API stability

Arqen is approaching beta, but not every module has the same compatibility promise.

Supported surface

Use arqen::prelude for application code. The prelude includes application state, configuration, storage factories and adapters, validation, modules, jobs, health, and vendor-neutral metrics. arqen::http is the supported HTTP facade; applications do not need to import Axum directly.

The ThingdBackend contract, memory backend, native adapter, HTTP policy, scoped backend, schema report, and Thingd 0.79.0 sync client types are supported public APIs. Sync workers and schema inspection are opt-in operational APIs; Thingd remains authoritative for replication, conflicts, encryption, and migrations. Native thingd's synchronous store remains available as an explicit advanced API, while Arqen's async adapter always runs it on blocking threads.

Experimental surface

Cloud storage and JWKS rotation remain experimental or blocked until Thingd Cloud publishes versioned public contracts. Thingd 0.79.0 synchronization and cursor APIs now have a public contract, but Arqen's worker integration remains experimental and opt-in. Arqen will not define a private replication protocol.

Experimental modules may change without the normal deprecation window. They are marked in Rust documentation and the feature-status table.

SemVer and deprecations

Public types and trait methods follow SemVer. Breaking changes require a major release. Deprecated APIs remain available for at least one minor release when practical and include a replacement in their Rust docs and the migration guide. Internal modules under crates/arqen/src are not a compatibility promise unless re-exported from the crate root or prelude.

Before upgrading, run:

cargo test -p arqen --all-features
cargo clippy -p arqen --all-targets --all-features -- -D warnings
cargo doc -p arqen --all-features --no-deps