The author built a custom coding agent harness called pi-ai, which provides a unified API for interacting with various LLM providers. The author was motivated by the need for a simple and predictable tool, as existing solutions had become too complex and changed frequently. The pi-ai project includes several components, including pi-ai, pi-agent-core, pi-tui, and pi-coding-agent, which provide features such as multi-provider support, context handoff, and minimal system prompts. The author is generally satisfied with the result, which has been used in several production projects.