Gl/feat/a2a refactor (#3793)

* feat: agent metaclass, refactor a2a to wrappers

* feat: a2a schemas and utils

* chore: move agent class, update imports

* refactor: organize imports to avoid circularity, add a2a to console

* feat: pass response_model through call chain

* feat: add standard openapi spec serialization to tools and structured output

* feat: a2a events

* chore: add a2a to pyproject

* docs: minimal base for learn docs

* fix: adjust a2a conversation flow, allow llm to decide exit until max_retries

* fix: inject agent skills into initial prompt

* fix: format agent card as json in prompt

* refactor: simplify A2A agent prompt formatting and improve skill display

* chore: wide cleanup

* chore: cleanup logic, add auth cache, use json for messages in prompt

* chore: update docs

* fix: doc snippets formatting

* feat: optimize A2A agent card fetching and improve error reporting

* chore: move imports to top of file

* chore: refactor hasattr check

* chore: add httpx-auth, update lockfile

* feat: create base public api

* chore: cleanup modules, add docstrings, types

* fix: exclude extra fields in prompt

* chore: update docs

* tests: update to correct import

* chore: lint for ruff, add missing import

* fix: tweak openai streaming logic for response model

* tests: add reimport for test

* tests: add reimport for test

* fix: don't set a2a attr if not set

* fix: don't set a2a attr if not set

* chore: update cassettes

* tests: fix tests

* fix: use instructor and dont pass response_format for litellm

* chore: consolidate event listeners, add typing

* fix: address race condition in test, update cassettes

* tests: add correct mocks, rerun cassette for json

* tests: update cassette

* chore: regenerate cassette after new run

* fix: make token manager access-safe

* fix: make token manager access-safe

* merge

* chore: update test and cassete for output pydantic

* fix: tweak to disallow deadlock

* chore: linter

* fix: adjust event ordering for threading

* fix: use conditional for batch check

* tests: tweak for emission

* tests: simplify api + event check

* fix: ensure non-function calling llms see json formatted string

* tests: tweak message comparison

* fix: use internal instructor for litellm structure responses

---------

Co-authored-by: Mike Plachta <mike@crewai.com>

lib/crewai/tests/cli/test_token_manager.py

@@ -29,7 +29,12 @@ class TestTokenManager(unittest.TestCase):
     @patch("crewai.cli.shared.token_manager.Fernet.generate_key")
     @patch("crewai.cli.shared.token_manager.TokenManager.read_secure_file")
     @patch("crewai.cli.shared.token_manager.TokenManager.save_secure_file")
-    def test_get_or_create_key_new(self, mock_save, mock_read, mock_generate):
+    @patch("crewai.cli.shared.token_manager.TokenManager._acquire_lock")
+    @patch("crewai.cli.shared.token_manager.TokenManager._release_lock")
+    @patch("builtins.open", new_callable=unittest.mock.mock_open)
+    def test_get_or_create_key_new(
+        self, mock_open, mock_release_lock, mock_acquire_lock, mock_save, mock_read, mock_generate
+    ):
         mock_key = b"new_key"
         mock_read.return_value = None
         mock_generate.return_value = mock_key
@@ -37,9 +42,14 @@ class TestTokenManager(unittest.TestCase):
         result = self.token_manager._get_or_create_key()
 
         self.assertEqual(result, mock_key)
-        mock_read.assert_called_once_with("secret.key")
+        # read_secure_file is called twice: once for fast path, once inside lock
+        self.assertEqual(mock_read.call_count, 2)
+        mock_read.assert_called_with("secret.key")
         mock_generate.assert_called_once()
         mock_save.assert_called_once_with("secret.key", mock_key)
+        # Verify lock was acquired and released
+        mock_acquire_lock.assert_called_once()
+        mock_release_lock.assert_called_once()
 
     @patch("crewai.cli.shared.token_manager.TokenManager.save_secure_file")
     def test_save_tokens(self, mock_save):
@@ -136,3 +146,21 @@ class TestTokenManager(unittest.TestCase):
         mock_path.__truediv__.return_value.unlink.assert_called_once_with(
             missing_ok=True
         )
+
+    @patch("crewai.cli.shared.token_manager.Fernet.generate_key")
+    @patch("crewai.cli.shared.token_manager.TokenManager.read_secure_file")
+    @patch("crewai.cli.shared.token_manager.TokenManager.save_secure_file")
+    @patch("builtins.open", side_effect=OSError(9, "Bad file descriptor"))
+    def test_get_or_create_key_oserror_fallback(
+        self, mock_open, mock_save, mock_read, mock_generate
+    ):
+        """Test that OSError during file locking falls back to lock-free creation."""
+        mock_key = Fernet.generate_key()
+        mock_read.return_value = None
+        mock_generate.return_value = mock_key
+
+        result = self.token_manager._get_or_create_key()
+
+        self.assertEqual(result, mock_key)
+        self.assertGreaterEqual(mock_generate.call_count, 1)
+        self.assertGreaterEqual(mock_save.call_count, 1)