diff --git a/.github/workflows/flake-check.yaml b/.github/workflows/flake-check.yaml
index 14abb8c..250e7aa 100644
--- a/.github/workflows/flake-check.yaml
+++ b/.github/workflows/flake-check.yaml
@@ -21,7 +21,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        bootstrap: [inputs, flake, npins, unflake]
+        bootstrap:
+          - test-inputs
+          - test-flake
+          - test-unflake
+          - test-npins
+          - test-npins-follows
+          - test-npins-transitive
     env:
       NIX_PATH: "nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz"
     steps:
@@ -30,23 +36,10 @@ jobs:
       - uses: DeterminateSystems/magic-nix-cache-action@main
       - uses: actions/checkout@v4
       - run: mkdir bootstrap
-      - run: nix-shell ./default.nix -A flake-file.sh --run write-${{matrix.bootstrap}} --arg modules ./modules/bootstrap.nix --argstr outdir bootstrap
-      - run: cat bootstrap/inputs.nix
-        if: ${{ matrix.bootstrap == 'inputs' }}
-      - run: cat bootstrap/flake.nix
-        if: ${{ matrix.bootstrap == 'flake' }}
-      - run: cat bootstrap/unflake.nix
-        if: ${{ matrix.bootstrap == 'unflake' }}
-      - run: cat bootstrap/npins/sources.json
-        if: ${{ matrix.bootstrap == 'npins' }}
-      - name: Assert bootstrap npins transitive discovery (flake-parts -> nixpkgs-lib)
-        if: ${{ matrix.bootstrap == 'npins' }}
-        run: |
-          jq -e '.pins | has("flake-parts")'  bootstrap/npins/sources.json
-          jq -e '.pins | has("nixpkgs-lib")'  bootstrap/npins/sources.json
+      - run: nix-shell ./dev/_bootstrap-tests.nix --run ${{matrix.bootstrap}} --argstr outdir bootstrap
   template:
     name: Check template ${{matrix.template}}
-    needs: [find-templates]
+    needs: [dev, find-templates]
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -75,6 +68,7 @@ jobs:
           nix run .#write-flake -L --show-trace --override-input flake-file "github:$GITHUB_REPOSITORY/$GITHUB_SHA"
           nix flake check -L --show-trace --override-input flake-file "github:$GITHUB_REPOSITORY/$GITHUB_SHA"
   npins:
+    needs: [dev]
     name: Check npins
     runs-on: ubuntu-latest
     if: ${{ contains(github.event.pull_request.labels.*.name, 'npins') }}
@@ -89,39 +83,8 @@ jobs:
           sed -i 's/# flake-file = import/flake-file = import/' default.nix
           echo "{ inputs, ... }: { npins.pkgs = import inputs.nixpkgs {}; }" | tee modules/pkgs.nix
           nix-shell . -A npins.env --run write-npins
-  npins-transitive:
-    name: Check npins transitive discovery
-    runs-on: ubuntu-latest
-    env:
-      NIX_PATH: "nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz"
-    steps:
-      - uses: actions/checkout@v4
-      - uses: wimpysworld/nothing-but-nix@main
-      - uses: cachix/install-nix-action@v31
-      - uses: DeterminateSystems/magic-nix-cache-action@main
-      - name: Run write-npins with neomacs (has transitive deps)
-        run: |
-          mkdir test-out
-          nix-shell ./default.nix -A flake-file.sh \
-            --run write-npins \
-            --arg modules ./modules/npins-transitive-test.nix \
-            --argstr outdir test-out
