diff --git a/dashcaddy-api/__tests__/network-technitium.test.js b/dashcaddy-api/__tests__/network-technitium.test.js
new file mode 100644
index 0000000..0677cda
--- /dev/null
+++ b/dashcaddy-api/__tests__/network-technitium.test.js
@@ -0,0 +1,489 @@
+/**
+ * Tests for src/network/technitium.js (DC-146).
+ *
+ * Hermetic: fetchImpl is a jest.fn() stub, credentialManager and the
+ * network registry are stub objects (same rigor as
+ * __tests__/network-provider-tailscale.test.js). No real Technitium,
+ * no real sockets.
+ */
+
+'use strict';
+
+const {
+  createTechnitiumClient,
+  createTechnitiumService,
+} = require('../src/network/technitium');
+const { ProviderError } = require('../src/network/errors');
+
+/* ------------------------------------------------------------------ *
+ * HTTP stub helpers
+ * ------------------------------------------------------------------ */
+
+const _JSON_HEADERS = { 'Content-Type': 'application/json' };
+
+function jsonResponse(status, body) {
+  return {
+    ok: status >= 200 && status < 300,
+    status,
+    statusText: 'stub',
+    json: async () => Promise.resolve(body),
+  };
+}
+
+function textResponse(status, text) {
+  return {
+    ok: status >= 200 && status < 300,
+    status,
+    statusText: text,
+    json: async () => Promise.reject(new Error('not json')),
+  };
+}
+
+/** fetch stub that routes by URL path; handlers appended as [matcher, fn]. */
+function makeFetch(routes = [], { defaultResponse } = {}) {
+  const calls = [];
+  const fn = async (url, init) => {
+    calls.push({ url: String(url), init });
+    const u = new URL(String(url));
+    for (const [match, handler] of routes) {
+      if (u.pathname.endsWith(match)) return handler(u, init, calls.length - 1);
+    }
+    if (defaultResponse) return defaultResponse(u, init);
+    return jsonResponse(404, { status: 'error', errorMessage: 'no route' });
+  };
+  fn.mock = {}; // jest.fn()-shape compatibility if inspected
+  fn.calls = calls;
+  return fn;
+}
+
+function credMgr(token) {
+  const retrieve = async () => (token === undefined ? null : token);
+  return { retrieve: jest.fn(retrieve) };
+}
+
+const noopLogger = { info() {}, warn: jest.fn(), error: jest.fn(), debug() {} };
+
+function makeClient(routes, { token = 'tok123', host = 'dns.local', ...rest } = {}) {
+  const fetchImpl = typeof routes === 'function' ? routes : makeFetch(routes);
+  const getToken = async () => token;
+  const client = createTechnitiumClient({
+    host,
+    getToken,
+    fetchImpl,
+    logger: noopLogger,
+    ...rest,
+  });
+  return { client, fetchImpl };
+}
+
+/* ------------------------------------------------------------------ *
+ * Client: zones
+ * ------------------------------------------------------------------ */
+
+describe('technitium client: listZones + ensureZone idempotency', () => {
+  test('listZones normalizes the response array', async () => {
+    const { client } = makeClient([
+      ['/zones/list', () => jsonResponse(200, { status: 'ok', response: [{ name: 'corp', type: 'Primary' }] })],
+    ]);
+    const zones = await client.listZones();
+    expect(zones).toEqual([{ name: 'corp', type: 'Primary' }]);
+  });
+
+  test('ensureZone creates a Primary zone only when absent', async () => {
+    const zones = [];
+    const fetchImpl = makeFetch([
+      ['/zones/list', () => jsonResponse(200, { status: 'ok', response: zones })],
+      ['/zones/create', () => { zones.push({ name: 'corp', type: 'Primary' }); return jsonResponse(200, { status: 'ok' }); }],
+    ]);
+    const client = createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl });
+
+    const first = await client.ensureZone('corp');
+    expect(first).toEqual({ created: true, unchanged: false });
+    expect(fetchImpl.calls.filter((c) => c.url.includes('/zones/create'))).toHaveLength(1);
+
+    const second = await client.ensureZone('corp'); // now present
+    expect(second).toEqual({ created: false, unchanged: true });
+    expect(fetchImpl.calls.filter((c) => c.url.includes('/zones/create'))).toHaveLength(1);
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Client: upsertRecord three paths
+ * ------------------------------------------------------------------ */
+
+describe('technitium client: upsertRecord', () => {
+  function recordApi(existing, handlers = {}) {
+    let rec = existing;
+    const routes = [
+      ['/zones/records/get', (u) => {
+        if (handlers.get) return handlers.get(u);
+        if (!rec) return jsonResponse(200, { status: 'error', errorMessage: 'Record not found.' });
+        return jsonResponse(200, { status: 'ok', response: rec });
+      }],
+      ['/zones/records/delete', (u, init) => {
+        if (handlers.del) return handlers.del(u, init);
+        rec = null;
+        return jsonResponse(200, { status: 'ok' });
+      }],
+      ['/zones/records/add', (u, init) => {
+        if (handlers.add) return handlers.add(u, init);
+        const body = JSON.parse(init.body);
+        rec = { name: body.name, type: body.type, rData: { ipAddress: body.ipAddress } };
+        return jsonResponse(200, { status: 'ok' });
+      }],
+    ];
+    return makeFetch(routes);
+  }
+
+  test('absent record → created (single add, no delete)', async () => {
+    const fetchImpl = recordApi(null);
+    const client = createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl });
+    const out = await client.upsertRecord({ zone: 'corp', name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } });
