diff --git a/pkgs/clan-cli/clan_cli/machines/inventory.py b/pkgs/clan-cli/clan_cli/machines/inventory.py
index 0eeac102c..a2b6397bf 100644
--- a/pkgs/clan-cli/clan_cli/machines/inventory.py
+++ b/pkgs/clan-cli/clan_cli/machines/inventory.py
@@ -1,4 +1,5 @@
 import json
+import os
 from pathlib import Path
 
 from clan_cli.clan_uri import FlakeId
@@ -16,6 +17,10 @@ def get_all_machines(flake: FlakeId, nix_options: list[str]) -> list[Machine]:
         nix_build([f'{flake}#clanInternals.all-machines-json."{system}"'])
     ).stdout
 
+    tmp_store = os.environ.get("TMP_STORE", None)
+    if tmp_store:
+        json_path = f"{tmp_store}/{json_path}"
+
     machines_json = json.loads(Path(json_path.rstrip()).read_text())
 
     machines = []
diff --git a/pkgs/clan-cli/clan_cli/machines/machines.py b/pkgs/clan-cli/clan_cli/machines/machines.py
index be7547263..ff06ebf1f 100644
--- a/pkgs/clan-cli/clan_cli/machines/machines.py
+++ b/pkgs/clan-cli/clan_cli/machines/machines.py
@@ -1,6 +1,7 @@
 import importlib
 import json
 import logging
+import os
 from dataclasses import dataclass, field
 from functools import cached_property
 from pathlib import Path
@@ -329,6 +330,10 @@ class Machine:
             return self._build_cache[attr]
 
         output = self.nix("build", attr, extra_config, nix_options)
+        assert isinstance(output, Path), "Nix build did not result in a single path"
+        tmp_store = os.environ.get("TMP_STORE", None)
+        if tmp_store is not None:
+            output = Path(f"{tmp_store}/{output!s}")
         if isinstance(output, Path):
             self._build_cache[attr] = output
             return output
diff --git a/pkgs/clan-cli/clan_cli/nix/__init__.py b/pkgs/clan-cli/clan_cli/nix/__init__.py
index a7cef7f63..d1dc6a083 100644
--- a/pkgs/clan-cli/clan_cli/nix/__init__.py
+++ b/pkgs/clan-cli/clan_cli/nix/__init__.py
@@ -10,7 +10,11 @@ from clan_cli.errors import ClanError
 
 
 def nix_command(flags: list[str]) -> list[str]:
-    return ["nix", "--extra-experimental-features", "nix-command flakes", *flags]
+    args = ["nix", "--extra-experimental-features", "nix-command flakes", *flags]
+    store = os.environ.get("TMP_STORE", None)
+    if store:
+        args += ["--store", store]
+    return args
 
 
 def nix_flake_show(flake_url: str | Path) -> list[str]:
diff --git a/pkgs/clan-cli/default.nix b/pkgs/clan-cli/default.nix
index 2ff012557..dcfc96454 100644
--- a/pkgs/clan-cli/default.nix
+++ b/pkgs/clan-cli/default.nix
@@ -150,14 +150,38 @@ python3.pkgs.buildPythonApplication {
           '';
       clan-pytest-with-core =
         runCommand "clan-pytest-with-core"
-          { nativeBuildInputs = [ pythonWithTestDeps ] ++ testDependencies; }
+          {
+            nativeBuildInputs = [ pythonWithTestDeps ] ++ testDependencies;
+            buildInputs = [
+              pkgs.bash
+              pkgs.coreutils
+              pkgs.nix
+            ];
+            closureInfo = pkgs.closureInfo {
+              rootPaths = [
+                pkgs.bash
+                pkgs.coreutils
+                pkgs.jq.dev
+                pkgs.stdenv
+                pkgs.stdenvNoCC
+              ];
+            };
+          }
           ''
             cp -r ${source} ./src
             chmod +w -R ./src
             cd ./src
 
