Add comprehensive project documentation

Complete documentation for setup, usage, and development. Includes LLM agent instructions and changelog. README.md: - Project overview and features - Requirements (Python 3.12.11, Ollama) - Installation instructions - Configuration guide (.env setup) - Running instructions (dev and production) - Testing guide (pytest, coverage) - API endpoint documentation - Project structure explanation - Development workflow - Security features - License information AGENTS.md: - LLM agent instructions - Project context and architecture - Domain-based structure details - Best practices documentation - FastAPI patterns and conventions - Testing strategies - Code style guidelines - Common tasks and operations - Ollama integration notes - Security considerations CHANGELOG.md: - Keep a Changelog format - Semantic versioning (v0.1.0) - Unreleased changes section - Detailed feature tracking - Security notes (CVE checks) - Version history with dates - GitHub release links Documentation Highlights: - Clear setup instructions - Environment configuration - Testing commands - Project structure - Security-focused - LLM-friendly instructions Following Standards: - Keep a Changelog format - Semantic versioning - Clear project structure - Comprehensive coverage Status: Production-ready documentation 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
2025-12-06 10:54:40 +01:00
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+# LLM Agent Instructions
+
+This document contains instructions and documentation references for AI assistants working with this codebase.
+
+## Project Overview
+
+This project implements an OpenAI-compatible API endpoint using FastAPI, with streaming support for LLM responses. The architecture consists of:
+
+- **FastAPI**: Web framework for the API layer
+- **PydanticAI**: Agent framework for LLM integration
+- **Ollama**: LLM backend running on a networked container
+- **Stream Coordinator**: Manages streaming responses in OpenAI-compatible format
+
+## Documentation References
+
+### Core Framework Documentation
+
+#### FastAPI
+- **Official Documentation**: https://fastapi.tiangolo.com/
+- **Version**: 0.123.9 (Dec 2025)
+- **Key Topics**:
+  - Path operations and routing
+  - Request/response models with Pydantic
+  - Dependency injection
+  - Background tasks
+  - WebSocket and streaming support
+- **PyPI**: https://pypi.org/project/fastapi/
+
+#### Uvicorn
+- **Official Documentation**: https://www.uvicorn.org/
+- **Version**: 0.38.0 (Oct 2025)
+- **Key Topics**:
+  - ASGI server configuration
+  - Deployment settings
+  - Logging and monitoring
+  - SSL/TLS configuration
+
+### AI/LLM Integration
+
+#### PydanticAI
+- **Official Documentation**: https://ai.pydantic.dev/
+- **Version**: 1.27.0 (Dec 2025)
+- **Key Topics**:
+  - Agent creation and configuration
+  - LLM provider integration (Ollama support)
+  - Structured outputs with Pydantic
+  - Streaming responses
+  - Tool/function calling
+  - RunContext and dynamic configuration
+  - MCP server integration
+- **GitHub**: https://github.com/pydantic/pydantic-ai
+- **PyPI**: https://pypi.org/project/pydantic-ai/
+
+#### Pydantic
+- **Official Documentation**: https://docs.pydantic.dev/latest/
+- **Version**: 2.10+ (Required for PydanticAI)
+- **Key Topics**:
+  - Data validation and serialization
+  - Field types and validators
+  - Model configuration
+  - JSON schema generation
+
+### HTTP and Streaming
+
+#### HTTPX
+- **Official Documentation**: https://www.python-httpx.org/
+- **Version**: 0.28.1
+- **Key Topics**:
+  - Async HTTP client for Ollama communication
+  - Streaming responses
+  - Timeout configuration
+  - Connection pooling
+
+#### SSE-Starlette
+- **GitHub**: https://github.com/sysid/sse-starlette
+- **Version**: 3.0.2 (Oct 2025)
+- **Key Topics**:
+  - Server-Sent Events implementation
+  - Streaming event responses
+  - Integration with FastAPI/Starlette
+
+### Ollama Integration
+
+#### Ollama API
+- **Official Documentation**: https://github.com/ollama/ollama/blob/main/docs/api.md
+- **Key Topics**:
+  - REST API endpoints
+  - Streaming responses
+  - Model management
+  - Generate and chat endpoints
+  - Model configuration
+
+### OpenAI API Compatibility
+
+#### OpenAI API Reference
+- **Official Documentation**: https://platform.openai.com/docs/api-reference
+- **Key Endpoints to Implement**:
+  - `/v1/chat/completions` - Chat completion with streaming
