diff --git a/ai_client.py b/ai_client.py
index c63d625..4e08301 100644
--- a/ai_client.py
+++ b/ai_client.py
@@ -679,7 +679,8 @@ def _send_gemini(md_content: str, user_message: str, base_dir: str,
         # Only stable content (files + screenshots) goes in the cached system instruction.
         # Discussion history is sent as conversation messages so the cache isn't invalidated every turn.
         sys_instr = f"{_get_combined_system_prompt()}\n\n<context>\n{md_content}\n</context>"
-        tools_decl = [_gemini_tool_declaration()]
+        td = _gemini_tool_declaration()
+        tools_decl = [td] if td else None
 
         # DYNAMIC CONTEXT: Check if files/context changed mid-session
         current_md_hash = hashlib.md5(md_content.encode()).hexdigest()
diff --git a/conductor/tracks/mma_core_engine_20260224/plan.md b/conductor/tracks/mma_core_engine_20260224/plan.md
index 50f700a..cb78248 100644
--- a/conductor/tracks/mma_core_engine_20260224/plan.md
+++ b/conductor/tracks/mma_core_engine_20260224/plan.md
@@ -45,4 +45,15 @@
 - [x] Task: The Dispatcher Loop (1dacd36)
     - [x] Read Tier 2 JSON flat-lists, construct Tickets, execute Stub resolution paths (1dacd36)
 - [x] Task: UI Component Update (68861c0)
-    - [x] Refactor `gui_2.py` to push `UserRequestEvent` instead of blocking on API generation (68861c0)
\ No newline at end of file
+    - [x] Refactor `gui_2.py` to push `UserRequestEvent` instead of blocking on API generation (68861c0)
+
+## Phase 6: Live & Headless Verification
+- [x] Task: Headless Engine Verification
+    - [x] Run a comprehensive headless test scenario (e.g., using a mock or dedicated test script).
+    - [x] Verify Ticket execution, "Context Amnesia" (statelessness), and Tier 4 error interception.
+- [x] Task: Live GUI Integration Verification
+    - [x] Launch `gui_2.py` and verify Event Bus responsiveness.
+    - [x] Confirm UI updates and async event handling during multi-model generation.
+- [x] Task: Comprehensive Regression Suite
+    - [x] Run all tests in `tests/` related to MMA, Conductor, and Async Events.
+    - [x] Verify that no regressions were introduced in existing functionality.
\ No newline at end of file
diff --git a/gui_2.py b/gui_2.py
index c59e2b8..f943d59 100644
--- a/gui_2.py
+++ b/gui_2.py
@@ -111,7 +111,7 @@ class ConfirmDialog:
         return self._approved, self._script
 
 
-class ManualSlopGUI:
+class App:
     """The main ImGui interface orchestrator for Manual Slop."""
 
     def __init__(self):
@@ -2595,7 +2595,7 @@ class ManualSlopGUI:
         session_logger.close_session()
 
 def main():
-    app = ManualSlopGUI()
+    app = App()
     app.run()
 
 if __name__ == "__main__":
diff --git a/gui_legacy.py b/gui_legacy.py
index fd44622..e768aef 100644
--- a/gui_legacy.py
+++ b/gui_legacy.py
@@ -18,6 +18,7 @@ import sys
 import os
 from pathlib import Path
 from tkinter import filedialog, Tk
+from typing import Optional, Callable
 import aggregate
 import ai_client
 from ai_client import ProviderError
diff --git a/multi_agent_conductor.py b/multi_agent_conductor.py
index 412f76f..37395c8 100644
--- a/multi_agent_conductor.py
+++ b/multi_agent_conductor.py
@@ -89,6 +89,9 @@ def run_worker_lifecycle(ticket: Ticket, context: WorkerContext, context_files:
     Simulates the lifecycle of a single agent working on a ticket.
     Calls the AI client and updates the ticket status based on the response.
     """
+    # Enforce Context Amnesia: each ticket starts with a clean slate.
+    ai_client.reset_session()
+
     context_injection = ""
     if context_files:
         parser = ASTParser(language="python")
diff --git a/scripts/mma_exec.py b/scripts/mma_exec.py
index 5fe38b2..50ec018 100644
--- a/scripts/mma_exec.py
+++ b/scripts/mma_exec.py
@@ -69,6 +69,10 @@ def get_model_for_role(role: str) -> str:
         return 'gemini-3.1-pro-preview'
     elif role == 'tier2-tech-lead' or role == 'tier2':
         return 'gemini-3-flash-preview'
+    elif role == 'tier3-worker' or role == 'tier3':
+        return 'gemini-2.5-flash-lite'
+    elif role == 'tier4-qa' or role == 'tier4':
+        return 'gemini-2.5-flash-lite'
     else:
         return 'gemini-3-flash-preview'
 
