Agentic Brownfield Coding — Development skill for Claude Code

Agentic Brownfield Coding (ABC)

This Claude Code plugin repo assists complex software projects in their first steps towards agentic coding:

1. Scaffolding and gradually augmenting an existing codebase with an efficient harness setup.
2. Learning controlled agentic development workflows with a human-in-the-loop mindset.

Background

The ABC project arose from a dissatisfaction with the built-in `/init` command of Claude Code, which tries to derive agent instructions by scanning the existing repository content. Especially for large and complex codebases, this approach generally leads to poor results, as [summarized comprehensively](https://addyosmani.com/blog/agents-md/) by Google engineer Addy Osmani.

Another major inspiration was Dexter Horthy's work on [AI in Complex Codebases](https://github.com/humanlayer/advanced-context-engineering-for-coding-agents/blob/main/ace-fca.md) which has become known for the RPI workflow. Together with co-founder Kyle Mistele, he promotes disciplined [harness engineering](https://www.humanlayer.dev/blog/skill-issue-harness-engineering-for-coding-agents) and controlled interactive workflows to rein in the non-determinism of coding agents.

Details about the concrete hypotheses and design philosophy behind the ABC solutions can be found in the full length [background essay](BACKGROUND.md).

System Requirements

• Linux — natively supported, requires jq installed
• macOS — supported (agent will substitute GNU-only utilities), requires jq installed
• Windows — requires Git Bash and jq on PATH

Installation

claude plugin marketplace add ralfstrobel/agentic-brownfield-coding

claude plugin install abc-init@agentic-brownfield-coding
claude plugin install abc@agentic-brownfield-coding

[!TIP] The separate init plugin is only required on