diff --git a/.envrc b/.envrc
new file mode 100644
index 000000000..3550a30f2
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/.gitignore b/.gitignore
index 80e292024..46903fb6d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,3 +35,6 @@ __pycache__/
 
 # Claude Code local preview/dev-server config
 .claude/launch.json
+
+# nix-direnv
+.direnv/
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 000000000..fd09ceec8
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,151 @@
+{
+  description = "Open CAD Studio - 2D drafting and 3D modeling in Rust";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    # rust-overlay ships upstream Rust binaries rather than building them, so
+    # following nixpkgs costs it no binary cache.
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, rust-overlay }:
+    let
+      systems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forAllSystems = f:
+        nixpkgs.lib.genAttrs systems (system: f (import nixpkgs {
+          inherit system;
+          overlays = [ rust-overlay.overlays.default ];
+        }));
+    in
+    {
+      packages = forAllSystems (pkgs:
+        let
+          inherit (pkgs) lib stdenv;
+
+          toolchain = pkgs.rust-bin.stable.latest.default.override {
+            targets = [ "wasm32-unknown-unknown" ];
+          };
+
+          # Build with the overlay's toolchain rather than the nixpkgs default,
+          # so the package and the devShell compile with the same rustc.
+          rustPlatform = pkgs.makeRustPlatform {
+            cargo = toolchain;
+            rustc = toolchain;
+          };
+
+          # winit/wgpu dlopen these at run time, so they must also be on the
+          # wrapped binary's LD_LIBRARY_PATH, not just at link time.
+          runtimeLibs = with pkgs; [
+            libGL
+            libxkbcommon
+            vulkan-loader
+            wayland
+            xorg.libX11
+            xorg.libXcursor
+            xorg.libXi
+            xorg.libXrandr
+          ];
+        in
+        rec {
+          default = opencadstudio;
+
+          opencadstudio = rustPlatform.buildRustPackage {
+            pname = "opencadstudio";
+            version = (lib.importTOML ./Cargo.toml).package.version;
+            src = self;
+
+            cargoLock = {
+              lockFile = ./Cargo.lock;
+              # One entry per distinct git source in Cargo.lock. Replace each
+              # lib.fakeHash with the sha256 that `nix build` prints on the
+              # first attempt; they must be refreshed whenever the matching
+              # rev in Cargo.toml moves.
+              outputHashes = {
+                "acadrust-0.5.5" = lib.fakeHash;
+                "cadkernel-0.1.0" = lib.fakeHash;
+                "iced-0.15.0-dev" = lib.fakeHash;
+                "iced_aw-0.14.1" = lib.fakeHash;
+              };
+            };
+
+            nativeBuildInputs = with pkgs; [
+              pkg-config
+              makeWrapper
+            ];
+
+            buildInputs = with pkgs; [
+              fontconfig
+              freetype
+            ] ++ runtimeLibs
+            ++ lib.optionals stdenv.hostPlatform.isDarwin [ darwin.apple_sdk.frameworks.AppKit ];
+
+            # build.rs asks git for a revision and falls back to "unknown"
+            # when the repo or the binary is absent, which it is in the
+            # sandbox. Nothing to do but let it take the fallback.
+            doCheck = false;
+
+            postInstall = lib.optionalString stdenv.hostPlatform.isLinux ''
+              wrapProgram $out/bin/OpenCADStudio \
+                --prefix LD_LIBRARY_PATH : ${lib.makeLibraryPath runtimeLibs}
+            '';
+
+            meta = {
+              description = "Open-source 2D drafting and 3D modeling, built with Rust";
+              homepage = "https://www.opencadstudio.com";
+              license = lib.licenses.gpl3Only;
+              mainProgram = "OpenCADStudio";
+              platforms = systems;
+            };
+          };
+        });
+
+      devShells = forAllSystems (pkgs:
+        let
+          toolchain = pkgs.rust-bin.stable.latest.default.override {
+            extensions = [ "rust-src" "rust-analyzer" "clippy" "rustfmt" ];
+            targets = [ "wasm32-unknown-unknown" ];
+          };
+          runtimeLibs = with pkgs; [
+            libGL
+            libxkbcommon
+            vulkan-loader
+            wayland
+            xorg.libX11
+            xorg.libXcursor
+            xorg.libXi
+            xorg.libXrandr
+          ];
+        in
+        {
+          default = pkgs.mkShell {
+            packages = with pkgs; [
+              toolchain
+              pkg-config
+              fontconfig
+              freetype
+              git
+              # Web build: `trunk build` per Trunk.toml. wasm-bindgen-cli must
+              # match the wasm-bindgen version Cargo.lock resolves, the same
+              # constraint .github/workflows/pages.yml:83 reads out of the lock.
+              trunk
+              wasm-bindgen-cli
+              # Rasterises assets/logo.svg for packaging, as release.yml does.
+              librsvg
+            ] ++ runtimeLibs;
+
+            # A dev binary is run straight out of ./target, so it never gets
+            # the wrapper the package build applies.
+            LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath runtimeLibs;
+          };
+        });
+
+      checks = forAllSystems (pkgs: {
+        default = self.packages.${pkgs.stdenv.hostPlatform.system}.opencadstudio;
+      });
+
+      formatter = forAllSystems (pkgs: pkgs.nixpkgs-fmt);
+    };
+}