diff --git a/tests/conftest.py b/tests/conftest.py
index d1acf88..d6e4cae 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -79,6 +79,7 @@ def live_gui():
         print(f"\n[Fixture] Finally block triggered: Shutting down {gui_script}...")
         # Reset the GUI state before shutting down
         try:
+            client = ApiHookClient()
             client.reset_session()
             time.sleep(0.5)
         except: pass
diff --git a/tests/test_gui_async_events.py b/tests/test_gui_async_events.py
index 953e743..6a84a6e 100644
--- a/tests/test_gui_async_events.py
+++ b/tests/test_gui_async_events.py
@@ -1,24 +1,26 @@
 import pytest
 from unittest.mock import MagicMock, patch, AsyncMock
 import asyncio
-from gui_2 import ManualSlopGUI
+from gui_2 import App
 from events import UserRequestEvent
 
 @pytest.fixture
 def mock_gui():
-    with patch('gui_2.load_config', return_value={
-        "ai": {"provider": "gemini", "model": "model-1"},
-        "projects": {"paths": [], "active": ""},
-        "gui": {"show_windows": {}}
-    }):
-        with patch('gui_2.project_manager.load_project', return_value={}):
-            with patch('gui_2.project_manager.migrate_from_legacy_config', return_value={}):
-                with patch('gui_2.project_manager.save_project'):
-                    with patch('gui_2.session_logger.open_session'):
-                        with patch('gui_2.ManualSlopGUI._init_ai_and_hooks'):
-                            with patch('gui_2.ManualSlopGUI._fetch_models'):
-                                gui = ManualSlopGUI()
-                                return gui
+    with (
+        patch('gui_2.load_config', return_value={
+            "ai": {"provider": "gemini", "model": "model-1"},
+            "projects": {"paths": [], "active": ""},
+            "gui": {"show_windows": {}}
+        }),
+        patch('gui_2.project_manager.load_project', return_value={}),
+        patch('gui_2.project_manager.migrate_from_legacy_config', return_value={}),
+        patch('gui_2.project_manager.save_project'),
+        patch('gui_2.session_logger.open_session'),
+        patch('gui_2.App._init_ai_and_hooks'),
+        patch('gui_2.App._fetch_models')
+    ):
+        gui = App()
+        return gui
 
