Show HN: An SDK for building custom coding agents with tools and sub-agents

I’ve been experimenting with AI coding agents for a while, especially combining planners like o3 with executors like Claude Code.

Eventually I needed more control — so I built a TypeScript SDK that makes it easy to spin up custom coding agents, attach toolsets, define system prompts, and compose sub-agents. It also has a simple CLI for github actions or dangerously running things locally.

It’s open-source and early, but it already powers some of my other projects, such as a prompt-based PRD generator grounded in your codebase.

- Agent SDK GitHub: https://github.com/qckfx/agent-sdk

- Prompt Generator Use Case Github: https://github.com/qckfx/compose

Would love feedback, use cases, or ideas for where to take this next.