Reactive primitives

@starbeam/reactive exposes primitive reactive values for authors building Starbeam primitives, adapters, and integration layers. It is not the normal starting point for app state.

Most app and library models should start with @starbeam/collections, @starbeam/universal, or a framework adapter.

Install

pnpm add @starbeam/reactive

Primitive-building surface

Export	Use for
Cell	Store one reactive value inside a primitive.
Marker	Mark external storage as reactive without storing the value.
Formula	Compute a reactive value every time it is read.
CachedFormula	Cache a reactive computation until one of its reads changes.
Static	Wrap a non-changing value as reactive.
read	Read either a reactive value or a plain value.
CellOptions, Equality, FormulaFn, ReadValue	Helper types for primitive authors.

Use these APIs when the public value you are building is itself a reactive primitive or low-level abstraction. For ordinary app state, prefer reactive objects and collections.

Compatibility and implementor exports

@starbeam/reactive also exports lower-level APIs used by Starbeam adapters, runtime packages, and debug setup:

• tracking frames such as StartTrackingFrame, startFrame, and finishFrame;
• runtime and debug registration such as defineRuntime, defineDebug, DEBUG, and UNKNOWN_REACTIVE_VALUE;
• protocol helpers such as isReactive, isTagged, intoReactive, and isFormulaFn.

These remain exported for compatibility. They are not the app-facing primitive path.

Related docs

• Reactive README
• Collections and objects
• Universal APIs