diff --git a/omnigent/inner/acp_executor.py b/omnigent/inner/acp_executor.py
index b12abf8574..2a385515ac 100644
--- a/omnigent/inner/acp_executor.py
+++ b/omnigent/inner/acp_executor.py
@@ -74,6 +74,7 @@
     ToolCallStatus,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.inner.os_env import OSEnvironment, create_os_environment
 
@@ -472,7 +473,7 @@ async def _read_stdout(self) -> None:
             for fut in self._pending.values():
                 if not fut.done():
                     fut.set_exception(exc)
-            await self._queue.put({"type": "error", "message": str(exc)})
+            await self._queue.put({"type": "error", "message": describe_exception(exc)})
 
     async def _send(self, msg: _AcpJsonObject) -> None:
         """Write one newline-terminated JSON message to the agent's stdin."""
@@ -1057,7 +1058,7 @@ async def run_turn(
             await self._ensure_initialized()
             session_id = await self._ensure_session()
         except Exception as exc:  # noqa: BLE001
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
 
         # A fresh ACP session holds no prior context. Captured before the latch
diff --git a/omnigent/inner/antigravity_executor.py b/omnigent/inner/antigravity_executor.py
index 85606b6695..2767aea81f 100644
--- a/omnigent/inner/antigravity_executor.py
+++ b/omnigent/inner/antigravity_executor.py
@@ -69,6 +69,7 @@
     TurnCancelled,
     TurnComplete,
     classify_tool_result,
+    describe_exception,
 )
 
 logger = logging.getLogger(__name__)
@@ -498,7 +499,7 @@ async def run_turn(
                 tools=tools,
             )
         except ImportError as exc:
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
         except Exception as exc:
             logger.exception("Antigravity agent construction failed")
diff --git a/omnigent/inner/antigravity_native_executor.py b/omnigent/inner/antigravity_native_executor.py
index 5393ce9442..837611f29d 100644
--- a/omnigent/inner/antigravity_native_executor.py
+++ b/omnigent/inner/antigravity_native_executor.py
@@ -82,6 +82,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.llms.errors import PermanentLLMError
 from omnigent.reasoning_effort import ANTIGRAVITY_EFFORTS, validate_effort_or_llm_error
@@ -231,7 +232,7 @@ async def run_turn(
             try:
                 validate_effort_or_llm_error(effort, "antigravity", ANTIGRAVITY_EFFORTS)
             except PermanentLLMError as exc:
-                yield ExecutorError(message=str(exc))
+                yield ExecutorError(message=describe_exception(exc))
                 return
         text = _latest_user_text(messages, self._bridge_dir)
         if not text:
diff --git a/omnigent/inner/claude_native_executor.py b/omnigent/inner/claude_native_executor.py
index 0e27ff2e53..d42feca50a 100644
--- a/omnigent/inner/claude_native_executor.py
+++ b/omnigent/inner/claude_native_executor.py
@@ -29,6 +29,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.inner.native_attachments import attachment_reference_line
 
