From 7ef3914730e331c77f5a825c12a783013914e3f5 Mon Sep 17 00:00:00 2001
From: Hermes <hermes@nousagent.com>
Date: Sat, 3 Oct 2026 21:16:20 -0700
Subject: [PATCH] DC-140: network provider abstraction (src/network/) +
 tailscale provider + registry + tests

---
 .../network-provider-tailscale.test.js        | 444 ++++++++++++++++++
 .../__tests__/network-registry.test.js        | 166 +++++++
 dashcaddy-api/src/network/errors.js           |  59 +++
 dashcaddy-api/src/network/index.js            |  24 +
 dashcaddy-api/src/network/provider.js         |  75 +++
 .../src/network/providers/tailscale.js        | 389 +++++++++++++++
 dashcaddy-api/src/network/registry.js         | 151 ++++++
 7 files changed, 1308 insertions(+)
 create mode 100644 dashcaddy-api/__tests__/network-provider-tailscale.test.js
 create mode 100644 dashcaddy-api/__tests__/network-registry.test.js
 create mode 100644 dashcaddy-api/src/network/errors.js
 create mode 100644 dashcaddy-api/src/network/index.js
 create mode 100644 dashcaddy-api/src/network/provider.js
 create mode 100644 dashcaddy-api/src/network/providers/tailscale.js
 create mode 100644 dashcaddy-api/src/network/registry.js

diff --git a/dashcaddy-api/__tests__/network-provider-tailscale.test.js b/dashcaddy-api/__tests__/network-provider-tailscale.test.js
new file mode 100644
index 0000000..c390836
--- /dev/null
+++ b/dashcaddy-api/__tests__/network-provider-tailscale.test.js
@@ -0,0 +1,444 @@
+/**
+ * Tests for src/network/providers/tailscale.js (DC-140).
+ *
+ * Hermetic: the coordination client is a jest.fn() stub object, the local
+ * manager is a jest.mock of ../managers/tailscale-manager (same rigor as
+ * __tests__/tailscale-manager.test.js), and the whois execFile call is a
+ * plain stub — no network, no child processes.
+ */
+
+'use strict';
+
+jest.mock('../src/managers/tailscale-manager', () => ({
+  getSummary: jest.fn(),
+  getStatus: jest.fn(),
+}));
+
+const tailscaleManager = require('../src/managers/tailscale-manager');
+const { createTailscaleProvider, toProviderError } = require('../src/network/providers/tailscale');
+const { ProviderError } = require('../src/network/errors');
+const { TailscaleCoordError } = require('../src/managers/tailscale-coord');
+
+/** Coord client stub factory: every method is a jest.fn resolving []. */
+function makeCoord(overrides = {}) {
+  return {
+    listDevices: jest.fn(async () => []),
+    listUsers: jest.fn(async () => []),
+    deleteDevice: jest.fn(async () => ({ success: true })),
+    request: jest.fn(),
+    ...overrides,
+  };
+}
+
+function devicesFixture() {
+  return [
+    { id: 'dev1', name: 'laptop.tail3e209.ts.net', addresses: ['100.91.55.51'], user: '1001', os: 'linux' },
+    { id: 'dev2', name: 'phone.tail3e209.ts.net', addresses: ['100.92.60.10'], user: '1001', os: 'android' },
+    { id: 'dev3', name: 'nas.tail3e209.ts.net', addresses: ['100.93.7.7'], user: '2002', os: 'linux' },
+  ];
+}
+
+/** execFile stub (promise-style, matching promisify(execFile)) with canned stdout. */
+function makeExec(stdoutByIp = {}, { failAll = false } = {}) {
+  const calls = [];
+  const fn = (bin, args) => {
+    calls.push({ bin, args });
+    const ip = args && args[1];
+    if (failAll) return Promise.reject(new Error('tailscale CLI not available'));
+    return Promise.resolve({ stdout: stdoutByIp[ip] || '' });
+  };
+  fn.calls = calls;
+  return fn;
+}
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  tailscaleManager.getSummary.mockResolvedValue({ installed: true, connected: true, peerCount: 1 });
+  tailscaleManager.getStatus.mockResolvedValue(null);
+});
+
+describe('tailscale provider: id + capabilities', () => {
+  test('id() returns "tailscale"', () => {
+    expect(createTailscaleProvider().id()).toBe('tailscale');
+  });
+
+  test('capabilities() flags invites + splitDnsApi, no perPeerFirewall, not selfHosted', () => {
+    expect(createTailscaleProvider().capabilities()).toEqual({
+      invites: true,
+      splitDnsApi: true,
+      perPeerFirewall: false,
+      selfHosted: false,
+    });
+  });
+});
+
+describe('tailscale provider: getStatus()', () => {
+  test('wraps the local manager summary with provider framing', async () => {
+    tailscaleManager.getSummary.mockResolvedValue({ installed: true, connected: true, peerCount: 4 });
+    const p = createTailscaleProvider({ localManager: tailscaleManager });
+    const status = await p.getStatus();
+    expect(status).toMatchObject({ provider: 'tailscale', installed: true, connected: true });
+    expect(status.summary).toEqual({ installed: true, connected: true, peerCount: 4 });
+  });
+
+  test('degrades to installed:false when the CLI is missing', async () => {
+    tailscaleManager.getSummary.mockResolvedValue({ installed: false, connected: false });
+    const p = createTailscaleProvider({ localManager: tailscaleManager });
+    const status = await p.getStatus();
+    expect(status.installed).toBe(false);
+    expect(status.connected).toBe(false);
+  });
+});
+
+describe('tailscale provider: listDevices()', () => {
+  test('merges API devices with local online state by tailnet IP', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    tailscaleManager.getStatus.mockResolvedValue({
+      Peer: {
+        'nodekey:laptop': { TailscaleIPs: ['100.91.55.51'], Online: true },
+      },
+    });
+    const p = createTailscaleProvider({ coordClient: coord, localManager: tailscaleManager });
+    const devices = await p.listDevices();
+    expect(devices).toHaveLength(3);
+    expect(devices.find((d) => d.id === 'dev1')).toMatchObject({ ip: '100.91.55.51', online: true, userId: '1001' });
+    expect(devices.find((d) => d.id === 'dev3')).toMatchObject({ online: false });
+  });
+
+  test('works when local status is unavailable (all online false, no throw)', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    tailscaleManager.getStatus.mockResolvedValue(null);
+    const p = createTailscaleProvider({ coordClient: coord, localManager: tailscaleManager });
+    const devices = await p.listDevices();
+    expect(devices).toHaveLength(3);
+    expect(devices.every((d) => d.online === false)).toBe(true);
+  });
+
+  test('surfaces coord not-configured as ProviderError not_configured', async () => {
+    const p = createTailscaleProvider(); // no coord client attached
+    await expect(p.listDevices()).rejects.toMatchObject({
+      name: 'ProviderError',
+      code: 'not_configured',
+      retryable: false,
+    });
+  });
+});
+
+describe('tailscale provider: listPeople()', () => {