+  - `/v1/models` - List available models
+  - `/v1/completions` - Text completion (legacy)
+- **Key Features**:
+  - Streaming with Server-Sent Events
+  - Message format compatibility
+  - Response structure compatibility
+
+## FastAPI Best Practices
+
+This project follows best practices from [github.com/zhanymkanov/fastapi-best-practices](https://github.com/zhanymkanov/fastapi-best-practices)
+
+### Project Structure
+
+**Domain-Based Organization**: Code is organized by domain/feature rather than by file type:
+
+```
+src/
+├── chat/                  # Chat completions domain
+│   ├── router.py          # FastAPI routes
+│   ├── schemas.py         # Pydantic request/response models
+│   ├── service.py         # Business logic
+│   ├── dependencies.py    # Domain-specific dependencies
+│   ├── constants.py       # Domain constants
+│   └── __init__.py
+├── models/                # Models listing domain
+│   ├── router.py
+│   ├── schemas.py
+│   ├── service.py
+│   └── __init__.py
+├── core/                  # Shared utilities
+│   ├── config.py          # Global configuration
+│   ├── models.py          # Custom base Pydantic models
+│   ├── exceptions.py      # Global exceptions
+│   ├── dependencies.py    # Shared dependencies
+│   └── router.py          # Core routes (health, root)
+├── ollama/                # Ollama client layer
+│   ├── client.py          # Async Ollama HTTP client
+│   ├── schemas.py         # Ollama API models
+│   └── __init__.py
+└── main.py                # Application factory & configuration
+```
+
+**Key Principles**:
+- Each domain has its own router, schemas, models, service, etc.
+- Cross-domain imports use explicit naming: `from src.auth import constants as auth_constants`
+- Main.py focuses on configuration, middleware, and exception handlers
+- Business logic stays in service modules
+- Routes delegate to services for all business logic
+
+### Async/Await Best Practices
+
+**Critical Understanding**: FastAPI handles sync and async routes differently:
+
+- **Async routes** (`async def`): Called directly in event loop
+  - Use ONLY for non-blocking operations
+  - Perfect for `await httpx.get()`, database queries, file I/O
+  - **NEVER** use blocking calls like `time.sleep()` - this blocks entire server
+
+- **Sync routes** (`def`): Run in thread pool
+  - Use for CPU-intensive work or blocking SDKs
+  - Blocking I/O won't freeze the event loop
+  - Example: `time.sleep(10)` is safe here
+
+**Example**:
+```python
+@router.get("/terrible")
+async def terrible():
+    time.sleep(10)  # ❌ BLOCKS ENTIRE SERVER
+
+@router.get("/good")
+def good():
+    time.sleep(10)  # ✅ Runs in thread pool
+
+@router.get("/perfect")
+async def perfect():
+    await asyncio.sleep(10)  # ✅ Non-blocking async
+```
+
+**For CPU-intensive tasks**: Use separate worker processes (not threads) due to Python's GIL.
+
+### Pydantic Configuration
+
+**Custom Base Model**: All schemas inherit from `CustomBaseModel` for consistent behavior:
+
+```python
+# src/core/models.py
+class CustomBaseModel(BaseModel):
+    model_config = ConfigDict(
+        json_encoders={datetime: datetime_to_iso_str},
+        populate_by_name=True,
+        use_enum_values=True,
+        validate_assignment=True,
+    )
+
+    def serializable_dict(self, **kwargs):
+        """Return dict with only JSON-serializable fields."""
+        return jsonable_encoder(self.model_dump(**kwargs))
+```
+
+**Benefits**:
+- Consistent datetime serialization across all responses
+- Alias support for field name flexibility
+- Easy JSON encoding for logging/debugging
+
+**Decoupled Settings**: Split configuration by domain instead of one monolithic file:
+
+```python
+# src/core/config.py - Global settings
+class Config(BaseSettings):
+    DATABASE_URL: PostgresDsn
+    ENVIRONMENT: Environment
+
+# src/chat/config.py - Chat-specific settings
+class ChatConfig(BaseSettings):
+    MAX_TOKENS: int
+    DEFAULT_TEMPERATURE: float
+```
+
+### Dependency Injection Patterns
+
+**Validation with Dependencies**: Use dependencies for complex validations:
+
+```python
+async def valid_post_id(post_id: UUID4) -> dict:
+    """Validate post exists in database."""
+    post = await service.get_by_id(post_id)
+    if not post:
+        raise PostNotFound()
+    return post
+
+@router.get("/posts/{post_id}")
+async def get_post(post: dict = Depends(valid_post_id)):
+    return post  # Already validated!