@@ -192,7 +193,7 @@ async def run_turn(
                         content=text,
                     )
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/inner/claude_sdk_executor.py b/omnigent/inner/claude_sdk_executor.py
index 4fbbf2af8b..84bb3f9a25 100644
--- a/omnigent/inner/claude_sdk_executor.py
+++ b/omnigent/inner/claude_sdk_executor.py
@@ -71,6 +71,7 @@
     ToolSpec,
     TurnComplete,
     classify_tool_result,
+    describe_exception,
 )
 from .native_attachments import unresolved_attachment_marker
 from .sandbox import (
@@ -2361,7 +2362,7 @@ def _on_stderr(line: str) -> None:
                 cfg.extra.get("reasoning_effort"), "Claude Agent SDK", CLAUDE_EFFORTS
             )
         except ValueError as exc:
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
         if reasoning_effort is not None:
             options_kwargs["effort"] = reasoning_effort
diff --git a/omnigent/inner/codex_executor.py b/omnigent/inner/codex_executor.py
index cf16f897fe..35990439af 100644
--- a/omnigent/inner/codex_executor.py
+++ b/omnigent/inner/codex_executor.py
@@ -71,6 +71,7 @@
     ToolSpec,
     TurnComplete,
     classify_tool_result,
+    describe_exception,
 )
 from .hook_scripts.subagent_router import HOOK_TIMEOUT_HEADROOM_S as _ROUTER_HOOK_HEADROOM_S
 from .hook_scripts.subagent_router import REQUEST_TIMEOUT_S as _ROUTER_REQUEST_TIMEOUT_S
@@ -3319,7 +3320,7 @@ async def run_turn(
                 cfg.extra.get("reasoning_effort"), "codex", CODEX_EFFORTS
             )
         except ValueError as exc:
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
 
         app_session = await self._ensure_app_session(
diff --git a/omnigent/inner/cursor_native_executor.py b/omnigent/inner/cursor_native_executor.py
index 5ce198901f..ebf0a5c93a 100644
--- a/omnigent/inner/cursor_native_executor.py
+++ b/omnigent/inner/cursor_native_executor.py
@@ -32,6 +32,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 
 logger = logging.getLogger(__name__)
@@ -105,7 +106,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(inject_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         # Injection landed — now it's safe to consume the preamble so later
         # turns inject the plain user text.
diff --git a/omnigent/inner/executor.py b/omnigent/inner/executor.py
index d3045e944f..00ab4f0470 100644
--- a/omnigent/inner/executor.py
+++ b/omnigent/inner/executor.py
@@ -51,6 +51,22 @@
 ProviderStreamItem: TypeAlias = Any  # type: ignore[explicit-any]
 
 
+def describe_exception(exc: BaseException) -> str:
+    """Return a non-empty, human-readable description of *exc*.
+
+    ``str(exc)`` is empty for several stdlib exceptions raised without a
+    message (a bare ``RuntimeError()``, ``TimeoutError()``, etc.). Executors
+    that report a failure by ``str(exc)`` then surface a blank error to the
+    operator (issue #4281: "inner executor error: " with no detail). Fall back
+    to ``repr(exc)`` — which always includes the class name — so a failure is
+    never reported without at least naming its type.
+
+    :param exc: The exception to describe.
+    :returns: ``str(exc)`` when non-empty, otherwise ``repr(exc)``.
+    """
+    return str(exc) or repr(exc)
+
+
 @runtime_checkable
 class _ClosableIterator(Protocol):
     """Iterator that may optionally expose a ``close`` method.
diff --git a/omnigent/inner/goose_executor.py b/omnigent/inner/goose_executor.py
index 9fd3e987a2..bd04322b0f 100644
--- a/omnigent/inner/goose_executor.py
+++ b/omnigent/inner/goose_executor.py
@@ -56,6 +56,7 @@
     ToolCallStatus,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.inner.os_env import OSEnvironment, create_os_environment
 
@@ -456,7 +457,7 @@ async def _read_stdout(self) -> None:
             for fut in self._pending.values():
                 if not fut.done():
                     fut.set_exception(exc)
-            await self._queue.put({"type": "error", "message": str(exc)})
+            await self._queue.put({"type": "error", "message": describe_exception(exc)})
 
     async def _send(self, msg: _AcpJsonObject) -> None:
         """Write one newline-terminated JSON message to goose stdin."""
@@ -1102,7 +1103,7 @@ async def run_turn(
             await self._ensure_initialized()
             session_id = await self._ensure_session()
         except Exception as exc:  # noqa: BLE001
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
 
         # A fresh ACP session (first turn of a new/respawned process, or after
diff --git a/omnigent/inner/goose_native_executor.py b/omnigent/inner/goose_native_executor.py
index c0cf08cf2f..59a69901a2 100644
--- a/omnigent/inner/goose_native_executor.py
+++ b/omnigent/inner/goose_native_executor.py
@@ -26,6 +26,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 
 logger = logging.getLogger(__name__)
@@ -87,7 +88,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(inject_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/inner/hermes_native_executor.py b/omnigent/inner/hermes_native_executor.py
index da1c70b795..65b38a6489 100644
--- a/omnigent/inner/hermes_native_executor.py
+++ b/omnigent/inner/hermes_native_executor.py
@@ -27,6 +27,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 
 logger = logging.getLogger(__name__)
@@ -88,7 +89,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(inject_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/inner/kimi_native_executor.py b/omnigent/inner/kimi_native_executor.py
index c11cb4d142..7b65ee70c6 100644
--- a/omnigent/inner/kimi_native_executor.py
+++ b/omnigent/inner/kimi_native_executor.py
@@ -29,6 +29,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.kimi_native_bridge import BRIDGE_DIR_ENV_VAR, inject_user_message
 
@@ -91,7 +92,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(inject_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/inner/kiro_native_executor.py b/omnigent/inner/kiro_native_executor.py
index 34cd899d87..90a5a03cbe 100644
--- a/omnigent/inner/kiro_native_executor.py
+++ b/omnigent/inner/kiro_native_executor.py
@@ -16,6 +16,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.kiro_native_bridge import KIRO_NATIVE_BRIDGE_DIR_ENV_VAR, inject_user_message
 
@@ -65,7 +66,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(inject_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/inner/openai_agents_sdk_executor.py b/omnigent/inner/openai_agents_sdk_executor.py
index e772c73449..f8b833b696 100644
--- a/omnigent/inner/openai_agents_sdk_executor.py
+++ b/omnigent/inner/openai_agents_sdk_executor.py
@@ -47,6 +47,7 @@
     ToolSpec,
     TurnComplete,
     classify_tool_result,
+    describe_exception,
     split_transient_tail,
 )
 from .open_responses_sdk import (
@@ -1472,7 +1473,7 @@ async def run_turn(
                 cfg.extra.get("reasoning_effort"), "OpenAI Agents SDK", OPENAI_AGENTS_EFFORTS
             )
         except ValueError as exc:
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
 
         state = self._get_or_create_session_state(agents_sdk, session_key)
diff --git a/omnigent/inner/qwen_executor.py b/omnigent/inner/qwen_executor.py
index 12ca130286..2f878c55e1 100644
--- a/omnigent/inner/qwen_executor.py
+++ b/omnigent/inner/qwen_executor.py
@@ -47,6 +47,7 @@
     ToolCallStatus,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.inner.os_env import OSEnvironment, create_os_environment
 from omnigent.llms._usage_observer import notify_from_dict as _notify_usage_from_dict
@@ -531,7 +532,7 @@ async def _read_stdout(self) -> None:
             for fut in self._pending.values():
                 if not fut.done():
                     fut.set_exception(exc)
-            await self._queue.put({"type": "error", "message": str(exc)})
+            await self._queue.put({"type": "error", "message": describe_exception(exc)})
 
     async def _send(self, msg: _AcpJsonObject) -> None:
         """Write one newline-terminated JSON message to qwen stdin."""
@@ -1239,7 +1240,7 @@ async def run_turn(
             await self._ensure_initialized()
             session_id = await self._ensure_session()
         except Exception as exc:  # noqa: BLE001
-            yield ExecutorError(message=str(exc), retryable=False)
+            yield ExecutorError(message=describe_exception(exc), retryable=False)
             return
 
