ADR-0004: MSRV policy — current stable minus two releases

• Status: Accepted
• Date: 2026-08-18

Context

Consumers are primarily modern dev tools (Palamedes first), not distro packages. The byte-matching design relies on recent std APIs (e.g. OsStr::as_encoded_bytes, stable since 1.74). A vague or absent MSRV breaks library consumers; an overly conservative one costs API ergonomics.

Decision

MSRV is the current stable minus two releases (~3 months), declared via rust-version in Cargo.toml and verified by a dedicated CI job. A separate scheduled/manual policy check compares that value with Rust's official stable channel metadata; it deliberately does not run on ordinary pull requests, so temporary network failures cannot make routine CI flaky. During 0.x a bump may land in any minor release; from 1.0 on, bumps are minor-version events with a changelog entry.

Consequences

• Modern std APIs are usable without nightly.
• Enterprise/distro users on year-old toolchains are not a target audience.
• The policy is revisited at 1.0.