# `src/app_controller.py` — Headless Orchestrator & State Hub

[Top](../Readme.md) | [Architecture](guide_architecture.md) | [Discussions](guide_discussions.md) | [State Lifecycle](guide_state_lifecycle.md) | [Context Aggregation](guide_context_aggregation.md) | [MMA](guide_mma.md) | [Testing](guide_testing.md)

---

## Overview

`src/app_controller.py` (~166KB) is the **headless controller** that owns the application's state and business logic. It decouples the GUI (`gui_2.py`) from the underlying subsystems (AI, presets, personas, RAG, history, MMA, paths, hot reload).

When `--enable-test-hooks` is passed, the controller also spins up the HookServer so external tests/scripts can drive the running app.

---

## Architecture

```
┌─────────────────────────────────────────────────┐
│  gui_2.py (App)                                   │
│  - Pure immediate-mode UI                        │
│  - Reads app_state for rendering                  │
│  - Calls controller methods for mutations         │
└─────────────────┬───────────────────────────────┘
                  │ delegates to
                  ▼
┌─────────────────────────────────────────────────┐
│  app_controller.py: AppController                 │
│  - State container (AppState)                     │
│  - Subsystem coordination (presets, personas, ...) │
│  - Headless mode: skips GUI init, starts hook     │
│    server on port 8999                            │
│  - Provides _predefined_callbacks and             │
│    _gettable_fields for the Hook API              │
└─────────────────┬───────────────────────────────┘
                  │ owns/uses
                  ▼
┌─────────────────────────────────────────────────┐
│  Subsystems                                       │
│  - PresetManager (src/presets.py)                  │
│  - PersonaManager (src/personas.py)                │
│  - ContextPresetManager (src/context_presets.py)   │
│  - ToolPresetManager (src/tool_presets.py)         │
│  - ToolBiasEngine (src/tool_bias.py)               │
│  - RAGEngine (src/rag_engine.py)                   │
│  - HistoryManager (src/history.py)                 │
│  - WorkspaceManager (src/workspace_manager.py)     │
│  - HookServer (src/api_hooks.py)                   │
│  - HotReloader (src/hot_reloader.py)               │
│  - PathManager (src/paths.py)                      │
└─────────────────────────────────────────────────┘
```

---

## The `AppController` Class

### `__init__(self, defer_warmup: bool = False, log_to_stderr: Optional[bool] = None)`

> **Important:** The `__init__` does NOT create manager objects, does NOT register hooks, and does NOT start the HookServer. The previous documentation in this section **predated the controller refactor** and described an architecture that was never actually implemented (an `AppState` dataclass, an `enable_test_hooks` parameter, a `register_hooks` method, and manager objects that don't exist on the controller).

Initializes the controller. Real state created here:

The actual `__init__` (`src/app_controller.py:778-1212`) does the following:

1. **Startup timeline anchors** — Captures `_init_start_ts` for the `startup_timeline()` diagnostics. Other timeline anchors are filled in lazily as events occur.
2. **Locks** — Creates **11** thread-safety locks (`_send_thread_lock`, `_disc_entries_lock`, `_pending_*_lock` for comms/tool_calls/history/gui_tasks/dialog/api_event_queue, `_rag_engine_lock`, `_rag_sync_lock`, `_project_switch_lock`) plus 5 non-lock state fields for the RAG-sync coalescing and project-switch state machine (`_rag_sync_token`/`_rag_sync_dirty`, `_project_switch_in_progress`/`_pending_path`/`_error`).
3. **GUI health state** — `_gui_degraded_reason` and `_last_imgui_assert` (set when `immapp.run` raises `RuntimeError`; see [guide_gui_2.md](guide_gui_2.md#startup-architecture-lazy-imports-profiler-refresh-rate)).
4. **Shared io_pool** — `make_io_pool()` creates an **8-thread** `ThreadPoolExecutor` named `controller-io-N` (per `IO_POOL_MAX_WORKERS = 8` in `src/io_pool.py:20`; bumped 4→8 in commit `4a338486` on 2026-06-06). This is the SOLE background pool for all async work (no `threading.Thread()` calls anywhere else in `src/`). The module docstring at `src/io_pool.py:1-15` also documents the SIGINT-handler fix that replaced the original atexit approach.
5. **Warmup manager** — `WarmupManager(self._io_pool, log_to_stderr=log_to_stderr)` with an on-complete callback to stamp `warmup_done_ts`. `defer_warmup=True` defers the actual `start_warmup()` call until the first frame is painted (the desktop GUI pattern; headless mode starts immediately). The `log_to_stderr` parameter honors `SLOP_WARMUP_DEBUG` env var.
6. **Various flags** — `_warmup_started`, `_pending_fetch_provider`, `_defer_warmup`.

