Internals

These pages are for people changing Embedded React rather than using it: how the repository is laid out, what a backend has to get right, how the tests are tiered, how a release is cut, and the rules that keep the engine portable.

• Architecture: the monorepo's layers, the one boundary that matters (the C ABI between everything and the engine), and how each piece is built.
• Engine internals: the layout solver, scratch buffers, damage tracking, hidden subtrees, the arc widget, frame instrumentation, and every compile-time flag.
• Flow B packages: the design of the package the Flow B compiler emits and the runtime that verifies and runs it.
• Writing a backend: the five callbacks, the optional extensions, and the conventions learned from the four backends that run on hardware.
• Testing: engine CTest suites, the bridge's unit, runtime and bytecode tiers, the AOT smoke tests, the parity harness, and what CI runs.
• Releasing: one lockstep version, release.mjs, the tag-gated publish workflow, and how the docs site follows a release.
• Contributing: the engine invariants, documentation conventions, and code style.

These pages are the reference. The READMEs in the repository are short pointers back here, plus the build commands for their own folder.