+  test('projects API users to { id, displayName, email, createdAt }', async () => {
+    const coord = makeCoord({
+      listUsers: jest.fn(async () => [
+        { id: '1001', loginName: 'sami@example.com', displayName: 'Sami', created: '2026-01-01T00:00:00Z' },
+        { id: '2002', loginName: 'guest-user', created: '2026-02-02T00:00:00Z' },
+      ]),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const people = await p.listPeople();
+    expect(people).toEqual([
+      { id: '1001', displayName: 'Sami', email: 'sami@example.com', createdAt: '2026-01-01T00:00:00Z' },
+      { id: '2002', displayName: 'guest-user', email: null, createdAt: '2026-02-02T00:00:00Z' },
+    ]);
+  });
+});
+
+describe('tailscale provider: createInvite()', () => {
+  test('with email: POSTs user-invites including the email field', async () => {
+    const coord = makeCoord({
+      request: jest.fn(async () => ({ id: 'inv1', inviteUrl: 'https://login.tailscale.com/a/abc123' })),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const invite = await p.createInvite({ role: 'member', email: 'friend@example.com' });
+    expect(invite).toEqual({ inviteUrl: 'https://login.tailscale.com/a/abc123', id: 'inv1' });
+    expect(coord.request).toHaveBeenCalledWith('POST', '/tailnet/-/user-invites', {
+      body: { inviteTailnet: true, email: 'friend@example.com' },
+    });
+  });
+
+  test('without email: body omits the email field entirely (link-first)', async () => {
+    const coord = makeCoord({
+      request: jest.fn(async () => ({ id: 'inv2', inviteUrl: 'https://login.tailscale.com/a/nomail' })),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const invite = await p.createInvite({ role: 'member' });
+    expect(invite.inviteUrl).toBe('https://login.tailscale.com/a/nomail');
+    expect(coord.request).toHaveBeenCalledWith('POST', '/tailnet/-/user-invites', {
+      body: { inviteTailnet: true },
+    });
+  });
+
+  test('missing inviteUrl in the response maps to a ProviderError', async () => {
+    const coord = makeCoord({ request: jest.fn(async () => ({ id: 'inv3' })) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.createInvite({ role: 'member' })).rejects.toMatchObject({
+      name: 'ProviderError',
+      code: 'provider_error',
+    });
+  });
+
+  test('invalid email input is rejected as bad_input before any API call', async () => {
+    const coord = makeCoord();
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.createInvite({ role: 'member', email: 'not-an-email' })).rejects.toMatchObject({
+      code: 'bad_input',
+    });
+    expect(coord.request).not.toHaveBeenCalled();
+  });
+
+  test('missing role is rejected as bad_input', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.createInvite({})).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: revokeInvite()', () => {
+  test('DELETEs the user-invite by id', async () => {
+    const coord = makeCoord({ request: jest.fn(async () => ({})) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.revokeInvite('inv1');
+    expect(res).toEqual({ revoked: true });
+    expect(coord.request).toHaveBeenCalledWith('DELETE', '/tailnet/-/user-invites/inv1');
+  });
+
+  test('requires an id', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.revokeInvite()).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: blockPerson()', () => {
+  test('expires the key of EVERY device owned by the user', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.blockPerson('1001');
+    expect(res).toEqual({ expired: ['dev1', 'dev2'], count: 2 });
+    const expireCalls = coord.request.mock.calls.filter((c) => c[1].endsWith('/expire'));
+    expect(expireCalls.map((c) => c[1])).toEqual(['/device/dev1/expire', '/device/dev2/expire']);
+    expireCalls.forEach((c) => expect(c[0]).toBe('POST'));
+    // no expiry for other users' devices
+    expect(coord.request.mock.calls.some((c) => c[1] === '/device/dev3/expire')).toBe(false);
+  });
+
+  test('user with zero devices → empty result, no expire calls', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.blockPerson('9999');
+    expect(res).toEqual({ expired: [], count: 0 });
+    expect(coord.request).not.toHaveBeenCalled();
+  });
+
+  test('matches userId numerically-or-stringly (API returns numbers)', async () => {
+    const coord = makeCoord({
+      listDevices: jest.fn(async () => devicesFixture().map((d) => ({ ...d, user: Number(d.user) }))),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.blockPerson('1001');
+    expect(res.count).toBe(2);
+  });
+
+  test('requires a userId', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.blockPerson()).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: unblockPerson()', () => {
+  test('is a no-op at the Tailscale level and returns { restored: true }', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.unblockPerson('1001')).resolves.toEqual({ restored: true });
+  });
+});
+
+describe('tailscale provider: removePerson()', () => {
+  test('DELETEs every device owned by the user', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.removePerson('1001');
+    expect(res).toEqual({ deleted: ['dev1', 'dev2'], count: 2 });
+    expect(coord.deleteDevice).toHaveBeenCalledTimes(2);
+    expect(coord.deleteDevice).toHaveBeenCalledWith('dev1');
+    expect(coord.deleteDevice).toHaveBeenCalledWith('dev2');
+    expect(coord.deleteDevice).not.toHaveBeenCalledWith('dev3');
+  });
+
+  test('requires a userId', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.removePerson()).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: revokeDevice()', () => {
+  test('expires the single device key via POST /device/{id}/expire', async () => {
+    const coord = makeCoord({ request: jest.fn(async () => ({})) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.revokeDevice('dev2');
+    expect(res).toEqual({ expired: 'dev2' });
+    expect(coord.request).toHaveBeenCalledWith('POST', '/device/dev2/expire', { body: {} });
+  });
+
+  test('requires a deviceId', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.revokeDevice()).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: syncAccess()', () => {
+  test('throws ProviderError code=not_implemented_in_provider (DC-148 lands later)', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.syncAccess({}, [])).rejects.toMatchObject({
+      name: 'ProviderError',
+      code: 'not_implemented_in_provider',
+      retryable: false,
+    });
+  });
+});
+
+describe('tailscale provider: whois()', () => {
+  test('resolves identity via the local tailscale CLI', async () => {
+    const exec = makeExec({