+    expect(out).toEqual({ created: true });
+    expect(fetchImpl.calls.filter((c) => c.url.includes('/add'))).toHaveLength(1);
+    expect(fetchImpl.calls.filter((c) => c.url.includes('/delete'))).toHaveLength(0);
+  });
+
+  test('present record with same rData → unchanged no-op (no add, no delete)', async () => {
+    const fetchImpl = recordApi({ name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } });
+    const client = createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl });
+    const out = await client.upsertRecord({ zone: 'corp', name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } });
+    expect(out).toEqual({ unchanged: true });
+    expect(fetchImpl.calls).toHaveLength(1); // only the get
+  });
+
+  test('present record with different rData → delete + add → updated', async () => {
+    const fetchImpl = recordApi({ name: 'app', type: 'A', rData: { ipAddress: '10.53.0.9' } });
+    const client = createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl });
+    const out = await client.upsertRecord({ zone: 'corp', name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } });
+    expect(out).toEqual({ updated: true });
+    const add = fetchImpl.calls.find((c) => c.url.includes('/add'));
+    expect(JSON.parse(add.init.body)).toMatchObject({ zone: 'corp', name: 'app', type: 'A', ipAddress: '10.53.0.5' });
+    expect(fetchImpl.calls.some((c) => c.url.includes('/delete'))).toBe(true);
+  });
+
+  test('auth token rides on every request (query param on GET, body on POST)', async () => {
+    const fetchImpl = recordApi(null);
+    const client = createTechnitiumClient({ host: 'h', getToken: async () => 'sekrit', fetchImpl });
+    await client.upsertRecord({ zone: 'corp', name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } });
+    const get = fetchImpl.calls[0];
+    expect(new URL(get.url).searchParams.get('token')).toBe('sekrit');
+    const add = fetchImpl.calls.find((c) => c.url.includes('/add'));
+    expect(JSON.parse(add.init.body).token).toBe('sekrit');
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Client: error mapping + timeout
+ * ------------------------------------------------------------------ */
+
+describe('technitium client: error mapping', () => {
+  test('HTTP 401/403 → ProviderError auth_failed', async () => {
+    const { client } = makeClient([
+      ['/zones/list', () => jsonResponse(401, { status: 'error', errorMessage: 'Unauthorized' })],
+    ]);
+    await expect(client.listZones()).rejects.toMatchObject({ code: 'auth_failed', name: 'ProviderError' });
+  });
+
+  test('envelope status:"error" with "not found" → not_found (getRecord → null)', async () => {
+    const { client } = makeClient([
+      ['/zones/records/get', () => jsonResponse(200, { status: 'error', errorMessage: 'Record not found.' })],
+    ]);
+    await expect(client.getRecord('corp', 'app', 'A')).resolves.toBeNull();
+  });
+
+  test('envelope token error → auth_failed', async () => {
+    const { client } = makeClient([
+      ['/zones/list', () => jsonResponse(200, { status: 'error', errorMessage: 'Invalid token' })],
+    ]);
+    await expect(client.listZones()).rejects.toMatchObject({ code: 'auth_failed' });
+  });
+
+  test('HTTP 500 → api_error; transport throw → network_error', async () => {
+    const { client: c1 } = makeClient([
+      ['/zones/list', () => textResponse(500, 'boom')],
+    ]);
+    await expect(c1.listZones()).rejects.toMatchObject({ code: 'api_error' });
+
+    const fetchThrows = jest.fn(async () => { const e = new Error('ECONNREFUSED'); e.name = 'FetchError'; throw e; });
+    const c2 = createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl: fetchThrows });
+    await expect(c2.listZones()).rejects.toMatchObject({ code: 'network_error' });
+  });
+
+  test('timeout: fetch that never settles → network_error within the budget', async () => {
+    const fetchImpl = jest.fn(() => new Promise(() => {})); // hangs forever
+    const client = createTechnitiumClient({
+      host: 'h',
+      getToken: async () => 't',
+      fetchImpl,
+      timeoutMs: 50,
+    });
+    const t0 = Date.now();
+    await expect(client.listZones()).rejects.toMatchObject({ code: 'network_error' });
+    expect(Date.now() - t0).toBeLessThan(2000);
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Service: syncRecords
+ * ------------------------------------------------------------------ */
+
+describe('technitium service: syncRecords', () => {
+  function serviceWith(existingByFqdn) {
+    const state = { ...existingByFqdn };
+    const fetchImpl = makeFetch([
+      ['/zones/records/get', (u) => {
+        const name = u.searchParams.get('name');
+        const rec = state[name];
+        if (!rec) return jsonResponse(200, { status: 'error', errorMessage: 'Record not found.' });
+        return jsonResponse(200, { status: 'ok', response: rec });
+      }],
+      ['/zones/records/delete', (u, init) => {
+        const body = JSON.parse(init.body);
+        delete state[body.name];
+        return jsonResponse(200, { status: 'ok' });
+      }],
+      ['/zones/records/add', (u, init) => {
+        const body = JSON.parse(init.body);
+        state[body.name] = { name: body.name, type: body.type, rData: { ipAddress: body.ipAddress } };
+        return jsonResponse(200, { status: 'ok' });
+      }],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    return { svc, state };
+  }
+
+  test('resources + devices → name.zone records; three upsert paths in one batch', async () => {
