diff --git a/examples/arc_agi_3/run_solver.py b/examples/arc_agi_3/run_solver.py
index 5d9e10232..7a0533139 100644
--- a/examples/arc_agi_3/run_solver.py
+++ b/examples/arc_agi_3/run_solver.py
@@ -562,6 +562,7 @@ def _sig_teardown(signum, _frame):
             "[run] harness exited without result.json — check "
             f"{run_dir}/harness.log and {run_dir}/launcher.err"
         )
+        return 1
 
     return 0
 
diff --git a/tests/test_arc_run_solver_exit.py b/tests/test_arc_run_solver_exit.py
new file mode 100644
index 000000000..e008aca46
--- /dev/null
+++ b/tests/test_arc_run_solver_exit.py
@@ -0,0 +1,90 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""The ARC runner reports missing results as failure, independently of harness exit."""
+
+import importlib.util
+import json
+import sys
+from pathlib import Path
+from types import SimpleNamespace
+from unittest.mock import Mock
+
+import pytest
+
+RUN_SOLVER = Path(__file__).resolve().parents[1] / "examples/arc_agi_3/run_solver.py"
+
+
+@pytest.mark.parametrize("harness_exit", [0, 1], ids=["harness-success", "harness-nonzero"])
+@pytest.mark.parametrize("has_result", [False, True], ids=["missing-result", "valid-result"])
+def test_run_solver_exit_requires_result(tmp_path, monkeypatch, harness_exit, has_result):
+    # Import the real stdlib-only script without retaining its sys.path insertion.
+    monkeypatch.setattr(sys, "path", sys.path.copy())
+    spec = importlib.util.spec_from_file_location("_arc_run_solver", RUN_SOLVER)
+    assert spec and spec.loader
+    runner = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(runner)
+
+    # No SDK, credentials, signals, subprocesses, or real shared /tmp directories.
+    monkeypatch.setattr(runner, "_set_parent_death_signal", Mock())
+    monkeypatch.setattr(runner, "_load_dotenv", Mock())
+    monkeypatch.setattr(runner, "os", SimpleNamespace(environ={}))
+    monkeypatch.setattr(runner, "REPO_ROOT", tmp_path)
+    monkeypatch.setattr(runner, "DATA_DIR", tmp_path)
+    monkeypatch.setattr(runner.signal, "signal", Mock())
+    monkeypatch.setattr(runner.tempfile, "gettempdir", lambda: str(tmp_path / "neutral"))
+    monkeypatch.setattr(runner.time, "sleep", Mock(side_effect=AssertionError("unexpected wait")))
+
+    launcher = Mock(pid=12345)
+    launcher.poll.return_value = None
+    harness = Mock(pid=12346)
+    harness.poll.return_value = harness_exit
+    log_handles = []
+    neutral_dirs = []
+    result = {"termination_reason": "game_over", "levels_completed": 0, "total_steps": 1}
+
+    def spawn(command, **kwargs):
+        neutral = Path(command[command.index("--run-dir") + 1])
+        assert neutral.is_relative_to(tmp_path)
+        neutral_dirs.append(neutral)
+        log_handles.append(kwargs["stdout"])
+        if Path(command[1]).name == "harness.py":
+            if has_result:
+                (neutral / "result.json").write_text(json.dumps(result))
+            return harness
+        assert Path(command[1]).name == "launcher.py"
+        return launcher
+
+    popen = Mock(side_effect=spawn)
+    monkeypatch.setattr(runner.subprocess, "Popen", popen)
+    results_root = tmp_path / "results"
+    monkeypatch.setattr(
+        sys,
+        "argv",
+        [
+            "run_solver.py",
+            "--game",
+            "synthetic",
+            "--variant",
+            "mdfiles",
+            "--sandbox",
+            "off",
+            "--results-root",
+            str(results_root),
+            "--model",
+            "synthetic-model",
+        ],
+    )
+
+    exit_code = runner.main()
+
+    assert popen.call_count == 2
+    launcher.terminate.assert_called_once()
+    assert all(handle.closed for handle in log_handles)
+    assert all(not directory.exists() for directory in neutral_dirs)
+    [run_dir] = results_root.glob("nemo_solver/*_synthetic_mdfiles")
+    if has_result:
+        assert json.loads((run_dir / "result.json").read_text()) == result
+        assert exit_code == 0
+    else:
+        assert not (run_dir / "result.json").exists()
+        assert exit_code == 1