+      '100.91.55.51': 'user: sami@example.com\nnodeKey: nodekey:abc123\nnode: laptop.tail3e209.ts.net\n',
+    });
+    const p = createTailscaleProvider({ coordClient: makeCoord(), execFileImpl: exec });
+    const who = await p.whois('100.91.55.51');
+    expect(exec.calls).toEqual([{ bin: 'tailscale', args: ['whois', '100.91.55.51'] }]);
+    expect(who).toEqual({
+      nodeKey: 'nodekey:abc123',
+      userId: null,
+      loginName: 'sami@example.com',
+      hostname: 'laptop.tail3e209.ts.net',
+    });
+  });
+
+  test('captures userid when present', async () => {
+    const exec = makeExec({ '1.2.3.4': 'userid: 1001\nuser: sami@example.com\n' });
+    const p = createTailscaleProvider({ execFileImpl: exec });
+    await expect(p.whois('1.2.3.4')).resolves.toMatchObject({ userId: 1001 });
+  });
+
+  test('CLI failure resolves to null (unknown identity is not an error)', async () => {
+    const exec = makeExec({}, { failAll: true });
+    const p = createTailscaleProvider({ execFileImpl: exec });
+    await expect(p.whois('100.0.0.1')).resolves.toBeNull();
+  });
+
+  test('empty CLI output resolves to null', async () => {
+    const exec = makeExec({});
+    const p = createTailscaleProvider({ execFileImpl: exec });
+    await expect(p.whois('100.0.0.2')).resolves.toBeNull();
+  });
+
+  test('missing ip is bad_input', async () => {
+    const p = createTailscaleProvider();
+    await expect(p.whois()).rejects.toMatchObject({ code: 'bad_input' });
+  });
+
+  test('never touches the coordination client', async () => {
+    const coord = makeCoord();
+    const exec = makeExec({ '9.9.9.9': 'user: x@example.com\n' });
+    const p = createTailscaleProvider({ coordClient: coord, execFileImpl: exec });
+    await p.whois('9.9.9.9');
+    expect(coord.request).not.toHaveBeenCalled();
+    expect(coord.listDevices).not.toHaveBeenCalled();
+  });
+});
+
+describe('tailscale provider: configureDns()', () => {
+  test('POSTs split-DNS nameservers for the zone (capability-flagged)', async () => {
+    const coord = makeCoord({ request: jest.fn(async () => ({})) });
+    const p = createTailscaleProvider({ coordClient: coord });
+    const res = await p.configureDns({ zone: 'internal', server: '100.100.100.10' });
+    expect(res).toEqual({ configured: true, zone: 'internal', server: '100.100.100.10' });
+    expect(coord.request).toHaveBeenCalledWith('POST', '/tailnet/-/dns/nameservers', {
+      body: { dns: ['100.100.100.10'], domains: ['internal'] },
+    });
+  });
+
+  test('requires both zone and server', async () => {
+    const p = createTailscaleProvider({ coordClient: makeCoord() });
+    await expect(p.configureDns({ zone: 'internal' })).rejects.toMatchObject({ code: 'bad_input' });
+    await expect(p.configureDns({ server: '1.1.1.1' })).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+describe('tailscale provider: error mapping', () => {
+  test('listPeople surfaces a coord error as ProviderError', async () => {
+    const coord = makeCoord({
+      listUsers: jest.fn(async () => {
+        throw new TailscaleCoordError('Tailscale API 404: no users', { status: 404 });
+      }),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.listPeople()).rejects.toBeInstanceOf(ProviderError);
+    await expect(p.listPeople()).rejects.toMatchObject({ code: 'not_found' });
+  });
+
+  test('unauthorized coord error → ProviderError code unauthorized, not retryable', async () => {
+    const coord = makeCoord({
+      listUsers: jest.fn(async () => {
+        throw new TailscaleCoordError('Tailscale API 401: bad token', { status: 401 });
+      }),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.listPeople()).rejects.toMatchObject({
+      name: 'ProviderError',
+      code: 'unauthorized',
+      retryable: false,
+    });
+  });
+
+  test('rate_limited coord error → ProviderError retryable, retryAfter preserved', async () => {
+    const coord = makeCoord({
+      listUsers: jest.fn(async () => {
+        throw new TailscaleCoordError('Tailscale API 429: slow down', {
+          status: 429,
+          retryAfter: '30',
+        });
+      }),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.listPeople()).rejects.toMatchObject({
+      code: 'rate_limited',
+      retryable: true,
+      retryAfter: '30',
+    });
+  });
+
+  test('server_error coord error → ProviderError retryable', async () => {
+    const coord = makeCoord({
+      listUsers: jest.fn(async () => {
+        throw new TailscaleCoordError('Tailscale API 502: bad gateway', { status: 502 });
+      }),
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.listPeople()).rejects.toMatchObject({ code: 'server_error', retryable: true });
+  });
+
+  test('generic thrown errors become retryable provider_error', () => {
+    const mapped = toProviderError(new Error('boom'));
+    expect(mapped).toBeInstanceOf(ProviderError);
+    expect(mapped.code).toBe('provider_error');
+    expect(mapped.retryable).toBe(true);
+  });
+
+  test('ProviderError passes through toProviderError unchanged', () => {
+    const original = new ProviderError('keep me', { code: 'bad_input' });
+    expect(toProviderError(original)).toBe(original);
+  });
+
+  test('coord errors thrown mid-block propagate as ProviderError', async () => {
+    const coord = makeCoord({ listDevices: jest.fn(async () => devicesFixture()) });
+    coord.request = jest.fn(async () => {
+      throw new TailscaleCoordError('Tailscale API 403: forbidden', { status: 403 });
+    });
+    const p = createTailscaleProvider({ coordClient: coord });
+    await expect(p.blockPerson('1001')).rejects.toMatchObject({ code: 'unauthorized' });
+  });
+});
+
+describe('tailscale provider: attachCoordClient()', () => {
+  test('late-binding a client flips not_configured → working', async () => {
+    const p = createTailscaleProvider();
+    await expect(p.listPeople()).rejects.toMatchObject({ code: 'not_configured' });
+    p.attachCoordClient(makeCoord({ listUsers: jest.fn(async () => []) }));
+    await expect(p.listPeople()).resolves.toEqual([]);
+  });
+});
diff --git a/dashcaddy-api/__tests__/network-registry.test.js b/dashcaddy-api/__tests__/network-registry.test.js
new file mode 100644
index 0000000..d128200
--- /dev/null
+++ b/dashcaddy-api/__tests__/network-registry.test.js
@@ -0,0 +1,166 @@
+/**
+ * Tests for src/network/registry.js (DC-140).
+ *
+ * Hermetic: no network, no filesystem. Providers are stub factories whose
+ * instances are plain objects implementing the documented contract surface
+ * (see src/network/provider.js).
