diff --git a/dashcaddy-api/__tests__/network-wg-firewall.test.js b/dashcaddy-api/__tests__/network-wg-firewall.test.js
new file mode 100644
index 0000000..58cbffc
--- /dev/null
+++ b/dashcaddy-api/__tests__/network-wg-firewall.test.js
@@ -0,0 +1,473 @@
+/**
+ * Tests for src/network/wg-firewall.js (DC-151).
+ * Coverage:
+ *   - golden ruleset text: single resource single grant, group grant
+ *     expansion, blocked person absent from ALL sets, default-deny tails,
+ *     admin ports only from admin set
+ *   - corrected baseline: WG UDP handshake rule NOT bound to dcnet0
+ *     (externalInterface scoping + null → unscoped), peer-to-peer forward
+ *     default-deny (oifname dcnet0 drop)
+ *   - name sanitization: 'plex-2!' → net_dc_res_plex_2, collision guard
+ *   - admin lockout guard; assertAdminIsolation (positive + adversarial)
+ *   - transactional apply (mocked execFile + fs): check-failure → no apply
+ *     + temp deleted; apply-failure → {applied:false} + rollback file
+ *     unchanged; verify-mismatch → rollback attempted; rollback() re-applies
+ *     previous; unique temp paths across applies
+ */
+
+'use strict';
+
+const {
+  compileRuleset,
+  createWgFirewallApplier,
+  assertAdminIsolation,
+  resourceSetName,
+  FirewallCheckError,
+  FirewallApplyError,
+} = require('../src/network/wg-firewall');
+
+// --------------------------------------------------------------------------
+// Fixtures
+// --------------------------------------------------------------------------
+
+const PEOPLE = [
+  {
+    id: 'admin1',
+    displayName: 'Admin',
+    groups: ['family'],
+    status: 'active',
+    devices: [{ keyId: 'k1', name: 'laptop', ip: '10.53.0.10' }],
+  },
+  {
+    id: 'alice',
+    displayName: 'Alice',
+    groups: ['family'],
+    status: 'active',
+    devices: [{ keyId: 'k2', name: 'phone', ip: '10.53.1.20' }],
+  },
+  {
+    id: 'bob',
+    displayName: 'Bob',
+    groups: [],
+    status: 'active',
+    devices: [{ keyId: 'k3', name: 'pc', ip: '10.53.2.30' }],
+  },
+  {
+    id: 'mallory',
+    displayName: 'Mallory',
+    groups: ['family'],
+    status: 'blocked',
+    devices: [{ keyId: 'k4', name: 'tab', ip: '10.53.3.40' }],
+  },
+];
+
+const PEERS = {
+  'admin1/dev1': '10.53.0.10',
+  'alice/dev1': '10.53.1.20',
+  'bob/dev1': '10.53.2.30',
+  'mallory/dev1': '10.53.3.40',
+};
+
+const RESOURCES = {
+  plex: { ip: '10.53.0.1', port: 32400, protocol: 'tcp' },
+  nas: { ip: '10.53.9.9', port: 445, protocol: 'tcp' },
+};
+
+const BASE = {
+  accessMap: { grants: [] },
+  people: PEOPLE,
+  peerAddresses: PEERS,
+  resources: RESOURCES,
+  adminPeers: ['admin1'],
+};
+
+// --------------------------------------------------------------------------
+// Compiler: golden ruleset text
+// --------------------------------------------------------------------------
+
+describe('wg-firewall: compileRuleset golden text', () => {
+  test('single resource single grant — exact set element + accept rule', () => {
+    const text = compileRuleset({
+      ...BASE,
+      accessMap: {
+        grants: [{ principal: { type: 'person', id: 'alice' }, resource: 'plex', allowed: true }],
+      },
+      resources: { plex: RESOURCES.plex },
+    });
+    expect(text).toContain('set net_dc_res_plex {');
+    expect(text).toContain('elements = { 10.53.1.20 }');
+    expect(text).toContain(
+      'ip saddr @net_dc_res_plex ip daddr 10.53.0.1 tcp dport 32400 accept comment "resource plex"'
+    );
+    // blocked + ungranted peers are NOT in the plex resource set
+    const plexSet = text.split('set net_dc_res_plex {')[1].split('}')[0];
+    expect(plexSet).not.toContain('10.53.3.40'); // mallory
+    expect(plexSet).not.toContain('10.53.2.30'); // bob
+    expect(plexSet).not.toContain('10.53.0.10'); // admin not granted plex → not in res set
+    expect(plexSet).toContain('elements = { 10.53.1.20');
+  });
+
+  test('group grant expands to every active member (person-override honored)', () => {
+    const text = compileRuleset({
+      ...BASE,
+      accessMap: {
+        grants: [
+          { principal: { type: 'group', id: 'family' }, resource: 'nas', allowed: true },
+          { principal: { type: 'person', id: 'alice' }, resource: 'nas', allowed: false },
+        ],
+      },
+      resources: { nas: RESOURCES.nas },
+    });
+    // family = admin1, alice, mallory(blocked); alice overridden to false
+    expect(text).toMatch(/set net_dc_res_nas \{\s*\n\s*type ipv4_addr\s*\n\s*elements = \{ 10\.53\.0\.10 \}/);
+    expect(text).toContain('ip saddr @net_dc_res_nas ip daddr 10.53.9.9 tcp dport 445 accept');
+  });
+
+  test('blocked person absent from ALL sets (resource sets and admin set)', () => {
+    const text = compileRuleset({
+      ...BASE,
+      accessMap: {
+        grants: [{ principal: { type: 'group', id: 'family' }, resource: 'plex', allowed: true }],
+      },
+      adminPeers: ['admin1', 'mallory'], // mallory blocked → must NOT get admin
+    });
+    const adminSetMatch = text.match(/set net_dc_admins \{[^}]*elements = \{ ([^}]*) \}/);
+    expect(adminSetMatch).toBeTruthy();
+    const adminEls = adminSetMatch[1].split(', ');
+    expect(adminEls).toEqual(['10.53.0.10']); // mallory's 10.53.3.40 excluded
+    expect(adminEls).not.toContain('10.53.3.40');
+  });
+
+  test('default-deny tails present: hub input, peer egress, peer-to-peer', () => {