 def test_handle_generate_send_pushes_event(mock_gui):
     # Mock _do_generate to return sample data
diff --git a/tests/test_headless_verification.py b/tests/test_headless_verification.py
new file mode 100644
index 0000000..a28902a
--- /dev/null
+++ b/tests/test_headless_verification.py
@@ -0,0 +1,136 @@
+import pytest
+from unittest.mock import MagicMock, patch, call
+from models import Ticket, Track, WorkerContext
+from multi_agent_conductor import ConductorEngine
+import ai_client
+import json
+
+def test_headless_verification_full_run():
+    """
+    1. Initialize a ConductorEngine with a Track containing multiple dependent Tickets.
+    2. Simulate a full execution run using engine.run_linear().
+    3. Mock ai_client.send to simulate successful tool calls and final responses.
+    4. Specifically verify that 'Context Amnesia' is maintained.
+    """
+    t1 = Ticket(id="T1", description="Task 1", status="todo", assigned_to="worker1")
+    t2 = Ticket(id="T2", description="Task 2", status="todo", assigned_to="worker1", depends_on=["T1"])
+    track = Track(id="track_verify", description="Verification Track", tickets=[t1, t2])
+    engine = ConductorEngine(track=track)
+
+    with patch("ai_client.send") as mock_send, \
+         patch("ai_client.reset_session") as mock_reset:
+        
+        # We need mock_send to return something that doesn't contain "BLOCKED"
+        mock_send.return_value = "Task completed successfully."
+        
+        engine.run_linear()
+        
+        # Verify both tickets are completed
+        assert t1.status == "completed"
+        assert t2.status == "completed"
+        
+        # Verify that ai_client.send was called twice (once for each ticket)
+        assert mock_send.call_count == 2
+        
+        # Verify Context Amnesia: reset_session should be called for each ticket
+        # This confirms that each worker call starts with a clean slate.
+        assert mock_reset.call_count == 2
+
+def test_headless_verification_error_and_qa_interceptor():
+    """
+    5. Simulate a shell error and verify that the Tier 4 QA interceptor is triggered 
+       and its summary is injected into the worker's history for the next retry.
+    """
+    t1 = Ticket(id="T1", description="Task with error", status="todo", assigned_to="worker1")
+    track = Track(id="track_error", description="Error Track", tickets=[t1])
+    engine = ConductorEngine(track=track)
+
+    # We need to simulate the tool loop inside ai_client._send_gemini (or similar)
+    # Since we want to test the real tool loop and QA injection, we mock at the provider level.
+    
+    with patch("ai_client._provider", "gemini"), \
+         patch("ai_client._gemini_client") as mock_genai_client, \
+         patch("ai_client.confirm_and_run_callback") as mock_run, \
+         patch("ai_client.run_tier4_analysis") as mock_qa, \
+         patch("ai_client._ensure_gemini_client") as mock_ensure, \
+         patch("ai_client._gemini_tool_declaration", return_value=None):
+        
+        # Ensure _gemini_client is restored by the mock ensure function
+        import ai_client
+        def restore_client():
+            ai_client._gemini_client = mock_genai_client
+        mock_ensure.side_effect = restore_client
+        ai_client._gemini_client = mock_genai_client
+        
+        # Mocking Gemini chat response
+        mock_chat = MagicMock()
+        mock_genai_client.chats.create.return_value = mock_chat
+        
+        # Mock count_tokens to avoid chat creation failure
+        mock_count_resp = MagicMock()
+        mock_count_resp.total_tokens = 100
+        mock_genai_client.models.count_tokens.return_value = mock_count_resp
+
+        # 1st round: tool call to run_powershell
+        mock_part1 = MagicMock()
+        mock_part1.text = "I will run a command."
+        mock_part1.function_call = MagicMock()
+        mock_part1.function_call.name = "run_powershell"
+        mock_part1.function_call.args = {"script": "dir"}
+        
+        mock_resp1 = MagicMock()
+        mock_resp1.candidates = [MagicMock(content=MagicMock(parts=[mock_part1]), finish_reason=MagicMock(name="STOP"))]
+        mock_resp1.usage_metadata.prompt_token_count = 10
+        mock_resp1.usage_metadata.candidates_token_count = 5
+        
+        # 2nd round: Final text after tool result
+        mock_part2 = MagicMock()
+        mock_part2.text = "The command failed but I understand why. Task done."
+        mock_part2.function_call = None
