Trebell

Trebell Code is a desktop coding app with its own harness, which works with models from Meta, OpenAI, Anthropic and more. The problem it solves is the cost: official harnesses carry heavy overhead, like long system prompts and background helpers, so the same model costs more than it should. Our harness keeps the prompt short and cache friendly, loads tools only when needed, and checks its own work by running it, along with other model-based optimizations. With Meta's Muse Spark 1.3 on 178 Terminal-Bench and Terminal-Bench Pro tasks, Trebell Code outperformed Meta's official harness, Muse Code, while costing about a third as much on tasks both solved. It can also run Muse Code, Codex, Claude Code and other agents in one place.