+    const text = compileRuleset(BASE);
+    expect(text).toContain('ct state new drop comment "default-deny: hub input"');
+    expect(text).toContain('drop comment "default-deny: peer egress without grant"');
+    expect(text).toContain('drop comment "default-deny: peer-to-peer / new hub-to-peer"');
+  });
+
+  test('admin ports only from admin set (3001 + 22)', () => {
+    const text = compileRuleset(BASE);
+    expect(text).toContain(
+      'iifname "dcnet0" ip saddr @net_dc_admins tcp dport { 22, 3001 } accept comment "admin ports: admin peers only"'
+    );
+  });
+
+  test('table declared as inet dcnet with destroy-first', () => {
+    const text = compileRuleset(BASE);
+    expect(text).toContain('destroy table inet dcnet');
+    expect(text).toContain('table inet dcnet {');
+  });
+});
+
+// --------------------------------------------------------------------------
+// Compiler: corrected baseline (judge gate)
+// --------------------------------------------------------------------------
+
+describe('wg-firewall: WG UDP handshake + peer-to-peer baseline (corrected)', () => {
+  test('UDP allow rule is NOT bound to dcnet0 — scoped to external interface', () => {
+    const text = compileRuleset({ ...BASE, externalInterface: 'eth0' });
+    const udpLines = text.split('\n').filter((l) => l.includes('udp dport 51820'));
+    expect(udpLines).toHaveLength(1);
+    expect(udpLines[0]).toContain('iifname "eth0"');
+    expect(udpLines[0]).not.toContain('dcnet0');
+  });
+
+  test('externalInterface null → unscoped UDP rule with comment', () => {
+    const text = compileRuleset(BASE);
+    const udpLines = text.split('\n').filter((l) => l.includes('udp dport 51820'));
+    expect(udpLines).toHaveLength(1);
+    expect(udpLines[0]).not.toContain('iifname');
+    expect(udpLines[0]).toContain('external iface unspecified');
+  });
+
+  test('custom listen port honored', () => {
+    const text = compileRuleset({ ...BASE, wgListenPort: 51821, externalInterface: 'ens3' });
+    expect(text).toContain('iifname "ens3" udp dport 51821 accept');
+  });
+
+  test('peer-to-peer forwarding default-deny: oifname dcnet0 drop tail', () => {
+    const text = compileRuleset(BASE);
+    expect(text).toContain('oifname "dcnet0" drop');
+    // and no accept rule that would let peer→peer through ahead of it
+    const forward = text.split('chain forward {')[1].split('}')[0];
+    expect(forward).not.toMatch(/oifname "dcnet0".*accept/);
+  });
+
+  test('hub-local resource lands in input chain; peer resource in forward chain', () => {
+    const text = compileRuleset({
+      ...BASE,
+      accessMap: {
+        grants: [{ principal: { type: 'person', id: 'alice' }, resource: 'nas', allowed: true }],
+      },
+    });
+    const input = text.split('chain input {')[1].split('chain forward')[0];
+    const forward = text.split('chain forward {')[1];
+    expect(input).toContain('@net_dc_res_plex');
+    expect(input).not.toContain('@net_dc_res_nas');
+    expect(forward).toContain('@net_dc_res_nas');
+    expect(forward).not.toContain('@net_dc_res_plex');
+  });
+});
+
+// --------------------------------------------------------------------------
+// Compiler: sanitization + guards
+// --------------------------------------------------------------------------
+
+describe('wg-firewall: sanitization and guards', () => {
+  test("resource 'plex-2!' sanitizes to a safe set name", () => {
+    expect(resourceSetName('plex-2!')).toBe('net_dc_res_plex_2');
+    const text = compileRuleset({
+      ...BASE,
+      resources: { 'plex-2!': { ip: '10.53.0.1', port: 32400 } },
+      accessMap: {
+        grants: [{ principal: { type: 'person', id: 'alice' }, resource: 'plex-2!', allowed: true }],
+      },
+    });
+    expect(text).toContain('set net_dc_res_plex_2 {');
+    expect(text).toContain('@net_dc_res_plex_2');
+    expect(text).toContain('ip saddr @net_dc_res_plex_2 ip daddr 10.53.0.1 tcp dport 32400 accept');
+  });
+
+  test('set-name collision between distinct resources throws', () => {
+    expect(() =>
+      compileRuleset({ ...BASE, resources: { 'plex 1': { ip: '10.53.0.1', port: 1 }, 'plex!1': { ip: '10.53.0.2', port: 2 } } })
+    ).toThrow(/collision/);
+  });
+
+  test('admin lockout guard: zero resolvable admin peers throws', () => {
+    expect(() => compileRuleset({ ...BASE, adminPeers: ['ghost'] })).toThrow(/lockout/);
+  });
+
+  test('invalid resource (missing ip / bad port) throws', () => {
+    expect(() => compileRuleset({ ...BASE, resources: { x: { port: 80 } } })).toThrow(/ip required/);
+    expect(() => compileRuleset({ ...BASE, resources: { x: { ip: '10.53.0.1', port: 0 } } })).toThrow(/port/);
+  });
+});
+
+// --------------------------------------------------------------------------
+// assertAdminIsolation
+// --------------------------------------------------------------------------
+
+describe('wg-firewall: assertAdminIsolation', () => {
+  test('passes on a correctly compiled ruleset', () => {
+    const text = compileRuleset(BASE);
+    expect(assertAdminIsolation(text, { adminPeers: ['admin1'] })).toBe(true);
+  });
+
+  test('rejects an admin port allowed without the admin set', () => {
+    const bad = 'iifname "dcnet0" tcp dport 22 accept';
+    expect(() => assertAdminIsolation(bad)).toThrow(/without @net_dc_admins/);
+  });
+
+  test('rejects an admin port allowed from a resource set', () => {