+ */
+
+'use strict';
+
+const { registry } = require('../src/network');
+const { ProviderNotActiveError, ProviderError } = require('../src/network/errors');
+const { CONTRACT_METHODS } = require('../src/network/provider');
+
+/** Build a minimal contract-satisfying stub provider. */
+function stubProvider(id, caps = {}) {
+  const p = {};
+  for (const m of CONTRACT_METHODS) {
+    p[m] = m === 'id' ? () => id : m === 'capabilities' ? () => ({
+      invites: false,
+      splitDnsApi: false,
+      perPeerFirewall: false,
+      selfHosted: false,
+      ...caps,
+    }) : async () => ({});
+  }
+  return p;
+}
+
+beforeEach(() => {
+  registry.reset();
+});
+
+describe('network registry: inactive default', () => {
+  test('defaults to inactive — getActiveProvider() throws ProviderNotActiveError', () => {
+    expect(() => registry.getActiveProvider()).toThrow(ProviderNotActiveError);
+  });
+
+  test('getCapabilities() throws ProviderNotActiveError when unset', () => {
+    expect(() => registry.getCapabilities()).toThrow(ProviderNotActiveError);
+  });
+
+  test('active id is null before activation', () => {
+    expect(registry.getActiveProviderId()).toBeNull();
+  });
+});
+
+describe('network registry: registration', () => {
+  test('registerProvider stores a factory under its id', () => {
+    registry.registerProvider('stub-a', () => stubProvider('stub-a'));
+    expect(registry.listProviderIds()).toContain('stub-a');
+  });
+
+  test('registerProvider rejects a non-function factory', () => {
+    expect(() => registry.registerProvider('bad', 'not-a-function')).toThrow(TypeError);
+  });
+
+  test('registerProvider rejects an empty id', () => {
+    expect(() => registry.registerProvider('', () => stubProvider('x'))).toThrow(TypeError);
+  });
+
+  test('registerProvider re-registers over an existing id', () => {
+    registry.registerProvider('stub-a', () => stubProvider('stub-a'));
+    registry.registerProvider('stub-a', () => stubProvider('stub-a'));
+    expect(registry.listProviderIds().filter((i) => i === 'stub-a')).toHaveLength(1);
+  });
+});
+
+describe('network registry: activation + resolution', () => {
+  test('setActiveProvider(id) resolves the instance via the factory', () => {
+    const sentinel = stubProvider('stub-a');
+    registry.registerProvider('stub-a', () => sentinel);
+    const active = registry.setActiveProvider('stub-a');
+    expect(active).toBe(sentinel);
+    expect(registry.getActiveProvider()).toBe(sentinel);
+    expect(registry.getActiveProviderId()).toBe('stub-a');
+  });
+
+  test('setActiveProvider throws for an unregistered id', () => {
+    expect(() => registry.setActiveProvider('does-not-exist')).toThrow(/Unknown network provider/);
+  });
+
+  test('setActiveProvider rebuilds the instance when the factory is replaced', () => {
+    const first = stubProvider('stub-a');
+    const second = stubProvider('stub-a');
+    registry.registerProvider('stub-a', () => first);
+    registry.setActiveProvider('stub-a');
+    registry.registerProvider('stub-a', () => second);
+    expect(registry.getActiveProvider()).toBe(second);
+  });
+
+  test('setActiveProvider rejects an instance missing contract methods', () => {
+    registry.registerProvider('incomplete', () => ({ id: () => 'incomplete' }));
+    expect(() => registry.setActiveProvider('incomplete')).toThrow(/contract/i);
+  });
+
+  test('setActiveProvider rejects an instance whose id() mismatches', () => {
+    registry.registerProvider('stub-a', () => stubProvider('stub-b'));
+    expect(() => registry.setActiveProvider('stub-a')).toThrow(/different id/i);
+  });
+
+  test('reset() returns the registry to inactive', () => {
+    registry.registerProvider('stub-a', () => stubProvider('stub-a'));
+    registry.setActiveProvider('stub-a');
+    registry.reset();
+    expect(() => registry.getActiveProvider()).toThrow(ProviderNotActiveError);
+    expect(registry.getActiveProviderId()).toBeNull();
+  });
+});
+
+describe('network registry: capability flags', () => {
+  test('getCapabilities() returns the active provider capabilities', () => {
+    registry.registerProvider(
+      'stub-ts',
+      () => stubProvider('stub-ts', { invites: true, splitDnsApi: true })
+    );
+    registry.setActiveProvider('stub-ts');
+    expect(registry.getCapabilities()).toEqual({
+      invites: true,
+      splitDnsApi: true,
+      perPeerFirewall: false,
+      selfHosted: false,
+    });
+  });
+});
+
+describe('network errors', () => {
+  test('ProviderNotActiveError is a ProviderError with code provider_not_active', () => {
+    const e = new ProviderNotActiveError();
+    expect(e).toBeInstanceOf(ProviderError);
+    expect(e.code).toBe('provider_not_active');
+    expect(e.retryable).toBe(false);
+  });
+
+  test('ProviderError derives retryable from code when not given', () => {
+    expect(new ProviderError('x', { code: 'rate_limited' }).retryable).toBe(true);
+    expect(new ProviderError('x', { code: 'server_error' }).retryable).toBe(true);
+    expect(new ProviderError('x', { code: 'network_error' }).retryable).toBe(true);
+    expect(new ProviderError('x', { code: 'unauthorized' }).retryable).toBe(false);
+    expect(new ProviderError('x', { code: 'bad_input' }).retryable).toBe(false);
+  });
+
+  test('ProviderError honors an explicit retryable override', () => {
+    expect(new ProviderError('x', { code: 'rate_limited', retryable: false }).retryable).toBe(false);
+    expect(new ProviderError('x', { code: 'unknown', retryable: true }).retryable).toBe(true);
+  });
+});
+
+describe('network index: built-in tailscale registration', () => {
+  test('tailscale is registered and activatable via the package entry point', () => {
+    // The package entry registers the real tailscale factory; activation
+    // builds a real provider instance (lazy deps, no network at build time).
+    expect(registry.listProviderIds()).toContain('tailscale');
+    const provider = registry.setActiveProvider('tailscale');
+    expect(provider.id()).toBe('tailscale');
+    expect(provider.capabilities()).toEqual({
+      invites: true,
+      splitDnsApi: true,
+      perPeerFirewall: false,
+      selfHosted: false,
+    });
+    // And it deactivates cleanly again.
+    registry.reset();
+    expect(() => registry.getActiveProvider()).toThrow(ProviderNotActiveError);
+  });
+});
diff --git a/dashcaddy-api/src/network/errors.js b/dashcaddy-api/src/network/errors.js
new file mode 100644
index 0000000..5cc7650
--- /dev/null
+++ b/dashcaddy-api/src/network/errors.js
@@ -0,0 +1,59 @@
+/**
+ * Provider error types for the DashCaddy Private Network abstraction
+ * (DC-140, specs/PRIVATE-NETWORK-SPEC.md §3).
+ *
+ * Every provider-facing failure surfaces as a ProviderError carrying a
+ * machine-readable `code` and a `retryable` hint, so feature modules can
+ * degrade cleanly without knowing which provider is active.
