rust-impl-workspaces

A Cargo workspace is one or more packages (the members) that share a single Cargo.lock, a single target/ directory, and a single root manifest. For any project larger than one crate (binary + reusable library, a CLI plus its core, a monorepo of microservices, a plugin host plus plugins), workspaces are the only correct organisational unit. Without them you get duplicate target/ directories, drifting dependency versions, duplicated metadata, and lockfile divergence across crates.

Cross-references: [[rust-impl-cargo-project]] (single-crate Cargo.toml basics, profiles, features), [[rust-core-language-versions]] (resolver 3 ships with Rust 1.84; edition 2024 defaults to it), [[rust-core-toolchain]] (rust-toolchain.toml and rustup channels for the whole workspace).

When to use this skill

• The user has, or is about to have, more than one crate in the same repository.
• A binary depends on a library that lives in the same repo.
• The user asks "how do I share serde = "1" across all my crates without copy-pasting the version".
• The user wants to set edition = "2024" once and not in every member.
• The user is choosing between resolver = "2" and resolver = "3".
• The user hits "two different versions of serde in one build" (lockfile drift between standalone Cargo projects in the same repo, fixed by promoting them to a workspace).
• The user sees target/ appearing in three different crate directories.