diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
deleted file mode 100644
index 617355d6..00000000
--- a/.github/workflows/lint.yml
+++ /dev/null
@@ -1,75 +0,0 @@
-name: Lint
-
-on: [pull_request]
-
-concurrency:
-  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
-defaults:
-  run:
-    shell: nix develop --fallback --command bash -e {0}
-
-jobs:
-  golangci-lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          fetch-depth: 0
-      - name: Get changed files
-        id: changed-files
-        uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3.0.2
-        with:
-          filters: |
-            files:
-              - '*.nix'
-              - 'go.*'
-              - '**/*.go'
-              - 'integration_test/'
-              - 'config-example.yaml'
-      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
-        if: steps.changed-files.outputs.files == 'true'
-      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
-        if: steps.changed-files.outputs.files == 'true'
-
-      - name: golangci-lint
-        if: steps.changed-files.outputs.files == 'true'
-        run: golangci-lint run
-          --new-from-rev=${{github.event.pull_request.base.sha}}
-          --output.text.path=stdout
-          --output.text.print-linter-name
-          --output.text.print-issued-lines
-          --output.text.colors
-
-  prettier-lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          fetch-depth: 2
-      - name: Get changed files
-        id: changed-files
-        uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3.0.2
-        with:
-          filters: |
-            files:
-              - '*.nix'
-              - '**/*.md'
-              - '**/*.yml'
-              - '**/*.yaml'
-              - '**/*.ts'
-              - '**/*.js'
-              - '**/*.sass'
-              - '**/*.css'
-              - '**/*.scss'
-              - '**/*.html'
-      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
-        if: steps.changed-files.outputs.files == 'true'
-      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
-        if: steps.changed-files.outputs.files == 'true'
-
-      - name: Prettify code
-        if: steps.changed-files.outputs.files == 'true'
-        run: prettier --no-error-on-unmatched-pattern
-          --ignore-unknown --check **/*.{ts,js,md,yaml,yml,sass,css,scss,html}
diff --git a/.github/workflows/nix-checks.yml b/.github/workflows/nix-checks.yml
new file mode 100644
index 00000000..03c4b8e8
--- /dev/null
+++ b/.github/workflows/nix-checks.yml
@@ -0,0 +1,56 @@
+name: Nix Flake Checks
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+# Each job only runs `nix build .#checks.<system>.<name>`; the check logic lives
+# in flake.nix via the flake-checks library. The fileset-filtered checks hit the
+# hestia cache when their inputs are unchanged, so no changed-files gating.
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
+      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
+      - name: build
+        run: nix build -L .#checks.x86_64-linux.build
+
+  gotest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
+      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
+      - name: gotest
+        run: nix build -L .#checks.x86_64-linux.gotest
+
+  golangci-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
+      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
+      - name: golangci-lint
+        run: nix build -L .#checks.x86_64-linux.golangci-lint
+
+  formatting:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
+      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
+      - name: formatting
+        run: nix build -L .#checks.x86_64-linux.formatting
diff --git a/.github/workflows/servertest.yml b/.github/workflows/servertest.yml
new file mode 100644
index 00000000..795b2959
--- /dev/null
+++ b/.github/workflows/servertest.yml
@@ -0,0 +1,36 @@
+name: Server Tests
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+# hscontrol/servertest is excluded from the sandboxed gotest flake check: it is
+# slow (10s+ convergence cases) and timing-sensitive (race/stress/HA property
+# tests), so it runs here in the devShell with a generous timeout instead.
+defaults:
+  run:
+    shell: nix develop --fallback --command bash -e {0}
+
+permissions:
+  contents: read
+
+jobs:
+  servertest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
+      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
+
+      - name: go test ./hscontrol/servertest
+        env:
+          CGO_ENABLED: "0"
+        run: go test -timeout=20m ./hscontrol/servertest/...
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
deleted file mode 100644
index dadacddc..00000000
--- a/.github/workflows/test.yml
+++ /dev/null
@@ -1,47 +0,0 @@
-name: Tests
-
-on: [push, pull_request]
-
-concurrency:
-  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
-defaults:
-  run:
-    shell: nix develop --fallback --command bash -e {0}
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          fetch-depth: 2
-
-      - name: Get changed files
-        id: changed-files
-        uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3.0.2
-        with:
-          filters: |
-            files:
-              - '*.nix'
-              - 'go.*'
-              - '**/*.go'
-              - 'integration_test/'
-              - 'config-example.yaml'
-
-      - uses: NixOS/nix-installer-action@6b8548fe06acfb0155a50ab5d561accb215764cc # main
-        if: steps.changed-files.outputs.files == 'true'
-      - uses: Mic92/hestia/action@ff07bb902a9968ac0c3d0e51d90a606662a375d8 # main
-        if: steps.changed-files.outputs.files == 'true'
-
-      - name: Run tests
-        if: steps.changed-files.outputs.files == 'true'
-        env:
-          # As of 2025-01-06, these env vars was not automatically
-          # set anymore which breaks the initdb for postgres on
-          # some of the database migration tests.
