diff --git a/swe_af/execution/coding_loop.py b/swe_af/execution/coding_loop.py
index 9790e9e..394d5e2 100644
--- a/swe_af/execution/coding_loop.py
+++ b/swe_af/execution/coding_loop.py
@@ -35,8 +35,8 @@ async def _call_with_timeout(coro, timeout: int = 2700, label: str = ""):
     """Wrap a coroutine with asyncio.wait_for timeout."""
     try:
         return await asyncio.wait_for(coro, timeout=timeout)
-    except asyncio.TimeoutError:
-        raise TimeoutError(f"Agent call '{label}' timed out after {timeout}s")
+    except asyncio.TimeoutError as exc:
+        raise TimeoutError(f"Agent call '{label}' timed out after {timeout}s") from exc
 
 
 # ---------------------------------------------------------------------------
diff --git a/swe_af/execution/dag_executor.py b/swe_af/execution/dag_executor.py
index 212000b..46480cf 100644
--- a/swe_af/execution/dag_executor.py
+++ b/swe_af/execution/dag_executor.py
@@ -42,10 +42,10 @@ async def _call_with_timeout(coro, timeout: int = 2700, label: str = ""):
     """
     try:
         return await asyncio.wait_for(coro, timeout=timeout)
-    except asyncio.TimeoutError:
+    except asyncio.TimeoutError as exc:
         raise TimeoutError(
             f"Agent call '{label}' timed out after {timeout}s"
-        )
+        ) from exc
 
 
 # ---------------------------------------------------------------------------
diff --git a/tests/test_call_with_timeout.py b/tests/test_call_with_timeout.py
new file mode 100644
index 0000000..1bc1d47
--- /dev/null
+++ b/tests/test_call_with_timeout.py
@@ -0,0 +1,23 @@
+"""Unit tests for the timeout wrappers used by the execution engine."""
+
+from __future__ import annotations
+
+import asyncio
+
+import pytest
+
+from swe_af.execution.coding_loop import _call_with_timeout as coding_loop_timeout
+from swe_af.execution.dag_executor import _call_with_timeout as dag_executor_timeout
+
+
+@pytest.mark.parametrize("fn", [coding_loop_timeout, dag_executor_timeout])
+async def test_call_with_timeout_chains_original_exception(fn):
+    """TimeoutError must carry the original asyncio.TimeoutError as its cause."""
+
+    async def slow():
+        raise asyncio.TimeoutError("simulated")
+
+    with pytest.raises(TimeoutError) as exc_info:
+        await fn(slow(), timeout=1, label="test")
+
+    assert isinstance(exc_info.value.__cause__, asyncio.TimeoutError)