+    const bad = 'iifname "dcnet0" ip saddr @net_dc_res_plex tcp dport 3001 accept';
+    expect(() => assertAdminIsolation(bad)).toThrow(/resource set/);
+  });
+
+  test('rejects an admin port allowed from a literal peer IP', () => {
+    const bad = 'iifname "dcnet0" ip saddr 10.53.4.4 tcp dport 22 accept';
+    expect(() => assertAdminIsolation(bad)).toThrow(/literal peer saddr/);
+  });
+});
+
+// --------------------------------------------------------------------------
+// Transactional applier (hermetic: mocked execFile + fs)
+// --------------------------------------------------------------------------
+
+function mockFs() {
+  const files = new Map();
+  return {
+    files,
+    writeFileSync: jest.fn((p, c) => files.set(p, c)),
+    readFileSync: jest.fn((p) => {
+      if (!files.has(p)) { const e = new Error('ENOENT'); e.code = 'ENOENT'; throw e; }
+      return files.get(p);
+    }),
+    existsSync: jest.fn((p) => files.has(p)),
+    unlinkSync: jest.fn((p) => files.delete(p)),
+  };
+}
+
+/** execFile mock with a per-call script of behaviors keyed by args. */
+function mockExec({ current = 'table inet dcnet { }', checkErr, applyErr, verifyOut } = {}) {
+  const calls = [];
+  const impl = async (cmd, args) => { // eslint-disable-line require-await -- scripted mock, no awaits by design
+    calls.push({ cmd, args: [...args] });
+    const joined = args.join(' ');
+    if (joined.startsWith('-c -f')) {
+      if (checkErr) {
+        const e = new Error('check failed');
+        e.stderr = 'syntax error near unexpected token';
+        throw e;
+      }
+      return { stdout: '' };
+    }
+    if (joined.startsWith('-f')) {
+      if (applyErr) {
+        const e = new Error('apply failed');
+        e.stderr = 'operation failed: Device or resource busy';
+        throw e;
+      }
+      return { stdout: '' };
+    }
+    if (joined.startsWith('list table')) {
+      if (verifyOut !== undefined) return { stdout: verifyOut };
+      return { stdout: current };
+    }
+    return { stdout: '' };
+  };
+  return { impl, calls };
+}
+
+const RULESET = compileRuleset(BASE);
+const RULESET2 = compileRuleset({
+  ...BASE,
+  accessMap: { grants: [{ principal: { type: 'person', id: 'bob' }, resource: 'plex', allowed: true }] },
+});
+
+describe('wg-firewall: transactional apply', () => {
+  test('happy path: check → rollback write → apply → verify; temp cleaned up', async () => {
+    const fs = mockFs();
+    const { impl, calls } = mockExec();
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl,
+      fsImpl: fs,
+      tempDir: '/tmp/x',
+      rollbackPath: '/tmp/x/rollback.nft',
+    });
+    const res = await applier.apply(RULESET);
+    expect(res.applied).toBe(true);
+    expect(res.verified).toBe(true);
+    // order: check(-c -f) before rollback write before apply(-f) before verify
+    const checkIdx = calls.findIndex((c) => c.args[0] === '-c');
+    const applyIdx = calls.findIndex((c) => c.args[0] === '-f');
+    const listIdxs = calls.map((c, i) => (c.args[0] === 'list' ? i : -1)).filter((i) => i >= 0);
+    expect(checkIdx).toBe(0);
+    expect(applyIdx).toBeGreaterThan(checkIdx);
+    // one `list` before apply (capture previous) + one after (verify)
+    expect(listIdxs).toHaveLength(2);
+    expect(listIdxs[0]).toBeLessThan(applyIdx);
+    expect(listIdxs[1]).toBeGreaterThan(applyIdx);
+    const writePaths = fs.writeFileSync.mock.calls.map((c) => c[0]);
+    const tempWrites = writePaths.filter((p) => p !== '/tmp/x/rollback.nft');
+    expect(tempWrites).toHaveLength(1);
+    const tempPath = tempWrites[0];
+    // write order: temp (for check) then rollback BEFORE the apply exec
+    expect(writePaths).toEqual([tempPath, '/tmp/x/rollback.nft']);
+    const applyCall = calls[applyIdx];
+    expect(applyCall.args).toEqual(['-f', tempPath]);
+    expect(applyCall.args[1]).not.toBe('/tmp/x/rollback.nft');
+    // rollback file holds the PREVIOUS table dump
+    expect(fs.readFileSync('/tmp/x/rollback.nft')).toBe('table inet dcnet { }');
+    // temp file deleted at the end
+    expect(fs.existsSync(tempPath)).toBe(false);
+    expect(res.previousExisted).toBe(true);
+  });
+
+  test('check failure → no apply, temp deleted, FirewallCheckError with stderr', async () => {
+    const fs = mockFs();
+    const { impl, calls } = mockExec({ checkErr: true });
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    await expect(applier.apply(RULESET)).rejects.toMatchObject({
+      name: 'FirewallCheckError',
+      code: 'check_failed',
+      applied: false,
+      stderr: expect.stringContaining('syntax error'),
+    });
+    // NOTHING applied: no bare `-f` run, no `nft list` verify, no rollback write
+    expect(calls.filter((c) => c.args[0] === '-f')).toHaveLength(0);
+    expect(calls.filter((c) => c.args[0] === 'list')).toHaveLength(0);
+    expect(fs.writeFileSync).toHaveBeenCalledTimes(1); // only the temp file
+    expect(fs.files.size).toBe(0); // temp deleted
+  });
+
+  test('apply failure → {applied:false} thrown, rollback file unchanged, old rules intact', async () => {
+    const fs = mockFs();
+    fs.files.set('/tmp/x/rollback.nft', 'PREVIOUS-ROLLBACK-CONTENT');
+    const { impl, calls } = mockExec({ applyErr: true });
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    await expect(applier.apply(RULESET)).rejects.toMatchObject({
