Developer guide

This guide is for developers digging into the code: understanding why a boundary exists, tracing a behavior across processes, finding the implementation that owns it, running the right test, and preparing a reviewable change.

New Old World is a native macOS host, a PowerPC Carbon guest, a bundled optional resident extension, and a retained 68K Toolbox sibling. The alpha includes the first three but does not install the extension by default, and excludes the currently stale pre-Carbon build. They share a versioned wire contract, but not a UI architecture or implementation language.

Start with orientation, then use the architecture pages to find the owning boundary and the workflow pages to make a specific kind of change. The generated AsyncAPI reference is useful for lookup; contract/asyncapi.yaml remains authoritative.

If you are a coding agent, begin with the separate coding agent guide. It overlays operating protocol on this guide; it does not duplicate the architecture.

The documentation standard records the web-facing choices: Diátaxis, AsyncAPI 3.0, Mermaid with text equivalents, a WCAG 2.2 AA target, Schema.org metadata, and RFC 9116 release assets. The alpha feature profile is machine-readable and drives feature-page availability notices. The distribution and bundle standard maps that feature authority into release artifacts, licensed inputs, and guest deployment policy without copying the feature states.

Change map

Change	Start here	Required gate
Wire behavior	Change the contract	scripts/test-all
Host or guest module	Add a module	module inventory plus platform tests
Resident component	Resident components	bake gate plus full suite
Public documentation	Documentation and gates	scripts/test-docs
Emulator or hardware evidence	Emulator and metal	identity and machine guards