+    const { svc } = serviceWith({ 'app': { name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } } });
+    const out = await svc.syncRecords({
+      zone: 'corp',
+      providerMode: 'wireguard',
+      resources: [
+        { name: 'app', ip: '10.53.0.5' }, // unchanged
+        { name: 'git', ip: '10.53.1.7' }, // created
+      ],
+      devices: [
+        { slug: 'laptop', ip: '10.53.2.9' }, // created
+      ],
+    });
+    expect(out.zone).toBe('corp');
+    expect(out.count).toBe(3);
+    expect(Object.fromEntries(out.results.map((r) => [r.name, r.action]))).toEqual({
+      'app.corp': 'unchanged',
+      'git.corp': 'created',
+      'laptop.corp': 'created',
+    });
+  });
+
+  test('tailscale mode prefers tailnetIp; wireguard mode prefers ip', async () => {
+    const seen = {};
+    const fetchImpl = makeFetch([
+      ['/zones/records/get', () => jsonResponse(200, { status: 'error', errorMessage: 'Record not found.' })],
+      ['/zones/records/add', (u, init) => {
+        const b = JSON.parse(init.body);
+        seen[b.name] = b.ipAddress;
+        return jsonResponse(200, { status: 'ok' });
+      }],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    const entry = { name: 'nas', tailnetIp: '100.91.55.51', ip: '10.53.0.9' };
+    await svc.syncRecords({ zone: 'corp', providerMode: 'tailscale', resources: [entry] });
+    expect(seen.nas).toBe('100.91.55.51');
+    await svc.syncRecords({ zone: 'corp', providerMode: 'wireguard', resources: [entry] });
+    expect(seen.nas).toBe('10.53.0.9');
+  });
+
+  test('per-record failure isolation: one bad record does not block the rest', async () => {
+    let n = 0;
+    const fetchImpl = makeFetch([
+      ['/zones/records/get', () => {
+        n += 1;
+        if (n === 1) return Promise.reject(new Error('ECONNRESET')); // first record fails at transport
+        return jsonResponse(200, { status: 'error', errorMessage: 'Record not found.' });
+      }],
+      ['/zones/records/add', () => jsonResponse(200, { status: 'ok' })],
+    ]);
+    const logger = { ...noopLogger, warn: jest.fn() };
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger,
+    });
+    const out = await svc.syncRecords({
+      zone: 'corp',
+      resources: [{ name: 'bad', ip: '10.53.0.1' }, { name: 'ok', ip: '10.53.0.2' }],
+    });
+    expect(out.count).toBe(2);
+    expect(out.results[0]).toMatchObject({ name: 'bad.corp', action: 'failed' });
+    expect(typeof out.results[0].error).toBe('string');
+    expect(out.results[0].error).toContain('network_error');
+    expect(out.results[1]).toEqual({ name: 'ok.corp', action: 'created' });
+    expect(logger.warn).toHaveBeenCalled();
+  });
+
+  test('missing zone → bad_input ProviderError', async () => {
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl: makeFetch([]) }),
+      logger: noopLogger,
+    });
+    await expect(svc.syncRecords({ resources: [] })).rejects.toMatchObject({ code: 'bad_input' });
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Service: verifyResolution
+ * ------------------------------------------------------------------ */
+
+describe('technitium service: verifyResolution', () => {
+  test('falls back to API read-back when no dnsServer (method noted)', async () => {
+    const fetchImpl = makeFetch([
+      ['/zones/records/get', () => jsonResponse(200, { status: 'ok', response: { name: 'app', type: 'A', rData: { ipAddress: '10.53.0.5' } } })],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    const out = await svc.verifyResolution({ name: 'app.corp', type: 'A', expectedIp: '10.53.0.5' });
+    expect(out.method).toBe('api-readback');
+    expect(out.verified).toBe(true);
+  });
+
+  test('read-back mismatch → verified:false', async () => {
+    const fetchImpl = makeFetch([
+      ['/zones/records/get', () => jsonResponse(200, { status: 'ok', response: { rData: { ipAddress: '10.53.0.99' } } })],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    const out = await svc.verifyResolution({ name: 'app.corp', expectedIp: '10.53.0.5' });
+    expect(out.verified).toBe(false);
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Service: configureSplitDns capability gating
+ * ------------------------------------------------------------------ */
+
+describe('technitium service: configureSplitDns capability gate', () => {
+  function providerStub({ splitDnsApi, id = 'stub' }) {
+    return {
+      id: () => id,
+      capabilities: () => ({ invites: true, splitDnsApi, perPeerFirewall: false, selfHosted: true }),
+      configureDns: jest.fn(async ({ zone, server }) => ({ delegated: true, zone, server })),
+    };
+  }
+
+  test('tailscale (splitDnsApi:true) → delegates to provider.configureDns', async () => {
+    const ts = providerStub({ splitDnsApi: true, id: 'tailscale' });
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl: makeFetch([]) }),
+      getActiveProvider: () => ts,
+      logger: noopLogger,
+    });
+    const out = await svc.configureSplitDns({ zone: 'corp', dnsServerIp: '10.53.0.1' });
+    expect(out).toMatchObject({ configured: true, provider: 'tailscale' });
+    expect(ts.configureDns).toHaveBeenCalledWith({ zone: 'corp', server: '10.53.0.1' });
+  });
+
+  test('wireguard (splitDnsApi:false) → {configured:false, reason} per spec', async () => {
+    const wg = providerStub({ splitDnsApi: false, id: 'wireguard' });
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl: makeFetch([]) }),
+      getActiveProvider: () => wg,