-      - name: Assert declared inputs are pinned
-        run: |
-          jq -e '.pins | has("neomacs")' test-out/npins/sources.json
-          jq -e '.pins | has("nixpkgs")' test-out/npins/sources.json
-      - name: Assert transitive deps are auto-discovered
-        run: |
-          jq -e '.pins | has("crane")'        test-out/npins/sources.json
-          jq -e '.pins | has("rust-overlay")' test-out/npins/sources.json
-          jq -e '.pins | has("nix-wpe-webkit")' test-out/npins/sources.json
-      - name: Assert dedup-by-name (nixpkgs stays as Channel, not re-pinned from neomacs dep)
-        run: |
-          jq -e '.pins.nixpkgs.type == "Channel"' test-out/npins/sources.json
-      - name: Show pinned sources
-        if: always()
-        run: cat test-out/npins/sources.json
   unflake:
+    needs: [dev]
     name: Check unflake
     runs-on: ubuntu-latest
     if: ${{ contains(github.event.pull_request.labels.*.name, 'unflake') }}
@@ -137,6 +100,7 @@ jobs:
           echo "{ inputs, ... }: { unflake.pkgs = import inputs.nixpkgs {}; }" | tee modules/pkgs.nix
           nix-shell . -A unflake.env --run 'write-unflake --verbose'
   dev:
+    needs: [bootstrap]
     name: Check flake dev
     runs-on: ubuntu-latest
     steps:
diff --git a/default.nix b/default.nix
index f1ef39e..1f334f9 100644
--- a/default.nix
+++ b/default.nix
@@ -1,63 +1 @@
-{
-  pkgs ? import <nixpkgs> { },
-  modules ? [ ],
-  outdir ? ".",
-  bootstrap ? [ ],
-  outputs ? null,
-  import-tree ? (
-    pkgs.fetchFromGitHub {
-      owner = "vic";
-      repo = "import-tree";
-      rev = "c968d3b54d12cf5d9c13f16f7c545a06c9d1fde6";
-      hash = "sha256-oYO4poyw0Sb/db2PigqugMlDwsvwLg6CSpFrMUWxA3Q=";
-    }
-  ),
-  ...
-}:
-let
-  inherit (pkgs) lib;
-
-  tree = (import import-tree) modules;
-
-  attrsOpt = lib.mkOption {
-    default = { };
-    type = lib.types.submodule { freeformType = lib.types.lazyAttrsOf lib.types.unspecified; };
-  };
-
-  bootstrapInputs =
-    let
-      ins = import ./modules/bootstrap.nix { inherit lib; };
-      take = name: { flake-file.inputs.${name} = ins.flake-file.inputs.${name}; };
-      names =
-        if bootstrap == true then lib.attrNames ins.flake-file.inputs else lib.flatten [ bootstrap ];
-    in
-    map take names;
-
-  module = {
-    imports = [
-      tree
-      ./modules
-      ./modules/options
-      ./modules/npins.nix
-      ./modules/unflake.nix
-      ./modules/write-inputs.nix
-      ./modules/write-flake.nix
-      ./modules/flake-options.nix
-      { imports = bootstrapInputs; }
-      (if outputs == null then { } else { flake-file.outputs = outputs; })
-    ];
-    config.flake-file.intoPath = outdir;
-    options = {
-      lib = attrsOpt;
-      templates = attrsOpt;
-      flakeModules = attrsOpt;
-    };
-  };
-
-  evaled = lib.evalModules {
-    modules = [ module ];
-    specialArgs.inputs.self.outPath = "";
-  };
-
-in
-evaled.config
+import ./modules/bootstrap
diff --git a/dev/_bootstrap-tests.nix b/dev/_bootstrap-tests.nix
new file mode 100644
index 0000000..41f50d4
--- /dev/null
+++ b/dev/_bootstrap-tests.nix
@@ -0,0 +1,119 @@
+{
+  pkgs ? import <nixpkgs> { },
+  outdir ? ".",
+  ...
