{
  description = "Storage engine playground: Rust workspace for FlowLog, DBSP, CRDT, and Geomerge experiments.";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    rust-overlay = {
      url = "github:oxalica/rust-overlay";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ rust-overlay.overlays.default ];
        };

        # Pinned to match workspace.package.rust-version in Cargo.toml.
        rustToolchain = pkgs.rust-bin.stable."1.85.0".default.override {
          extensions = [ "rust-src" "rust-analyzer" "clippy" "rustfmt" ];
        };
      in
      {
        devShells.default = pkgs.mkShell {
          name = "storage-engine-playground";

          packages = [
            rustToolchain
            # Diagram regeneration in crates/geomerge-demo/docs/diagrams.
            pkgs.graphviz
            # Cargo helpers.
            pkgs.cargo-watch
            pkgs.cargo-nextest
            # Pre-commit hooks (see .pre-commit-config.yaml, Makefile setup-hooks).
            pkgs.pre-commit
            pkgs.python3
          ];

          env = {
            RUST_BACKTRACE = "1";
          };

          shellHook = ''
            echo "storage-engine-playground dev shell"
            echo "  rustc: $(rustc --version)"
            echo "  cargo: $(cargo --version)"
            echo "  dot:   $(dot -V 2>&1)"
          '';
        };

        formatter = pkgs.nixpkgs-fmt;
      });
}