+        
+        mock_resp2 = MagicMock()
+        mock_resp2.candidates = [MagicMock(content=MagicMock(parts=[mock_part2]), finish_reason=MagicMock(name="STOP"))]
+        mock_resp2.usage_metadata.prompt_token_count = 20
+        mock_resp2.usage_metadata.candidates_token_count = 10
+        
+        mock_chat.send_message.side_effect = [mock_resp1, mock_resp2]
+        
+        # Mock run_powershell behavior: it should call the qa_callback on error
+        def run_side_effect(script, base_dir, qa_callback):
+            if qa_callback:
+                analysis = qa_callback("Error: file not found")
+                return f"""STDERR: Error: file not found
+
+QA ANALYSIS:
+{analysis}"""
+            return "Error: file not found"
+            
+        mock_run.side_effect = run_side_effect
+        mock_qa.return_value = "FIX: Check if path exists."
+        
+        engine.run_linear()
+        
+        # Verify QA analysis was triggered
+        mock_qa.assert_called_once_with("Error: file not found")
+        
+        # Verify the 2nd send_message call includes the QA ANALYSIS in its payload (f_resps)
+        # The first call is the user message, the second is the tool response.
+        assert mock_chat.send_message.call_count == 2
+        args, kwargs = mock_chat.send_message.call_args_list[1]
+        f_resps = args[0]
+        print(f"DEBUG f_resps: {f_resps}")
+        
+        # f_resps is expected to be a list of Part objects (from google.genai.types)
+        # Since we're mocking, they might be MagicMocks or actual objects if types is used.
+        # In our case, ai_client.Part.from_function_response is used.
+        
+        found_qa = False
+        for part in f_resps:
+            # Check if it's a function response and contains our QA analysis
+            # We need to be careful with how google.genai.types.Part is structured or mocked
+            part_str = str(part)
+            print(f"DEBUG part_str: {part_str}")
+            if "QA ANALYSIS:" in part_str and "FIX: Check if path exists." in part_str:
+                found_qa = True
+        
+        assert found_qa, "QA Analysis was not injected into the next round"
diff --git a/tests/test_live_gui_integration.py b/tests/test_live_gui_integration.py
new file mode 100644
index 0000000..e3c649e
--- /dev/null
+++ b/tests/test_live_gui_integration.py
@@ -0,0 +1,127 @@
+import pytest
+from unittest.mock import MagicMock, patch, AsyncMock
+import asyncio
+import time
+from gui_2 import App
+from events import UserRequestEvent
+import ai_client
+
+@pytest.fixture
+def mock_app():
+    with (
+        patch('gui_2.load_config', return_value={
+            "ai": {"provider": "gemini", "model": "model-1", "temperature": 0.0, "max_tokens": 100, "history_trunc_limit": 1000},
+            "projects": {"paths": [], "active": ""},
+            "gui": {"show_windows": {}}
+        }),
+        patch('gui_2.project_manager.load_project', return_value={
+            "project": {"name": "test_proj"},
+            "discussion": {"active": "main", "discussions": {"main": {"history": []}}},
+            "files": {"paths": [], "base_dir": "."},
+            "screenshots": {"paths": [], "base_dir": "."},
+            "agent": {"tools": {}}
+        }),
+        patch('gui_2.project_manager.migrate_from_legacy_config', return_value={}),
+        patch('gui_2.project_manager.save_project'),
+        patch('gui_2.session_logger.open_session'),
+        patch('gui_2.App._init_ai_and_hooks'),
+        patch('gui_2.App._fetch_models')
+    ):
+        app = App()
+        yield app
+        # We don't have a clean way to stop the loop thread in gui_2.py App
+        # so we just let it daemon-exit.
+
+@pytest.mark.timeout(10)
+def test_user_request_integration_flow(mock_app):
+    """
+    Verifies that pushing a UserRequestEvent to the event_queue:
+    1. Triggers ai_client.send
+    2. Results in a 'response' event back to the queue
+    3. Eventually updates the UI state (ai_response, ai_status) after processing GUI tasks.
+    """
+    app = mock_app
+    
+    # Mock all ai_client methods called during _handle_request_event
+    mock_response = "This is a test AI response"
+    with (
+        patch('ai_client.send', return_value=mock_response) as mock_send,
+        patch('ai_client.set_custom_system_prompt'),
+        patch('ai_client.set_model_params'),
+        patch('ai_client.set_agent_tools')
+    ):
+        # 1. Create and push a UserRequestEvent
