Feature Implementation

Systematic approach to implementing new features in the Rust memory system.

Quick Reference

• Process - Implementation phases (planning, design, implementation, testing)
• Structure - Module structure and file organization
• Patterns - Code patterns and conventions
• Quality - Quality standards and checklists

When to Use

• Adding new functionality to the codebase
• Following project conventions for feature development
• Maintaining code quality and test coverage

Core Process

1. Planning - Understand requirements and constraints
2. Design - Architecture and module structure
3. Implementation - Write code following patterns
4. Testing - Add tests with >90% coverage
5. Documentation - Update docs and examples

See process.md for detailed phases and patterns.md for Rust code patterns.

Project Standards

• File size: ≤ 500 LOC per file
• Async/Tokio patterns for I/O
• Error handling: anyhow::Result
• Storage: Turso (durable) + redb (cache)
• Serialization: postcard

StorageBackend Surface Guardrails

• A new defaulted StorageBackend method must be classified in scripts/storage-backend-capabilities.toml in the same PR, or the fail-closed checker in fast-gate blocks every PR (regenerate docs/generated/storage-backend-capabilities.json with --write).
• Use fail-closed when the default returns Error::CapabilityUnavailable but there is no predicate to name; capability-gated requires a real supports_*/can_* predicate in the trait source.
• A new capability predicate belongs on StorageBackendCapabilities (default false), and every cache/durability caller gates on it before treating a write as durable (ADR-081 style).
• Every StorageBackend test double needs the StorageBackendCapabilities impl (impl StorageBackendCapabilities for T {} is enough when it advertises nothing).