+      logger: noopLogger,
+    });
+    const out = await svc.configureSplitDns({ zone: 'corp', dnsServerIp: '10.53.0.1' });
+    expect(out).toEqual({
+      configured: false,
+      reason: 'splitDnsApi unsupported — set DNS in client config',
+    });
+  });
+
+  test('no active provider → same unsupported result, no throw', async () => {
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl: makeFetch([]) }),
+      getActiveProvider: () => { throw new ProviderError('none', { code: 'provider_not_active' }); },
+      logger: noopLogger,
+    });
+    await expect(svc.configureSplitDns({ zone: 'corp', dnsServerIp: '10.53.0.1' })).resolves.toMatchObject({
+      configured: false,
+    });
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Service: checkSetup (wizard, DC-152)
+ * ------------------------------------------------------------------ */
+
+describe('technitium service: checkSetup red/green', () => {
+  test('green: reachable + valid token + zone present', async () => {
+    const fetchImpl = makeFetch([
+      ['/zones/list', () => jsonResponse(200, { status: 'ok', response: [{ name: 'corp', type: 'Primary' }] })],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    await expect(svc.checkSetup({ zone: 'corp' })).resolves.toEqual({
+      apiReachable: true,
+      tokenValid: true,
+      zoneExists: true,
+    });
+  });
+
+  test('red: unreachable → apiReachable:false, tokenValid:false', async () => {
+    const fetchImpl = jest.fn(async () => { const e = new Error('connect ECONNREFUSED'); e.name = 'FetchError'; throw e; });
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 't', fetchImpl }),
+      logger: noopLogger,
+    });
+    const out = await svc.checkSetup({ zone: 'corp' });
+    expect(out).toMatchObject({ apiReachable: false, tokenValid: false, zoneExists: false });
+    expect(out.error).toContain('network_error');
+  });
+
+  test('yellow: reachable but bad token → apiReachable:true, tokenValid:false', async () => {
+    const fetchImpl = makeFetch([
+      ['/zones/list', () => jsonResponse(401, { status: 'error', errorMessage: 'Unauthorized' })],
+    ]);
+    const svc = createTechnitiumService({
+      client: createTechnitiumClient({ host: 'h', getToken: async () => 'bad', fetchImpl }),
+      logger: noopLogger,
+    });
+    const out = await svc.checkSetup({ zone: 'corp' });
+    expect(out).toMatchObject({ apiReachable: true, tokenValid: false, zoneExists: false });
+  });
+});
+
+/* ------------------------------------------------------------------ *
+ * Service: credential-manager wiring
+ * ------------------------------------------------------------------ */
+
+describe('technitium service: credential wiring', () => {
+  test('token resolved from credentialManager.retrieve("technitium"); {token} object supported', async () => {
+    const cm = credMgr({ token: 'obj-tok' });
+    const fetchImpl = makeFetch([
+      ['/zones/list', () => jsonResponse(200, { status: 'ok', response: [] })],
+    ]);
+    const svc = createTechnitiumService({
+      credentialManager: cm,
+      config: { technitium: { host: 'dns.internal' } },
+      fetchImpl,
+      logger: noopLogger,
+    });
+    await svc.listZones();
+    expect(cm.retrieve).toHaveBeenCalledWith('technitium');
+    expect(new URL(fetchImpl.calls[0].url).searchParams.get('token')).toBe('obj-tok');
+  });
+
+  test('client construction requires host or baseUrl (never hardcoded)', () => {
+    expect(() => createTechnitiumClient({ getToken: async () => 't', fetchImpl: makeFetch([]) }))
+      .toThrow(ProviderError);
+  });
+});
diff --git a/dashcaddy-api/src/network/technitium.js b/dashcaddy-api/src/network/technitium.js
new file mode 100644
index 0000000..03778af
--- /dev/null
+++ b/dashcaddy-api/src/network/technitium.js
@@ -0,0 +1,575 @@
+/**
+ * Technitium DNS Server integration (DC-146, specs/PRIVATE-NETWORK-SPEC.md §6).
+ *
+ * Two layers:
+ *
+ *   1. createTechnitiumClient({ baseUrl, getToken, fetchImpl, logger, timeoutMs })
+ *      Thin HTTP client over the Technitium HTTP API (default
+ *      http://<host>:5380/api). Token auth via credential-manager
+ *      (key 'technitium' by default — host+token are CONFIG, never hardcoded).
+ *      All calls go through a fetchT-style timeout wrapper (default 10s) and
+ *      every failure surfaces as ProviderError with a machine-readable code
+ *      (auth_failed | network_error | not_found | api_error).
+ *
+ *   2. createTechnitiumService({ client, credentialManager, registry, ... })
+ *      Feature-facing orchestration:
+ *        - syncRecords({zone, resources, devices, providerMode}) — idempotent
+ *          upserts (by name+type) of per-resource / per-device A/AAAA records.
+ *          Never throws wholesale: one bad record is reported as
+ *          {action:'failed', error} while the rest proceed.
+ *        - verifyResolution({name, type, expectedIp, dnsServer}) — independent
+ *          DNS-over-UDP resolve (node dgram; dns.resolve4 cannot target a
+ *          specific server per call). Falls back to a getRecord API read-back
+ *          (noted via method:'api-readback') when UDP is unavailable.
+ *        - configureSplitDns({zone, dnsServerIp}) — delegates to the ACTIVE
+ *          provider ONLY when capabilities().splitDnsApi is true (Tailscale);
+ *          WireGuard mode returns
+ *          {configured:false, reason:'splitDnsApi unsupported — set DNS in client config'}
+ *          per spec §8.3 (client config carries 10.53.0.1 instead).
