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# Periscope Cursor Engineering Rules

Mandatory for every Cursor agent working on Periscope. This section is copied from `docs/development/CODING_CONSTITUTION.md` and must not contradict that master.

## 3. Rust

- Periscope’s product code is Python/TypeScript today. If a Rust crate is added, it is original Periscope code, not a paste of an AGPL PinScope module.
- Rust slices follow the same verify-then-switch rule: tests first, then wire into the Python/TS surface.
- Use `rustfmt` + `clippy` on that crate. No `unsafe` without a comment that names the invariant.
- Do not introduce Rust to dodge AGPL or to empty-delete Python in `dependency/`.