FIX: Anthropic multimodal(Image) message for Anthropic >= 0.48 aware (#6054)

## Why are these changes needed?
This PR fixes a `TypeError: Cannot instantiate typing.Union` that occurs
when using the `MultimodalWebSurfer_agent` with Anthropic models. The
error was caused by the incorrect usage of `typing.Union` as a class
constructor instead of a type hint within the `_anthropic_client.py`
file. The code was attempting to instantiate `typing.Union`, which is
not allowed. The fix correctly uses `typing.Union` within type hints,
and uses the correct `Base64ImageSourceParam` type. It also updates the
`pyproject.toml` dependency.

## Related issue number
Closes #6035 

## Checks

- [ ] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [ ] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [v] I've made sure all auto checks have passed.

---------

Co-authored-by: Victor Dibia <victordibia@microsoft.com>

python/packages/autogen-ext/pyproject.toml

@@ -19,6 +19,7 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+anthropic = ["anthropic>=0.48"]
 langchain = ["langchain_core~= 0.3.3"]
 azure = [
     "azure-ai-inference>=1.0.0b7",

python/packages/autogen-ext/src/autogen_ext/models/anthropic/_anthropic_client.py

@@ -25,6 +25,7 @@ from typing import (
 import tiktoken
 from anthropic import AsyncAnthropic, AsyncStream
 from anthropic.types import (
+    Base64ImageSourceParam,
     ContentBlock,
     ImageBlockParam,
     Message,
@@ -36,7 +37,6 @@ from anthropic.types import (
     ToolResultBlockParam,
     ToolUseBlock,
 )
-from anthropic.types.image_block_param import Source
 from autogen_core import (
     EVENT_LOGGER_NAME,
     TRACE_LOGGER_NAME,
@@ -160,7 +160,7 @@ def user_message_to_anthropic(message: UserMessage) -> MessageParam:
                 blocks.append(
                     ImageBlockParam(
                         type="image",
-                        source=Source(
+                        source=Base64ImageSourceParam(
                             type="base64",
                             media_type=get_mime_type_from_image(part),
                             data=part.to_base64(),

python/uv.lock

@@ -290,7 +290,7 @@ wheels = [
 
 [[package]]
 name = "anthropic"
-version = "0.45.2"
+version = "0.49.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "anyio" },
@@ -301,9 +301,9 @@ dependencies = [
     { name = "sniffio" },
     { name = "typing-extensions" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/15/74/2b2485fc120da834c0c5be07462541ec082e9fa8851d845f2587e480535a/anthropic-0.45.2.tar.gz", hash = "sha256:32a18b9ecd12c91b2be4cae6ca2ab46a06937b5aa01b21308d97a6d29794fb5e", size = 200901 }
+sdist = { url = "https://files.pythonhosted.org/packages/86/e3/a88c8494ce4d1a88252b9e053607e885f9b14d0a32273d47b727cbee4228/anthropic-0.49.0.tar.gz", hash = "sha256:c09e885b0f674b9119b4f296d8508907f6cff0009bc20d5cf6b35936c40b4398", size = 210016 }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/74/86/e81814e542d1eaeec84d2312bec93a99b9ef1d78d9bfae1fc5dd74abdf15/anthropic-0.45.2-py3-none-any.whl", hash = "sha256:ecd746f7274451dfcb7e1180571ead624c7e1195d1d46cb7c70143d2aedb4d35", size = 222797 },
+    { url = "https://files.pythonhosted.org/packages/76/74/5d90ad14d55fbe3f9c474fdcb6e34b4bed99e3be8efac98734a5ddce88c1/anthropic-0.49.0-py3-none-any.whl", hash = "sha256:bbc17ad4e7094988d2fa86b87753ded8dce12498f4b85fe5810f208f454a8375", size = 243368 },
 ]
 
 [[package]]
@@ -589,6 +589,9 @@ dependencies = [
 ]
 
 [package.optional-dependencies]
+anthropic = [
+    { name = "anthropic" },
+]
 azure = [
     { name = "azure-ai-inference" },
     { name = "azure-core" },
@@ -719,6 +722,7 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "aiofiles", marker = "extra == 'openai'" },
+    { name = "anthropic", marker = "extra == 'anthropic'", specifier = ">=0.48" },
     { name = "asyncio-atexit", marker = "extra == 'docker'", specifier = ">=1.0.1" },
     { name = "autogen-agentchat", marker = "extra == 'file-surfer'", editable = "packages/autogen-agentchat" },
     { name = "autogen-agentchat", marker = "extra == 'magentic-one'", editable = "packages/autogen-agentchat" },