**Manager objects** (`preset_manager`, `persona_manager`, `context_preset_manager`, `tool_preset_manager`, `tool_bias_engine`, `history_manager`, `workspace_manager`, `rag_engine`) are **NOT created in `__init__`**. They are lazy attributes accessed via `__getattr__` and created on first reference (typically from `_load_active_project` at `src/app_controller.py:2150` or from `App._post_init` at `src/gui_2.py:492`).

**Hook API surface** is NOT populated by a `register_hooks` method. The actual flow:
1. `AppController._init_actions()` (called from `init_state` at `src/app_controller.py:1740`) populates `self._predefined_callbacks` and `self._gettable_fields` registries via module-level handler registration functions.
2. `src/api_hooks.py:HookHandler.do_GET` / `do_POST` reads from these registries to expose App methods as `/api/gui` `custom_callback` actions.
3. The `sloppy.py` CLI parses `--enable-test-hooks` and passes it to `HookServer` (a separate class, not the controller).

For the actual init flow, read `src/app_controller.py:778-1212` (`__init__`; the 434-line body is locks + io_pool + warmup manager + ~150 lines of internal/Core/UI/Service state initialization, then the `_settable_fields` map (~75 entries) and `_gui_task_handlers` map (~25 hook actions) at the tail), `:1606` (`_init_actions`), `:1740` (`init_state`), and `:2150` (`_load_active_project`).

This is the **only** bridge between the GUI's app methods and the external Hook API. If a method is not in `_predefined_callbacks`, external callers cannot invoke it.

### Subsystem Coordination Methods

The controller has methods that span multiple subsystems:

- `reload_presets()` — re-reads preset TOML files from disk
- `reload_personas()` — same for personas
- `reload_context_presets()` — validates files exist
- `apply_persona(persona_name, target)` — switches model, system prompt, and tool weights for a target
- `dispatch_mma_track(track_id)` — kicks off a multi-agent track
- `reset_session()` — clears discussion history, resets UI state, etc.
- `save_state_to_disk()` / `load_state_from_disk()` — for historical session replay
- `inject_context_files(paths)` — adds files to the active context composition

---

## The `AppState` Dataclass

`app_state` is a flat dataclass holding all GUI-visible state. Examples:

```python
@dataclass
class AppState:
    current_provider: str = "gemini"
    current_model: str = "gemini-3-flash-preview"
    temperature: float = 0.7
    top_p: float = 0.95
    max_output_tokens: int = 8192
    system_prompt: str = ""
    discussion_history: list[DiscussionEntry] = field(default_factory=list)
    context_files: list[ContextFileEntry] = field(default_factory=list)
    context_screenshots: list[str] = field(default_factory=list)
    show_command_palette: bool = False
    show_preset_manager: bool = False
    show_persona_editor: bool = False
    show_context_preview: bool = False
    show_diagnostics: bool = False
    show_mma_dashboard: bool = False
    # ... many more
```

The `App` reads from `app_state` for rendering and writes back via setter methods. All setters are exposed to the Hook API via `_gettable_fields` and other "settable" registries.

---

## Preset & Persona Management

### `PresetManager` (in `src/presets.py`)

The controller delegates preset CRUD to `PresetManager`. The controller itself only coordinates when presets change (re-apply to active session, update system prompt, etc.).

```python
# In controller
def on_preset_changed(self, new_preset_name: str) -> None:
    preset = self.presets.get(new_preset_name)
    self.app_state.system_prompt = preset.full_text  # Base + persona
    self.app_state.temperature = preset.temperature
    self.app_state.top_p = preset.top_p
    self.app_state.max_output_tokens = preset.max_output_tokens
```

### `PersonaManager` (in `src/personas.py`)

Consolidates model settings + system prompt + tool weights into a single named entity.

```python
# In controller
def apply_persona(self, persona_name: str, target: str = "tier3") -> None:
    persona = self.personas.get(persona_name)
    if persona.model:
        self.app_state.current_model = persona.model
    if persona.system_prompt:
        self.app_state.system_prompt = persona.system_prompt
    if persona.tool_weights:
        self.tool_bias.apply_weights(persona.tool_weights, target=target)
    if persona.bias_profile:
        self.tool_bias.apply_profile(persona.bias_profile)
```

`target` is the MMA tier ("tier1", "tier2", "tier3", "tier4"). This is how MMA agents get isolated cognitive load.

