fix: skip code extraction regex without delimiters

src/google/adk/code_executors/code_execution_utils.py

@@ -144,6 +144,8 @@ def extract_code_and_truncate_content(
 
     first_text_part = copy.deepcopy(text_parts[0])
     response_text = '\n'.join([p.text for p in text_parts])
+    if not any(d[0] in response_text for d in code_block_delimiters):
+      return
 
     # Find the first code block.
     leading_delimiter_pattern = '|'.join(d[0] for d in code_block_delimiters)

tests/unittests/code_executors/test_code_execution_utils.py

@@ -0,0 +1,54 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from unittest.mock import patch
+
+from google.adk.code_executors import code_execution_utils as utils_module
+from google.adk.code_executors.code_execution_utils import CodeExecutionUtils
+from google.genai import types
+
+
+CODE_BLOCK_DELIMITERS = [('```python\n', '\n```')]
+
+
+def test_extract_code_skips_regex_when_opening_delimiter_is_missing():
+  content = types.Content(parts=[types.Part(text='x' * 100_000)])
+
+  with patch.object(
+      utils_module.re,
+      'compile',
+      side_effect=AssertionError('the full regex should be skipped'),
+  ):
+    code = CodeExecutionUtils.extract_code_and_truncate_content(
+        content, CODE_BLOCK_DELIMITERS
+    )
+
+  assert code is None
+  assert content.parts[0].text == 'x' * 100_000
+
+
+def test_extract_code_from_text_part_still_truncates_after_first_block():
+  content = types.Content(
+      parts=[
+          types.Part(text='before ```python\nprint("ok")\n``` after'),
+      ]
+  )
+
+  code = CodeExecutionUtils.extract_code_and_truncate_content(
+      content, CODE_BLOCK_DELIMITERS
+  )
+
+  assert code == 'print("ok")'
+  assert content.parts[0].text == 'before '
+  assert content.parts[1].executable_code.code == 'print("ok")'