fix(runtime): terminate invalid background followups

tests/test_wave3_background_followup.py

@@ -0,0 +1,84 @@
+"""Permanent linkage loss suppresses continuation without granting authority."""
+import asyncio
+import sys
+from types import ModuleType, SimpleNamespace
+import time
+
+import pytest
+from src import bg_jobs, bg_monitor
+from src.agent_runtime import process_resources as resources
+from tests.test_background_resource_identity import store, seed
+
+
+@pytest.fixture
+def monitor_session(monkeypatch):
+    messages = []
+    sess = SimpleNamespace(id='thread', owner='alice', model='test-model', get_context_messages=lambda: [])
+    sm = SimpleNamespace(get_session=lambda sid: sess, add_message=lambda *args: messages.append(args), save_sessions=lambda: None)
+    ai = ModuleType('src.ai_interaction'); ai.get_session_manager = lambda: sm
+    monkeypatch.setitem(sys.modules, 'src.ai_interaction', ai)
+    import src.agent_runs
+    monkeypatch.setattr(src.agent_runs, 'is_active', lambda sid: False)
+    async def drain(*args, **kwargs):
+        messages.append('drained')
+        return 'continued', []
+    monkeypatch.setattr(bg_monitor, '_drain_agent', drain)
+    return messages
+
+
+@pytest.mark.parametrize('damage', ['missing', 'corrupt', 'wrong_owner', 'wrong_pid'])
+async def test_invalid_linkage_is_terminal_without_message(store, monkeypatch, monitor_session, damage):
+    resource, rec = seed(store, status='done')
+    sidecar = bg_jobs._JOBS_DIR / 'job.authority.json'
+    if damage == 'missing': sidecar.unlink()
+    elif damage == 'corrupt': sidecar.write_text('{}')
+    else:
+        jobs = bg_jobs._load()
+        if damage == 'wrong_owner': jobs['job']['resource_identity']['owner'] = 'bob'
+        else: jobs['job']['pid'] = 99999
+        bg_jobs._save(jobs)
+        rec = jobs['job']
+    # Invalid data must not even be rendered into a synthetic result message.
+    monkeypatch.setattr(bg_monitor, '_background_result_message', lambda rec: pytest.fail('Invalid result rendered'))
+    assert await bg_monitor._process_followup(rec) is bg_monitor.FollowupResult.TERMINAL_UNFOLLOWABLE
+    assert not monitor_session
+    assert not bg_jobs.pending_followups()
+    assert bg_jobs.peek('job')['followup_state'] == 'terminal_unfollowable'
+    assert not bg_jobs.peek('job').get('followed_up')
+    with pytest.raises(ResourceIdentityError):
+        resources.validate_job(resource)
+
+
+from src.agent_runtime.resources import ResourceIdentityError
+
+
+async def test_busy_session_retries_then_continues(store, monkeypatch, monitor_session):
+    _, rec = seed(store, status='done')
+    import src.agent_runs
+    monkeypatch.setattr(src.agent_runs, 'is_active', lambda sid: True)
+    assert await bg_monitor._process_followup(rec) is bg_monitor.FollowupResult.RETRYABLE_LATER
+    assert bg_jobs.pending_followups() and not monitor_session
+    monkeypatch.setattr(src.agent_runs, 'is_active', lambda sid: False)
+    assert await bg_monitor._process_followup(rec) is bg_monitor.FollowupResult.COMPLETED
+    assert bg_jobs.peek('job')['followed_up']
+    assert monitor_session and not bg_jobs.pending_followups()
+
+
+async def test_terminal_record_prunes_exact_generation(store, monitor_session):
+    resource, rec = seed(store, status='done')
+    rec['ended_at'] = time.time() - bg_jobs._RETENTION_S - 10
+    bg_jobs._save({'job': rec})
+    (bg_jobs._JOBS_DIR / 'job.authority.json').unlink()
+    assert await bg_monitor._process_followup(rec) is bg_monitor.FollowupResult.TERMINAL_UNFOLLOWABLE
+    assert not bg_jobs.pending_followups()
+    assert bg_jobs.peek('job') is None
+    assert not resources.launch_path(resource.generation).exists()
+    assert not monitor_session
+
+
+def test_stale_terminal_snapshot_cannot_suppress_new_generation(store):
+    _, old = seed(store, status='done')
+    new, _ = seed(store, status='done')
+    assert not bg_jobs.mark_unfollowable('job', expected_record=old)
+    assert 'followup_state' not in bg_jobs.peek('job')
+    assert resources.launch_path(new.generation).exists()