         # A fresh ACP session (first turn of a new/respawned process, or after
diff --git a/omnigent/inner/qwen_native_executor.py b/omnigent/inner/qwen_native_executor.py
index 1b8326d185..493477df97 100644
--- a/omnigent/inner/qwen_native_executor.py
+++ b/omnigent/inner/qwen_native_executor.py
@@ -31,6 +31,7 @@
     Message,
     ToolSpec,
     TurnComplete,
+    describe_exception,
 )
 from omnigent.qwen_native_bridge import (
     BRIDGE_DIR_ENV_VAR,
@@ -131,7 +132,7 @@ async def run_turn(
             async with self._inject_lock:
                 await asyncio.to_thread(submit_user_message, self._bridge_dir, content=text)
         except RuntimeError as exc:
-            yield ExecutorError(message=str(exc))
+            yield ExecutorError(message=describe_exception(exc))
             return
         yield TurnComplete(response=None)
 
diff --git a/omnigent/runtime/harnesses/_executor_adapter.py b/omnigent/runtime/harnesses/_executor_adapter.py
index efc2563483..a3514fba9f 100644
--- a/omnigent/runtime/harnesses/_executor_adapter.py
+++ b/omnigent/runtime/harnesses/_executor_adapter.py
@@ -457,7 +457,14 @@ async def run_turn(self, request: CreateResponseRequest, ctx: TurnContext) -> No
                                 error=event.message,
                             )
                             agent_span = None
-                        raise RuntimeError(f"inner executor error: {event.message}")
+                        # Never surface a blank "inner executor error: " to the
+                        # operator: an ExecutorError whose message is empty (e.g.
+                        # built from a bare exception) would otherwise report a
+                        # failure with no detail at all (#4281). Executors now
+                        # fall back to repr() at the source; this is the last-line
+                        # guard for any other empty-message path.
+                        detail = event.message or "no detail reported (see runner/harness logs)"
+                        raise RuntimeError(f"inner executor error: {detail}")
         except ElicitationDeclinedError:
             # Fallback for executors that propagate the exception directly
             # (non-SDK / non-spawned-task paths). SDK-based executors use
diff --git a/tests/inner/test_acp_executor.py b/tests/inner/test_acp_executor.py
index ebda3e3a4a..0e068bb379 100644
--- a/tests/inner/test_acp_executor.py
+++ b/tests/inner/test_acp_executor.py
@@ -35,6 +35,7 @@
     ToolCallRequest,
     ToolCallStatus,
     TurnComplete,
+    describe_exception,
 )
 
 # ---------------------------------------------------------------------------
@@ -589,6 +590,38 @@ async def deny(tool_name: str, tool_input: dict) -> bool:
     assert any(isinstance(e, TurnComplete) for e in events)
 
 
+# ---------------------------------------------------------------------------
+# describe_exception — never report a blank turn error (#4281)
+# ---------------------------------------------------------------------------
+
+
+def test_describe_exception_falls_back_to_repr_for_blank_message():
+    """A bare exception whose ``str()`` is empty is described by ``repr()``.
+
+    Regression for #4281: executors reported failures via ``str(exc)``, so a
+    bare ``RuntimeError()`` reached the operator as "inner executor error: "
+    with no detail. The fallback must at least name the exception type.
+    """
+    assert str(RuntimeError()) == ""  # the exact blank-message case from the bug
+    described = describe_exception(RuntimeError())
+    assert described != ""
+    assert "RuntimeError" in described
+
+
+def test_describe_exception_preserves_a_real_message():
+    """When the exception carries a message, it is used verbatim (no repr noise)."""
+    assert describe_exception(ValueError("boom: bad line")) == "boom: bad line"
+
+
+@pytest.mark.parametrize(
+    "exc",
+    [RuntimeError(), TimeoutError(), OSError(), Exception()],
+)
+def test_describe_exception_never_blank(exc: BaseException):
+    """No bare stdlib exception yields an empty description."""
+    assert describe_exception(exc).strip() != ""
+
+    
 # ---------------------------------------------------------------------------
 # Spawn env: the agent must actually receive credentials (#4281)
 # ---------------------------------------------------------------------------