+ *
+ * Canonical codes (providers may add, but these are the shared vocabulary):
+ *   - not_configured        provider has no credentials yet
+ *   - unauthorized          token rejected (401/403)
+ *   - not_found             entity does not exist upstream
+ *   - rate_limited          upstream 429 (retryable, honor retryAfter)
+ *   - server_error          upstream 5xx (retryable)
+ *   - network_error         transport failure (retryable)
+ *   - bad_input             caller passed invalid arguments
+ *   - not_implemented_in_provider  capability exists but lands in a later DC
+ *   - provider_not_active   registry has no active provider
+ */
+
+'use strict';
+
+/** Codes for which a retry (possibly after a backoff) is reasonable. */
+const RETRYABLE_CODES = new Set(['rate_limited', 'server_error', 'network_error']);
+
+class ProviderError extends Error {
+  /**
+   * @param {string} message - human-readable description
+   * @param {object} [opts]
+   * @param {string} [opts.code='unknown'] - machine-readable error code
+   * @param {boolean} [opts.retryable] - defaults to derived-from-code
+   * @param {*} [opts.cause] - original error (e.g. TailscaleCoordError)
+   * @param {*} [opts.retryAfter] - upstream retry-after hint, seconds
+   */
+  constructor(message, { code, retryable, cause, retryAfter } = {}) {
+    super(message);
+    this.name = 'ProviderError';
+    this.code = code || 'unknown';
+    this.retryable = retryable !== undefined ? !!retryable : RETRYABLE_CODES.has(this.code);
+    if (retryAfter !== undefined) this.retryAfter = retryAfter;
+    if (cause !== undefined) this.cause = cause;
+  }
+}
+
+/**
+ * Thrown by the registry when no provider has been activated yet
+ * (default state until the setup wizard connects one — DC-152).
+ */
+class ProviderNotActiveError extends ProviderError {
+  constructor(message) {
+    super(message || 'No active network provider configured', {
+      code: 'provider_not_active',
+      retryable: false,
+    });
+    this.name = 'ProviderNotActiveError';
+  }
+}
+
+module.exports = { ProviderError, ProviderNotActiveError };
diff --git a/dashcaddy-api/src/network/index.js b/dashcaddy-api/src/network/index.js
new file mode 100644
index 0000000..b697922
--- /dev/null
+++ b/dashcaddy-api/src/network/index.js
@@ -0,0 +1,24 @@
+/**
+ * src/network entry point (DC-140).
+ *
+ * Registers the built-in providers with the registry on first require.
+ * The WireGuard provider (DC-149) registers itself here when it lands.
+ *
+ * Usage (feature modules — the ONLY sanctioned import):
+ *   const { registry } = require('../network');
+ *   const provider = registry.getActiveProvider(); // throws if unset
+ *   if (registry.getCapabilities().invites) { ... }
+ */
+
+'use strict';
+
+const registry = require('./registry');
+const { createTailscaleProvider } = require('./providers/tailscale');
+
+registry.registerProvider('tailscale', createTailscaleProvider);
+
+module.exports = {
+  registry,
+  errors: require('./errors'),
+  CONTRACT_METHODS: require('./provider').CONTRACT_METHODS,
+};
diff --git a/dashcaddy-api/src/network/provider.js b/dashcaddy-api/src/network/provider.js
new file mode 100644
index 0000000..22be3bb
--- /dev/null
+++ b/dashcaddy-api/src/network/provider.js
@@ -0,0 +1,75 @@
+/**
+ * NetworkProvider interface — the documented contract for DashCaddy
+ * Private Network providers (DC-140, specs/PRIVATE-NETWORK-SPEC.md §3).
+ *
+ * Everything above the provider (people, groups, resources, access map,
+ * forward_auth, Technitium names, the CA, the UI) is shared and talks to
+ * the network ONLY through this contract — never to a provider module
+ * directly. Resolution goes through src/network/registry.js.
+ *
+ * ## Capability flags
+ *
+ * `capabilities()` returns:
+ *   - invites        provider can mint invite URLs itself (TS user-invites /
+ *                    WG one-time token). When false, DashCaddy mints its own.
+ *   - splitDnsApi    provider exposes a split-DNS API (Tailscale does;
+ *                    WireGuard writes Technitium directly instead).
+ *   - perPeerFirewall provider enforces per-peer rules natively (WG nftables;
+ *                    Tailscale relies on ACLs, so false).
+ *   - selfHosted     no outside control-plane dependency (WG true, TS false).
+ *
+ * Feature modules MUST check capabilities and degrade cleanly.
+ *
+ * ## Methods (all async, all return plain JSON, all validated)
+ *
+ *   id() → 'tailscale' | 'wireguard'
+ *   capabilities() → { invites, splitDnsApi, perPeerFirewall, selfHosted }
+ *   getStatus() → provider health/summary (TS: local `tailscale status`;
+ *                 WG: `wg show dump` + iface state)
+ *   listDevices() → device list merged with local online state
+ *   listPeople() → provider users projected to
+ *                 { id, displayName, email, createdAt }
+ *   createInvite({ role, email? }) → { inviteUrl, id } — email is OPTIONAL;
+ *                 when omitted, the provider returns a link without sending
+ *                 (link-first, DC-085 pattern; never log inviteUrl raw)
+ *   revokeInvite(id) → { revoked: true }
+ *   blockPerson(userId) → reversible network-level block (TS: expire every
+ *                 device key owned by the user; WG: drop peer + deny set)
+ *   unblockPerson(userId) → reverse of blockPerson (TS: no-op at provider
+ *                 level, DashCaddy re-grants via syncAccess)
+ *   removePerson(userId) → delete provider devices + revoke invites
+ *   revokeDevice(deviceId) → expire/remove a single device's access
+ *   syncAccess(accessMap, resources) → compile + dry-run + push provider
+ *                 rules (hash-guarded). Injected per provider in later DCs
+ *                 (TS ACL compiler = DC-148; WG nftables = DC-150).
+ *   whois(ip) → which person owns the connecting device
+ *   configureDns({ zone, server }) → split-DNS setup when splitDnsApi
+ *
+ * ## Error contract
+ *
+ * All failures throw ProviderError (src/network/errors.js) with a `code`
+ * and `retryable` hint. Providers map their native errors at the boundary
+ * so no provider-specific error type ever escapes this package.
+ */
+
+'use strict';
+
+module.exports = {
+  /** Method names every provider must implement (documented contract). */
+  CONTRACT_METHODS: [
+    'id',
+    'capabilities',
+    'getStatus',
+    'listDevices',
+    'listPeople',
+    'createInvite',
+    'revokeInvite',
+    'blockPerson',
+    'unblockPerson',
+    'removePerson',
+    'revokeDevice',
+    'syncAccess',
+    'whois',
+    'configureDns',
+  ],
+};
diff --git a/dashcaddy-api/src/network/providers/tailscale.js b/dashcaddy-api/src/network/providers/tailscale.js
new file mode 100644
index 0000000..ab11239
--- /dev/null
+++ b/dashcaddy-api/src/network/providers/tailscale.js
@@ -0,0 +1,389 @@
+/**
+ * Tailscale provider for the DashCaddy Private Network (DC-140,
+ * specs/PRIVATE-NETWORK-SPEC.md §3).
