nexu-io-open-design/nix

Open Design — Nix flake

This flake exposes Open Design as a reproducible package, a nix run entry point, a dev shell, and Home Manager / NixOS modules. The architecture mirrors the runtime: the daemon (od CLI, Express API on /api/*) and the web frontend (Next.js static SPA at apps/web/out/) are separate packages and separate services — you can run either or both.

Outputs

Output	What it is
packages.<system>.daemon	The @open-design/daemon package — produces bin/od. Default output.
packages.<system>.web	The Next.js static export (apps/web/out/) ready to drop into any static file server.
apps.<system>.default	nix run github:nexu-io/open-design — boots the daemon.
devShells.<system>.default	Node 24 + Corepack-pinned pnpm 10.33 — reproduces pnpm install locally.
homeManagerModules.{default,open-design}	Home Manager module — primary individual-developer interface.
nixosModules.{default,open-design}	NixOS module — secondary, for shared/server installs.

Try it without installing

nix run github:nexu-io/open-design        # boots the daemon on :7457
nix develop github:nexu-io/open-design    # drop into the dev shell

(1) Home Manager — the recommended path

For an individual workstation, add the flake as an input and import the default module:

{
  inputs.open-design.url = "github:nexu-io/open-design";

  outputs = { self, home-manager, open-design, ... }: {
    homeConfigurations.you = home-manager.lib.homeManagerConfiguration {
      modules = [
        open-design.homeManagerModules.default
        {
          services.open-design = {
            enable = true;
            autoStart = true;            # systemd --user / launchd agent
            webFrontend.enable = true;   # also run the static SPA on :5174
          };
        }
      ];
    };
  };
}

What this wires up:

• Linux: systemd --user units open-design.service and (optionally) open-design-web.service. systemctl --user status open-design.
• macOS: launchd agents io.nexu.open-design and (optionally) io.nexu.open-design-web. launchctl print gui/$UID/io.nexu.open-design.
• Data lives in $HOME/.od/ by default — override dataDir to relocate.

(2) NixOS — for shared/server installs

{
  imports = [ inputs.open-design.nixosModules.default ];

  services.open-design = {
    enable = true;
    autoStart = true;
    openFirewall = true;
    webFrontend.enable = true;
    user = "open-design";
    group = "open-design";
  };
}

This creates a system user, drops a tmpfiles rule for /var/lib/open-design, and runs the daemon under hardened systemd (ProtectSystem=strict, PrivateTmp, ReadWritePaths scoped to the data directory). Use this when you want a single shared instance — for individual user configuration prefer the Home Manager module.

(3) webFrontend — when to use it, when to bring your own server

Open Design's frontend is a static SPA that issues relative /api/*, /artifacts/*, and /frames/* requests. Three serving options:

Option	When
webFrontend.enable = true	You want one-line setup. The module spawns a tiny Caddy file server on webFrontend.port (default 5174) that serves the SPA and reverse-proxies the three path prefixes to the daemon.
webFrontend.enable = false (default)	You're running nginx / Caddy / Apache / Traefik yourself. Point your server's document root at ${pkgs.open-design.web} (or the packages.<system>.web output) and replicate the proxy contract in section (4).
Skip the frontend entirely	You only need the daemon's API for headless agent dispatch.

The two services are independent. autoStart controls the daemon; webFrontend.enable controls the static server. Mix freely.

Bring-your-own-server gotcha: if your proxy listens on any origin that differs from the daemon's bind (different host or different port — even loopback split-port like http://127.0.0.1:8080 while the daemon stays on :7457), the daemon's same-origin gate will 403 the SPA's writes until you tell it about that origin. Either set services.open-design.webFrontend.allowedOrigins = [ "<your-proxy-origin>" ] (which feeds OD_ALLOWED_ORIGINS) or, for the loopback-only split-port case, set extraEnv.OD_WEB_PORT = "<proxy-port>". See section (4) for the full decision tree.

