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This Month in Hax: August 2026

In August, we successfully merged 46 pull requests!

We extended our CLI functionality significantly: hax can now be installed via cargo binstall cargo-hax, and it can automatically download and manage its aeenas and charon dependencies. Moreover, users can declare proof scenarios in a hax.toml file to specify exactly which options they want to use for a particular project, and then run those scenarios via a new cargo hax extract command.

We extended our models of Rust core further and improved its testing infrastructure to make sure that it is an accurate model of Rust core. These models benefit both the Lean and the F* backend.

For the new Lean backend, we added support for hax_lib::requires, hax_lib::ensures, and other attributes and for the hax_lib::prop and hax_lib::int specification helpers.

This was our final sprint towards a release candidate for hax v0.4.0. The release candidate was published yesterday. Now, we are testing it, fixing bugs, and finalizing its documentation.

Thanks to the many external contributors we had this month!

Full list of PRs

Contributors