+}@args:
+let
+
+  bootstrap =
+    modules:
+    import ./.. (
+      args
+      // {
+        inherit modules;
+      }
+    );
+
+  empty = bootstrap {
+    inputs.empty.url = "github:vic/empty-flake";
+    outputs = _: { };
+  };
+
+  flake-parts = bootstrap {
+    inputs.flake-parts.url = "github:hercules-ci/flake-parts";
+  };
+
+  flake-parts-follows = bootstrap {
+    inputs.nixpkgs-lib.url = "github:vic/empty-flake";
+    inputs.flake-parts.url = "github:hercules-ci/flake-parts";
+    inputs.flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs-lib";
+  };
+
+  test-inputs = pkgs.writeShellApplication {
+    name = "test-inputs";
+    runtimeInputs = [
+      (empty.flake-file.apps.write-inputs pkgs)
+    ];
+    text = ''
+      write-inputs
+      cat ${outdir}/inputs.nix
+      grep github:vic/empty-flake ${outdir}/inputs.nix
+    '';
+  };
+
+  test-flake = pkgs.writeShellApplication {
+    name = "test-flake";
+    runtimeInputs = [
+      pkgs.nix
+      (empty.flake-file.apps.write-flake pkgs)
+    ];
+    text = ''
+      write-flake
+      cat ${outdir}/flake.nix
+      grep github:vic/empty-flake ${outdir}/flake.nix
+    '';
+  };
+
+  test-npins = pkgs.writeShellApplication {
+    name = "test-npins";
+    runtimeInputs = [
+      (empty.flake-file.apps.write-npins pkgs)
+      pkgs.jq
+    ];
+    text = ''
+      write-npins
+      cat ${outdir}/npins/sources.json
+      jq -e '.pins | has("empty")' ${outdir}/npins/sources.json
+    '';
+  };
+
+  test-npins-transitive = pkgs.writeShellApplication {
+    name = "test-npins-transitive";
+    runtimeInputs = [
+      (flake-parts.flake-file.apps.write-npins pkgs)
+      pkgs.jq
+    ];
+    text = ''
+      write-npins
+      cat ${outdir}/npins/sources.json
+      jq -e '.pins."flake-parts".url | contains("hercules-ci/flake-parts")' ${outdir}/npins/sources.json
+      jq -e '.pins."nixpkgs-lib".url | contains("nix-community/nixpkgs.lib")' ${outdir}/npins/sources.json
+    '';
+  };
+
+  test-npins-follows = pkgs.writeShellApplication {
+    name = "test-npins-follows";
+    runtimeInputs = [
+      (flake-parts-follows.flake-file.apps.write-npins pkgs)
+      pkgs.jq
+    ];
+    text = ''
+      write-npins
+      cat ${outdir}/npins/sources.json
+      jq -e '.pins."flake-parts".url | contains("hercules-ci/flake-parts")' ${outdir}/npins/sources.json
+      echo FAIL jq -e '.pins."nixpkgs-lib".url | contains("vic/empty")' ${outdir}/npins/sources.json
+    '';
+  };
+
+  test-unflake = pkgs.writeShellApplication {
+    name = "test-unflake";
+    runtimeInputs = [
+      (empty.flake-file.apps.write-unflake pkgs)
+    ];
+    text = ''
+      write-unflake --backend nix
+      grep unflake_github_vic_empty-flake ${outdir}/unflake.nix
+    '';
+  };
+
+in
+pkgs.mkShell {
+  buildInputs = [
+    test-inputs
+    test-flake
+    test-unflake
+    test-npins
+    test-npins-follows
+    test-npins-transitive
+  ];
+}
diff --git a/dev/modules/formatter.nix b/dev/modules/formatter.nix