+ *
+ * Wraps — and does not duplicate — the two existing tailscale modules:
+ *   - src/managers/tailscale-coord.js  — cloud control-plane client
+ *     (api.tailscale.com: devices, users, user-invites, device expire,
+ *     device delete, split-DNS preferences)
+ *   - src/managers/tailscale-manager.js — local CLI daemon (status, whois)
+ *
+ * This adapter adds the provider-contract semantics on top: people
+ * projection, device key expiry as "block", error normalization into
+ * ProviderError, and capability flags.
+ *
+ * API facts (Tailscale API v2, Oct 2026):
+ *   POST   /tailnet/{t}/user-invites   email optional → { inviteUrl, id }
+ *   DELETE /tailnet/{t}/user-invites/{id}
+ *   GET    /tailnet/{t}/user-invites
+ *   POST   /device/{id}/expire         expire device key (reversible: user re-auths)
+ *   DELETE /device/{id}                remove device
+ *   POST   /tailnet/{t}/dns/nameservers  split-DNS search domains
+ *   POST   /tailnet/{t}/preferences    feature prefs incl. MagicDNS
+ * Free-plan fact: ACL groups capped at 3, so compiled ACLs must reference
+ * users directly — handled by the ACL compiler (DC-148), not here.
+ */
+
+'use strict';
+
+const { execFile } = require('child_process');
+const { promisify } = require('util');
+const { ProviderError } = require('../errors');
+
+const execFileAsyncDefault = promisify(execFile);
+const CLI_TIMEOUT_MS = 5000;
+
+/** Map a TailscaleCoordError code to the shared ProviderError vocabulary. */
+const COORD_CODE_MAP = {
+  not_configured: 'not_configured',
+  unauthorized: 'unauthorized',
+  not_found: 'not_found',
+  rate_limited: 'rate_limited',
+  server_error: 'server_error',
+  network_error: 'network_error',
+  bad_input: 'bad_input',
+};
+
+/**
+ * Normalize any thrown value into a ProviderError. Coord errors keep their
+ * code (mapped) + retryAfter; unknown errors land as retryable
+ * 'provider_error' so callers can distinguish transport-ish failures from
+ * contract violations.
+ * @returns {ProviderError}
+ */
+function toProviderError(err) {
+  if (err instanceof ProviderError) return err;
+  if (err && err.name === 'TailscaleCoordError') {
+    const code = COORD_CODE_MAP[err.code] || 'provider_error';
+    const opts = { code, cause: err };
+    if (err.retryAfter !== undefined) opts.retryAfter = err.retryAfter;
+    return new ProviderError('tailscale: ' + err.message, opts);
+  }
+  const message = (err && err.message) ? err.message : String(err);
+  return new ProviderError('tailscale: ' + message, {
+    code: 'provider_error',
+    retryable: true,
+    cause: err,
+  });
+}
+
+/**
+ * Build the Tailscale NetworkProvider.
+ *
+ * @param {object} deps - all injectable, all optional
+ * @param {object} deps.coordClient - object with the TailscaleCoordClient
+ *   method surface. When omitted the provider expects the registry/caller
+ *   to supply one via `provider.attachCoordClient(client)` (wiring to the
+ *   context singleton lands with routes/network.js — keeps this module
+ *   free of app-context requires).
+ * @param {object} deps.localManager - tailscale-manager module (default:
+ *   require it lazily). Used for getStatus(); may be a jest mock.
+ * @param {Function} deps.execFileImpl - optional execFile(cb) override for
+ *   the whois CLI call (tests inject a stub instead of spawning processes).
+ */
+function createTailscaleProvider({
+  coordClient = null,
+  localManager,
+  execFileImpl,
+} = {}) {
+  // Lazy default require keeps jest.mock('.../tailscale-manager') effective.
+  /* eslint-disable global-require -- see above */
+  const manager = localManager || require('../../managers/tailscale-manager');
+  const execFn = execFileImpl || execFileAsyncDefault;
+  let coord = coordClient;
+
+  function requireCoord() {
+    if (!coord) {
+      throw new ProviderError(
+        'Tailscale coordination client not attached (API token not configured?)',
+        { code: 'not_configured', retryable: false }
+      );
+    }
+    return coord;
+  }
+
+  /** Normalized single-flight wrapper for coord calls. */
+  async function coordCall(_methodName, fn) {
+    try {
+      return await fn(requireCoord(_methodName));
+    } catch (err) {
+      throw toProviderError(err);
+    }
+  }
+
+  const provider = {
+    id() {
+      return 'tailscale';
+    },
+
+    capabilities() {
+      return {
+        invites: true,
+        splitDnsApi: true,
+        perPeerFirewall: false,
+        selfHosted: false,
+      };
+    },
+
+    /**
+     * Health/summary from the LOCAL daemon (existing manager, cached there).
+     * Returns null-ish manager output unchanged — the manager already
+     * degrades gracefully ({ installed: false } / { connected: false }).
+     */
+    async getStatus() {
+      try {
+        const summary = await manager.getSummary();
+        return {
+          provider: 'tailscale',
+          installed: !!(summary && summary.installed),
+          connected: !!(summary && summary.connected),
+          summary,
+        };
+      } catch (err) {
+        throw toProviderError(err, 'getStatus');
+      }
+    },
+
+    /** Devices from the API, online state merged from local status. */
+    async listDevices() {
+      try {
+        const [devices, local] = await Promise.all([
+          coordCall('listDevices', (c) => c.listDevices({ skipCache: false })),
+          Promise.resolve(manager.getStatus()).catch(() => null),
+        ]);
+        const localPeers = {};
+        if (local && local.Peer && typeof local.Peer === 'object') {
+          for (const [nodeKey, peer] of Object.entries(local.Peer)) {
+            if (peer && Array.isArray(peer.TailscaleIPs) && peer.TailscaleIPs[0]) {
+              localPeers[peer.TailscaleIPs[0]] = { nodeKey, online: !!peer.Online };
+            }
+          }
+        }
+        return (devices || []).map((d) => {
+          const addr = Array.isArray(d.addresses) ? d.addresses[0] : null;
+          const localInfo = addr ? localPeers[addr] : undefined;
+          return {
+            id: d.id,
+            name: d.name || d.hostname || null,
+            hostname: d.hostname || null,
+            ip: addr,
+            os: d.os || null,
+            online: localInfo ? localInfo.online : !!d.online,
+            lastSeen: d.lastSeen || null,
+            userId: d.user !== undefined ? d.user : null,
+            tags: d.tags || [],
+            keyExpiry: d.keyExpiry || null,
+          };
+        });
+      } catch (err) {
+        throw err instanceof ProviderError ? err : toProviderError(err, 'listDevices');
+      }
+    },
+
+    /** API users → people projection { id, displayName, email, createdAt }. */
+    listPeople() {
+      return coordCall('listPeople', async (c) => {
+        const users = await c.listUsers({ skipCache: false });
+        return (users || []).map((u) => ({
+          id: u.id,
+          displayName: u.displayName || u.loginName || null,
+          email: u.loginName && u.loginName.includes('@') ? u.loginName : null,
+          createdAt: u.created || null,
+        }));
+      });
+    },
+
+    /**
+     * Create a user invite. Email is OPTIONAL — when omitted, Tailscale
+     * returns an inviteUrl WITHOUT sending email (link-first, spec §5).
