Improve agent repair retries

tests/test_worker.py

@@ -74,6 +74,27 @@ def test_validation_commands_are_logged_without_output(caplog) -> None:
     assert "sensitive output" not in caplog.text
 
 
+def test_failed_validation_preserves_start_and_end_of_long_output() -> None:
+    worker = AutomationWorker(settings())
+    workspace = Mock()
+    workspace.run.return_value = Mock(
+        returncode=1,
+        stdout="DECISIVE ASSERTION\n" + "x" * 13_000,
+        stderr="FINAL ERROR",
+    )
+
+    try:
+        worker._run_tests(workspace)
+    except RuntimeError as exception:
+        failure = str(exception)
+    else:
+        raise AssertionError("Expected failed validation")
+
+    assert "DECISIVE ASSERTION" in failure
+    assert "...[middle omitted]..." in failure
+    assert "FINAL ERROR" in failure
+
+
 def test_long_stage_emits_heartbeat(caplog) -> None:
     worker = AutomationWorker(settings())