Imported from nfl0/orchard-coppice (AGENTS.md). Install upstream with npx skills add nfl0/orchard-coppice. Copyright stays with the author.

Orchard - Agent Guidelines

Conventions for working in this crate. They mirror the shared conventions in the librustzcash repository's AGENTS.md; when a convention changes in one repo, keep the other aligned. Orchard is #![no_std] (the std feature is optional) and is a payment-protocol crate, so some librustzcash conventions about database / storage layout do not apply, but the ones below do.

Code Conventions

• Never use magic numbers. Do not inline a bare numeric (or string) literal whose meaning is not obvious from context. Give it a const with a doc-commented rationale, and reuse the protocol's own named constants rather than re-deriving their values. This applies to production code, tests, and fixtures alike.

• Public APIs use semantic types, never bare primitives. A pub function, trait method, field accessor, or constructor must not represent a domain quantity as a bare integer, byte array, or scalar: note values are NoteValue, value sums are ValueSum, tree roots are Anchor, commitments are ValueCommitment / ExtractedNoteCommitment, and so on. Reuse the crate's existing newtypes, or introduce one when none exists. Bare primitives are acceptable only for genuinely unitless quantities (counts, indices) and in module-internal arithmetic, converting at the public boundary.

• Keep domain types whole, and convert only at the wire edge. A newtype hides its inner primitive (private field plus a constructor and accessor), so no caller can pass a raw scalar where a value or an anchor is meant. Collections and options carry the newtype too (Vec<NoteValue>, never Vec<u64>). Down-convert to a bare primitive in exactly one place, the serialization / wire boundary, and convert straight back on read.

• Canonical binary serialization lives with the type. A type's on-wire byte format is a property of the type, not of any one consumer: define it next to the definition (read<R: Read>(r) -> io::Result<Self> and write<W: Write>(&self, w) -> io::Result<()>) over corez::io::{Read, Write}, so it stays no_std. Do NOT hand-roll a bespoke byte codec for an orchard type inside a downstream crate, and do NOT use serde for the canonical consensus binary format (reserve serde for JSON / structured metadata such as PCZT proprietary fields and test vectors).

• A proptest strategy lives with the type it generates. An arb_* strategy belongs in that type's module, in a pub mod testing gated #[cfg(any(test, feature = "test-dependencies"))] (e.g. arb_note in note, arb_spending_key in keys, arb_action in action, arb_spendable_note in builder), NOT redefined in each consumer's test module. Before writing an arb_*, search this repo (and the wider ecosystem, e.g. zcash_protocol::value::testing::arb_zatoshis) for an existing one and reuse it; compose canonical leaf strategies into strategies for larger types rather than re-deriving the leaves. Tests receive the generated values as inputs (the strategy is the fixture) and focus on assertions. Downstream crates reuse these strategies through the test-dependencies feature.

Testing

• Property tests use proptest. Expose reusable strategies through the test-dependencies feature in pub mod testing modules (see the strategy convention above), so other crates in the ecosystem reuse them instead of re-deriving fixtures. A #[test] that hand-builds the values it exercises is a smell: extract the value-building into an arb_* and drive the test with it.