Add a Nix flake

.gitignore

@@ -1,2 +1,3 @@
 /target
 /.idea
+/result

README.md

@@ -22,6 +22,21 @@ cargo test              # 115 tests; the workspace integration tests shell out t
 cargo clippy --all-targets
 ```
 
+## Nix
+
+A flake is provided. It builds faff and wraps the binary so `jj` and `wezterm` are on
+`PATH` at runtime (`claude` still comes from your interactive session, since faff spawns it
+inside a WezTerm pane).
+
+```sh
+nix run github:Jezza/faff              # run without installing
+nix profile install github:Jezza/faff  # install into your profile
+nix develop                            # dev shell with the toolchain + jj + wezterm
+```
+
+To install declaratively, add the flake as an input and reference
+`faff.packages.${system}.default`.
+
 ## Usage
 
 From your repo root, inside WezTerm:

flake.nix

@@ -0,0 +1,79 @@
+{
+  description = "faff — a TUI for running several Claude Code agents in parallel on one repo";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    flake-utils,
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = import nixpkgs {inherit system;};
+
+        # Runtime dependencies faff shells out to by bare name. jj drives the
+        # workspaces and wezterm drives the panes. `claude` is intentionally NOT
+        # here: faff spawns it via `wezterm cli spawn -- claude ...`, so it runs
+        # in the user's interactive shell inside the pane, not from faff's PATH.
+        runtimeDeps = [
+          pkgs.jujutsu # provides `jj`
+          pkgs.wezterm # provides `wezterm`
+        ];
+
+        cargoToml = pkgs.lib.importTOML ./Cargo.toml;
+
+        faff = pkgs.rustPlatform.buildRustPackage {
+          pname = cargoToml.package.name;
+          version = cargoToml.package.version;
+
+          src = self;
+
+          cargoLock.lockFile = ./Cargo.lock;
+
+          nativeBuildInputs = [pkgs.makeWrapper];
+
+          # rusqlite's `bundled` feature compiles SQLite from C; the stdenv cc
+          # covers that, no extra buildInputs needed.
+
+          # The test suite (115 tests) shells out to a real `jj`, which is not
+          # available in the build sandbox, so skip it during the Nix build.
+          doCheck = false;
+
+          postInstall = ''
+            wrapProgram $out/bin/faff \
+              --prefix PATH : ${pkgs.lib.makeBinPath runtimeDeps}
+          '';
+
+          meta = {
+            description = "TUI for running several Claude Code agents in parallel on one repo, each in its own jj workspace and WezTerm pane";
+            homepage = "https://github.com/Jezza/faff";
+            mainProgram = "faff";
+          };
+        };
+      in {
+        packages.default = faff;
+        packages.faff = faff;
+
+        apps.default = {
+          type = "app";
+          program = "${faff}/bin/faff";
+        };
+
+        devShells.default = pkgs.mkShell {
+          inputsFrom = [faff];
+          packages =
+            runtimeDeps
+            ++ [
+              pkgs.cargo
+              pkgs.rustc
+              pkgs.clippy
+              pkgs.rustfmt
+            ];
+        };
+      }
+    );
+}