+ *        - checkSetup({zone}) — {apiReachable, tokenValid, zoneExists} for the
+ *          setup-wizard connectivity step (DC-152).
+ *
+ * Hermetic by construction: fetchImpl / credentialManager / logger / registry
+ * are all injectable; tests never touch a real Technitium instance.
+ */
+
+'use strict';
+
+const dgram = require('dgram');
+const { ProviderError } = require('./errors');
+
+const DEFAULT_TIMEOUT_MS = 10_000;
+const DEFAULT_CREDENTIAL_KEY = 'technitium';
+const DEFAULT_PORT = 5380;
+
+/** Query-type numbers for the DNS-over-UDP verifier. */
+const DNS_QTYPE = { A: 1, AAAA: 28 };
+
+/* ------------------------------------------------------------------ *
+ * Client
+ * ------------------------------------------------------------------ */
+
+/** Classify a status/error-message pair into a ProviderError code. */
+function classifyStatus(status, msg) {
+  const lower = msg.toLowerCase();
+  if (status === 401 || status === 403) return 'auth_failed';
+  if (lower.includes('unauthorized') || lower.includes('forbidden') ||
+      (lower.includes('token') && (lower.includes('invalid') || lower.includes('denied')))) return 'auth_failed';
+  if (lower.includes('not found') || lower.includes('does not exist') || lower.includes('no record')) return 'not_found';
+  return 'api_error';
+}
+
+/**
+ * Map a fetch/transport/HTTP/API failure to a ProviderError.
+ * Shared by every client call so callers only ever see {code} errors.
+ */
+function toTechnitiumError(err) {
+  if (err instanceof ProviderError) return err;
+  const msg = (err && err.message) || String(err);
+  const status = err && typeof err.httpStatus === 'number' ? err.httpStatus : null;
+
+  if (err && (err.name === 'AbortError' || err.name === 'TimeoutError')) {
+    return new ProviderError(`Technitium request timed out: ${msg}`, {
+      code: 'network_error',
+      cause: err,
+    });
+  }
+  if (status === 401 || status === 403) {
+    return new ProviderError(`Technitium auth failed (${status}): ${msg}`, { code: 'auth_failed', cause: err });
+  }
+  if (status !== null && status >= 500) {
+    return new ProviderError(`Technitium server error (${status}): ${msg}`, { code: 'api_error', cause: err });
+  }
+  if (err instanceof Error && err.name === 'FetchError') {
+    return new ProviderError(`Technitium unreachable: ${msg}`, { code: 'network_error', cause: err });
+  }
+  const code = status !== null ? classifyStatus(status, msg) : 'network_error';
+  const prefix = code === 'network_error' ? 'Technitium network error' : 'Technitium API error';
+  return new ProviderError(`${prefix}: ${msg}`, { code, cause: err });
+}
+
+/**
+ * Extract the credential token. Supports both a plain string secret and
+ * { token } objects so operators can store host+token together.
+ */
+function extractToken(stored) {
+  if (!stored) return null;
+  if (typeof stored === 'string') return stored;
+  if (typeof stored === 'object' && typeof stored.token === 'string') return stored.token;
+  return null;
+}
+
+/**
+ * @param {object} opts
+ * @param {string}  [opts.baseUrl]      e.g. 'http://10.53.0.1:5380/api'
+ * @param {string}  [opts.host]         host when baseUrl is omitted (port 5380)
+ * @param {Function} [opts.getToken]    async () => token string (or null)
+ * @param {Function} [opts.fetchImpl]   fetch-compatible (default global fetch)
+ * @param {object}   [opts.logger]
+ * @param {number}   [opts.timeoutMs]   per-request timeout, default 10000
+ */
+function createTechnitiumClient(opts = {}) {
+  const {
+    baseUrl,
+    host,
+    getToken,
+    fetchImpl = (typeof fetch === 'function' ? fetch : null),
+    timeoutMs = DEFAULT_TIMEOUT_MS,
+  } = opts;
+
+  if (!baseUrl && !host) {
+    throw new ProviderError('Technitium client requires baseUrl or host (config-supplied, never hardcoded)', {
+      code: 'bad_input',
+    });
+  }
+  if (typeof fetchImpl !== 'function') {
+    throw new ProviderError('Technitium client requires a fetch implementation', { code: 'bad_input' });
+  }
+
+  const base = (baseUrl || `http://${host}:${DEFAULT_PORT}/api`).replace(/\/+$/, '');
+
+  /** fetchT-style timeout wrapper: races the call against a timer. */
+  async function callWithTimeout(url, init) {
+    let timer = null;
+    try {
+      return await Promise.race([
+        Promise.resolve(fetchImpl(url, init)),
+        new Promise((_, reject) => {
+          timer = setTimeout(() => {
+            const e = new Error(`timeout after ${timeoutMs}ms`);
+            e.name = 'TimeoutError';
+            reject(e);
+          }, timeoutMs);
+        }),
+      ]);
+    } finally {
+      if (timer) clearTimeout(timer);
+    }
+  }
+
+  /**
+   * One API round-trip. GET → query string; POST → JSON body. Token rides
+   * along on every call. Normalizes Technitium's `{status, response,
+   * errorMessage}` envelope into { ok, payload, errorMessage }.