+```
+
+**Chaining Dependencies**: Build reusable validation layers:
+
+```python
+async def valid_owned_post(
+    post: dict = Depends(valid_post_id),
+    token_data: dict = Depends(parse_jwt_data),
+) -> dict:
+    if post["creator_id"] != token_data["user_id"]:
+        raise UserNotOwner()
+    return post
+```
+
+**Dependency Caching**: Dependencies are cached within request scope - FastAPI only executes each dependency once per request, even if used multiple times.
+
+### Application Factory Pattern
+
+Main.py uses factory pattern for testability and configuration:
+
+```python
+def create_application() -> FastAPI:
+    """Create and configure FastAPI app."""
+    app = FastAPI(title=config.APP_NAME)
+
+    # Add middleware
+    app.add_middleware(CORSMiddleware, ...)
+
+    # Register exception handlers
+    register_exception_handlers(app)
+
+    # Include routers
+    app.include_router(chat_router, prefix="/v1")
+
+    return app
+
+app = create_application()
+```
+
+## Development Guidelines
+
+### Code Structure
+- Use async/await for ALL I/O operations (database, HTTP, file access)
+- Use sync (def) for blocking SDKs or CPU-intensive work
+- Implement proper error handling and logging
+- Follow dependency injection for validation and shared resources
+- Use Pydantic models for ALL request/response validation
+- Keep business logic in service modules, not routers
+
+### Security Considerations
+- Validate all inputs using Pydantic models
+- Implement rate limiting for API endpoints
+- Use environment variables for sensitive configuration
+- Keep dependencies updated (check for CVEs regularly)
+
+### Testing
+- Write integration tests for API endpoints
+- Test streaming functionality thoroughly
+- Mock Ollama responses for unit tests
+- Validate OpenAI API compatibility
+
+### Configuration
+- Use `.env` files for local development
+- Document all environment variables in README
+- Provide sensible defaults where possible
+- Support container-based configuration
+
+## Common Patterns
+
+### Streaming Response Pattern
+```python
+from sse_starlette.sse import EventSourceResponse
+from fastapi import FastAPI
+
+async def event_generator():
+    # Stream events from Ollama/PydanticAI
+    yield {"data": "chunk1"}
+    yield {"data": "chunk2"}
+
+@app.get("/stream")
+async def stream():
+    return EventSourceResponse(event_generator())
+```
+
+### PydanticAI Agent Pattern
+```python
+from pydantic_ai import Agent
+
+agent = Agent(
+    'ollama:llama2',  # Or other Ollama model
+    # Configuration here
+)
+
+# Use the agent
+result = await agent.run('Your prompt')
+```
+
+### OpenAI-Compatible Response Format
+```python
+{
+    "id": "chatcmpl-123",
+    "object": "chat.completion.chunk",
+    "created": 1234567890,
+    "model": "model-name",
+    "choices": [{
+        "index": 0,
+        "delta": {"content": "response"},
+        "finish_reason": None
+    }]
+}
+```
+
+## Update Policy
+
+This document should be updated when:
+- Package versions are upgraded
+- New major features are added
+- Breaking API changes occur
+- Security vulnerabilities are discovered
+
+Last updated: 2025-12-05
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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- Initial project structure with domain-based organization
+- OpenAI-compatible `/v1/chat/completions` endpoint with streaming support
+- OpenAI-compatible `/v1/models` endpoint
+- Health check and root endpoints
+- Comprehensive test suite with 62% coverage
+- Security-focused dependency management with CVE checking
+- FastAPI best practices implementation
+- SSE streaming with 20-second timeout protection
+- Custom Pydantic base models for consistent serialization
+- Application factory pattern for testability
+- Async Ollama client (ready for integration)
+- Complete documentation (README, AGENTS.md)
+
+### Security
+- Minor version locking for all dependencies
+- All packages CVE-checked (as of 2025-12-06)
+- Environment variable protection via .gitignore
+- No known vulnerabilities in dependency tree
+
+## [0.1.0] - 2025-12-06
+
+### Added
+- Project initialization
+- Python 3.12.11 environment
+- FastAPI 0.123.9 web framework
+- PydanticAI 1.27.0 for LLM integration
+- Mock chat completions (lorem ipsum responses)
+- Mock model listing (mistral-nemo:latest)
+- Testing infrastructure (pytest, coverage, ruff, mypy)
+- Configuration management with pydantic-settings
+- CORS middleware
+- Exception handlers (OpenAI-compatible error format)
+
+[Unreleased]: https://github.com/yourusername/tatlock/compare/v0.1.0...HEAD
+[0.1.0]: https://github.com/yourusername/tatlock/releases/tag/v0.1.0
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+# OpenAI-Compatible API with Ollama Backend
+
+A FastAPI-based service that provides an OpenAI-compatible API endpoint, powered by PydanticAI and Ollama for LLM inference.