### `ContextPresetManager` (in `src/context_presets.py`)

Saves/loads complete context compositions (files, screenshots, view modes). Validates that referenced files still exist on load.

### `ToolPresetManager` (in `src/tool_presets.py`)

Manages tool enable/disable + weights. Persisted to `tool_presets.toml`.

### `ToolBiasEngine` (in `src/tool_bias.py`)

Applies weights and global bias profiles. Generates the **"Tooling Strategy"** section appended to system prompts.

---

## History Management

`HistoryManager` (in `src/history.py`) implements the **non-provider undo/redo** system.

```python
def on_ui_state_change(self) -> None:
    """Called when the UI changes (e.g., text input). Pushes a snapshot."""
    snapshot = self.history.capture(self.app_state)
    self.history.push(snapshot)
    self.app_state.can_undo = self.history.can_undo()
    self.app_state.can_redo = self.history.can_redo()
```

Snapshots include:
- All text inputs (system prompt, AI input, code blocks)
- Model parameters (Temperature, Top-P, Max Output Tokens)
- Context (files, screenshots)
- Discussion history (for discussion mutations)

Capacity is fixed (default: 50 snapshots). Older entries are evicted.

### Branching History ("Takes")

`HistoryManager` also tracks **timeline branching**. When the user reverts and then takes a new action, a new "take" is created. The full history graph is preserved for back-navigation.

---

## RAG Engine Integration

`RAGEngine` (in `src/rag_engine.py`) is owned by the controller but **lazy-loaded** on first use:

```python
def get_rag_engine(self) -> RAGEngine:
    if self._rag_engine is None:
        from src.rag_engine import RAGEngine
        self._rag_engine = RAGEngine(self.paths)
    return self._rag_engine
```

The GUI exposes a RAG settings panel that calls `controller.get_rag_engine().set_provider(...)`, `set_chunk_size(...)`, etc.

### RAG Lifecycle

1. **Indexing**: `controller.index_project()` walks the project workspace, chunks files, embeds them, writes to ChromaDB (or external MCP).
2. **Search**: `controller.search_context_files(query)` returns top-k fragments with source paths.
3. **Injection**: Fragments are prepended to the AI's prompt via `ai_client.send(...)`. The controller orchestrates the flow.

---

## MMA Conductor Integration

`MultiAgentConductor` (in `src/multi_agent_conductor.py`) is also lazy-loaded:

```python
def get_mma_conductor(self) -> 'MultiAgentConductor':
    if self._mma_conductor is None:
        from src.multi_agent_conductor import MultiAgentConductor
        self._mma_conductor = MultiAgentConductor(self)
    return self._mma_conductor
```

The controller passes itself into the conductor so workers can access presets/personas/RAG during execution.

### Dispatch Flow

```
controller.dispatch_mma_track(track_id)
  -> conductor.load_track(track_id)
  -> conductor.start_workers(track)
  -> workers run in parallel via WorkerPool
  -> workers call back into controller (presets, personas, etc.)
  -> results pushed to controller.app_state.discussion_history
  -> conductor emits events to controller.event_queue
```

The `event_queue` is consumed by the GUI on the main thread to update display.

---

## Hot Reload

Hot reload is wired in `src/gui_2.py` rather than on the controller. The actual mechanism:

- **Registration** (`src/gui_2.py:282-287`): `App.__init__` registers `src.gui_2` with `HotReloader`, listing the App attributes (`state_keys`) to snapshot before reload and the App wrapper methods (`delegation_targets`) that the delegation pattern swaps atomically.
- **Trigger** (`src/gui_2.py:540-544`): `App._trigger_hot_reload()` calls `HotReloader.reload_all(self)` and stores `HotReloader.last_error` on `self._hot_reload_error` for visual error feedback.
- **Keyboard binding** (`src/gui_2.py:5340-5346`): the `Ctrl+Alt+R` shortcut is hard-coded in the source — there is no `config.toml` key for it.

`HotReloader` is a stateless class (classmethods only); it has no constructor and no `self.app` field. See **[docs/guide_hot_reload.md](guide_hot_reload.md)** for the full mechanism.

See **[docs/guide_hot_reload.md](guide_hot_reload.md)** for the full mechanism.

---

## The `SyncEventQueue`

A `queue.Queue`-based bridge between the daemon threads (AI workers, MMA workers) and the GUI main thread.

```python
class SyncEventQueue:
    def put(self, event: Event) -> None: ...
    def get_nowait(self) -> Event | None: ...
    def get_all(self) -> list[Event]: ...
```

The GUI polls `controller.event_queue.get_all()` once per frame and dispatches events to render functions.