             export CLAN_CORE=${clan-core-path}
-            export NIX_STATE_DIR=$TMPDIR/nix IN_NIX_SANDBOX=1 PYTHONWARNINGS=error
+            export NIX_STATE_DIR=$TMPDIR/nix
+            export IN_NIX_SANDBOX=1
+            export PYTHONWARNINGS=error
+            export TMP_STORE=$TMPDIR/store
+            # required to prevent concurrent 'nix flake lock' operations
+            export LOCK_NIX=$TMPDIR/nix_lock
+            mkdir -p $TMP_STORE/nix/store
+            xargs cp --recursive --target "$TMP_STORE/nix/store"  < "$closureInfo/store-paths"
+            nix-store --load-db --store $TMP_STORE < "$closureInfo/registration"
             ${pythonWithTestDeps}/bin/python -m pytest -m "not impure and with_core" ./tests
             touch $out
           '';
diff --git a/pkgs/clan-cli/flake-module.nix b/pkgs/clan-cli/flake-module.nix
index 297c4ee8d..5aadcaca2 100644
--- a/pkgs/clan-cli/flake-module.nix
+++ b/pkgs/clan-cli/flake-module.nix
@@ -14,30 +14,88 @@
     let
       flakeLock = lib.importJSON (self + /flake.lock);
       flakeInputs = builtins.removeAttrs inputs [ "self" ];
-      flakeLockVendoredDeps = flakeLock // {
-        nodes =
-          flakeLock.nodes
-          // (lib.flip lib.mapAttrs flakeInputs (
-            name: _:
-            flakeLock.nodes.${name}
-            // {
-              locked = {
-                inherit (flakeLock.nodes.${name}.locked) narHash;
-                lastModified =
-                  # lol, nixpkgs has a different timestamp on the fs???
-                  if name == "nixpkgs" then 0 else 1;
-                path = "${inputs.${name}}";
-                type = "path";
-              };
-            }
-          ));
+      flakeLockVendoredDeps =
+        flakeLock:
+        flakeLock
+        // {
+          nodes =
+            flakeLock.nodes
+            // (lib.flip lib.mapAttrs flakeInputs (
+              name: _:
+              # remove follows and let 'nix flake lock' re-compute it later
+              # (lib.removeAttrs flakeLock.nodes.${name} ["inputs"])
+              flakeLock.nodes.${name}
+              // {
+                locked = {
+                  inherit (flakeLock.nodes.${name}.locked) narHash;
+                  lastModified =
+                    # lol, nixpkgs has a different timestamp on the fs???
+                    if name == "nixpkgs" then 0 else 1;
+                  path = "${inputs.${name}}";
+                  type = "path";
+                };
+              }
+            ));
+        };
+      clanCoreLock = flakeLockVendoredDeps flakeLock;
+      clanCoreLockFile = builtins.toFile "clan-core-flake.lock" (builtins.toJSON clanCoreLock);
+      clanCoreNode = {
+        inputs = lib.mapAttrs (name: _input: name) flakeInputs;
+        locked = {
+          lastModified = 1;
+          path = "${self}";
+          type = "path";
+        };
+        original = {
+          type = "tarball";
+          url = "https://git.clan.lol/clan/clan-core/archive/main.tar.gz";
+        };
       };
-      flakeLockFile = builtins.toFile "clan-core-flake.lock" (builtins.toJSON flakeLockVendoredDeps);
-      clanCoreWithVendoredDeps = pkgs.runCommand "clan-core-with-vendored-deps" { } ''
-        cp -r ${self} $out
-        chmod +w -R $out
-        cp ${flakeLockFile} $out/flake.lock
-      '';
+      # generate a lock file that nix will accept for our flake templates,
+      # in order to not require internet access during tests.
+      templateLock = clanCoreLock // {
+        nodes = clanCoreLock.nodes // {
+          clan-core = clanCoreNode;
+          nixpkgs-lib = clanCoreLock.nodes.nixpkgs; # required by flake-parts
+          root = clanCoreLock.nodes.root // {
+            inputs = clanCoreLock.nodes.root.inputs // {
+              clan-core = "clan-core";
+              nixpkgs = "nixpkgs";
+              nixpkgs-lib = "nixpkgs-lib";
+            };
+          };
+        };
+      };
+      templateLockFile = builtins.toFile "template-flake.lock" (builtins.toJSON templateLock);
+      clanCoreWithVendoredDeps =
+        pkgs.runCommand "clan-core-with-vendored-deps"
+          {
+            buildInputs = [
+              pkgs.findutils
+              pkgs.git
+              pkgs.jq
+              pkgs.nix
+            ];
+          }
+          ''
+            set -e
+            export HOME=$(realpath .)
+            export NIX_STATE_DIR=$HOME
+            cp -r ${self} $out
+            chmod +w -R $out
+            cp ${clanCoreLockFile} $out/flake.lock
+            nix flake lock $out --extra-experimental-features 'nix-command flakes'
+            clanCoreHash=$(nix hash path ${self} --extra-experimental-features 'nix-command')
+            for templateDir in $(find $out/templates -mindepth 1 -maxdepth 1 -type d); do
+              if ! [ -e "$templateDir/flake.nix" ]; then
+                continue
+              fi
+              cp ${templateLockFile} $templateDir/flake.lock
+              cat $templateDir/flake.lock | jq ".nodes.\"clan-core\".locked.narHash = \"$clanCoreHash\"" > $templateDir/flake.lock.final
+              mv $templateDir/flake.lock.final $templateDir/flake.lock
+              nix flake lock $templateDir --extra-experimental-features 'nix-command flakes'
+            done
+          '';
     in
     {
       devShells.clan-cli = pkgs.callPackage ./shell.nix {
diff --git a/pkgs/clan-cli/tests/fixtures_flakes.py b/pkgs/clan-cli/tests/fixtures_flakes.py
index c9b7f2e15..2e92f1006 100644
--- a/pkgs/clan-cli/tests/fixtures_flakes.py
+++ b/pkgs/clan-cli/tests/fixtures_flakes.py
@@ -11,11 +11,16 @@ from typing import Any, NamedTuple
 