+      name: 'FirewallApplyError',
+      applied: false,
+    });
+    // rollback file NOT overwritten by the failed apply (old rules intact)
+    expect(fs.readFileSync('/tmp/x/rollback.nft')).toBe('PREVIOUS-ROLLBACK-CONTENT');
+    // temp cleaned, only the rollback file remains
+    expect(fs.files.size).toBe(1);
+    // verify never reached: the only `nft -f` run is the failed apply —
+    // no rollback re-apply, and exactly one `list` (the pre-apply capture)
+    expect(calls.filter((c) => c.args[0] === '-f')).toHaveLength(1);
+    expect(calls.filter((c) => c.args[0] === 'list')).toHaveLength(1);
+  });
+
+  test('verify mismatch → rollback attempted, verify error carries rolledBack', async () => {
+    const fs = mockFs();
+    const { impl, calls } = mockExec({ verifyOut: '' }); // list returns no table
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    await expect(applier.apply(RULESET)).rejects.toMatchObject({
+      name: 'FirewallVerifyError',
+      code: 'verify_failed',
+      rolledBack: true,
+    });
+    // last exec is the rollback `nft -f <rollbackFile>`
+    const last = calls[calls.length - 1];
+    expect(last.args).toEqual(['-f', '/tmp/x/rollback.nft']);
+  });
+
+  test('rollback() re-applies the previous ruleset file', async () => {
+    const fs = mockFs();
+    fs.files.set('/tmp/x/rollback.nft', 'table inet dcnet { OLD }');
+    const { impl, calls } = mockExec();
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    const res = await applier.rollback();
+    expect(res.applied).toBe(true);
+    expect(calls).toHaveLength(1);
+    expect(calls[0].args).toEqual(['-f', '/tmp/x/rollback.nft']);
+  });
+
+  test('rollback() without a rollback file throws', async () => {
+    const fs = mockFs();
+    const { impl } = mockExec();
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    await expect(applier.rollback()).rejects.toThrow(/no rollback file/);
+  });
+
+  test('two applies never share a temp path', async () => {
+    const fs = mockFs();
+    const { impl } = mockExec();
+    const applier = createWgFirewallApplier({
+      execFileImpl: impl, fsImpl: fs, tempDir: '/tmp/x', rollbackPath: '/tmp/x/rollback.nft',
+    });
+    const r1 = await applier.apply(RULESET);
+    const r2 = await applier.apply(RULESET2);
+    expect(r1.tempPath).not.toBe(r2.tempPath);
+    expect(r1.tempPath).toMatch(/dcnet-nft-/);
+    expect(r2.tempPath).toMatch(/dcnet-nft-/);
+  });
+
+  test('apply rejects empty/non-string ruleset before any I/O', async () => {
+    const fs = mockFs();
+    const { impl, calls } = mockExec();
+    const applier = createWgFirewallApplier({ execFileImpl: impl, fsImpl: fs });
+    await expect(applier.apply('')).rejects.toThrow(/non-empty/);
+    expect(calls).toHaveLength(0);
+    expect(fs.writeFileSync).not.toHaveBeenCalled();
+  });
+
+  test('FirewallCheckError is exported and distinguishable', () => {
+    const e = new FirewallCheckError('x', { stderr: 's' });
+    expect(e instanceof Error).toBe(true);
+    expect(e.applied).toBe(false);
+    expect(new FirewallApplyError('y').applied).toBe(false);
+  });
+});
diff --git a/dashcaddy-api/src/network/wg-firewall.js b/dashcaddy-api/src/network/wg-firewall.js
new file mode 100644
index 0000000..2d9549c
--- /dev/null
+++ b/dashcaddy-api/src/network/wg-firewall.js
@@ -0,0 +1,628 @@
+/**
+ * WireGuard hub firewall for the DashCaddy Private Network (DC-151,
+ * specs/PRIVATE-NETWORK-SPEC.md §4 "Layer 1 — WireGuard" + §8.1 baseline).
+ *
+ * Two halves:
+ *
+ * 1. compileRuleset() — a PURE compiler (no I/O, fully deterministic):
+ *    access map + people + peer addresses + resources → the complete
+ *    nftables ruleset text for table `inet dcnet`.
+ *
+ *    Baseline model (corrected per judge-gate review of §8.1):
+ *      - The WireGuard UDP listen port carries HANDSHAKE traffic that
+ *        arrives on the EXTERNAL interface, never on dcnet0. The accept
+ *        rule is scoped to `externalInterface` when given, otherwise
+ *        emitted interface-unscoped with an explanatory comment.
+ *      - dcnet0 LOCAL input (input chain, iifname "dcnet0"): established/
+ *        related, ICMP from 10.53.0.0/16, admin ports (API 3001 / SSH 22)
+ *        ONLY from the admin set, hub-local resource ports to 10.53.0.1,
+ *        then drop other new inbound to the hub IP.
+ *      - PEER traffic (forward chain): per-resource nft sets
+ *        (`net_dc_res_<name>`) gate saddr→resource ip:dport for resources
+ *        living at peer /32s; default-deny tails drop ALL other iifname
+ *        "dcnet0" (peer egress without a grant) and oifname "dcnet0"
+ *        (peer-to-peer + new hub→peer) traffic.
+ *
+ *    Default-deny everywhere on dcnet0-derived traffic; blocked people's
+ *    IPs appear in NO set (resource sets nor the admin set).
+ *
+ * 2. createWgFirewallApplier() — transactional apply with injectable
+ *    { execFileImpl, fsImpl }: write to a UNIQUE temp file, `nft -c -f`
+ *    (check), write the rollback file (previous ruleset) BEFORE applying,
+ *    `nft -f` (apply), verify via `nft list table inet dcnet`, roll back
+ *    on verify mismatch. A check failure deletes the temp file and throws
+ *    FirewallCheckError with NOTHING applied; an apply failure leaves the
+ *    old rules and the rollback file untouched and throws with
+ *    { applied: false }.