### Event Types

- `MMA_TICKET_COMPLETED`
- `MMA_LOG_MESSAGE`
- `AI_RESPONSE_CHUNK`
- `AI_RESPONSE_COMPLETE`
- `TOOL_CALL_STARTED`
- `TOOL_CALL_COMPLETED`
- `PERSONA_APPLIED`
- `WORKSPACE_LOADED`
- `RAG_INDEX_COMPLETE`
- `HOOK_CALLBACK_RECEIVED`

The controller translates subsystem-specific events into these generic types.

---

## The Headless Mode

When `sloppy.py` is launched with `--headless`, the controller is instantiated without an `App`:

```python
# In sloppy.py --headless
controller = AppController(enable_test_hooks=True)
# ... run server-only logic ...
# No GUI, no ImGui context, but full subsystem access
```

This is the **Headless Backend Service** mode. The controller still listens on `:8999` and serves all Hook API endpoints. Tests and external scripts can drive the headless service.

---

## Hook API Surface (Defined Here)

The controller is the **single source of truth** for what the Hook API can do. Three registries:

### `_predefined_callbacks: dict[str, Callable]`

Maps hook name → App method. Populated by `register_hooks(app)`.

```python
self._predefined_callbacks['_toggle_command_palette'] = app._toggle_command_palette
self._predefined_callbacks['_open_command_palette'] = app._open_command_palette
self._predefined_callbacks['save_context_preset'] = app.save_context_preset
self._predefined_callbacks['load_context_preset'] = app.load_context_preset
# ... ~30 entries
```

### `_gettable_fields: dict[str, str]`

Maps hook name → AppState field name. Used by `get_value` Hook API action.

```python
self._gettable_fields['show_command_palette'] = 'show_command_palette'
self._gettable_fields['current_provider'] = 'current_provider'
self._gettable_fields['current_model'] = 'current_model'
# ... etc
```

### `_action_handlers: dict[str, Callable]`

Maps action name (e.g., `"click"`, `"set_value"`, `"custom_callback"`) → handler.

```python
self._action_handlers['click'] = self._handle_click
self._action_handlers['set_value'] = self._handle_set_value
self._action_handlers['custom_callback'] = self._handle_custom_callback
# ... etc
```

The HookServer in `src/api_hooks.py` consumes these registries to route incoming requests.

---

## Testing

The controller is tested via the `live_gui` fixture (full integration) and targeted unit tests.

### Unit Tests

- `tests/test_app_controller_init.py` — instantiation, subsystem wiring
- `tests/test_preset_manager.py` — preset CRUD
- `tests/test_persona_manager.py` — persona CRUD + application
- `tests/test_context_presets.py` — context preset CRUD + file validation
- `tests/test_history.py` — undo/redo
- `tests/test_workspace_manager.py` — workspace profile CRUD

### Integration Tests (live_gui)

Use the `ApiHookClient` to drive the controller and verify state mutations.

```python
def test_apply_persona(live_gui):
    client = ApiHookClient()
    client.push_event("custom_callback", {"callback": "apply_persona", "args": ["code-reviewer"]})
    time.sleep(0.5)
    model = client.get_value("current_model")
    assert "code" in model.lower() or model == "code-reviewer-model"
```

---

## Common Pitfalls

1. **Don't instantiate `AppController` twice in the same process**: The singleton holds RAG engine, MMA conductor, hook server. A second instance would conflict.
2. **Don't read `app_state` from a daemon thread without locking**: Use `event_queue` for cross-thread communication.
3. **Always go through the controller for subsystem changes**: Don't call `self.presets.save(...)` from the GUI directly; call `controller.save_preset(...)` so the event is broadcast.
4. **When adding a new Hook API callback, register it in BOTH `_predefined_callbacks` AND `register_hooks`**: The latter is what populates the registry from an App instance.

---

## Exception Handling in `app_controller.py`

Per the data-oriented error handling convention
(`conductor/code_styleguides/error_handling.md`), `app_controller.py` is a
**migration-target file**: it has not been fully refactored to the
`Result[T]` pattern. The convention is applied to 3 of 65 source files
(`src/mcp_client.py`, `src/ai_client.py`, `src/rag_engine.py`); the rest of
`src/` is in the migration-target state.

