From 21c9a5656274ac5b0840d44159550c6b0a3a8afb Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Sat, 30 May 2026 15:22:23 +0800
Subject: [PATCH 1/7] Fix auto function calling stripping explicit null
 arguments (fixes #5934)

---
 python/packages/core/agent_framework/_tools.py |  6 +++---
 python/packages/core/tests/core/test_tools.py  | 17 +++++++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/python/packages/core/agent_framework/_tools.py b/python/packages/core/agent_framework/_tools.py
index 93722a8987..1605c5443d 100644
--- a/python/packages/core/agent_framework/_tools.py
+++ b/python/packages/core/agent_framework/_tools.py
@@ -636,7 +636,7 @@ async def invoke(
                     parsed_arguments = dict(arguments)
                     if self.input_model is not None and not self._schema_supplied:
                         parsed_arguments = self.input_model.model_validate(parsed_arguments).model_dump(
-                            exclude_none=True
+                            exclude_none=False
                         )
                 elif isinstance(arguments, BaseModel):
                     if (
@@ -645,7 +645,7 @@ async def invoke(
                         and not isinstance(arguments, self.input_model)
                     ):
                         raise TypeError(f"Expected {self.input_model.__name__}, got {type(arguments).__name__}")
-                    parsed_arguments = arguments.model_dump(exclude_none=True)
+                    parsed_arguments = arguments.model_dump(exclude_none=False)
                 else:
                     raise TypeError(
                         f"Expected mapping-like arguments for tool '{self.name}', got {type(arguments).__name__}"
@@ -1492,7 +1492,7 @@ async def _auto_invoke_function(
         runtime_kwargs["session"] = invocation_session
     try:
         if not cast(bool, getattr(tool, "_schema_supplied", False)) and tool.input_model is not None:
-            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_none=True)
+            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_none=False)
         else:
             args = dict(parsed_args)
         args = _validate_arguments_against_schema(
diff --git a/python/packages/core/tests/core/test_tools.py b/python/packages/core/tests/core/test_tools.py
index b3762bf4ef..df161a056d 100644
--- a/python/packages/core/tests/core/test_tools.py
+++ b/python/packages/core/tests/core/test_tools.py
@@ -1,4 +1,5 @@
 # Copyright (c) Microsoft. All rights reserved.
+import asyncio
 from typing import Annotated, Any, Literal, get_args, get_origin
 from unittest.mock import Mock
 
@@ -1462,4 +1463,20 @@ def test_skip_parsing_is_singleton() -> None:
     assert repr(SKIP_PARSING) == "SKIP_PARSING"
 
 
+def test_invoke_preserves_explicit_none_arguments() -> None:
+    """Optional parameters explicitly set to None must not be stripped before invocation."""
+
+    @tool
+    def greet(name: str, greeting: str | None = None) -> str:
+        return f"{greeting or 'Hello'}, {name}!"
+
+    result = asyncio.run(greet.invoke(arguments={"name": "World", "greeting": None}))
+    assert isinstance(result, list)
+    assert result[0].text == "Hello, World!"
+
+    result = asyncio.run(greet.invoke(arguments={"name": "World"}))
+    assert isinstance(result, list)
+    assert result[0].text == "Hello, World!"
+
+
 # endregion

From 2436b5e34d5bca0ebd5fcad605299220ef2eda0c Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Sat, 30 May 2026 15:38:52 +0800
Subject: [PATCH 2/7] fix: re-role trailing assistant message to user for
 Anthropic (fixes #5008)

---
 .../agent_framework_anthropic/_chat_client.py | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
index 98c181f152..0c6a70e798 100644
--- a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
+++ b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
@@ -696,11 +696,26 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
 
         This skips the first message if it is a system message,
         as Anthropic expects system instructions as a separate parameter.
+
+        Anthropic's API requires that the conversation ends with a user message.
+        If the last message is from the assistant, its role is changed to user
+        to satisfy this constraint.
         """
         # first system message is passed as instructions
         if messages and isinstance(messages[0], Message) and messages[0].role == "system":
-            return [self._prepare_message_for_anthropic(msg) for msg in messages[1:]]
-        return [self._prepare_message_for_anthropic(msg) for msg in messages]
+            msgs = list(messages[1:])
+        else:
+            msgs = list(messages)
+
+        result = [self._prepare_message_for_anthropic(msg) for msg in msgs]
+
+        # Anthropic requires the conversation to end with a user message.
+        # Re-role a trailing assistant message as user so chained agent
+        # outputs work as valid context for the next agent.
+        if result and result[-1].get("role") == "assistant":
+            result[-1] = {**result[-1], "role": "user"}
+
+        return result
 
     def _prepare_message_for_anthropic(self, message: Message) -> dict[str, Any]:
         """Prepare a Message for the Anthropic client.

From 7cfe88fcf58d06ed82ae232807ae157eb0ba5fb9 Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Tue, 2 Jun 2026 12:24:18 +0800
Subject: [PATCH 3/7] fix: address Copilot review feedback (exclude_unset, test
 coverage, synthetic user turn)

---
 .../agent_framework_anthropic/_chat_client.py          |  6 +++---
 .../packages/anthropic/tests/test_anthropic_client.py  |  4 +++-
 python/packages/core/agent_framework/_tools.py         |  4 ++--
 python/packages/core/tests/core/test_tools.py          | 10 ++++++----
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
index 0c6a70e798..46d0b2447a 100644
--- a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
+++ b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
@@ -710,10 +710,10 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
         result = [self._prepare_message_for_anthropic(msg) for msg in msgs]
 
         # Anthropic requires the conversation to end with a user message.
-        # Re-role a trailing assistant message as user so chained agent
-        # outputs work as valid context for the next agent.
+        # Append a synthetic user turn so chained agent outputs work as
+        # valid context for the next agent without rewriting the assistant message.
         if result and result[-1].get("role") == "assistant":
-            result[-1] = {**result[-1], "role": "user"}
+            result.append({"role": "user", "content": "Continue"})
 
         return result
 
diff --git a/python/packages/anthropic/tests/test_anthropic_client.py b/python/packages/anthropic/tests/test_anthropic_client.py
index 0cfec3423c..5fbb750aae 100644
--- a/python/packages/anthropic/tests/test_anthropic_client.py
+++ b/python/packages/anthropic/tests/test_anthropic_client.py
@@ -618,9 +618,11 @@ def test_prepare_messages_for_anthropic_without_system(
 
     result = client._prepare_messages_for_anthropic(messages)
 
-    assert len(result) == 2
+    assert len(result) == 3
     assert result[0]["role"] == "user"
     assert result[1]["role"] == "assistant"
+    assert result[2]["role"] == "user"
+    assert result[2]["content"] == "Continue"
 
 
 # Tool Conversion Tests
diff --git a/python/packages/core/agent_framework/_tools.py b/python/packages/core/agent_framework/_tools.py
index 1605c5443d..271e232b40 100644
--- a/python/packages/core/agent_framework/_tools.py
+++ b/python/packages/core/agent_framework/_tools.py
@@ -636,7 +636,7 @@ async def invoke(
                     parsed_arguments = dict(arguments)
                     if self.input_model is not None and not self._schema_supplied:
                         parsed_arguments = self.input_model.model_validate(parsed_arguments).model_dump(
-                            exclude_none=False
+                            exclude_unset=True, exclude_none=False
                         )
                 elif isinstance(arguments, BaseModel):
                     if (
@@ -645,7 +645,7 @@ async def invoke(
                         and not isinstance(arguments, self.input_model)
                     ):
                         raise TypeError(f"Expected {self.input_model.__name__}, got {type(arguments).__name__}")
-                    parsed_arguments = arguments.model_dump(exclude_none=False)
+                    parsed_arguments = arguments.model_dump(exclude_unset=True, exclude_none=False)
                 else:
                     raise TypeError(
                         f"Expected mapping-like arguments for tool '{self.name}', got {type(arguments).__name__}"
diff --git a/python/packages/core/tests/core/test_tools.py b/python/packages/core/tests/core/test_tools.py
index df161a056d..fe7dfa2810 100644
--- a/python/packages/core/tests/core/test_tools.py
+++ b/python/packages/core/tests/core/test_tools.py
@@ -1467,16 +1467,18 @@ def test_invoke_preserves_explicit_none_arguments() -> None:
     """Optional parameters explicitly set to None must not be stripped before invocation."""
 
     @tool
-    def greet(name: str, greeting: str | None = None) -> str:
-        return f"{greeting or 'Hello'}, {name}!"
+    def greet(name: str, greeting: str | None = "Hi") -> str:
+        if greeting is None:
+            return f"Custom, {name}!"
+        return f"{greeting}, {name}!"
 
     result = asyncio.run(greet.invoke(arguments={"name": "World", "greeting": None}))
     assert isinstance(result, list)
-    assert result[0].text == "Hello, World!"
+    assert result[0].text == "Custom, World!"
 
     result = asyncio.run(greet.invoke(arguments={"name": "World"}))
     assert isinstance(result, list)
-    assert result[0].text == "Hello, World!"
+    assert result[0].text == "Hi, World!"
 
 
 # endregion

From 01a706eacd8e781bd7cd554c49227ae0b3665eb5 Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Tue, 2 Jun 2026 21:18:02 +0800
Subject: [PATCH 4/7] fix: update docstring and extend exclude_unset to
 auto_invoke_function

---
 .../anthropic/agent_framework_anthropic/_chat_client.py       | 4 ++--
 python/packages/core/agent_framework/_tools.py                | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
index 46d0b2447a..dfb35c9dfd 100644
--- a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
+++ b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
@@ -698,8 +698,8 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
         as Anthropic expects system instructions as a separate parameter.
 
         Anthropic's API requires that the conversation ends with a user message.
-        If the last message is from the assistant, its role is changed to user
-        to satisfy this constraint.
+        If the last message is from the assistant, a synthetic user turn is
+        appended to satisfy this constraint.
         """
         # first system message is passed as instructions
         if messages and isinstance(messages[0], Message) and messages[0].role == "system":
diff --git a/python/packages/core/agent_framework/_tools.py b/python/packages/core/agent_framework/_tools.py
index 271e232b40..de2152aea9 100644
--- a/python/packages/core/agent_framework/_tools.py
+++ b/python/packages/core/agent_framework/_tools.py
@@ -1492,7 +1492,7 @@ async def _auto_invoke_function(
         runtime_kwargs["session"] = invocation_session
     try:
         if not cast(bool, getattr(tool, "_schema_supplied", False)) and tool.input_model is not None:
-            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_none=False)
+            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_unset=True, exclude_none=False)
         else:
             args = dict(parsed_args)
         args = _validate_arguments_against_schema(

From 7f68a30856e76c115ed769a24ac604aafdff9e2a Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Tue, 2 Jun 2026 21:44:46 +0800
Subject: [PATCH 5/7] revert: remove unrelated core _tools.py changes from
 Anthropic PR

The exclude_none/exclude_unset changes in the core package are out of scope
for this Anthropic-specific fix. This PR now only contains the Anthropic
chat client docstring fix and the synthetic user turn append.
---
 .../packages/core/agent_framework/_tools.py   |  6 +++---
 python/packages/core/tests/core/test_tools.py | 19 -------------------
 2 files changed, 3 insertions(+), 22 deletions(-)