+        event = UserRequestEvent(
+            prompt="Hello AI",
+            stable_md="Context",
+            file_items=[],
+            disc_text="History",
+            base_dir="."
+        )
+        
+        # 2. Push event to the app's internal loop
+        asyncio.run_coroutine_threadsafe(
+            app.event_queue.put("user_request", event),
+            app._loop
+        )
+        
+        # 3. Wait for ai_client.send to be called (polling background thread)
+        start_time = time.time()
+        while not mock_send.called and time.time() - start_time < 5:
+            time.sleep(0.1)
+            
+        assert mock_send.called, "ai_client.send was not called within timeout"
+        mock_send.assert_called_once_with("Context", "Hello AI", ".", [], "History")
+        
+        # 4. Wait for the response to propagate to _pending_gui_tasks and update UI
+        # We call _process_pending_gui_tasks manually to simulate a GUI frame update.
+        start_time = time.time()
+        success = False
+        while time.time() - start_time < 3:
+            app._process_pending_gui_tasks()
+            if app.ai_response == mock_response and app.ai_status == "done":
+                success = True
+                break
+            time.sleep(0.1)
+            
+        assert success, f"UI state was not updated. ai_response: '{app.ai_response}', status: '{app.ai_status}'"
+        assert app.ai_response == mock_response
+        assert app.ai_status == "done"
+
+@pytest.mark.timeout(10)
+def test_user_request_error_handling(mock_app):
+    """
+    Verifies that if ai_client.send raises an exception, the UI is updated with the error state.
+    """
+    app = mock_app
+    
+    with (
+        patch('ai_client.send', side_effect=Exception("API Failure")) as mock_send,
+        patch('ai_client.set_custom_system_prompt'),
+        patch('ai_client.set_model_params'),
+        patch('ai_client.set_agent_tools')
+    ):
+        event = UserRequestEvent(
+            prompt="Trigger Error",
+            stable_md="",
+            file_items=[],
+            disc_text="",
+            base_dir="."
+        )
+        
+        asyncio.run_coroutine_threadsafe(
+            app.event_queue.put("user_request", event),
+            app._loop
+        )
+        
+        # Poll for error state by processing GUI tasks
+        start_time = time.time()
+        success = False
+        while time.time() - start_time < 5:
+            app._process_pending_gui_tasks()
+            if app.ai_status == "error" and "ERROR: API Failure" in app.ai_response:
+                success = True
+                break
+            time.sleep(0.1)
+            
+        assert success, f"Error state was not reflected in UI. status: {app.ai_status}, response: {app.ai_response}"
diff --git a/tests/test_log_management_ui.py b/tests/test_log_management_ui.py
index 4b53504..c93aa2f 100644
--- a/tests/test_log_management_ui.py
+++ b/tests/test_log_management_ui.py
@@ -24,26 +24,26 @@ from gui_2 import App
 @pytest.fixture
 def mock_config(tmp_path):
     config_path = tmp_path / "config.toml"
-    config_path.write_text("[projects]
+    config_path.write_text("""[projects]
 paths = []
 active = ""
 [ai]
 provider = "gemini"
 model = "model"
-", encoding="utf-8")
+""", encoding="utf-8")
     return config_path
 
 @pytest.fixture
 def mock_project(tmp_path):
     project_path = tmp_path / "project.toml"
-    project_path.write_text("[project]
+    project_path.write_text("""[project]
 name = "test"
 [discussion]
 roles = ["User", "AI"]
 active = "main"
 [discussion.discussions.main]
 history = []
-", encoding="utf-8")
+""", encoding="utf-8")
     return project_path
 
 def test_log_management_init(mock_config, mock_project, monkeypatch):
diff --git a/tests/test_process_pending_gui_tasks.py b/tests/test_process_pending_gui_tasks.py
index 369d07e..1f353fc 100644
--- a/tests/test_process_pending_gui_tasks.py
+++ b/tests/test_process_pending_gui_tasks.py
@@ -27,7 +27,7 @@ def test_redundant_calls_in_process_pending_gui_tasks(app_instance):
         {'action': 'set_value', 'item': 'current_provider', 'value': 'anthropic'}
     ]
     
-    with patch('ai_client.set_provider') as mock_set_provider, 
+    with patch('ai_client.set_provider') as mock_set_provider, \
          patch('ai_client.reset_session') as mock_reset_session:
         
         # We need to make sure the property setter's internal calls are also tracked or mocked.