 import pytest
 from clan_cli.dirs import nixpkgs_source
+from clan_cli.locked_open import locked_open
 from fixture_error import FixtureError
 from root import CLAN_CORE
 
 log = logging.getLogger(__name__)
 
+lock_nix = os.environ.get("LOCK_NIX", "")
+if not lock_nix:
+    lock_nix = tempfile.NamedTemporaryFile().name  # NOQA: SIM115
+
 
 # allows defining nested dictionary in a single line
 def def_value() -> defaultdict:
@@ -151,13 +156,20 @@ class ClanFlake:
         sp.run(["chmod", "+w", "-R", str(self.path)], check=True)
         self.substitute()
         if not (self.path / ".git").exists():
-            sp.run(
-                ["nix", "flake", "lock"],
-                cwd=self.path,
-                check=True,
-            )
-            with pytest.MonkeyPatch.context() as mp:
-                init_git(mp, self.path)
+            with locked_open(Path(lock_nix), "w"):
+                sp.run(
+                    [
+                        "nix",
+                        "flake",
+                        "lock",
+                        "--extra-experimental-features",
+                        "flakes nix-command",
+                    ],
+                    cwd=self.path,
+                    check=True,
+                )
+                with pytest.MonkeyPatch.context() as mp:
+                    init_git(mp, self.path)
 
     def refresh(self) -> None:
         if not self.path.exists():
diff --git a/pkgs/clan-cli/tests/test_vars.py b/pkgs/clan-cli/tests/test_vars.py
index 16a8bbee3..6335fedf1 100644
--- a/pkgs/clan-cli/tests/test_vars.py
+++ b/pkgs/clan-cli/tests/test_vars.py
@@ -93,7 +93,7 @@ def test_required_generators() -> None:
     ]
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generate_public_var(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -128,7 +128,7 @@ def test_generate_public_var(
     assert json.loads(vars_eval) == "hello\n"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generate_secret_var_sops(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -166,7 +166,7 @@ def test_generate_secret_var_sops(
 
