Software Development Kit

Use a Once language library when an application needs to store and retrieve cache data directly. Use the command line instead when the goal is to execute scripts, build targets, run tests, or manage runtime sessions.

The language libraries intentionally expose the same small cache surface:

• Store and retrieve content-addressed byte payloads.
• Associate an action digest with a completed action result.
• Remove an action result without deleting its referenced payloads.
• Inspect local cache statistics.

They do not execute commands or load the repository graph.

Choose A Language

Language	Package	Call style	Guide
Rust	once crate	Asynchronous	Rust
Swift	Once.xcframework and the matching Swift wrapper	Asynchronous	Swift
Ruby	buildonce gem	Synchronous	Ruby
JavaScript	buildonce package for Node.js	Promise-based	JavaScript

Choose the binding used by the process that owns the integration. All four bindings use compatible digests and action-result concepts, so separate tools can share a configured cache without translating records.

Before You Embed Once

An application using the cache is responsible for defining stable action payloads and deciding which inputs affect them. The library stores completed results, but it cannot determine whether an application omitted an input or whether replaying a result is safe.

Start with the smallest useful operation in the language guide, then add action-result storage only after the application has a deterministic action identity.