+ *
+ * 3. assertAdminIsolation() — static guard (tests + DC-148-style callers):
+ *    every admin-port rule must be scoped to the admin set only.
+ */
+
+'use strict';
+
+const { execFile } = require('child_process');
+const { promisify } = require('util');
+const fsDefault = require('fs');
+const os = require('os');
+const path = require('path');
+
+const execFileDefault = promisify(execFile);
+
+const HUB_IP = '10.53.0.1';
+const PEER_CIDR = '10.53.0.0/16';
+const WG_IFACE = 'dcnet0';
+const TABLE = 'inet dcnet';
+const DEFAULT_ADMIN_PORTS = [22, 3001];
+const DEFAULT_WG_LISTEN_PORT = 51820;
+const ADMIN_SET = 'net_dc_admins';
+const RES_SET_PREFIX = 'net_dc_res_';
+
+// ---------------------------------------------------------------------------
+// Errors
+// ---------------------------------------------------------------------------
+
+class FirewallError extends Error {
+  /**
+   * @param {string} message
+   * @param {object} [opts]
+   * @param {string} [opts.code] - machine-readable code
+   * @param {boolean} [opts.applied] - did any part of the new ruleset land?
+   * @param {string} [opts.stderr] - captured nft stderr, when available
+   * @param {*} [opts.cause]
+   */
+  constructor(message, { code, applied, stderr, cause, rolledBack } = {}) {
+    super(message);
+    this.name = this.constructor.name;
+    this.code = code || 'firewall_error';
+    this.applied = !!applied;
+    if (stderr !== undefined) this.stderr = stderr;
+    if (cause !== undefined) this.cause = cause;
+    if (rolledBack !== undefined) this.rolledBack = !!rolledBack;
+  }
+}
+
+/** `nft -c -f` rejected the ruleset. Nothing was applied; temp deleted. */
+class FirewallCheckError extends FirewallError {
+  constructor(message, opts = {}) {
+    super(message, { ...opts, code: 'check_failed', applied: false });
+  }
+}
+
+/** `nft -f` failed. Old rules and rollback file are untouched. */
+class FirewallApplyError extends FirewallError {
+  constructor(message, opts = {}) {
+    super(message, { ...opts, code: 'apply_failed', applied: false });
+  }
+}
+
+/** Post-apply verification failed. Rollback was attempted. */
+class FirewallVerifyError extends FirewallError {
+  constructor(message, opts = {}) {
+    super(message, { ...opts, code: 'verify_failed', applied: true });
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Pure compiler
+// ---------------------------------------------------------------------------
+
+/**
+ * Sanitize a resource name into a safe nftables identifier segment.
+ * 'plex-2!' → 'plex_2'; leading digits get a 'res_' prefix; empty → 'unnamed'.
+ * @param {string} name
+ * @returns {string}
+ */
+function sanitizeResourceSegment(name) {
+  const raw = String(name)
+    .toLowerCase()
+    .replace(/[^a-z0-9_]+/g, '_')
+    .replace(/^_+|_+$/g, '');
+  if (!raw) return 'unnamed';
+  return /^[0-9]/.test(raw) ? 'res_' + raw : raw;
+}
+
+/** Full set name for a resource: net_dc_res_<sanitized>. */
+function resourceSetName(resourceName) {
+  return RES_SET_PREFIX + sanitizeResourceSegment(resourceName);
+}
+
+function _personStatus(person) {
+  return person && typeof person.status === 'string' ? person.status : 'active';
+}
+
+/**
+ * Effective access for one person, mirroring the access store semantics
+ * (src/security/network-access-store.js effectiveAccess): union of the
+ * grants of every group they belong to, then person-level grants OVERRIDE
+ * group grants in both directions.
+ * @returns {Object<string, boolean>} resource → allowed
+ */
+function computePersonAccess(accessMap, person) {
+  const grants = accessMap && Array.isArray(accessMap.grants) ? accessMap.grants : [];
+  const groups = new Set(
+    Array.isArray(person.groups) ? person.groups.filter((g) => typeof g === 'string') : []
+  );
+  const resources = {};
+  for (const g of grants) {
+    if (g && g.principal && g.principal.type === 'group' && groups.has(g.principal.id)) {
+      resources[g.resource] = g.allowed;
+    }
+  }
+  for (const g of grants) {
+    if (g && g.principal && g.principal.type === 'person' && g.principal.id === person.id) {
+      resources[g.resource] = g.allowed;
+    }
+  }
+  return resources;
+}
+
+/**
+ * All assigned peer IPs for a person. `peerAddresses` is the flat map
+ * `${personId}/${deviceId}` → 10.53.x.y (canonical), with a nested
+ * { [personId]: { [deviceId]: ip } } shape also accepted.
+ * @returns {string[]} sorted unique IPs
+ */
+function peerIpsForPerson(peerAddresses, person) {
+  const ips = [];
+  const prefix = person.id + '/';
+  for (const [key, ip] of Object.entries(peerAddresses || {})) {
+    if (typeof ip === 'string' && key.startsWith(prefix) && key.length > prefix.length) {
+      ips.push(ip);
+    }
+  }
+  const nested = peerAddresses ? peerAddresses[person.id] : null;
+  if (nested && typeof nested === 'object') {
+    for (const ip of Object.values(nested)) {
+      if (typeof ip === 'string') ips.push(ip);
+    }
+  }
+  return [...new Set(ips)].sort();
+}
+
+function _dportList(ports) {
+  const sorted = [...ports].map((p) => parseInt(p, 10)).sort((a, b) => a - b);
+  return `{ ${sorted.join(', ')} }`;
+}
+
+/**
+ * Resolve the admin set IPs from ACTIVE admin people. Blocked/removed admins
+ * contribute nothing. Throws (lockout guard) when admin ports would be
+ * emitted with zero reachable admin peers.
