BuildContext

A build-time "CompositionLocal for mosaic-server" — a ThreadLocal-backed ambient value store, modeled directly on Jetpack Compose's own CompositionLocal mechanism, letting a value set by an outer block of the DSL (via CompositionLocalProvider) reach a builder several levels deep without every intermediate function threading it through as an explicit parameter.

Not read/written directly by DSL authors — dev.catbit.mosaic.server.builder.composition_local.CompositionLocal.current reads through get, CompositionLocalProvider overrides via with, and dev.catbit.mosaic.server.builder.GenericBuilderScope snapshots/restores a builder's own values around its dev.catbit.mosaic.server.builder.GenericBuilder.build call — that snapshot/restore dance (not just a plain "current ambient value") is what keeps a builder's ambient state correct even though build() may run later, and at a different call-stack depth, than the DSL call that registered it.

snapshotLocals()-style reads must happen before a builder is handed to addBuilder(), never inside the lambda passed to it — by the time that lambda runs, the CompositionLocalProvider block that set the value may have already restored the previous one.