+     * The inviteUrl is the artifact; never log it raw (routes enforce).
+     * @returns {{ inviteUrl: string, id: string }}
+     */
+    async createInvite({ role, email } = {}) {
+      if (!role || typeof role !== 'string') {
+        throw new ProviderError('createInvite: role is required', { code: 'bad_input' });
+      }
+      if (email !== undefined && (typeof email !== 'string' || !email.includes('@'))) {
+        throw new ProviderError('createInvite: email must be a valid address when provided', {
+          code: 'bad_input',
+        });
+      }
+      // Input validation above throws synchronously by design (bad_input);
+      // everything below is async and normalized through coordCall.
+      const invitePromise = coordCall('createInvite', async (c) => {
+        const body = { inviteTailnet: true };
+        if (email) body.email = email;
+        const res = await c.request('POST', '/tailnet/-/user-invites', { body });
+        if (!res || !res.inviteUrl) {
+          throw new ProviderError('Tailscale user-invite response missing inviteUrl', {
+            code: 'provider_error',
+            retryable: true,
+          });
+        }
+        return { inviteUrl: res.inviteUrl, id: res.id || null };
+      });
+      return await invitePromise.catch((err) => Promise.reject(toProviderError(err)));
+    },
+
+    /** Revoke a user invite: DELETE /tailnet/{t}/user-invites/{id}. */
+    async revokeInvite(id) {
+      if (!id) {
+        throw new ProviderError('revokeInvite: id is required', { code: 'bad_input' });
+      }
+      return await coordCall('revokeInvite', async (c) => {
+        await c.request('DELETE', '/tailnet/-/user-invites/' + encodeURIComponent(id));
+        return { revoked: true };
+      });
+    },
+
+    /**
+     * Block a person at the network level: expire the key of every device
+     * they own (POST /device/{id}/expire). Reversible — unexpired devices
+     * re-authenticate; DashCaddy re-grants via syncAccess on unblock.
+     * @returns {{ expired: string[], count: number }}
+     */
+    async blockPerson(userId) {
+      if (!userId) {
+        throw new ProviderError('blockPerson: userId is required', { code: 'bad_input' });
+      }
+      return await coordCall('blockPerson', async (c) => {
+        const devices = await c.listDevices({ skipCache: true });
+        const owned = (devices || []).filter((d) => String(d.user) === String(userId));
+        const expired = [];
+        for (const d of owned) {
+          await c.request('POST', '/device/' + encodeURIComponent(d.id) + '/expire', { body: {} });
+          expired.push(d.id);
+        }
+        return { expired, count: expired.length };
+      });
+    },
+
+    /**
+     * Unblock is a no-op at the Tailscale level: key expiry is reversed by
+     * the user re-authenticating, and access restoration happens when
+     * DashCaddy re-syncs the ACL (syncAccess). Kept in the contract so the
+     * orchestration layer (DC-143) can call it uniformly across providers.
+     */
+    async unblockPerson() {
+      await Promise.resolve(); // uniform async surface (contract: all async)
+      return { restored: true };
+    },
+
+    /**
+     * Remove a person permanently: DELETE every device they own. (Invite
+     * revocation and the DashCaddy person record are handled by the
+     * orchestration layer, which owns that state.)
+     * @returns {{ deleted: string[], count: number }}
+     */
+    async removePerson(userId) {
+      if (!userId) {
+        throw new ProviderError('removePerson: userId is required', { code: 'bad_input' });
+      }
+      return await coordCall('removePerson', async (c) => {
+        const devices = await c.listDevices({ skipCache: true });
+        const owned = (devices || []).filter((d) => String(d.user) === String(userId));
+        const deleted = [];
+        for (const d of owned) {
+          await c.deleteDevice(d.id);
+          deleted.push(d.id);
+        }
+        return { deleted, count: deleted.length };
+      });
+    },
+
+    /** Expire one device's key (kick a single machine, keep the person). */
+    async revokeDevice(deviceId) {
+      if (!deviceId) {
+        throw new ProviderError('revokeDevice: deviceId is required', { code: 'bad_input' });
+      }
+      return await coordCall('revokeDevice', async (c) => {
+        await c.request('POST', '/device/' + encodeURIComponent(deviceId) + '/expire', { body: {} });
+        return { expired: deviceId };
+      });
+    },
+
+    /**
+     * Compile + push ACLs. NOT in this provider yet — the ACL compiler is
+     * DC-148 and will be injected (hash-guarded push, lockout guard, dry-run
+     * preview). Feature modules must treat this code as "coming soon", not
+     * as a silent no-op.
+     */
+    async syncAccess() {
+      await Promise.reject(
+        new ProviderError('syncAccess lands with the ACL compiler (DC-148)', {
+          code: 'not_implemented_in_provider',
+          retryable: false,
+        })
+      );
+    },
+
+    /**
+     * Who owns the device at this tailnet IP? Local CLI only — never the
+     * cloud API — because forward_auth sits on the same host as tailscaled.
+     * Returns null when the CLI cannot resolve the ip (offline peer,
+     * unknown address) rather than throwing.
+     * @returns {Promise<{nodeKey:string, userId:number|null, loginName:string|null, hostname:string|null}|null>}
+     */
+    async whois(ip) {
+      if (!ip || typeof ip !== 'string') {
+        throw new ProviderError('whois: ip is required', { code: 'bad_input' });
+      }
+      let out;
+      try {
+        out = await execFn('tailscale', ['whois', ip], { timeout: CLI_TIMEOUT_MS });
+      } catch (err) {
+        // CLI failure (not installed / daemon down / unknown ip): identity
+        // unknown is a legitimate answer for forward_auth, not an error.
+        return null;
+      }
+      const stdout = (out && out.stdout) || '';
+      if (!stdout.trim()) return null;
+      // `tailscale whois` prints lines "key=value" per detail, e.g.
+      //   user: sami@example.com
+      //   nodeKey: nodekey:abc...
+      //   node: dns2-sami.tail3e209.ts.net
+      // plus a "via" line when routed. Parse defensively.
+      const fields = {};
+      for (const line of stdout.split('\n')) {
+        const m = line.match(/^\s*([a-zA-Z]+):\s*(.+)$/);
+        if (m) fields[m[1].toLowerCase()] = m[2].trim();
+      }
+      if (!fields.user && !fields.nodekey) return null;
+      return {
+        nodeKey: fields.nodekey || null,
+        userId: fields.userid ? Number(fields.userid) : null,
+        loginName: fields.user || null,
+        hostname: fields.node || null,
+      };
+    },
+
+    /**
+     * Split-DNS via the coordination API (capability-flagged: splitDnsApi).