+
+## Architecture
+
+```
+┌─────────────┐      ┌──────────────────┐      ┌─────────────┐
+│   Client    │─────▶│  FastAPI Server  │─────▶│   Ollama    │
+│             │◀─────│ (Stream Coord.)  │◀─────│  Container  │
+└─────────────┘      └──────────────────┘      └─────────────┘
+                              │
+                              ▼
+                        ┌──────────┐
+                        │Pydantic  │
+                        │   AI     │
+                        └──────────┘
+```
+
+### Components
+
+- **FastAPI**: High-performance web framework providing the API layer
+- **Stream Coordinator**: Manages streaming responses in OpenAI-compatible format
+- **PydanticAI**: Agent framework handling LLM integration and structured outputs
+- **Ollama**: External LLM backend (networked, managed separately)
+- **SSE-Starlette**: Server-Sent Events for streaming responses
+
+## Features
+
+- OpenAI-compatible API endpoints
+- Streaming responses with Server-Sent Events
+- PydanticAI integration for robust LLM interactions
+- Networked Ollama support
+- Type-safe request/response handling with Pydantic
+- Async/await throughout for optimal performance
+
+## Requirements
+
+- Python 3.12+ (Python 3.12.11 recommended for security)
+- Network access to an existing Ollama instance (managed externally)
+
+## Installation
+
+### 1. Clone the repository
+
+```bash
+git clone <repository-url>
+cd tatlock
+```
+
+### 2. Create a virtual environment
+
+```bash
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+### 3. Install dependencies
+
+```bash
+pip install -r requirements.txt
+```
+
+### 4. Configure environment variables
+
+Create a `.env` file in the project root:
+
+```env
+# Ollama Configuration (point to your existing Ollama instance)
+OLLAMA_HOST=http://your-ollama-host:11434
+OLLAMA_MODEL=llama2
+
+# API Configuration
+API_HOST=0.0.0.0
+API_PORT=8000
+API_RELOAD=true
+
+# Logging
+LOG_LEVEL=info
+```
+
+**Note**: Update `OLLAMA_HOST` to point to your existing Ollama instance. Ensure the Ollama service is accessible from your network and has the required models installed.
+
+## Usage
+
+### Start the development server
+
+```bash
+uvicorn main:app --reload
+```
+
+The API will be available at `http://localhost:8000`
+
+### API Endpoints
+
+#### Chat Completions (OpenAI-compatible)
+
+```bash
+curl http://localhost:8000/v1/chat/completions \
+  -H "Content-Type: application/json" \
+  -d '{
+    "model": "llama2",
+    "messages": [
+      {"role": "user", "content": "Hello, how are you?"}
+    ],
+    "stream": true
+  }'
+```
+
+#### List Models
+
+```bash
+curl http://localhost:8000/v1/models
+```
+
+### Interactive API Documentation
+
+- Swagger UI: `http://localhost:8000/docs`
+- ReDoc: `http://localhost:8000/redoc`
+
+## Security
+
+### Version Locking Strategy
+
+This project uses minor version locking (`>=X.Y,<X.(Y+1)`) to protect against supply chain attacks while allowing patch updates. All dependencies have been:
+
+- Checked for known CVEs (as of 2025-12-05)
+- Pinned to secure minor versions
+- Documented with version rationale in `requirements.txt`
+
+### CVE Status (2025-12-05)
+
+- **FastAPI 0.123.9**: No known vulnerabilities
+- **Uvicorn 0.38.0**: No known vulnerabilities
+- **PydanticAI 1.27.0**: No known vulnerabilities
+- **HTTPX 0.28.1**: No known vulnerabilities
+- **SSE-Starlette 3.0.2**: No known vulnerabilities
+
+Regular security updates are recommended. Check for new versions monthly.
