Stability policy

This section contains information on how cargo-nextest will evolve in a backwards-compatible way over time.

The cargo-nextest binary

The cargo-nextest binary follows semantic versioning, where the public API consists of exactly the following:

  1. command-line arguments, options and flags
  2. machine-readable output
  3. the configuration file format

Experimental features are not part of the public API. They may change or be removed in a patch release.

Within a version series, the public API will be append-only. New options or keys may be added, but existing keys will continue to be as they were. Existing options may be deprecated but will not be removed within a version series.

The public API does not include human-readable output generated by nextest, or in general anything printed to stderr.


The libraries used by cargo-nextest, nextest-metadata and nextest-runner, follow the standard Rust library versioning policy.


nextest-metadata contains data structures for deserializing cargo-nextest's machine-readable output.

nextest-metadata is forward-compatible with cargo-nextest. A given version of nextest-metadata will continue to work with all future versions of cargo-nextest (within the same version series).

However, currently, nextest-metadata is not backwards-compatible: a new version of nextest-metadata may not be able to parse metadata generated by older versions of cargo-nextest. In other words, each version of nextest-metadata has a minimum supported cargo-nextest version, analogous to a crate's minimum supported Rust version (MSRV).

A bump to the minimum supported cargo-nextest version is considered a breaking change, and will be paired with a major version bump.

(The policy around backwards compatibility may be relaxed in the future based on user needs.)


nextest-runner is built to serve the needs of cargo-nextest. Every cargo-nextest release is likely to correspond to a breaking change to nextest-runner.

Minimum supported Rust version (MSRV)

The MSRV of cargo-nextest or dependent crates may be changed in a patch release. At least the last 3 versions of Rust will be supported at any time.