Post-Coding Development (PCD, “Piccadilly”)

Specifications, not source code, are the human deliverable.

A PCD specification is structured Markdown that captures what a piece of software has to do, the data it works with, the external systems it depends on, and the rules that must always hold. An LLM produces the working implementation from it: source code, packaging, documentation, tests, and an audit bundle.

The target language is never declared in the specification — it is chosen by the deployment template. A spec written today for a Go binary produces a Rust binary in 2045 if the template changes; the specification is untouched. Every generated artifact carries a verifiable link back to the specification it was produced from.

The reference tools in this repository — pcd-lint and mcp-server-pcd — were specified in PCD and generated by an LLM. Zero hand-written implementation code.

If you’ve used “skills”

For personal workflows, the pattern is already familiar: write a Markdown file describing what you want, let the model handle the rest. That pattern is widely known as “skills.”

PCD answers the next question: what does the Markdown have to carry when the…