docs: add error handling patterns and module dependencies to CLAUDE.md

- Document 3 graceful degradation patterns with code examples
- Add Service Fallback Matrix for optional services
- Add module dependency tree with change impact guide

chore: fix typecheck environment

- Add mypy to dev dependencies in pyproject.toml
- Fix tox.ini typecheck environment to install mypy explicitly

CLAUDE.md

@@ -111,6 +111,55 @@ tox -e dev              # Start dashboard with auto-reload
 
 ---
 
+## Error Handling Patterns
+
+All optional services (Ollama, Redis, AirLLM, voice, etc.) must degrade gracefully. Three approved patterns:
+
+### Pattern 1: Optional Return (data retrieval)
+```python
+def get_user_setting(key: str) -> Optional[str]:
+    try:
+        return db.query(...)
+    except Exception as exc:
+        logger.warning("Setting lookup failed: %s", exc)
+        return None
+```
+
+### Pattern 2: Fallback Value (computations)
+```python
+def compute_embedding(text: str) -> list[float]:
+    try:
+        return model.encode(text)
+    except Exception as exc:
+        logger.warning("Embedding failed, using hash: %s", exc)
+        return hash_based_fallback(text)
+```
+
+### Pattern 3: Feature Disable (optional services)
+```python
+async def transcribe_audio(audio: bytes) -> str:
+    try:
+        return await voice_service.transcribe(audio)
+    except ServiceUnavailable:
+        logger.warning("Voice service unavailable — feature disabled")
+        return ""  # Silently disable feature
+```
+
+### Service Fallback Matrix
+
+| Service | When Unavailable | Fallback Behavior |
+|---------|------------------|-------------------|
+| Ollama | No local LLM | Claude backend (if ANTHROPIC_API_KEY set) |
+| Redis | Cache/storage down | In-memory dict (ephemeral) |
+| AirLLM | Import error or no Apple Silicon | Ollama backend |
+| Voice (Piper) | Service down | Browser Web Speech API |
+| WebSocket | Connection failed | HTTP polling (degraded) |
+| Telegram/Discord | No token configured | Bot doesn't start (logs only) |
+
+**Rule:** Never crash the app when an optional service is down. Log at WARNING level and continue.
+
+---
+
 ## Frontend Architecture
 
 ### Stylesheets
@@ -181,3 +230,50 @@ McToast.show('Request failed', 'error');       // red border
 | `brain/` | Identity system, memory interface |
 | `timmy_serve/` | API server |
 | `config.py` | Pydantic settings (foundation for all modules) |
+
+## Module Dependencies
+
+```
+config.py                    # Foundation — no internal dependencies
+    │
+    ├── timmy/               # Core agent
+    │   ├── Uses: config, brain, infrastructure
+    │   └── Impact: 🔴 High — used by dashboard, integrations, timmy_serve
+    │
+    ├── brain/               # Memory system
+    │   ├── Uses: config
+    │   └── Impact: 🟡 Medium — used by timmy, spark
+    │
+    ├── infrastructure/      # Shared services
+    │   ├── Uses: config
+    │   └── Impact: 🔴 High — used by ALL packages
+    │       ├── ws_manager   # WebSocket connections
+    │       ├── notifier     # Push notifications
+    │       └── event_bus    # Pub/sub events
+    │
+    ├── spark/               # Intelligence engine
+    │   ├── Uses: config, brain
+    │   └── Impact: 🟢 Low — self-contained
+    │
+    ├── integrations/        # External services
+    │   ├── Uses: config, infrastructure
+    │   └── Impact: 🟡 Medium — isolated by vendor
+    │
+    ├── dashboard/           # Web UI
+    │   ├── Uses: ALL packages
+    │   └── Impact: 🔴 High — entry point, orchestrates everything
+    │
+    └── timmy_serve/         # API server
+        ├── Uses: config, timmy, infrastructure
+        └── Impact: 🟡 Medium — standalone service
+```
+
+### Change Impact Guide
+
+| If you modify... | You should test... |
+|------------------|-------------------|
+| `config.py` | Full suite (`tox -e ci`) — affects everything |
+| `infrastructure/` | Unit + integration + functional |
+| `timmy/` | Unit tests + chat/CLI tests |
+| `dashboard/routes/` | Dashboard route tests (usually isolated) |
+| `brain/` | Brain client/worker tests + timmy tests |

pyproject.toml

@@ -73,6 +73,7 @@ selenium = ">=4.20.0"
 pytest-randomly = "^4.0.1"
 pytest-xdist = "^3.8.0"
 ruff = ">=0.8.0"
+mypy = ">=1.0.0"
 
 [tool.poetry.scripts]
 timmy = "timmy.cli:main"

tox.ini

@@ -38,6 +38,9 @@ commands =
 
 [testenv:typecheck]
 description = Static type checking with mypy
+commands_pre =
+deps =
+    mypy>=1.0.0
 commands =
     mypy src --ignore-missing-imports --no-error-summary