+   */
+  async function api(method, path, params = {}) {
+    const token = (await getToken()) || '';
+    const url = new URL(base + path);
+    const init = { method };
+
+    if (method === 'GET') {
+      url.search = new URLSearchParams({ ...params, token }).toString();
+    } else {
+      init.headers = { 'Content-Type': 'application/json' };
+      init.body = JSON.stringify({ ...params, token });
+    }
+
+    let res;
+    try {
+      res = await callWithTimeout(url.toString(), init);
+    } catch (err) {
+      throw toTechnitiumError(err);
+    }
+
+    let body = null;
+    try {
+      body = await res.json();
+    } catch (_err) {
+      body = null;
+    }
+
+    if (res.status === 401 || res.status === 403) {
+      const e = new ProviderError(`Technitium auth failed (HTTP ${res.status})`, { code: 'auth_failed' });
+      throw e;
+    }
+    if (!res.ok) {
+      const e = new ProviderError(
+        `Technitium API error (HTTP ${res.status}): ${(body && body.errorMessage) || res.statusText || ''}`,
+        { code: 'api_error' }
+      );
+      e.httpStatus = res.status;
+      throw e;
+    }
+
+    // Technitium envelope: {status:'ok'|'error', response, errorMessage}
+    if (body && typeof body === 'object' && 'status' in body) {
+      if (body.status === 'error') {
+        const msg = body.errorMessage || 'unknown Technitium error';
+        const lower = String(msg).toLowerCase();
+        let code = 'api_error';
+        if (lower.includes('not found') || lower.includes('does not exist') || lower.includes('no record')) {
+          code = 'not_found';
+        } else if (lower.includes('unauthorized') || lower.includes('token') || lower.includes('forbidden')) {
+          code = 'auth_failed';
+        }
+        throw new ProviderError(`Technitium: ${msg}`, { code });
+      }
+      return body.response;
+    }
+    return body;
+  }
+
+  return {
+    baseUrl: base,
+
+    /** GET /zones/list → array of {name, type, ...} */
+    async listZones() {
+      const zones = await api('GET', '/zones/list');
+      if (Array.isArray(zones)) return zones;
+      if (zones && Array.isArray(zones.zones)) return zones.zones;
+      return [];
+    },
+
+    /**
+     * Create the zone as Primary if absent (idempotent).
+     * @returns {Promise<{created:boolean, unchanged:boolean}>}
+     */
+    async ensureZone(name) {
+      if (!name) throw new ProviderError('ensureZone: name is required', { code: 'bad_input' });
+      const zones = await this.listZones();
+      const exists = zones.some((z) => String(z.name).toLowerCase() === String(name).toLowerCase());
+      if (exists) return { created: false, unchanged: true };
+      await api('POST', '/zones/create', { name, type: 'Primary' });
+      return { created: true, unchanged: false };
+    },
+
+    /**
+     * GET /zones/records/get → record object or null when absent.
+     * Technitium answers status:'error' + "Record not found" → not_found → null.
+     */
+    async getRecord(zone, name, type) {
+      try {
+        const rec = await api('GET', '/zones/records/get', { zone, name, type });
+        if (Array.isArray(rec)) {
+          if (rec.length) return rec[0];
+          return null;
+        }
+        return rec || null;
+      } catch (err) {
+        if (err.code === 'not_found') return null;
+        throw err;
+      }
+    },
+
+    /**
+     * Idempotent upsert by name+type:
+     *   absent            → add            → {created:true}
+     *   present, same IP  → no-op          → {unchanged:true}
+     *   present, differs  → delete + add   → {updated:true}
+     */
+    async upsertRecord({ zone, name, type = 'A', rData }) {
+      if (!zone || !name || !type || !rData) {
+        throw new ProviderError('upsertRecord: zone, name, type and rData are required', { code: 'bad_input' });
+      }
+      const existing = await this.getRecord(zone, name, type);
+      const sameIp =
+        existing &&
+        String((existing.rData && existing.rData.ipAddress) || existing.ipAddress || '').toLowerCase() ===
+          String(rData.ipAddress).toLowerCase();
+
+      if (existing && sameIp) return { unchanged: true };
+      if (existing) {
+        await api('POST', '/zones/records/delete', { zone, name, type });
+      }
+      // rData fields are flattened into the add payload (ipAddress for A/AAAA).