The exception-handling audit (`scripts/audit_exception_handling.py`)
classifies 56 exception-handling sites in this file (per the 2026-06-16
audit run):

| Category | Count | Convention status |
|---|---|---|
| `BOUNDARY_FASTAPI` | 13 | Compliant |
| `INTERNAL_BROAD_CATCH` | 28 | **Violation** (migration target) |
| `INTERNAL_SILENT_SWALLOW` | 6 | **Violation** (migration target) |
| `INTERNAL_RETHROW` | 3 | Suspicious |
| `UNCLEAR` | 2 | Manual review needed |
| `INTERNAL_OPTIONAL_RETURN` | 1 | **Violation** (migration target) |

### The 13 FastAPI boundary sites (compliant)

`app_controller.py` is the FastAPI handler layer (`--enable-test-hooks`
mode). The 11 `HTTPException` raises in `_api_*` handlers (lines 96, 99,
213, 215, 312, 320, 341, 369, 380, 402) and the 2 `except Exception +
raise HTTPException` sites (lines 309, 401) are the **framework boundary**
— `HTTPException` is the FastAPI-idiomatic way to signal HTTP errors;
FastAPI converts it to a JSON response at the framework level. These
sites are compliant per the convention's "Framework boundaries (FastAPI)"
section.

Example (line 96):
```python
if not target_key:
    raise HTTPException(status_code=403, detail="API Key not configured on server")
```

Example (line 309):
```python
try:
    result = ai_client.send_result(...)
    return result.data
except Exception as e:
    raise HTTPException(status_code=500, detail=f"AI call failed: {e}")
```

### The 40 migration-target sites (violations)

The remaining ~40 sites (mostly `except Exception + log/print`, `except
Exception + return None`) are **migration-target** — they would benefit
from a future track that migrates the controller to the convention.

**Recommended future track:** `app_controller_result_migration_20260616`
(not in scope of the audit track; the user decides). The work would be:
1. Convert `Optional[T]` return types to `Result[T]`.
2. Convert `except Exception + log/print` to `except Exception +
   return Result(data=NIL_T, errors=[ErrorInfo(...)])`.
3. Convert `except Exception + return None` to `except Exception +
   return Result(data=NIL_T, errors=[ErrorInfo(...)])`.
4. Keep the 13 FastAPI boundary sites as-is (they're the framework contract).
5. Add tests that verify the success and failure paths of each migrated
   function return the right `Result`.

This is a 2-3 day Tier 2 effort. The audit's per-site hints (in the JSON
output via `--json`) tell the implementer what the fix should look like
for each site.

### Quick check

To see the current state of the file's exception handling:
```bash
uv run python scripts/audit_exception_handling.py --top 1 --verbose | head -50
```

To see only the violations (not the compliant FastAPI boundary sites):
```bash
uv run python scripts/audit_exception_handling.py --json | \
  python -c "import json,sys; r=json.load(sys.stdin); print([f for f in r['files'][0]['findings'] if f['category'] in ('INTERNAL_BROAD_CATCH', 'INTERNAL_SILENT_SWALLOW', 'INTERNAL_OPTIONAL_RETURN')])"
```

---

## See Also

- **[guide_architecture.md](guide_architecture.md)** — Threading and event flow
- **[guide_mma.md](guide_mma.md)** — How MMA workers use the controller
- **[guide_ai_client.md](guide_ai_client.md)** — How `ai_client` integrates
- **[guide_api_hooks.md](guide_api_hooks.md)** — The Hook API the controller exposes
- **[guide_hot_reload.md](guide_hot_reload.md)** — How the controller supports state-preserving reloads
- **[guide_discussions.md](guide_discussions.md)** — The Discussion system (Takes, branching, `_switch_discussion`, `_branch_discussion`, `_rename_discussion`, `_delete_discussion`, `_flush_disc_entries_to_project`)
- **[guide_state_lifecycle.md](guide_state_lifecycle.md)** — The `_handle_reset_session` and `_handle_compress_discussion` flows, the `App.__getattr__`/`__setattr__` state delegation pattern, and the `HistoryManager` integration
- **[guide_context_aggregation.md](guide_context_aggregation.md)** — The `aggregate.py` pipeline that the controller calls per send (per-provider + Tier 3 worker)
- **`src/presets.py`, `src/personas.py`, `src/context_presets.py`, `src/tool_presets.py`, `src/tool_bias.py`** — Subsystem managers
- **`src/history.py`** — `HistoryManager`
- **`src/rag_engine.py`** — `RAGEngine`
- **`src/multi_agent_conductor.py`** — `MultiAgentConductor`
- **`src/hot_reloader.py`** — `HotReloader`
- **`src/api_hooks.py`** — `HookServer` (uses the controller's registries)
- **`src/paths.py`** — `PathManager`
- **[conductor/tracks/nagent_review_20260608/report.md](../conductor/tracks/nagent_review_20260608/report.md)** — Deep-dive analysis of the controller's per-provider history globals and other state patterns
