chore: add pinned Nix devShell

README.md

@@ -10,6 +10,16 @@ This repo is the home of BitGo's WASM libraries.
 
 # Developer Setup
 
+Enter the repository's Nix development shell to load the pinned toolchains:
+
+```bash
+nix develop
+```
+
+The shell provides Node.js 24.11.0 (matching `.nvmrc`), Rust nightly
+2025-10-23 (matching CI), and the WASM build tools. Install the JavaScript
+workspace dependencies from the repository root:
+
 ```bash
 npm install
 ```
@@ -19,6 +29,26 @@ This will:
 - Install all dependencies
 - Set up pre-commit hooks via Husky
 
+# wasm-ton Verification
+
+The wasm-ton npm tests import generated WebAssembly bindings, so build them
+before running the package tests:
+
+```bash
+npm run build:wasm --prefix packages/wasm-ton
+npm test --prefix packages/wasm-ton
+```
+
+Run the Rust parser tests and TypeScript build with:
+
+```bash
+cargo test --manifest-path packages/wasm-ton/Cargo.toml parser_tests
+npm run build:ts --prefix packages/wasm-ton
+```
+
+TypeScript and test tools are installed as npm workspace dependencies; no
+global TypeScript compiler is required.
+
 Pre-commit hooks automatically run on staged files:
 
 - **JS/TS**: Prettier formatting + ESLint

flake.nix

@@ -0,0 +1,52 @@
+{
+  description = "Development environment for BitGoWASM";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    nixpkgs-nodejs.url = "github:nixos/nixpkgs/1d4c88323ac36805d09657d13a5273aea1b34f0c";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = {
+    nixpkgs,
+    nixpkgs-nodejs,
+    rust-overlay,
+    ...
+  }: let
+    systems = [
+      "aarch64-darwin"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "x86_64-linux"
+    ];
+    forEachSystem = nixpkgs.lib.genAttrs systems;
+  in {
+    devShells = forEachSystem (system: let
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [rust-overlay.overlays.default];
+      };
+      rustToolchain = pkgs.rust-bin.nightly."2025-10-23".default.override {
+        extensions = ["clippy" "rustfmt"];
+        targets = ["wasm32-unknown-unknown"];
+      };
+    in {
+      default = pkgs.mkShell {
+        packages = [
+          nixpkgs-nodejs.legacyPackages.${system}.nodejs_24
+          rustToolchain
+          pkgs.binaryen
+          pkgs.gnumake
+          pkgs.wasm-pack
+        ];
+
+        shellHook = ''
+          export PATH="$(pwd)/node_modules/.bin:$PATH"
+        '';
+      };
+    });
+  };
+}