+      await api('POST', '/zones/records/add', { zone, name, type, ...rData });
+      return existing ? { updated: true } : { created: true };
+    },
+  };
+}
+
+/* ------------------------------------------------------------------ *
+ * DNS-over-UDP verifier (dns.resolve* cannot target a specific server)
+ * ------------------------------------------------------------------ */
+
+/** Encode a DNS query packet: header + QNAME + QTYPE/QCLASS. */
+function buildDnsQuery(name, qtype) {
+  const labels = String(name).split('.').filter(Boolean);
+  // QNAME (sum of 1+len per label + root) + QTYPE + QCLASS
+  const qlen = labels.reduce((n, l) => n + l.length + 1, 0) + 1 + 4;
+  const buf = Buffer.alloc(12 + qlen);
+  const id = Math.floor(Math.random() * 0xffff);
+  buf.writeUInt16BE(id, 0);
+  buf.writeUInt16BE(0x0100, 2); // RD=1
+  buf.writeUInt16BE(1, 4); // QDCOUNT
+  let off = 12;
+  for (const label of labels) {
+    buf[off++] = label.length;
+    buf.write(label, off, 'ascii');
+    off += label.length;
+  }
+  buf[off++] = 0;
+  buf.writeUInt16BE(qtype, off); off += 2;
+  buf.writeUInt16BE(1, off); // IN
+  return { buf, id };
+}
+
+/** Parse answers, returning string IPs for qtype records (follows CNAMEs' rdata lengths). */
+function parseDnsAnswer(msg, qtype) {
+  const qdcount = msg.readUInt16BE(4);
+  const ancount = msg.readUInt16BE(6);
+  let off = 12;
+  const skipName = () => {
+    while (off < msg.length) {
+      const len = msg[off];
+      if (len === 0) { off += 1; return; }
+      if ((len & 0xc0) === 0xc0) { off += 2; return; } // compression pointer
+      off += 1 + len;
+    }
+  };
+  for (let i = 0; i < qdcount; i++) { skipName(); off += 4; }
+
+  const ips = [];
+  for (let i = 0; i < ancount && off + 12 <= msg.length; i++) {
+    skipName();
+    const type = msg.readUInt16BE(off);
+    const rdlen = msg.readUInt16BE(off + 8);
+    const rdata = msg.slice(off + 10, off + 10 + rdlen);
+    if (type === 1 && qtype === DNS_QTYPE.A && rdlen === 4) {
+      ips.push(Array.from(rdata).join('.'));
+    } else if (type === 28 && qtype === DNS_QTYPE.AAAA && rdlen === 16) {
+      ips.push(Array.from({ length: 8 }, (_, g) => rdata.readUInt16BE(g * 2).toString(16)).join(':'));
+    }
+    off += 10 + rdlen;
+  }
+  return ips;
+}
+
+/**
+ * Resolve name@server over UDP. Rejects on timeout/parse failure.
+ * (dns.resolve4 has no per-call server override in Node, hence dgram.)
+ */
+function resolveOverUdp(server, name, type = 'A', timeoutMs = 3000) {
+  return new Promise((resolve, reject) => {
+    const qtype = DNS_QTYPE[type.toUpperCase()] || DNS_QTYPE.A;
+    const { buf, id } = buildDnsQuery(name, qtype);
+    const sock = dgram.createSocket('udp4');
+    let settled = false;
+    const finish = (fn, arg) => {
+      if (settled) return;
+      settled = true;
+      clearTimeout(timer);
+      try { sock.close(); } catch (_e) { /* already closed */ }
+      fn(arg);
+    };
+    const timer = setTimeout(() => finish(reject, new Error('UDP resolve timeout')), timeoutMs);
+    sock.on('error', (err) => finish(reject, err));
+    sock.on('message', (msg) => {
+      if (msg.readUInt16BE(0) !== id) return; // stale/off-topic reply
+      try {
+        const rcode = msg.readUInt16BE(2) & 0x0f;
+        if (rcode !== 0) return finish(reject, new Error(`DNS rcode ${rcode}`));
+        const ips = parseDnsAnswer(msg, qtype);
+        if (!ips.length) return finish(reject, new Error('empty answer'));
+        finish(resolve, ips);
+      } catch (err) {
+        finish(reject, err);
+      }
+    });
+    sock.send(buf, 53, server, (err) => {
+      if (err) finish(reject, err);
+    });
+  });
+}
+
+/* ------------------------------------------------------------------ *
+ * Service
+ * ------------------------------------------------------------------ */
+
+function nullLogger() {
+  return { info() {}, warn() {}, error() {}, debug() {} };
+}
+
+/** Pick the IP for a resource/device given the active provider mode. */
+function pickIp(entry, providerMode) {
+  if (!entry) return null;
+  if (providerMode === 'tailscale') {
+    return entry.tailnetIp || (Array.isArray(entry.addresses) && entry.addresses[0]) || entry.ip || null;
+  }
+  // wireguard: 10.53.x.y client-pool address
+  return entry.ip || (Array.isArray(entry.addresses) && entry.addresses[0]) || entry.tailnetIp || null;
+}
+
+/**
+ * @param {object} opts
+ * @param {object}  [opts.client]           createTechnitiumClient result
+ * @param {object}  [opts.credentialManager] credential-manager singleton pattern
+ * @param {string}  [opts.credentialKey='technitium']
+ * @param {object}  [opts.config]           { technitium: { host | baseUrl } }
+ * @param {Function} [opts.fetchImpl]
+ * @param {Function} [opts.getActiveProvider] defaults to registry.getActiveProvider
+ * @param {object}  [opts.registry]         network registry (DC-140)
+ * @param {object}  [opts.logger]
+ * @param {number}  [opts.timeoutMs]
+ */
+function createTechnitiumService(opts = {}) {
+  const {
+    client,
+    credentialManager,
+    credentialKey = DEFAULT_CREDENTIAL_KEY,
+    config,
+    fetchImpl,
+    getActiveProvider,
+    registry,
+    logger = nullLogger(),
+    timeoutMs = DEFAULT_TIMEOUT_MS,
+  } = opts;
+
+  const resolveActiveProvider = getActiveProvider ||
+    (registry ? () => registry.getActiveProvider() : null);
+
+  let tc = client;
+  if (!tc) {
+    const tconf = (config && config.technitium) || {};
+    tc = createTechnitiumClient({
+      baseUrl: tconf.baseUrl,
+      host: tconf.host,
+      fetchImpl,
+      timeoutMs,
+      getToken: async () => {
+        if (!credentialManager || typeof credentialManager.retrieve !== 'function') return null;
+        const stored = await credentialManager.retrieve(credentialKey);
+        return extractToken(stored);
+      },
+    });
+  }
+
+  /**
+   * Sync A/AAAA records for resources + devices into `zone`.
+   * Per-record isolation: every entry gets its own result row; a failure
+   * never aborts the batch.
