Architecture Decision Records for Rust

An Architecture Decision Record (ADR) captures one decision and the reason behind it. ADRs exist so that six months later, when the original engineer has left or forgotten, the next reader can rebuild the constraints rather than guess at them.

In Rust, decisions worth recording tend to encode invariants the compiler is already enforcing — typestate edges, trait bounds, lifetime annotations, unsafe contracts. The ADR is the cover letter the type signature cannot carry.

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