+ * @returns {string[]} sorted unique admin peer IPs
+ */
+function _resolveAdminIps(activePersons, adminPeers, peerAddresses) {
+  const adminIds = new Set(
+    Array.isArray(adminPeers) ? adminPeers.filter((id) => typeof id === 'string') : []
+  );
+  const ips = new Set();
+  for (const p of activePersons) {
+    if (!adminIds.has(p.id)) continue;
+    for (const ip of peerIpsForPerson(peerAddresses, p)) ips.add(ip);
+  }
+  if (ips.size === 0) {
+    throw new Error(
+      'wg-firewall: admin lockout guard — admin ports requested but no active admin peer IPs resolved'
+    );
+  }
+  return [...ips].sort();
+}
+
+/**
+ * Build the per-resource set entries and split resources into hub-local
+ * (input chain, ip === hub) vs peer (forward chain) buckets. Validates
+ * resource entries and guards against sanitization collisions.
+ * @returns {{resourceSets: Array, hubResources: Array, peerResources: Array}}
+ */
+function _buildResourceSets({ resources, activePersons, accessMap, peerAddresses }) {
+  const setNames = new Map(); // sanitized segment → resource name (collision guard)
+  const resourceSets = [];
+  const hubResources = [];
+  const peerResources = [];
+  for (const [name, resource] of Object.entries(resources)) {
+    if (!resource || typeof resource.ip !== 'string' || !resource.ip) {
+      throw new Error(`wg-firewall: resource ${name}: ip required`);
+    }
+    if (!Number.isInteger(resource.port) || resource.port < 1 || resource.port > 65535) {
+      throw new Error(`wg-firewall: resource ${name}: valid port required`);
+    }
+    const segment = sanitizeResourceSegment(name);
+    const collides = setNames.get(segment);
+    if (collides && collides !== name) {
+      throw new Error(
+        `wg-firewall: set-name collision — resources "${collides}" and "${name}" both sanitize to ${RES_SET_PREFIX}${segment}`
+      );
+    }
+    setNames.set(segment, name);
+
+    const ips = new Set();
+    for (const person of activePersons) {
+      if (computePersonAccess(accessMap, person)[name] === true) {
+        for (const ip of peerIpsForPerson(peerAddresses, person)) ips.add(ip);
+      }
+    }
+    const setName = RES_SET_PREFIX + segment;
+    resourceSets.push({ name, setName, ips: [...ips].sort() });
+    const bucket = resource.ip === HUB_IP ? hubResources : peerResources;
+    bucket.push({ name, setName, resource });
+  }
+  return { resourceSets, hubResources, peerResources };
+}
+
+function _resourceRule(setName, resource, comment) {
+  const proto = resource.protocol === 'udp' ? 'udp' : 'tcp';
+  return `ip saddr @${setName} ip daddr ${resource.ip} ${proto} dport ${resource.port} accept comment "${comment}"`;
+}
+
+/**
+ * Compile the full nftables ruleset for the WireGuard hub.
+ *
+ * @param {object} opts
+ * @param {object} opts.accessMap - { grants: [...] } (network-access.json)
+ * @param {Array<object>} opts.people - person records {id, groups[], status,
+ *   devices[]} from the people store
+ * @param {Object<string,string>} opts.peerAddresses - `${personId}/${deviceId}`
+ *   → 10.53.x.y (nested {personId:{deviceId:ip}} also accepted)
+ * @param {Object<string,{ip:string,port:number,protocol?:'tcp'|'udp'}>} opts.resources
+ * @param {string[]} opts.adminPeers - person IDs allowed admin ports
+ * @param {number[]} [opts.adminPorts=[22,3001]]
+ * @param {number} [opts.wgListenPort=51820] - UDP handshake listen port
+ * @param {string|null} [opts.externalInterface=null] - external iface name for
+ *   the WG handshake rule; null → unscoped rule with a comment
+ * @returns {string} complete nftables file text
+ * @throws {Error} on admin lockout (adminPorts with zero active admin peer
+ *   IPs), set-name collisions, or invalid resource entries
+ */
+function compileRuleset({
+  accessMap = { grants: [] },
+  people = [],
+  peerAddresses = {},
+  resources = {},
+  adminPeers = [],
+  adminPorts = DEFAULT_ADMIN_PORTS,
+  wgListenPort = DEFAULT_WG_LISTEN_PORT,
+  externalInterface = null,
+} = {}) {
+  if (!resources || typeof resources !== 'object' || Array.isArray(resources)) {
+    throw new Error('wg-firewall: resources map required');
+  }
+  const persons = Array.isArray(people) ? people : Object.values(people || {});
+  const active = persons.filter(
+    (p) => p && typeof p.id === 'string' && _personStatus(p) === 'active'
+  );
+
+  // ---- admin set (never includes blocked/removed people's IPs) ----------
+  const adminIps = _resolveAdminIps(active, adminPeers, peerAddresses);
+  const ports = adminPorts.length ? adminPorts : DEFAULT_ADMIN_PORTS;
+
+  // ---- per-resource sets + rule split (hub-local input vs peer forward) -
+  const { resourceSets, hubResources, peerResources } = _buildResourceSets({
+    resources,
+    activePersons: active,
+    accessMap,
+    peerAddresses,
+  });
+
+  // ---- emit -------------------------------------------------------------
+  const L = [];
+  L.push('#!/usr/sbin/nft -f');
+  L.push('# DashCaddy Private Network - WireGuard hub firewall (DC-151 wg-firewall)');
+  L.push('# GENERATED FILE - do not edit; recompiled from network-access.json.');
+  L.push('# Default-deny: blocked people appear in no set; unmatched dcnet0 traffic is dropped.');