-          LC_ALL: "en_US.UTF-8"
-          LC_CTYPE: "en_US.UTF-8"
-        run: gotestsum
diff --git a/flake.lock b/flake.lock
index 81b43806..c723d287 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,5 +1,27 @@
 {
   "nodes": {
+    "flake-checks": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "treefmt-nix": "treefmt-nix"
+      },
+      "locked": {
+        "lastModified": 1781951072,
+        "narHash": "sha256-hA9u6hB4QzpReP8hudxqiaa4vLhoRvtXi6YmUgJRGEs=",
+        "owner": "kradalby",
+        "repo": "flake-checks",
+        "rev": "3d2882efec5cf10f8b5a8a035d93ba6ba9f21717",
+        "type": "github"
+      },
+      "original": {
+        "owner": "kradalby",
+        "repo": "flake-checks",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -18,6 +40,24 @@
         "type": "github"
       }
     },
+    "flake-utils_2": {
+      "inputs": {
+        "systems": "systems_2"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1781153106,
@@ -36,7 +76,8 @@
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
+        "flake-checks": "flake-checks",
+        "flake-utils": "flake-utils_2",
         "nixpkgs": "nixpkgs"
       }
     },
@@ -54,6 +95,42 @@
         "repo": "default",
         "type": "github"
       }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "flake-checks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1780220602,
+        "narHash": "sha256-eynAfOmbmxJnkp7YewvCEbShNnnYJ9gLLqkzsYtBPeM=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "db947814a175b7ca6ded66e21383d938df01c227",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
     }
   },
   "root": "root",
diff --git a/flake.nix b/flake.nix
index 78daf742..0513aed7 100644
--- a/flake.nix
+++ b/flake.nix
@@ -9,12 +9,17 @@
     # once it ships go_1_26 >= 1.26.4.
     nixpkgs.url = "github:NixOS/nixpkgs/staging-next-26.05";
     flake-utils.url = "github:numtide/flake-utils";
+    # Reusable Go flake checks (build/test/lint/format); CI runs them via
+    # `nix build .#checks.<system>.<name>` instead of bespoke per-tool steps.
+    flake-checks.url = "github:kradalby/flake-checks";
+    flake-checks.inputs.nixpkgs.follows = "nixpkgs";
   };
 
   outputs =
     { self
     , nixpkgs
     , flake-utils
+    , flake-checks
     , ...
     }:
     let
@@ -176,6 +181,59 @@
           contents = [ pkgs.headscale ];
           config.Entrypoint = [ (pkgs.headscale + "/bin/headscale") ];
         };
+
+        # Go flake checks from the flake-checks library. CI gates on
+        # `nix build .#checks.<system>.<name>`; the logic lives here, not in
+        # bespoke workflow steps. Linux-only: parts of the tree are
+        # Linux-specific and the pure unit subset is validated by CI.
+        fc = flake-checks.lib;
+        common = {
+          inherit pkgs;
+          root = ./.;
+          pname = "headscale";
+          version = headscaleVersion;
+          vendorHash = (builtins.fromJSON (builtins.readFile ./flakehashes.json)).vendor.sri;
+          goPkg = pkgs.go_1_26;
+          # //go:embed targets and test-read files outside the default whitelist.
+          embedDirs = [ ./hscontrol/assets ./hscontrol/db/schema.sql ./config-example.yaml ];
+          extraSrc = [
+            ./hscontrol/testdata
+            ./hscontrol/types/testdata
+            ./hscontrol/db/testdata
+            ./hscontrol/policy/v2/testdata
+          ];
+        };
+        goChecks = {
+          build = fc.goBuild (common // { subPackages = [ "cmd/headscale" ]; });
+
+          # The pure unit subset. ./integration (Docker) and
+          # ./hscontrol/servertest (slow: 10s+ convergence plus race/stress/HA
+          # property tests — run by the servertest workflow instead) are dropped
+          # from the test set but kept in source so cmd/hi and friends still
+          # compile; TestPostgres* needs a server (the SQLite equivalents still
+          # run). CGO off matches the build.
+          gotest = fc.goTest (common // {
+            testExclude = [ "/integration" "/hscontrol/servertest" ];
+            goSkip = [ "TestPostgres" ];
+            testEnv = "export CGO_ENABLED=0";
+          });
+
+          # Full-tree golangci-lint (golines, gofumpt, etc.); uses the overlay's
+          # golangci-lint built against the pinned Go.
+          golangci-lint = fc.goLint common;
+
+          # nixpkgs-fmt + prettier, excluding generated output. goFmt = "off":
+          # Go formatting (golines, gofumpt) is enforced by the golangci-lint
+          # check, not treefmt. prettierExts matches the old prettier-lint glob
+          # (no json: testdata fixtures are hand-formatted).
+          formatting = fc.goFormat (common // {
+            goFmt = "off";
+            prettier = true;
+            prettierExts = [ "ts" "js" "md" "yaml" "yml" "sass" "css" "scss" "html" ];
+            # Mirror .prettierignore (docs/ are mkdocs-flavoured; gen/ generated).
+            fmtExclude = [ ./gen ./docs ];
+          });
+        };
       in
       {
         # `nix develop`
@@ -221,6 +279,9 @@
 
         checks = {
           headscale = pkgs.testers.nixosTest (import ./nix/tests/headscale.nix);
-        };
+        }
+        # The Go build/test checks are gated to Linux: parts of the tree are
+        # Linux-specific and the pure unit subset is validated by CI.
+        // pkgs.lib.optionalAttrs pkgs.stdenv.isLinux goChecks;
       });
 }