diff --git a/loopx/cli_commands/goal_channel_operation.py b/loopx/cli_commands/goal_channel_operation.py
index 92eb137c1e..cc8e70ef9e 100644
--- a/loopx/cli_commands/goal_channel_operation.py
+++ b/loopx/cli_commands/goal_channel_operation.py
@@ -245,6 +245,30 @@ def _operation_error_packet(
     return packet
 
 
+def _safe_validation_reason(exc: BaseException) -> str:
+    """Return the operator-actionable validation reason without private paths.
+
+    The typed-operation normalizer and proposal helpers raise code-authored
+    ValueErrors ("operation payload_digest does not match payload", "operation
+    executor binding is invalid", ...). Collapsing every one of them into
+    "the Goal Channel configuration is invalid" hides the real cause from the
+    operator and from the agent. Keep the message when it is clearly a
+    code-authored phrase, and fall back to the exception class otherwise.
+    """
+
+    text = str(exc).strip()
+    if (
+        not text
+        or len(text) > 240
+        or "/" in text
+        or "\\" in text
+        or "~" in text
+        or any(ord(character) < 32 for character in text)
+    ):
+        return type(exc).__name__
+    return text
+
+
 def run_goal_channel_operation(
     args: argparse.Namespace,
     *,
@@ -352,11 +376,14 @@ def run_goal_channel_operation(
             blocker="operation_handoff_conflict",
             summary=str(exc),
         )
-    except ValueError:
+    except ValueError as exc:
+        # Keep the compatibility blocker, but never discard the real reason the
+        # typed-operation owner rejected this request.
         return _operation_error_packet(
             request=request,
             blocker="invalid_configuration",
             summary="the Goal Channel configuration is invalid",
+            details={"validation_reason": _safe_validation_reason(exc)},
         )
     except Exception:
         return _operation_error_packet(
diff --git a/tests/extensions/test_lark_goal_channel_operation.py b/tests/extensions/test_lark_goal_channel_operation.py
index 6d241e911e..def1a9cfa0 100644
--- a/tests/extensions/test_lark_goal_channel_operation.py
+++ b/tests/extensions/test_lark_goal_channel_operation.py
@@ -19,6 +19,7 @@
 from loopx.cli_commands.goal_channel_operation import (
     GoalChannelOperationContext,
     _prepare_goal_channel_operation,
+    _safe_validation_reason,
     run_goal_channel_operation,
 )
 from loopx.control_plane.collaboration.operation_handoff import agent_operation_action
@@ -2405,3 +2406,26 @@ def failing_record(
     assert exc_info.value.failure_stage == "record_delivery_receipt"
     assert exc_info.value.external_write_performed is None
     assert any("+messages-send" in call for call in calls)
+
+
+def test_safe_validation_reason_keeps_actionable_code_messages() -> None:
+    """A rejected prepare must surface its real reason, not a generic line."""
+
+    assert (
+        _safe_validation_reason(ValueError("operation executor binding is invalid"))
+        == "operation executor binding is invalid"
+    )
+    assert (
+        _safe_validation_reason(
+            ValueError("operation payload_digest does not match payload")
+        )
+        == "operation payload_digest does not match payload"
+    )
+    # Anything that could carry a private path or control characters collapses
+    # to the exception class instead of reaching the operator packet.
+    assert (
+        _safe_validation_reason(ValueError("private detail: /home/operator/secret"))
+        == "ValueError"
+    )
+    assert _safe_validation_reason(ValueError("line\nbreak")) == "ValueError"
+    assert _safe_validation_reason(ValueError("")) == "ValueError"