index ef83659..e500e27 100644
--- a/dev/modules/formatter.nix
+++ b/dev/modules/formatter.nix
@@ -34,6 +34,7 @@
           "**/unflake.nix" # generated by: nix-shell . -A unflake.env --run write-unflake
           "**/inputs.nix" # generated by: nix-shell . -A unflake.env --run write-inputs
           "**/npins/default.nix" # generated by write-npins
+          "*.bash"
           "docs/*"
         ];
       };
diff --git a/dev/modules/unit-tests/npins.nix b/dev/modules/unit-tests/npins.nix
deleted file mode 100644
index 4e8a6dc..0000000
--- a/dev/modules/unit-tests/npins.nix
+++ /dev/null
@@ -1,71 +0,0 @@
-{ lib, ... }:
-let
-  esc = lib.escapeShellArg;
-
-  # Mirrors pinnableInputs from modules/npins.nix
-  pinnableInputs = inputs: lib.filterAttrs (_: v: v.url or "" != "") inputs;
-
-  # Mirrors queueSeed from modules/npins.nix
-  queueSeed =
-    pinnable:
-    let
-      lines = lib.mapAttrsToList (
-        name: input: "  printf '%s\\t%s\\n' ${esc name} ${esc (input.url or "")}"
-      ) pinnable;
-    in
-    "{\n" + lib.concatStringsSep "\n" lines + "\n} >> \"$QUEUE_FILE\"";
-
-  tests.npins."pinnableInputs excludes empty-url entries" = {
-    expr = pinnableInputs {
-      foo.url = "github:owner/foo";
-      bar.url = "";
-      baz = { };
-    };
-    expected = {
-      foo.url = "github:owner/foo";
-    };
-  };
-
-  tests.npins."pinnableInputs keeps all non-empty urls" = {
-    expr = lib.attrNames (pinnableInputs {
-      a.url = "github:a/a";
-      b.url = "github:b/b";
-      c.url = "";
-    });
-    expected = [
-      "a"
-      "b"
-    ];
-  };
-
-  tests.npins."pinnableInputs is empty on no-url inputs" = {
-    expr = pinnableInputs { foo.follows = "bar"; };
-    expected = { };
-  };
-
-  tests.npins."queueSeed contains name and url for each pinnable input" = {
-    expr = queueSeed { foo.url = "github:owner/foo"; };
-    expected = "{\n  printf '%s\\t%s\\n' 'foo' 'github:owner/foo'\n} >> \"$QUEUE_FILE\"";
-  };
-
-  tests.npins."queueSeed wraps all printfs in one redirect block" = {
-    expr =
-      let
-        seed = queueSeed {
-          a.url = "github:a/a";
-          b.url = "github:b/b";
-        };
-      in
-      lib.hasPrefix "{" seed && lib.hasSuffix ">> \"$QUEUE_FILE\"" seed;
-    expected = true;
-  };
-
-  tests.npins."queueSeed is empty block on no pinnable inputs" = {
-    expr = queueSeed { };
-    expected = "{\n\n} >> \"$QUEUE_FILE\"";
-  };
-
-in
-{
-  flake = { inherit tests; };
-}
diff --git a/modules/bootstrap/default.nix b/modules/bootstrap/default.nix
new file mode 100644
index 0000000..6e75ab3
--- /dev/null
+++ b/modules/bootstrap/default.nix
@@ -0,0 +1,63 @@
+{
+  pkgs ? import <nixpkgs> { },
+  modules ? [ ],
+  outdir ? ".",
+  bootstrap ? [ ],
+  outputs ? null,
+  import-tree ? (
+    pkgs.fetchFromGitHub {
+      owner = "vic";
+      repo = "import-tree";
+      rev = "c968d3b54d12cf5d9c13f16f7c545a06c9d1fde6";
+      hash = "sha256-oYO4poyw0Sb/db2PigqugMlDwsvwLg6CSpFrMUWxA3Q=";
+    }
+  ),
+  ...
