_call_id=tool_call.id,
+                        args=tool_call.function.arguments,
+                    )
+                    for tool_call in msg.tool_calls
+                ])
+                result.append(ModelResponse(parts=parts))
+            elif msg.tool_calls:
                 for tool_call in msg.tool_calls:
                     tool_calls[tool_call.id] = tool_call.function.name
 
@@ -502,8 +517,7 @@ def _messages_from_ag_ui(messages: list[Message]) -> list[ModelMessage]:
                         ]
                     )
                 )
-
-            if msg.content:
+            elif msg.content:
                 result.append(ModelResponse(parts=[TextPart(content=msg.content)]))
         elif isinstance(msg, SystemMessage):
             result.append(ModelRequest(parts=[SystemPromptPart(content=msg.content)]))
@@ -528,7 +542,6 @@ def _messages_from_ag_ui(messages: list[Message]) -> list[ModelMessage]:
 
     return result
 
-
 @runtime_checkable
 class StateHandler(Protocol):
     """Protocol for state handlers in agent runs."""