Exposing the bundled frontend on a non-loopback host

By default webFrontend.host = "127.0.0.1" so enabling the bundled caddy does not publish anything beyond loopback. To intentionally share with a LAN, two settings must be widened together — the modules assert at eval time that the second is set whenever the first is widened:

services.open-design.webFrontend = {
  enable = true;
  host = "0.0.0.0";  # caddy listener
  # Every external origin browsers will load the SPA from. The daemon
  # matches each entry against the browser's `Origin` header AND adds
  # its host:port to the `Host`-header allowlist (Caddy v2 reverse_proxy
  # preserves the original Host upstream by default), so list each
  # scheme + hostname combo you actually use.
  allowedOrigins = [
    "http://laptop.local:5174"
    "https://laptop.local:5174"
  ];
};
# On NixOS you also need:
services.open-design.openFirewall = true;

Under the hood allowedOrigins is forwarded to the daemon as the OD_ALLOWED_ORIGINS environment variable (comma-separated). If you run the daemon outside the modules — for example, behind your own nginx/caddy — set OD_ALLOWED_ORIGINS directly in the daemon's environment with the same shape:

OD_ALLOWED_ORIGINS=http://host1:port,https://host1:port,http://host2:port

Each entry must be a bare origin (scheme://host[:port]); only http:// and https:// schemes are accepted, and the daemon refuses to start if any entry fails to parse. The variable widens only the general /api/* same-origin gate — connector-credential and live-artifact preview/refresh routes stay strictly loopback-only by design.

(4) Same-origin proxying contract

The web package is built with OD_DAEMON_URL = "" so the bundled JS issues relative requests — /api/*, /artifacts/*, /frames/* — instead of baking a daemon URL into the export. There is no runtime config endpoint; the SPA does not read OD_DAEMON_URL from the serving environment.

The serving contract is therefore: the static export must be served same-origin with a reverse proxy to the daemon. The bundled caddy service does exactly this — webFrontend listens on webFrontend.port and reverse-proxies the three path prefixes above to 127.0.0.1:<cfg.port>, with flush_interval -1 and no encode on /api/* so SSE streams flush immediately (gzip would buffer chunked responses for ~80s and surface as ERR_INCOMPLETE_CHUNKED_ENCODING).

If you serve the static bundle yourself, replicate that shape:

• Document root → ${pkgs.open-design.web} (or packages.<system>.web).
• Reverse-proxy /api/*, /artifacts/*, /frames/* to the daemon's bind address; /api/* must stream chunks immediately and skip response compression.
• SPA fallback for unmatched paths → index.html.

The static-server's environment does not need any Open Design env vars — but the daemon's environment usually does, because its same-origin gate is built from OD_BIND_HOST:port (loopback hosts included). The browser's Origin and Host are whatever your proxy exposes, so unless that matches 127.0.0.1:<daemon-port> exactly, the daemon will 403 every PUT/POST until told otherwise:

Your custom-server setup	What to set on the daemon
Proxy at http://127.0.0.1:<daemon-port> (same host, same port — unusual)	Nothing.
Proxy at a loopback host but different port (e.g. http://127.0.0.1:8080 while daemon is on :7457)	Either extraEnv.OD_WEB_PORT = "8080" (whitelists 8080 on every loopback host) or services.open-design.webFrontend.allowedOrigins.
Proxy on any non-loopback host (LAN IP, mDNS name, Tailscale name, public domain — https://od.example.com, http://laptop.local:5174, …)	services.open-design.webFrontend.allowedOrigins = [ "<full origin>" ]. List every scheme + host[:port] combo a browser might load the SPA from.

webFrontend.allowedOrigins is forwarded to the daemon as OD_ALLOWED_ORIGINS; if you run the daemon outside the modules, export OD_ALLOWED_ORIGINS directly with the same shape (see section (3)). The variable widens only the general /api/* gate — connector-credential and live-artifact preview/refresh routes stay strictly loopback-only by design.

(5) Secrets — DO NOT put them in your Nix config

The environmentFile option takes a path to a KEY=VALUE file that the service unit reads. Use it for BYOK API keys (Anthropic, OpenAI, Gemini), provider tokens, and anything else you do not want world-readable in /nix/store.

Recommended secret managers:

• sops-nix — age- or PGP-encrypted YAML, decrypted into runtime files at activation.
• agenix — age-encrypted single files, dropped into /run/agenix/ at boot.

Either renders to a file like /run/secrets/open-design.env; pass that path:

services.open-design.environmentFile = "/run/secrets/open-design.env";

Never inline a secret with pkgs.writeText or home.file.

First-build hash pinning

Both nix/package-daemon.nix and nix/package-web.nix vendor the pnpm store via a fixed-output derivation (pnpmDeps). The outputHash defaults to lib.fakeSha256 so nix build will fail with the expected hash printed. Copy that value into the matching pnpmDepsHash constant at the top of each file and re-run. Bump the hash whenever pnpm-lock.yaml changes.

CI

.github/workflows/nix-check.yml runs nix flake check on pushes to main and can also be started manually with workflow_dispatch. It is not a default pull request gate: the flake is a community installation and deployment surface, while regular PR validation stays focused on the primary product delivery checks. The flake check already builds the daemon and web checks declared in flake.nix.