 
 # TODO: it doesn't actually test if the group has access
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generate_secret_var_sops_with_default_group(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -219,7 +219,7 @@ def test_generate_secret_var_sops_with_default_group(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generated_shared_secret_sops(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -264,7 +264,7 @@ def test_generated_shared_secret_sops(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generate_secret_var_password_store(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -316,7 +316,7 @@ def test_generate_secret_var_password_store(
     assert "my_generator/my_secret" in vars_text
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_generate_secret_for_multiple_machines(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -378,7 +378,7 @@ def test_generate_secret_for_multiple_machines(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_dependant_generators(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -409,7 +409,7 @@ def test_dependant_generators(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 @pytest.mark.parametrize(
     ("prompt_type", "input_value"),
     [
@@ -447,7 +447,7 @@ def test_prompt(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_share_flag(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -514,7 +514,7 @@ def test_share_flag(
     assert json.loads(vars_eval) == "hello\n"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_depending_on_shared_secret_succeeds(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -540,7 +540,7 @@ def test_depending_on_shared_secret_succeeds(
     cli.run(["vars", "generate", "--flake", str(flake.path), "my_machine"])
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_prompt_create_file(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -572,7 +572,7 @@ def test_prompt_create_file(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_api_get_prompts(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -595,7 +595,7 @@ def test_api_get_prompts(
     assert api_prompts[0].prompts[0].previous_value == "input1"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_api_set_prompts(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -634,7 +634,7 @@ def test_api_set_prompts(
     assert store.get(Generator("my_generator"), "prompt1").decode() == "input2"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_commit_message(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -691,7 +691,7 @@ def test_commit_message(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_default_value(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -728,7 +728,7 @@ def test_default_value(
     assert json.loads(value_eval) == "hello"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_stdout_of_generate(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -809,7 +809,7 @@ def test_stdout_of_generate(
     assert "hello" not in output.out
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_migration_skip(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -837,7 +837,7 @@ def test_migration_skip(
     assert in_repo_store.get(Generator("my_generator"), "my_value").decode() == "world"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_migration(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -873,7 +873,7 @@ def test_migration(
     assert sops_store.get(Generator("my_generator"), "my_secret").decode() == "hello"
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_fails_when_files_are_left_from_other_backend(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -915,7 +915,7 @@ def test_fails_when_files_are_left_from_other_backend(
             )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_keygen(
     monkeypatch: pytest.MonkeyPatch,
     temporary_home: Path,
@@ -935,7 +935,7 @@ def test_keygen(
     assert (temporary_home / "sops" / "users" / "user").is_dir()
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_vars_get(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
@@ -962,7 +962,7 @@ def test_vars_get(
     )
 
 
-@pytest.mark.impure
+@pytest.mark.with_core
 def test_invalidation(
     monkeypatch: pytest.MonkeyPatch,
     flake: ClanFlake,
diff --git a/templates/minimal-flake-parts/flake.nix b/templates/minimal-flake-parts/flake.nix
index bf3f961e4..be0c31e8b 100644
--- a/templates/minimal-flake-parts/flake.nix
+++ b/templates/minimal-flake-parts/flake.nix
@@ -1,10 +1,10 @@
 {
   inputs = {
-    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
 
-    clan.url = "git+https://git.clan.lol/clan/clan-core";
-    clan.inputs.nixpkgs.follows = "nixpkgs";
-    clan.inputs.flake-parts.follows = "flake-parts";
+    clan-core.url = "https://git.clan.lol/clan/clan-core/archive/main.tar.gz";
+    clan-core.inputs.nixpkgs.follows = "nixpkgs";
+    clan-core.inputs.flake-parts.follows = "flake-parts";
 
     flake-parts.url = "github:hercules-ci/flake-parts";
     flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
diff --git a/templates/minimal/flake.nix b/templates/minimal/flake.nix
index 78301b9c9..3618b47df 100644
--- a/templates/minimal/flake.nix
+++ b/templates/minimal/flake.nix
@@ -1,5 +1,6 @@
 {
-  inputs.clan-core.url = "git+https://git.clan.lol/clan/clan-core";
+  inputs.clan-core.url = "https://git.clan.lol/clan/clan-core/archive/main.tar.gz";
+  inputs.nixpkgs.follows = "clan-core/nixpkgs";
 
   outputs =
     { self, clan-core, ... }:
diff --git a/templates/new-clan/flake.nix b/templates/new-clan/flake.nix
index 892b0bbd4..10594dcb5 100644
--- a/templates/new-clan/flake.nix
+++ b/templates/new-clan/flake.nix
@@ -2,6 +2,7 @@
   description = "<Put your description here>";
 
   inputs.clan-core.url = "https://git.clan.lol/clan/clan-core/archive/main.tar.gz";
+  inputs.nixpkgs.follows = "clan-core/nixpkgs";
 
   outputs =
     { self, clan-core, ... }: