Python: [BREAKING] Simplify API: ChatAgent -> Agent, ChatMessage -> Message (#3747)

* [BREAKING] Rename ChatAgent -> Agent, ChatMessage -> Message, ChatClientProtocol -> SupportsChatGetResponse

Simplify the public API by removing redundant 'Chat' prefix from core types:
- ChatAgent -> Agent
- RawChatAgent -> RawAgent
- ChatMessage -> Message
- ChatClientProtocol -> SupportsChatGetResponse

Also renamed internal WorkflowMessage (was Message in _runner_context) to avoid collision.

No backward compatibility aliases - this is a clean breaking change.

* [BREAKING] Rename Agent chat_client parameter to client

* Fix rebase issues: WorkflowMessage references and broken markdown links

* Fix formatting and lint issues from code quality checks

* Fix import ordering in workflow sample files

* fixed rebase

* Fix test failures: use WorkflowMessage and A2AMessage after ChatMessage→Message rename

- Replace Message(data=..., source_id=...) with WorkflowMessage(...) in workflow tests
- Fix isinstance check in A2A agent to use A2AMessage instead of Message
- Fix import in test_workflow_observability.py (Message→WorkflowMessage)

* Fix lint, fmt, and sample errors after ChatMessage→Message rename

- Auto-fix 70+ ruff lint issues across samples (ChatMessage→Message refs)
- Fix HostedVectorStoreContent→Content.from_hosted_vector_store in file search sample
- Fix _normalize_messages→normalize_messages in custom agent sample
- Fix context.terminate→raise MiddlewareTermination in middleware samples
- Fix with_update_hook→with_transform_hook in override middleware sample
- Add TOptions_co import back to custom_chat_client sample
- Add noqa for FastAPI File() default in chatkit sample
- Fix B023 loop variable capture in weather agent sample

* fix: update Agent constructor calls from chat_client to client in declaration-only tool tests

* fix: add register_cleanup to devui lazy-loading proxy and type stub

* fixed tests and updated new pieces

* fix agui typevar

* fix merge errors

* fix merge conflicts

* fiux merge

* Remove unused links

---------

Co-authored-by: Evan Mattson <evan.mattson@microsoft.com>

python/samples/getting_started/agents/azure_ai/azure_ai_provider_methods.py

@@ -23,7 +23,7 @@ This sample demonstrates the three main methods of AzureAIProjectAgentProvider:
 It also shows how to use a single provider instance to spawn multiple agents
 with different configurations, which is efficient for multi-agent scenarios.
 
-Each method returns a ChatAgent that can be used for conversations.
+Each method returns a Agent that can be used for conversations.
 """
 
 
@@ -41,7 +41,7 @@ async def create_agent_example() -> None:
     """Example of using provider.create_agent() to create a new agent.
 
     This method creates a new agent version on the Azure AI service and returns
-    a ChatAgent. Use this when you want to create a fresh agent with
+    a Agent. Use this when you want to create a fresh agent with
     specific configuration.
     """
     print("=== provider.create_agent() Example ===")
@@ -199,7 +199,7 @@ async def multiple_agents_example() -> None:
 async def as_agent_example() -> None:
     """Example of using provider.as_agent() to wrap an SDK object without HTTP calls.
 
-    This method wraps an existing AgentVersionDetails into a ChatAgent without
+    This method wraps an existing AgentVersionDetails into a Agent without
     making additional HTTP calls. Use this when you already have the full
     AgentVersionDetails from a previous SDK operation.
     """

python/samples/getting_started/agents/azure_ai/azure_ai_with_application_endpoint.py

@@ -3,7 +3,7 @@
 import asyncio
 import os
 
-from agent_framework import ChatAgent
+from agent_framework import Agent
 from agent_framework.azure import AzureAIClient
 from azure.ai.projects.aio import AIProjectClient
 from azure.identity.aio import AzureCliCredential
@@ -23,8 +23,8 @@ async def main() -> None:
         # Endpoint here should be application endpoint with format:
         # /api/projects/<project-name>/applications/<application-name>/protocols
         AIProjectClient(endpoint=os.environ["AZURE_AI_PROJECT_ENDPOINT"], credential=credential) as project_client,
-        ChatAgent(
-            chat_client=AzureAIClient(
+        Agent(
+            client=AzureAIClient(
                 project_client=project_client,
             ),
         ) as agent,

python/samples/getting_started/agents/azure_ai/azure_ai_with_code_interpreter_file_download.py

@@ -5,9 +5,9 @@ import tempfile
 from pathlib import Path
 
 from agent_framework import (
+    Agent,
     AgentResponseUpdate,
     Annotation,
-    ChatAgent,
     Content,
     HostedCodeInterpreterTool,
 )
@@ -33,7 +33,7 @@ QUERY = (
 )
 
 
-async def download_container_files(file_contents: list[Annotation | Content], agent: ChatAgent) -> list[Path]:
+async def download_container_files(file_contents: list[Annotation | Content], agent: Agent) -> list[Path]:
     """Download container files using the OpenAI containers API.
 
     Code interpreter generates files in containers, which require both file_id
@@ -45,7 +45,7 @@ async def download_container_files(file_contents: list[Annotation | Content], ag
     Args:
         file_contents: List of Annotation or Content objects
                       containing file_id and container_id.
-        agent: The ChatAgent instance with access to the AzureAIClient.
+        agent: The Agent instance with access to the AzureAIClient.
 
     Returns:
         List of Path objects for successfully downloaded files.
@@ -61,7 +61,7 @@ async def download_container_files(file_contents: list[Annotation | Content], ag
     print(f"\nDownloading {len(file_contents)} container file(s) to {output_dir.absolute()}...")
 
     # Access the OpenAI client from AzureAIClient
-    openai_client = agent.chat_client.client  # type: ignore[attr-defined]
+    openai_client = agent.client.client  # type: ignore[attr-defined]
 
     downloaded_files: list[Path] = []
 
@@ -139,7 +139,7 @@ async def non_streaming_example() -> None:
 
         # Check for annotations in the response
         annotations_found: list[Annotation] = []
-        # AgentResponse has messages property, which contains ChatMessage objects
+        # AgentResponse has messages property, which contains Message objects
         for message in result.messages:
             for content in message.contents:
                 if content.type == "text" and content.annotations:

python/samples/getting_started/agents/azure_ai/azure_ai_with_code_interpreter_file_generation.py

@@ -44,7 +44,7 @@ async def non_streaming_example() -> None:
 
         # Check for annotations in the response
         annotations_found: list[str] = []
-        # AgentResponse has messages property, which contains ChatMessage objects
+        # AgentResponse has messages property, which contains Message objects
         for message in result.messages:
             for content in message.contents:
                 if content.type == "text" and content.annotations:

python/samples/getting_started/agents/azure_ai/azure_ai_with_existing_agent.py

@@ -36,7 +36,7 @@ async def using_provider_get_agent() -> None:
         )
 
         try:
-            # Get newly created agent as ChatAgent by using provider.get_agent()
+            # Get newly created agent as Agent by using provider.get_agent()
             provider = AzureAIProjectAgentProvider(project_client=project_client)
             agent = await provider.get_agent(name=azure_ai_agent.name)
 

python/samples/getting_started/agents/azure_ai/azure_ai_with_hosted_mcp.py

@@ -3,7 +3,7 @@
 import asyncio
 from typing import Any
 
-from agent_framework import AgentResponse, AgentThread, ChatMessage, HostedMCPTool, SupportsAgentRun
+from agent_framework import AgentResponse, AgentThread, HostedMCPTool, Message, SupportsAgentRun
 from agent_framework.azure import AzureAIProjectAgentProvider
 from azure.identity.aio import AzureCliCredential
 
@@ -25,10 +25,10 @@ async def handle_approvals_without_thread(query: str, agent: "SupportsAgentRun")
                 f"User Input Request for function from {agent.name}: {user_input_needed.function_call.name}"
                 f" with arguments: {user_input_needed.function_call.arguments}"
             )
-            new_inputs.append(ChatMessage("assistant", [user_input_needed]))
+            new_inputs.append(Message("assistant", [user_input_needed]))
             user_approval = input("Approve function call? (y/n): ")
             new_inputs.append(
-                ChatMessage("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
+                Message("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
             )
 
         result = await agent.run(new_inputs, store=False)
@@ -48,7 +48,7 @@ async def handle_approvals_with_thread(query: str, agent: "SupportsAgentRun", th
             )
             user_approval = input("Approve function call? (y/n): ")
             new_input.append(
-                ChatMessage(
+                Message(
                     role="user",
                     contents=[user_input_needed.to_function_approval_response(user_approval.lower() == "y")],
                 )