fix: bound task failures and release stalled workers

tests/unit/agents/test_flash_runner_ledger.py

@@ -213,7 +213,8 @@ def test_observation_tail_has_pro_shape(mock_context):
         texts = [b["text"] for b in later.content]
         assert OBSERVATION_HEADER_RE.match(texts[0])
         assert "objective" not in "".join(texts).lower()
-        assert texts[1:] == [
+        assert "当前没有可用的元素索引" in texts[1]
+        assert texts[2:] == [
             "nudge",
             "[INJECTED]",
             'User instruction: "stop"',
@@ -408,6 +409,98 @@ def _report(status="completed", tc_id="tc-report", **extra):
 _INITIAL_OBSERVATION = ("shot0.png", b"IMG0", "[1] Settings")
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("fallback_succeeds", [True, False])
+async def test_failed_actions_have_finite_fallback_and_restore_primary(
+    mock_context, monkeypatch, fallback_succeeds
+):
+    monkeypatch.setattr("artemis.agents.flash.runner.settings.ARTEMIS_ACTION_FAILURE_ATTEMPTS", 3)
+    monkeypatch.setattr(
+        "artemis.agents.flash.runner.settings.ARTEMIS_TOOL_FALLBACK_MAX_NO_PROGRESS_ATTEMPTS", 3
+    )
+    action_count = 4 if fallback_succeeds else 6
+    responses = [
+        AIMessage(
+            content="try", tool_calls=[{"name": "click", "args": {"index": 1}, "id": f"tc-{i}"}]
+        )
+        for i in range(action_count)
+    ]
+    if fallback_succeeds:
+        responses.append(_report())
+    with patch("artemis.controllers.unified_controller.get_driver"):
+        runner = _make_runner(mock_context, responses)
+    fallback = Mock()
+    count = 0
+
+    def execute(name, args, tc_id, state, **kwargs):
+        nonlocal count
+        count += 1
+        result = _exec_result(tc_id, name, b"current-screen")
+        if count <= 3 or not fallback_succeeds:
+            result.status = "error"
+            result.text_summary = "目标不存在"
+        return result
+
+    runner.executor.execute = AsyncMock(side_effect=execute)
+    with (
+        patch(
+            "artemis.agents.flash.runner.capture_screenshot_and_parse_ui",
+            AsyncMock(return_value=_INITIAL_OBSERVATION),
+        ) as observe,
+        patch("artemis.agents.flash.runner.get_llm", return_value=fallback),
+    ):
+        outcome = await runner.run(State(initial_goal="Open Settings"))
+    primary = runner._init_llm.return_value
+    assert all(call["llm"] is primary for call in runner.calls[:3])
+    assert runner.calls[3]["llm"] is fallback
+    assert observe.await_count == 2  # initial + fresh observation before fallback
+    if fallback_succeeds:
+        assert outcome["status"] == "completed"
+        assert runner.calls[-1]["llm"] is primary
+    else:
+        assert outcome["status"] == "failed"
+        assert "兜底模型连续 3" in outcome["explanation"]
+        assert "目标不存在" in outcome["explanation"]
+        assert len(runner.calls) == 6
+
+
+@pytest.mark.asyncio
+async def test_empty_current_ui_clears_previous_turn_element_list(mock_context):
+    response = AIMessage(
+        content="tap", tool_calls=[{"name": "click", "args": {"index": 1}, "id": "tc"}]
+    )
+    with patch("artemis.controllers.unified_controller.get_driver"):
+        runner = _make_runner(mock_context, [response, _report()])
+    runner.executor.execute = AsyncMock(
+        return_value=_exec_result("tc", "click", b"fresh-screen", ui="")
+    )
+    with patch(
+        "artemis.agents.flash.runner.capture_screenshot_and_parse_ui",
+        AsyncMock(return_value=_INITIAL_OBSERVATION),
+    ):
+        await runner.run(State(initial_goal="Open Settings"))
+    tail = runner.calls[-1]["messages"][-1]
+    text = "\n".join(block.get("text", "") for block in tail.content)
+    assert "当前没有可用的元素索引" in text
+    assert "[1] Settings" not in text
+
+
+@pytest.mark.asyncio
+async def test_unavailable_screen_ends_before_any_model_call(mock_context):
+    from artemis.mcp.observation import DeviceObservationError
+
+    with patch("artemis.controllers.unified_controller.get_driver"):
+        runner = _make_runner(mock_context, [])
+    with patch(
+        "artemis.agents.flash.runner.capture_screenshot_and_parse_ui",
+        AsyncMock(side_effect=DeviceObservationError("设备断连")),
+    ):
+        outcome = await runner.run(State(initial_goal="Open Settings"))
+    assert outcome["code"] == "device_observation_failed"
+    assert outcome["error"] == "设备断连"
+    runner._invoke_model.assert_not_awaited()
+
+
 @pytest.mark.asyncio
 async def test_run_builds_prompt_from_ledger_with_session_offsets(mock_context):
     """Turn 2 must see: the static system prefix, the committed turn 1 (its