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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.

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