retry invalid artifact body immediately

src/clean_agent_preview.py

@@ -4814,6 +4814,32 @@ async def stream_preview(*, endpoint_url, model, messages, headers, turn_contrac
                                     history[-1] = {'role': 'assistant', 'content': confirmation}
                                     yield event({'type': 'final_response', 'content': confirmation})
                                     break
+                        if (
+                            not successful_artifact_write
+                            and artifact_body_handoff_attempts < 2
+                            and round_number < round_limit
+                        ):
+                            artifact_body_handoff_attempts += 1
+                            artifact_body_handoff_target = target
+                            force_no_tools_next_round = True
+                            replace_streamed_draft_on_finish = True
+                            history.append({
+                                'role': 'user',
+                                '_harness_control': True,
+                                'content': (
+                                    'The prior body-only artifact response was empty or did not '
+                                    f'match the required format for {target}. Return only the '
+                                    'complete raw file body now. Do not emit a tool call, JSON '
+                                    'wrapper, commentary, or another action plan.'
+                                ),
+                            })
+                            yield event({
+                                'type': 'completion_recovery',
+                                'reason': 'invalid_artifact_body_retry',
+                                'path': target,
+                                'attempt': artifact_body_handoff_attempts,
+                            })
+                            continue
                     if (
                         native_workspace_enabled
                         and required_artifacts

tests/test_clean_agent_preview.py

@@ -549,12 +549,6 @@ async def test_repeated_off_contract_calls_recover_via_required_artifact_body(mo
             })},
         }]}}]},
         {'choices': [{'delta': {'content': ''}}]},
-        {'choices': [{'delta': {'tool_calls': [{
-            'index': 0, 'id': 'bad-inspect',
-            'function': {'name': 'inspect_media', 'arguments': json.dumps({
-                'path': '/workspace/input.png',
-            })},
-        }]}}]},
         {'choices': [{'delta': {'content': '<html><body>Recovered</body></html>'}}]},
     ])
 
@@ -611,7 +605,7 @@ async def test_repeated_off_contract_calls_recover_via_required_artifact_body(mo
         event.get('type') == 'tool_output'
         and event.get('execution_attempted') is False
         for event in events
-    ) == 3
+    ) == 2
     assert any(
         event.get('type') == 'artifact_body_handoff'
         and event.get('path') == '/workspace/output.html'