+  L.push('');
+  L.push('destroy table inet dcnet');
+  L.push('');
+  L.push(`table ${TABLE} {`);
+  L.push('');
+  L.push('  # Admin peers allowed to reach hub admin ports');
+  L.push(`  set ${ADMIN_SET} {`);
+  L.push('    type ipv4_addr');
+  L.push(`    elements = { ${adminIps.join(', ')} }`);
+  L.push('  }');
+  L.push('');
+  for (const { name, setName, ips } of resourceSets) {
+    L.push(`  # Resource grants: ${name}`);
+    L.push(`  set ${setName} {`);
+    L.push('    type ipv4_addr');
+    if (ips.length) {
+      L.push(`    elements = { ${ips.join(', ')} }`);
+    }
+    L.push('  }');
+    L.push('');
+  }
+  L.push('  chain input {');
+  L.push('    type filter hook input priority 0; policy accept;');
+  L.push('');
+  L.push('    # WireGuard handshake: arrives on the EXTERNAL interface, never dcnet0');
+  if (externalInterface) {
+    L.push(
+      `    iifname "${externalInterface}" udp dport ${wgListenPort} accept comment "wg handshake on external iface"`
+    );
+  } else {
+    L.push(
+      `    udp dport ${wgListenPort} accept comment "wg handshake - external iface unspecified, left unscoped"`
+    );
+  }
+  L.push('');
+  L.push('    # dcnet0 local input');
+  L.push(`    iifname "${WG_IFACE}" ct state established,related accept comment "dcnet0 established/related"`);
+  L.push(
+    `    iifname "${WG_IFACE}" ip saddr ${PEER_CIDR} icmp type echo-request accept comment "icmp from peers"`
+  );
+  L.push(
+    `    iifname "${WG_IFACE}" ip saddr @${ADMIN_SET} tcp dport ${_dportList(ports)} accept comment "admin ports: admin peers only"`
+  );
+  for (const { name, setName, resource } of hubResources) {
+    L.push(
+      `    iifname "${WG_IFACE}" ${_resourceRule(setName, resource, `resource ${name}`)}`
+    );
+  }
+  L.push(
+    `    iifname "${WG_IFACE}" ip daddr ${HUB_IP} ct state new drop comment "default-deny: hub input"`
+  );
+  L.push('  }');
+  L.push('');
+  L.push('  chain forward {');
+  L.push('    type filter hook forward priority 0; policy accept;');
+  L.push('');
+  L.push(`    iifname "${WG_IFACE}" ct state established,related accept comment "dcnet0 established/related"`);
+  for (const { name, setName, resource } of peerResources) {
+    L.push(`    iifname "${WG_IFACE}" ${_resourceRule(setName, resource, `resource ${name}`)}`);
+  }
+  L.push(`    iifname "${WG_IFACE}" drop comment "default-deny: peer egress without grant"`);
+  L.push(`    oifname "${WG_IFACE}" drop comment "default-deny: peer-to-peer / new hub-to-peer"`);
+  L.push('  }');
+  L.push('}');
+  L.push('');
+  return L.join('\n');
+}
+
+// ---------------------------------------------------------------------------
+// Static admin-isolation guard
+// ---------------------------------------------------------------------------
+
+/**
+ * Assert that every admin-port rule in the ruleset references ONLY the
+ * admin set: an admin port may not be allowed from a resource set, a
+ * literal peer IP, or with no source scoping at all.
+ *
+ * @param {string} rulesetText - compiled nftables file text
+ * @param {object} [opts]
+ * @param {number[]} [opts.adminPorts=[22,3001]]
+ * @returns {true} when isolated
+ * @throws {Error} (name 'AdminIsolationError', .violations[]) otherwise
+ */
+function assertAdminIsolation(rulesetText, { adminPorts = DEFAULT_ADMIN_PORTS } = {}) {
+  const ports = new Set(adminPorts.map((p) => String(parseInt(p, 10))));
+  const violations = [];
+  for (const line of String(rulesetText).split('\n')) {
+    const m = line.match(/dport\s+(?:\{\s*([^}]*?)\s*\}|(\d+))/);
+    if (!m) continue;
+    const listed = (m[1] ? m[1].split(/[,\s]+/) : [m[2]]).filter(Boolean);
+    if (!listed.some((p) => ports.has(p))) continue;
+    const trimmed = line.trim();
+    if (!line.includes(`@${ADMIN_SET}`)) {
+      violations.push(`admin port allowed without @${ADMIN_SET}: ${trimmed}`);
+    }
+    if (line.includes(`@${RES_SET_PREFIX}`)) {
+      violations.push(`admin port rule references a resource set: ${trimmed}`);
+    }
+    if (/ip saddr 10\.53\.\d/.test(line)) {
+      violations.push(`admin port rule uses a literal peer saddr: ${trimmed}`);
+    }
+  }
+  if (violations.length) {
+    const err = new Error('admin isolation violation:\n  ' + violations.join('\n  '));
+    err.name = 'AdminIsolationError';
+    err.violations = violations;
+    throw err;
+  }
+  return true;
+}
+
+// ---------------------------------------------------------------------------
+// Transactional applier
+// ---------------------------------------------------------------------------
+
+let _tempSeq = 0;
+
+/** mkstemp-style unique temp path — never a fixed path. */
+function _uniqueTempPath(dir) {
+  _tempSeq += 1;
+  const rand = Math.random().toString(36).slice(2, 10);
+  return path.join(dir, `dcnet-nft-${process.pid}-${_tempSeq}-${rand}.nft`);
+}
+
+function _errStderr(err) {
+  if (!err) return '';
+  if (typeof err.stderr === 'string') return err.stderr;
+  return err.message || String(err);
+}
+
+function _bestEffortUnlink(fs, p) {
+  try {
+    fs.unlinkSync(p);
+  } catch {
+    /* already gone — fine */
+  }
+}
+
+/**
+ * Build the transactional nftables applier.
