diff --git a/tests/test_a2a_error_observability.py b/tests/test_a2a_error_observability.py
index 449069e..3df8104 100644
--- a/tests/test_a2a_error_observability.py
+++ b/tests/test_a2a_error_observability.py
@@ -5,21 +5,31 @@ diagnostic suffix. Before #51 an exception whose ``str(e)`` was empty
 (bare ``TimeoutError()``, ``BrokenPipeError()``, several httpx transport
 errors) produced ``"[A2A_ERROR] "`` with a trailing space and zero
 context, masking the real cause of peer-delegation failures.
+
+CI does not install pytest-asyncio — use the local _run helper pattern
+established in test_shared_runtime.py.
 """
 
 from __future__ import annotations
 
+import asyncio
 import os
-import sys
-
-import pytest
 
 # Set WORKSPACE_ID before importing molecule_runtime modules — platform_auth
 # evaluates it at import time and refuses to load otherwise.
 os.environ.setdefault("WORKSPACE_ID", "test-workspace")
 
-from molecule_runtime.a2a_client import _A2A_ERROR_PREFIX  # noqa: E402
 from molecule_runtime import a2a_client  # noqa: E402
+from molecule_runtime.a2a_client import _A2A_ERROR_PREFIX  # noqa: E402
+
+
+def _run(coro):
+    """Run an async coroutine synchronously (no pytest-asyncio available)."""
+    loop = asyncio.new_event_loop()
+    try:
+        return loop.run_until_complete(coro)
+    finally:
+        loop.close()
 
 
 class _BareException(Exception):
@@ -45,8 +55,7 @@ class _StubAsyncClient:
         raise self._exc
 
 
-@pytest.mark.asyncio
-async def test_bare_exception_yields_class_name(monkeypatch):
+def test_bare_exception_yields_class_name(monkeypatch):
     """When str(e) is empty the result must still include the exception class."""
 
     def _factory(*_a, **_kw):
@@ -56,15 +65,14 @@ async def test_bare_exception_yields_class_name(monkeypatch):
     monkeypatch.setattr(a2a_client, "PLATFORM_URL", "http://stub")
     monkeypatch.setattr(a2a_client, "auth_headers", lambda: {})
 
-    result = await a2a_client.send_a2a_message("peer-ws-id", "hi")
+    result = _run(a2a_client.send_a2a_message("peer-ws-id", "hi"))
     assert result.startswith(_A2A_ERROR_PREFIX)
     suffix = result[len(_A2A_ERROR_PREFIX):]
     assert suffix.strip() != "", f"expected non-empty suffix, got {result!r}"
     assert "BareException" in suffix
 
 
-@pytest.mark.asyncio
-async def test_exception_with_message_passes_through(monkeypatch):
+def test_exception_with_message_passes_through(monkeypatch):
     """Regular exception messages are preserved."""
 
     def _factory(*_a, **_kw):
@@ -74,5 +82,5 @@ async def test_exception_with_message_passes_through(monkeypatch):
     monkeypatch.setattr(a2a_client, "PLATFORM_URL", "http://stub")
     monkeypatch.setattr(a2a_client, "auth_headers", lambda: {})
 
-    result = await a2a_client.send_a2a_message("peer-ws-id", "hi")
+    result = _run(a2a_client.send_a2a_message("peer-ws-id", "hi"))
     assert result == f"{_A2A_ERROR_PREFIX}upstream 429"