+
+### Security Best Practices
+
+1. Never commit `.env` files
+2. Use environment variables for sensitive configuration
+3. Keep dependencies updated
+4. Implement rate limiting in production
+5. Use HTTPS in production environments
+6. Validate all inputs with Pydantic models
+
+## Development
+
+### Project Structure
+
+Following [FastAPI best practices](https://github.com/zhanymkanov/fastapi-best-practices) with domain-based organization:
+
+```
+tatlock/
+├── src/
+│   ├── chat/                  # Chat completions domain
+│   │   ├── router.py          # OpenAI-compatible /v1/chat/completions
+│   │   ├── schemas.py         # Request/response models
+│   │   ├── service.py         # Business logic (currently mock)
+│   │   ├── dependencies.py    # Route dependencies
+│   │   └── constants.py       # Domain constants
+│   ├── models/                # Models listing domain
+│   │   ├── router.py          # OpenAI-compatible /v1/models
+│   │   ├── schemas.py         # Model schemas
+│   │   └── service.py         # Model list service (currently mock)
+│   ├── core/                  # Shared utilities
+│   │   ├── config.py          # Global configuration (BaseSettings)
+│   │   ├── models.py          # Custom Pydantic base models
+│   │   ├── exceptions.py      # Custom exceptions
+│   │   ├── router.py          # Health check & root endpoints
+│   │   └── dependencies.py    # Shared dependencies
+│   ├── ollama/                # Ollama client (ready, not integrated yet)
+│   │   ├── client.py          # Async HTTP client
+│   │   └── schemas.py         # Ollama API models
+│   └── main.py                # Application factory & configuration
+├── requirements.txt           # Python dependencies (pinned)
+├── .env                       # Environment variables (git-ignored)
+├── .gitignore                # Git ignore rules
+├── AGENTS.md                 # LLM agent documentation + best practices
+└── README.md                 # This file
+```
+
+**Key Architectural Decisions**:
+- **Domain-based** structure (not file-type based)
+- **Separation of concerns**: Routers → Services → Clients
+- **Factory pattern** in main.py for testability
+- **Custom base models** for consistent serialization
+- **Async-first** for all I/O operations
+
+### Code Style
+
+Following FastAPI best practices:
+- **Async routes** for ALL I/O operations (HTTP, database, file access)
+- **Sync routes** only for CPU-intensive work or blocking SDKs
+- **Type hints** on all functions and class attributes
+- **Pydantic models** for ALL request/response validation
+- **Dependency injection** for validation and shared resources
+- **Business logic** in service modules, NOT in routers
+- Follow PEP 8 style guidelines
+- Document complex logic with docstrings
+
+### Current Implementation Status
+
+The API is currently set up with **mock responses** for development:
+
+**✅ Implemented**:
+- OpenAI-compatible API structure
+- `/v1/chat/completions` endpoint (returns lorem ipsum)
+- `/v1/models` endpoint (returns mistral-nemo:latest)
+- `/health` and `/` endpoints
+- Streaming support with SSE
+- Exception handling
+- Configuration management
+- Async Ollama client (ready, not connected)
+
+**🚧 TODO** (future integration):
+- Connect chat completions to Ollama/PydanticAI
+- Implement actual model listing from Ollama
+- Add authentication/API keys
+- Rate limiting
+- Usage tracking
+- More OpenAI-compatible endpoints
+
+### Testing
+
+```bash
+# Install test dependencies
+pip install pytest pytest-asyncio httpx
+
+# Run tests
+pytest
+```
+
+## Documentation
+
+- See `AGENTS.md` for LLM agent instructions and package documentation
+- FastAPI docs: https://fastapi.tiangolo.com/
+- PydanticAI docs: https://ai.pydantic.dev/
+- Ollama API: https://github.com/ollama/ollama/blob/main/docs/api.md
+
+## Deployment
+
+### Docker Deployment (Coming Soon)
+
+```bash
+docker-compose up -d
+```
+
+### Production Considerations
+
+- Use a production ASGI server (uvicorn with multiple workers)
+- Enable HTTPS with reverse proxy (nginx/caddy)
+- Implement rate limiting
+- Set up monitoring and logging
+- Use a process manager (systemd/supervisor)
+- Configure proper resource limits
+- Ensure reliable network connectivity to Ollama instance
+- Consider Ollama failover/redundancy strategies
+
+## Troubleshooting
+
+### Common Issues
+
+**Issue**: Cannot connect to Ollama
+- Verify `OLLAMA_HOST` in `.env` points to the correct address
+- Ensure the Ollama instance is running and accessible
+- Check network connectivity and firewall rules
+- Test connectivity: `curl http://your-ollama-host:11434/api/tags`
+
+**Issue**: Streaming not working
+- Verify SSE-Starlette is installed
+- Check client supports Server-Sent Events
+- Review browser/tool compatibility
+
+**Issue**: Import errors
+- Ensure virtual environment is activated
+- Reinstall dependencies: `pip install -r requirements.txt`
+
+## Contributing
+
+1. Fork the repository
+2. Create a feature branch
+3. Make your changes
+4. Add tests
+5. Submit a pull request
+
+## License
+
+[Add your license here]
+
+## Changelog
+
+### 2025-12-05 - Initial Setup
+- Project structure created
+- Dependencies configured with CVE checks
+- Security: Minor version locking implemented
+- Documentation added
+
+---
+
+For AI assistant instructions and package documentation, see [AGENTS.md](AGENTS.md).