+     * Sets the tailnet's global nameservers to the Technitium server for the
+     * given zone. Callers must check capabilities().splitDnsApi first.
+     */
+    async configureDns({ zone, server } = {}) {
+      if (!zone || typeof zone !== 'string') {
+        throw new ProviderError('configureDns: zone is required', { code: 'bad_input' });
+      }
+      if (!server || typeof server !== 'string') {
+        throw new ProviderError('configureDns: server is required', { code: 'bad_input' });
+      }
+      return await coordCall('configureDns', async (c) => {
+        await c.request('POST', '/tailnet/-/dns/nameservers', {
+          body: { dns: [server], domains: [zone] },
+        });
+        return { configured: true, zone, server };
+      });
+    },
+
+    /** Late-bind the coord client (context wiring lands with routes/network.js). */
+    attachCoordClient(client) {
+      coord = client;
+    },
+  };
+
+  return provider;
+}
+
+module.exports = { createTailscaleProvider, toProviderError };
diff --git a/dashcaddy-api/src/network/registry.js b/dashcaddy-api/src/network/registry.js
new file mode 100644
index 0000000..97877ac
--- /dev/null
+++ b/dashcaddy-api/src/network/registry.js
@@ -0,0 +1,151 @@
+/**
+ * Network provider registry (DC-140, specs/PRIVATE-NETWORK-SPEC.md §3).
+ *
+ * Single resolution point between feature modules and providers: no feature
+ * code may import a provider module directly — they call getActiveProvider().
+ *
+ * State is deliberately process-local and defaults to INACTIVE: no provider
+ * is active until the setup wizard (DC-152) connects one. Until then,
+ * getActiveProvider()/getCapabilities() throw ProviderNotActiveError.
+ *
+ * registerProvider(factory) — factory is a function ({ getCoordClient,
+ * localManager, execFileImpl } = {}) → provider instance. The tailscale
+ * factory defaults to lazily binding the existing singletons
+ * (src/context getCoordClient pattern + src/managers/tailscale-manager),
+ * but every dependency is injectable so tests stay hermetic.
+ */
+
+'use strict';
+
+const { ProviderNotActiveError } = require('./errors');
+const { CONTRACT_METHODS } = require('./provider');
+
+// id → factory(provider deps) → provider instance
+const _factories = new Map();
+let _activeId = null;
+let _activeProvider = null;
+
+/** Lately-bound defaults (required lazily so jest.mock stays effective). */
+function _defaultDeps() {
+  /* eslint-disable global-require -- lazy on purpose: keeps registry require-time
+     side effects at zero and respects jest module mocks. */
+  return {
+    localManager: require('../managers/tailscale-manager'),
+    execFileImpl: null,
+  };
+}
+
+/**
+ * Register a provider factory under its id.
+ * @param {string} id - provider id, e.g. 'tailscale' (must match provider.id())
+ * @param {Function} factory - (deps) => provider instance
+ * @returns {void}
+ */
+function registerProvider(id, factory) {
+  if (typeof id !== 'string' || !id) {
+    throw new TypeError('registerProvider: id must be a non-empty string');
+  }
+  if (typeof factory !== 'function') {
+    throw new TypeError('registerProvider: factory must be a function');
+  }
+  _factories.set(id, factory);
+  // If this id is currently active, drop the cached instance so the next
+  // getActiveProvider() rebuilds from the (possibly new) factory.
+  if (_activeId === id) _activeProvider = null;
+}
+
+/** Build (or rebuild) the instance for `_activeId` from its factory. */
+function _buildActive() {
+  const factory = _factories.get(_activeId);
+  const provider = factory ? factory(_defaultDeps()) : null;
+  if (!_isContractProvider(provider)) {
+    throw new Error('Provider "' + _activeId + '" does not satisfy the NetworkProvider contract');
+  }
+  _activeProvider = provider;
+  return _activeProvider;
+}
+
+/**
+ * True when the id refers to a registered provider whose instances satisfy
+ * the NetworkProvider contract surface (all CONTRACT_METHODS present).
+ */
+function _isContractProvider(p) {
+  if (!p) return false;
+  return CONTRACT_METHODS.every((m) => typeof p[m] === 'function');
+}
+
+/**
+ * Activate a registered provider. Rebuilding the instance resets any state
+ * the previous one carried.
+ * @param {string} id
+ * @returns {object} the newly active provider instance
+ * @throws {Error} when the id is not registered, or the instance built from
+ *   it does not satisfy the documented contract.
+ */
+function setActiveProvider(id) {
+  const factory = _factories.get(id);
+  if (!factory) {
+    throw new Error('Unknown network provider: ' + String(id));
+  }
+  const provider = factory(_defaultDeps());
+  if (!_isContractProvider(provider)) {
+    throw new Error('Provider "' + id + '" does not satisfy the NetworkProvider contract');
+  }
+  if (typeof provider.id !== 'function' || provider.id() !== id) {
+    throw new Error('Provider "' + id + '" reports a different id');
+  }
+  _activeId = id;
+  _activeProvider = provider;
+  return _activeProvider;
+}
+
+/**
+ * The active provider instance. Feature modules' ONLY entry point into
+ * provider functionality.
+ * @throws {ProviderNotActiveError} when no provider has been activated
+ */
+function getActiveProvider() {
+  if (!_activeId) {
+    throw new ProviderNotActiveError(
+      'No active network provider. Complete the Private Network setup wizard first.'
+    );
+  }
+  // Factory may have been re-registered since activation → rebuild lazily.
+  return _activeProvider || _buildActive();
+}
+
+/**
+ * Capability flags of the active provider (spec §3): feature modules check
+ * these and degrade cleanly when a capability is absent.
+ * @returns {{invites:boolean, splitDnsApi:boolean, perPeerFirewall:boolean, selfHosted:boolean}}
+ * @throws {ProviderNotActiveError} when no provider has been activated
+ */
+function getCapabilities() {
+  return getActiveProvider().capabilities();
+}
+
+/** List registered provider ids (setup wizard mode picker). */
+function listProviderIds() {
+  return [..._factories.keys()];
+}
+
+/** Deactivate (setup wizard disconnect / tests). Next getActiveProvider() throws. */
+function reset() {
+  _activeId = null;
+  _activeProvider = null;
+}
+
+/** Currently active provider id, or null — read-only introspection. */
+function getActiveProviderId() {
+  return _activeId;
+}
+
+module.exports = {
+  registerProvider,
+  setActiveProvider,
+  getActiveProvider,
+  getCapabilities,
+  listProviderIds,
+  getActiveProviderId,
+  reset,
+};