fix: handle missing a2a dep as optional

lib/crewai/src/crewai/a2a/__init__.py

@@ -1,18 +1,8 @@
 """Agent-to-Agent (A2A) protocol communication module for CrewAI."""
 
 from crewai.a2a.config import A2AConfig
-from crewai.a2a.errors import A2APollingTimeoutError
-from crewai.a2a.updates import (
-    PollingConfig,
-    PushNotificationConfig,
-    StreamingConfig,
-)
 
 
 __all__ = [
     "A2AConfig",
-    "A2APollingTimeoutError",
-    "PollingConfig",
-    "PushNotificationConfig",
-    "StreamingConfig",
 ]

lib/crewai/src/crewai/a2a/config.py

@@ -5,7 +5,7 @@ This module is separate from experimental.a2a to avoid circular imports.
 
 from __future__ import annotations
 
-from typing import Annotated, ClassVar
+from typing import Annotated, Any, ClassVar
 
 from pydantic import (
     BaseModel,
@@ -17,7 +17,12 @@ from pydantic import (
 )
 
 from crewai.a2a.auth.schemas import AuthScheme
-from crewai.a2a.updates import StreamingConfig, UpdateConfig
+
+
+try:
+    from crewai.a2a.updates import UpdateConfig
+except ImportError:
+    UpdateConfig = Any  # type: ignore[misc,assignment]
 
 
 http_url_adapter = TypeAdapter(HttpUrl)
@@ -30,6 +35,12 @@ Url = Annotated[
 ]
 
 
+def _get_default_update_config() -> UpdateConfig:
+    from crewai.a2a.updates import StreamingConfig
+
+    return StreamingConfig()
+
+
 class A2AConfig(BaseModel):
     """Configuration for A2A protocol integration.
 
@@ -68,6 +79,6 @@ class A2AConfig(BaseModel):
         description="If True, return A2A result directly when completed",
     )
     updates: UpdateConfig = Field(
-        default_factory=StreamingConfig,
+        default_factory=_get_default_update_config,
         description="Update mechanism config",
     )