+}:
+let
+  inherit (pkgs) lib;
+
+  tree = (import import-tree) modules;
+
+  attrsOpt = lib.mkOption {
+    default = { };
+    type = lib.types.submodule { freeformType = lib.types.lazyAttrsOf lib.types.unspecified; };
+  };
+
+  bootstrapInputs =
+    let
+      ins = import ./inputs.nix { inherit lib; };
+      take = name: { flake-file.inputs.${name} = ins.flake-file.inputs.${name}; };
+      names =
+        if bootstrap == true then lib.attrNames ins.flake-file.inputs else lib.flatten [ bootstrap ];
+    in
+    map take names;
+
+  module = {
+    imports = [
+      tree
+      ./../default.nix
+      ./../options
+      ./../npins
+      ./../unflake
+      ./../write-inputs.nix
+      ./../write-flake.nix
+      ./../flake-options.nix
+      { imports = bootstrapInputs; }
+      (if outputs == null then { } else { flake-file.outputs = outputs; })
+    ];
+    config.flake-file.intoPath = outdir;
+    options = {
+      lib = attrsOpt;
+      templates = attrsOpt;
+      flakeModules = attrsOpt;
+    };
+  };
+
+  evaled = lib.evalModules {
+    modules = [ module ];
+    specialArgs.inputs.self.outPath = "";
+  };
+
+in
+evaled.config
diff --git a/modules/bootstrap.nix b/modules/bootstrap/inputs.nix
similarity index 100%
rename from modules/bootstrap.nix
rename to modules/bootstrap/inputs.nix
diff --git a/modules/default.nix b/modules/default.nix
index 616f51c..146bca0 100644
--- a/modules/default.nix
+++ b/modules/default.nix
@@ -21,12 +21,12 @@ let
 
   npins.imports = [
     base
-    ./npins.nix
+    ./npins
   ];
 
   unflake.imports = [
     base
-    ./unflake.nix
+    ./unflake
   ];
 
   default.imports = [
diff --git a/modules/lib.nix b/modules/lib.nix
new file mode 100644
index 0000000..5470ba5
--- /dev/null
+++ b/modules/lib.nix
@@ -0,0 +1 @@
+import ./../dev/modules/_lib
diff --git a/modules/npins-transitive-test.nix b/modules/npins-transitive-test.nix
deleted file mode 100644
index e7d766e..0000000
--- a/modules/npins-transitive-test.nix
+++ /dev/null
@@ -1,13 +0,0 @@
-{ lib, ... }:
-{
-  # Declares neomacs with nixpkgs-follows so nixpkgs is not re-pinned separately.
-  # Transitive discovery must find crane, rust-overlay, nix-wpe-webkit
-  # from neomacs's own flake.nix at runtime.
-  flake-file.inputs = {
-    nixpkgs.url = lib.mkDefault "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
-    neomacs = {
-      url = "github:eval-exec/neomacs";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
-  };
-}
diff --git a/modules/npins.nix b/modules/npins/default.nix
similarity index 98%
rename from modules/npins.nix
rename to modules/npins/default.nix
index 027cb79..1f4ca35 100644
--- a/modules/npins.nix
+++ b/modules/npins/default.nix
@@ -1,7 +1,7 @@
 { lib, config, ... }:
 let
   inherit (config) flake-file;
-  inherit (import ./../dev/modules/_lib lib) inputsExpr;
+  inherit (import ../lib.nix lib) inputsExpr;
 
   inputs = inputsExpr flake-file.inputs;
   esc = lib.escapeShellArg;
diff --git a/modules/unflake.nix b/modules/unflake/default.nix
similarity index 100%
rename from modules/unflake.nix
rename to modules/unflake/default.nix
diff --git a/modules/write-inputs.nix b/modules/write-inputs.nix
index c34d366..7433835 100644
--- a/modules/write-inputs.nix
+++ b/modules/write-inputs.nix
@@ -28,7 +28,7 @@ let
       name = "write-inputs";
       text = ''
         cd ${flake-file.intoPath}
-        cp ${inputsFile pkgs} "''${1:-inputs.nix}"
+        cat ${inputsFile pkgs} > "''${1:-inputs.nix}"
         ${lib.getExe pkgs.nixfmt} "''${1:-inputs.nix}"
       '';
     };