Law that cannot hide inside a Boolean.
Fidryn (FID-rin) is a programming language for legal instruments: precise where law is mechanical, explicit where judgment enters, and incapable of hiding authority, discretion, or ambiguity inside a Boolean.
Research fixture. Not legal advice, not an operative instrument, and not a complete statement of any jurisdiction’s law.
What it does
No false determinacy
A determinate result only when it is invariant across every still-admissible resolution — or a competent authority has already determined it.
Open branches stay suspended
run never chooses a completion. Empty completion sets are not vacuous determinate answers. Open branches without a covering certificate stay Suspended.
Model boundary carried
Every outcome carries the declared modelBoundary so omitted interpretations cannot silently shrink the model.
Local mill
fidryn ui binds loopback only (default 127.0.0.1:8751). This public site does not expose live filing.
Install
cargo install --git https://github.com/BeeGass/fidryn --locked
Requires Rust 1.98+. Source files use the .fr extension. For a local checkout, cargo install --path crates/fidryn-cli works too. The GitHub repo must be public (or you need access) for --git install.
fidryn check examples/trust/bryan-revocable-trust.fr
fidryn ui --no-open
Mill binds loopback only (default http://127.0.0.1:8751). It checks modules in the browser — it does not live-file.