diff --git a/python/packages/core/agent_framework/_tools.py b/python/packages/core/agent_framework/_tools.py
index de2152aea9..93722a8987 100644
--- a/python/packages/core/agent_framework/_tools.py
+++ b/python/packages/core/agent_framework/_tools.py
@@ -636,7 +636,7 @@ async def invoke(
                     parsed_arguments = dict(arguments)
                     if self.input_model is not None and not self._schema_supplied:
                         parsed_arguments = self.input_model.model_validate(parsed_arguments).model_dump(
-                            exclude_unset=True, exclude_none=False
+                            exclude_none=True
                         )
                 elif isinstance(arguments, BaseModel):
                     if (
@@ -645,7 +645,7 @@ async def invoke(
                         and not isinstance(arguments, self.input_model)
                     ):
                         raise TypeError(f"Expected {self.input_model.__name__}, got {type(arguments).__name__}")
-                    parsed_arguments = arguments.model_dump(exclude_unset=True, exclude_none=False)
+                    parsed_arguments = arguments.model_dump(exclude_none=True)
                 else:
                     raise TypeError(
                         f"Expected mapping-like arguments for tool '{self.name}', got {type(arguments).__name__}"
@@ -1492,7 +1492,7 @@ async def _auto_invoke_function(
         runtime_kwargs["session"] = invocation_session
     try:
         if not cast(bool, getattr(tool, "_schema_supplied", False)) and tool.input_model is not None:
-            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_unset=True, exclude_none=False)
+            args = tool.input_model.model_validate(parsed_args).model_dump(exclude_none=True)
         else:
             args = dict(parsed_args)
         args = _validate_arguments_against_schema(
diff --git a/python/packages/core/tests/core/test_tools.py b/python/packages/core/tests/core/test_tools.py
index fe7dfa2810..b3762bf4ef 100644
--- a/python/packages/core/tests/core/test_tools.py
+++ b/python/packages/core/tests/core/test_tools.py
@@ -1,5 +1,4 @@
 # Copyright (c) Microsoft. All rights reserved.
-import asyncio
 from typing import Annotated, Any, Literal, get_args, get_origin
 from unittest.mock import Mock
 
@@ -1463,22 +1462,4 @@ def test_skip_parsing_is_singleton() -> None:
     assert repr(SKIP_PARSING) == "SKIP_PARSING"
 
 
-def test_invoke_preserves_explicit_none_arguments() -> None:
-    """Optional parameters explicitly set to None must not be stripped before invocation."""
-
-    @tool
-    def greet(name: str, greeting: str | None = "Hi") -> str:
-        if greeting is None:
-            return f"Custom, {name}!"
-        return f"{greeting}, {name}!"
-
-    result = asyncio.run(greet.invoke(arguments={"name": "World", "greeting": None}))
-    assert isinstance(result, list)
-    assert result[0].text == "Custom, World!"
-
-    result = asyncio.run(greet.invoke(arguments={"name": "World"}))
-    assert isinstance(result, list)
-    assert result[0].text == "Hi, World!"
-
-
 # endregion

From 98cd205f13543336fbf19ab0a807ea37c5205743 Mon Sep 17 00:00:00 2001
From: venti <1308199824@qq.com>
Date: Thu, 11 Jun 2026 19:44:00 +0800
Subject: [PATCH 6/7] fix: avoid appending user turn after Anthropic tool use

---
 .../agent_framework_anthropic/_chat_client.py | 12 +++++++--
 .../anthropic/tests/test_anthropic_client.py  | 26 +++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
index dfb35c9dfd..02da45b07e 100644
--- a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
+++ b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
@@ -699,7 +699,7 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
 
         Anthropic's API requires that the conversation ends with a user message.
         If the last message is from the assistant, a synthetic user turn is
-        appended to satisfy this constraint.
+        appended when it will not break Anthropic tool_use/tool_result pairing.
         """
         # first system message is passed as instructions
         if messages and isinstance(messages[0], Message) and messages[0].role == "system":
@@ -712,11 +712,19 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
         # Anthropic requires the conversation to end with a user message.
         # Append a synthetic user turn so chained agent outputs work as
         # valid context for the next agent without rewriting the assistant message.
-        if result and result[-1].get("role") == "assistant":
+        if result and result[-1].get("role") == "assistant" and not self._message_has_tool_use(result[-1]):
             result.append({"role": "user", "content": "Continue"})
 