+ *
+ * @param {object} [deps] - all injectable (hermetic tests mock these)
+ * @param {Function} [deps.execFileImpl] - promisified execFile(cmd, args)
+ * @param {object} [deps.fsImpl] - { writeFileSync, readFileSync, existsSync,
+ *   unlinkSync }
+ * @param {string} [deps.nftBinary='nft']
+ * @param {string} [deps.tempDir] - directory for unique temp ruleset files
+ * @param {string} [deps.rollbackPath] - where the previous ruleset is kept
+ */
+function createWgFirewallApplier({
+  execFileImpl,
+  fsImpl,
+  nftBinary = 'nft',
+  tempDir,
+  rollbackPath,
+} = {}) {
+  const execFn = execFileImpl || execFileDefault;
+  const fs = fsImpl || fsDefault;
+  const tmpDir = tempDir || path.join(os.tmpdir());
+  const rollbackFile =
+    rollbackPath || path.join(tmpDir, 'dashcaddy-dcnet-rollback.nft');
+
+  async function nft(args) { // eslint-disable-line require-await -- passthrough to injected execFile promise
+    return execFn(nftBinary, args);
+  }
+
+  /**
+   * Capture the currently-applied dcnet table, or null when absent.
+   * @returns {Promise<string|null>}
+   */
+  async function captureCurrent() {
+    try {
+      const res = await nft(['list', 'table', 'inet', 'dcnet']);
+      return res && typeof res.stdout === 'string' ? res.stdout : null;
+    } catch {
+      return null; // table does not exist yet — first apply
+    }
+  }
+
+  return {
+    rollbackFile,
+
+    /**
+     * Transactional apply:
+     *   1. write ruleset to a UNIQUE temp file
+     *   2. `nft -c -f` — on failure delete temp, throw FirewallCheckError,
+     *      nothing applied
+     *   3. write the rollback file (previous ruleset) BEFORE applying
+     *   4. `nft -f` — on failure delete temp, throw FirewallApplyError
+     *      {applied:false}; old rules + rollback file untouched
+     *   5. verify via `nft list table inet dcnet`; mismatch → attempt
+     *      rollback, throw FirewallVerifyError {applied:true, rolledBack}
+     *
+     * @param {string} rulesetText
+     * @returns {Promise<{applied:true, verified:true, tempPath:string,
+     *   rollbackFile:string, previousExisted:boolean}>}
+     */
+    async apply(rulesetText) {
+      if (typeof rulesetText !== 'string' || rulesetText.length === 0) {
+        throw new Error('wg-firewall: apply() requires non-empty ruleset text');
+      }
+      const tempPath = _uniqueTempPath(tmpDir);
+      fs.writeFileSync(tempPath, rulesetText);
+
+      // 1. check — reject before touching anything live.
+      try {
+        await nft(['-c', '-f', tempPath]);
+      } catch (err) {
+        _bestEffortUnlink(fs, tempPath);
+        throw new FirewallCheckError(
+          `nft -c rejected ruleset (${_errStderr(err).trim()})`,
+          { stderr: _errStderr(err) }
+        );
+      }
+
+      // 2. snapshot previous + write rollback BEFORE applying. Keep the
+      //    prior rollback file content so a FAILED apply leaves it (the
+      //    last-known-good rollback) untouched.
+      const previous = await captureCurrent();
+      let priorRollback;
+      try {
+        priorRollback = fs.readFileSync(rollbackFile);
+      } catch {
+        priorRollback = undefined; // no prior rollback file
+      }
+      const rollbackContent = previous !== null ? previous : 'destroy table inet dcnet\n';
+      fs.writeFileSync(rollbackFile, rollbackContent);
+
+      // 3. apply.
+      try {
+        await nft(['-f', tempPath]);
+      } catch (err) {
+        _bestEffortUnlink(fs, tempPath);
+        if (priorRollback !== undefined) {
+          fs.writeFileSync(rollbackFile, priorRollback);
+        } else {
+          _bestEffortUnlink(fs, rollbackFile);
+        }
+        throw new FirewallApplyError(`nft -f apply failed (${_errStderr(err).trim()})`, {
+          stderr: _errStderr(err),
+        });
+      }
+
+      // 4. verify.
+      let verified = false;
+      let verifyStderr = '';
+      try {
+        const res = await nft(['list', 'table', 'inet', 'dcnet']);
+        const out = res && typeof res.stdout === 'string' ? res.stdout : '';
+        verified = out.includes(TABLE);
+        if (!verified) verifyStderr = 'nft list table inet dcnet output missing table';
+      } catch (err) {
+        verifyStderr = _errStderr(err);
+      }
+      if (!verified) {
+        let rolledBack = false;
+        try {
+          await nft(['-f', rollbackFile]);
+          rolledBack = true;
+        } catch {
+          rolledBack = false;
+        }
+        _bestEffortUnlink(fs, tempPath);
+        throw new FirewallVerifyError(
+          `post-apply verify failed (${verifyStderr.trim()}); rollback ${
+            rolledBack ? 'succeeded' : 'FAILED — inspect host firewall manually'
+          }`,
+          { stderr: verifyStderr, rolledBack }
+        );
+      }
+
+      _bestEffortUnlink(fs, tempPath);
+      return {
+        applied: true,
+        verified: true,
+        tempPath,
+        rollbackFile,
+        previousExisted: previous !== null,
+      };
+    },
+
+    /**
+     * Re-apply the rollback file (the pre-apply ruleset).
+     * @returns {Promise<{applied:true, rollbackFile:string}>}
+     * @throws {Error} when no rollback file exists or re-apply fails
+     */
+    async rollback() {
+      if (!fs.existsSync(rollbackFile)) {
+        throw new Error(`wg-firewall: no rollback file at ${rollbackFile}`);
+      }
+      try {
+        await nft(['-f', rollbackFile]);
+      } catch (err) {
+        throw new FirewallApplyError(
+          `rollback re-apply failed (${_errStderr(err).trim()})`,
+          { stderr: _errStderr(err) }
+        );
+      }
+      return { applied: true, rollbackFile };
+    },
+  };
+}
+
+module.exports = {
+  compileRuleset,
+  createWgFirewallApplier,
+  assertAdminIsolation,
+  sanitizeResourceSegment,
+  resourceSetName,
+  FirewallError,
+  FirewallCheckError,
+  FirewallApplyError,
+  FirewallVerifyError,
+  ADMIN_SET,
+  HUB_IP,
+  PEER_CIDR,
+};