+   */
+  async function syncRecords({ zone, resources = [], devices = [], providerMode } = {}) {
+    if (!zone) throw new ProviderError('syncRecords: zone is required', { code: 'bad_input' });
+
+    const wanted = [];
+    for (const r of resources) {
+      const ip = pickIp(r, providerMode);
+      if (r && r.name && ip) wanted.push({ name: r.name, fqdn: `${r.name}.${zone}`, ip, type: r.type || 'A' });
+    }
+    for (const d of devices) {
+      const ip = pickIp(d, providerMode);
+      if (d && (d.slug || d.name) && ip) {
+        const slug = d.slug || d.name;
+        wanted.push({ name: slug, fqdn: `${slug}.${zone}`, ip, type: d.type || 'A' });
+      }
+    }
+
+    const results = [];
+    for (const w of wanted) {
+      try {
+        const out = await tc.upsertRecord({ zone, name: w.name, type: w.type, rData: { ipAddress: w.ip } });
+        results.push({ name: w.fqdn, action: out.created ? 'created' : out.updated ? 'updated' : 'unchanged' });
+      } catch (err) {
+        logger.warn('technitium syncRecords record failed', { name: w.fqdn, code: err.code });
+        results.push({ name: w.fqdn, action: 'failed', error: `${err.code}: ${err.message}` });
+      }
+    }
+    return { zone, providerMode, count: results.length, results };
+  }
+
+  /**
+   * Independent resolve check. Prefers a real DNS-over-UDP query against
+   * dnsServer; falls back to an API getRecord read-back (method noted).
+   */
+  async function verifyResolution({ name, type = 'A', expectedIp, dnsServer } = {}) {
+    if (!name || !expectedIp) {
+      throw new ProviderError('verifyResolution: name and expectedIp are required', { code: 'bad_input' });
+    }
+    if (dnsServer) {
+      try {
+        const ips = await resolveOverUdp(dnsServer, name, type);
+        const ok = ips.map((i) => i.toLowerCase()).includes(String(expectedIp).toLowerCase());
+        return { name, type, expectedIp, method: 'dns-udp', resolved: ips, verified: ok };
+      } catch (err) {
+        logger.debug('technitium UDP verify failed; falling back to API read-back', { name, error: err.message });
+      }
+    }
+    // Fallback: read the record back through the API (weaker — bypasses the
+    // resolver — but hermetic and always available). Note it explicitly.
+    const shortName = String(name).split('.')[0];
+    const zone = String(name).split('.').slice(1).join('.');
+    const rec = await tc.getRecord(zone, shortName, type);
+    const actual = rec && (rec.rData ? rec.rData.ipAddress : rec.ipAddress);
+    return {
+      name,
+      type,
+      expectedIp,
+      method: 'api-readback',
+      resolved: actual ? [actual] : [],
+      verified: String(actual || '').toLowerCase() === String(expectedIp).toLowerCase(),
+    };
+  }
+
+  /**
+   * Split-DNS: only when the ACTIVE provider exposes splitDnsApi
+   * (Tailscale). WireGuard devices get the Technitium hub IP in their
+   * generated client config instead (spec §8.3).
+   */
+  async function configureSplitDns({ zone, dnsServerIp } = {}) {
+    if (!zone || !dnsServerIp) {
+      throw new ProviderError('configureSplitDns: zone and dnsServerIp are required', { code: 'bad_input' });
+    }
+    const unsupported = {
+      configured: false,
+      reason: 'splitDnsApi unsupported — set DNS in client config',
+    };
+    if (!resolveActiveProvider) return unsupported;
+    let provider;
+    try {
+      provider = resolveActiveProvider();
+    } catch (_err) {
+      return unsupported;
+    }
+    const caps = provider.capabilities ? provider.capabilities() : {};
+    if (!caps.splitDnsApi) return unsupported;
+    const out = await provider.configureDns({ zone, server: dnsServerIp });
+    return { configured: true, provider: provider.id ? provider.id() : undefined, ...out };
+  }
+
+  /**
+   * Wizard connectivity check (DC-152): never throws.
+   * @returns {Promise<{apiReachable:boolean, tokenValid:boolean, zoneExists:boolean, error?:string}>}
+   */
+  async function checkSetup({ zone } = {}) {
+    const out = { apiReachable: false, tokenValid: false, zoneExists: false };
+    try {
+      const zones = await tc.listZones();
+      out.apiReachable = true;
+      out.tokenValid = true;
+      if (zone) {
+        out.zoneExists = zones.some((z) => String(z.name).toLowerCase() === String(zone).toLowerCase());
+      }
+      return out;
+    } catch (err) {
+      if (err.code === 'auth_failed') {
+        out.apiReachable = true; // server answered, token rejected
+      } else if (err.code === 'network_error') {
+        out.apiReachable = false;
+      } else {
+        out.apiReachable = true; // e.g. api_error / 5xx — the API is up
+      }
+      out.error = `${err.code}: ${err.message}`;
+      return out;
+    }
+  }
+
+  return {
+    client: tc,
+    syncRecords,
+    verifyResolution,
+    configureSplitDns,
+    checkSetup,
+    ensureZone: (name) => tc.ensureZone(name),
+    listZones: () => tc.listZones(),
+  };
+}
+
+module.exports = {
+  createTechnitiumClient,
+  createTechnitiumService,
+  resolveOverUdp,
+  buildDnsQuery,
+  parseDnsAnswer,
+  DEFAULT_CREDENTIAL_KEY,
+};