         return result
 
+    def _message_has_tool_use(self, message: dict[str, Any]) -> bool:
+        """Return whether an Anthropic message contains tool_use blocks."""
+        content = message.get("content")
+        return isinstance(content, list) and any(
+            isinstance(item, dict) and item.get("type") in {"tool_use", "mcp_tool_use", "server_tool_use"}
+            for item in content
+        )
+
     def _prepare_message_for_anthropic(self, message: Message) -> dict[str, Any]:
         """Prepare a Message for the Anthropic client.
 
diff --git a/python/packages/anthropic/tests/test_anthropic_client.py b/python/packages/anthropic/tests/test_anthropic_client.py
index 5fbb750aae..3e82ebb168 100644
--- a/python/packages/anthropic/tests/test_anthropic_client.py
+++ b/python/packages/anthropic/tests/test_anthropic_client.py
@@ -625,6 +625,32 @@ def test_prepare_messages_for_anthropic_without_system(
     assert result[2]["content"] == "Continue"
 
 
+def test_prepare_messages_for_anthropic_does_not_append_after_tool_use(
+    mock_anthropic_client: MagicMock,
+) -> None:
+    """Do not append plain user text after assistant tool_use blocks."""
+    client = create_test_anthropic_client(mock_anthropic_client)
+    messages = [
+        Message(role="user", contents=["What's the weather?"]),
+        Message(
+            role="assistant",
+            contents=[
+                Content.from_function_call(
+                    call_id="call_123",
+                    name="get_weather",
+                    arguments={"location": "Seattle"},
+                )
+            ],
+        ),
+    ]
+
+    result = client._prepare_messages_for_anthropic(messages)
+
+    assert len(result) == 2
+    assert result[1]["role"] == "assistant"
+    assert result[1]["content"][0]["type"] == "tool_use"
+
+
 # Tool Conversion Tests
 
 

From 7868bd94777705c79888cd9dd743b2c5c6308fc5 Mon Sep 17 00:00:00 2001
From: Evan Mattson <evan.mattson@microsoft.com>
Date: Fri, 19 Jun 2026 14:35:19 +0900
Subject: [PATCH 7/7] Fix Anthropic tool-use type narrowing

Use object-typed content narrowing before checking Anthropic tool-use block types so strict Pyright no longer treats dynamic message content as Unknown.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../agent_framework_anthropic/_chat_client.py | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
index 02da45b07e..c7d7906c39 100644
--- a/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
+++ b/python/packages/anthropic/agent_framework_anthropic/_chat_client.py
@@ -5,7 +5,7 @@
 import logging
 import sys
 from collections.abc import AsyncIterable, Awaitable, Callable, Mapping, Sequence
-from typing import Any, ClassVar, Final, Generic, Literal, TypedDict
+from typing import Any, ClassVar, Final, Generic, Literal, TypedDict, cast
 
 from agent_framework import (
     Annotation,
@@ -719,11 +719,19 @@ def _prepare_messages_for_anthropic(self, messages: Sequence[Message]) -> list[d
 
     def _message_has_tool_use(self, message: dict[str, Any]) -> bool:
         """Return whether an Anthropic message contains tool_use blocks."""
-        content = message.get("content")
-        return isinstance(content, list) and any(
-            isinstance(item, dict) and item.get("type") in {"tool_use", "mcp_tool_use", "server_tool_use"}
-            for item in content
-        )
+        content: object = message.get("content")
+        if not isinstance(content, list):
+            return False
+
+        content_blocks = cast(list[object], content)
+        for content_block in content_blocks:
+            match content_block:
+                case {"type": "tool_use" | "mcp_tool_use" | "server_tool_use"}:
+                    return True
+                case _:
+                    pass
+
+        return False
 
     def _prepare_message_for_anthropic(self, message: Message) -> dict[str, Any]:
         """Prepare a Message for the Anthropic client.