X-Lifestyle Core — Developer Guide

For anyone building an X-Change mod on top of X-Lifestyle Core (x-lifestyle-core, window.BMFT namespace). Self-contained — this file assumes only that you have Core's own source or a copy of this guide, not a checkout of the xls umbrella repo it's normally developed alongside. If a section here talks about "why," it's giving you enough to use the API correctly, not the full design history — that lives in x-lifestyle-core's own docs/ai/ if you have it.

New to building on Core? Start with Integration Guide instead — declaring the dependency, how the feature-gate/testing-mode system works, and the risk (and safety net) around "testing"-state features. This guide covers individual BMFT.* functions and macros once you're actually calling something specific.

This guide is reviewed on every Core release, not written once and left to rot. See "Keeping this guide honest" at the bottom before you rely on anything here for a version newer than what's in your own CHANGELOG.md.

Layout of this guide: Released features first — live for every player right now, safe to build against without any extra setup. Testing features below that — real, working code, but gated off in a real release build; see that section's own intro for how to switch on a "testing"-state feature while you develop.