rust-core-best-practiceslisted

## Outcome Produce a focused Rust change or review that follows the target repository's declared policy, uses idiomatic ownership and failure handling, and reports the exact evidence used to verify it. ## Compatibility Portable across Claude Code, Codex, and OpenCode. Inspect the target repository's selected Rust toolchain, edition, `rust-version`, lockfile, features, targets, and CI commands before applying defaults. Edition 2024 examples require Rust 1.85 or newer. Network access is optional and must be authorized; without it, report any current-source or dependency-version evidence gap. Native client compatibility remains unverified until a dated report records the client version and exact source SHA. ## Inputs - The requested outcome, affected crates or files, and acceptance criteria. - Repository instructions plus `Cargo.toml`, `Cargo.lock`, toolchain files, CI workflows, and nearby Rust code. - Permission to modify project files and to run the repository's existing checks. - Any declared MSRV, platform, feature, unsafe-code, public-API, or compatibility policy. Label assumptions instead of inventing missing policy. Ask only when a choice changes public API, compatibility, permissions, or destructive behavior. ## Safety - Inspect before writing. Preserve unrelated worktree changes and stay inside the requested scope. - Do not install toolchains, dependencies, Cargo subcommands, or system packages implicitly. - Do not commit, switch branches, publish crates, pus