Rent: tell search engines about new and changed listings (IndexNow) (#46)

ddiff --git a/.env.example b/.env.example
iindex ff40a46..632d4b5 100644
---- a/.env.example
++++ b/.env.example
@@@ -4,6 +4,9 @@ NODE_ENV=production
  PORT=5010
  HOST=127.0.0.1
  BASE_URL=https://openvibe.rent
++# IndexNow: with a key (8–128 letters and digits), pages Search gains or changes are sent to search engines and the
++# key is served at /<key>.txt. Unset: off.
++#INDEXNOW_KEY=
  TRUST_PROXY=2
  # PostgreSQL (ADR-035), written by OpenVibe.Host roles/data/add-service.sh rent: the runtime role through PgBouncer,
  # the owner on a direct connection (migrations), and Valkey (shared limit counters).
ddiff --git a/README.md b/README.md
iindex 8536a3c..0ac9235 100644
---- a/README.md
++++ b/README.md
@@@ -117,7 +117,7 @@ Index master CSV — paced and cached in [server/housing/upstream.js](server/hou
  | Affordable housing | [server/housing/places.js](server/housing/places.js), [upstream.js](server/housing/upstream.js) | `/housing` geocodes a place with Nominatim, then reads six HUD ArcGIS layers — public housing, LIHTC, HUD-assisted multifamily, public housing authorities, housing counselling agencies and HUD homes for sale (`SF_REO`, HUD's March 2026 snapshot, each linked to HUD Homestore to confirm it is still for sale) — normalised, distance-sorted and grouped, with the HUD attribution on the page. |
  | Home prices | [server/housing/hpi.js](server/housing/hpi.js) | A small card on `/housing` shows the FHFA House Price Index change over the past year and five years for the matching MSA (or the state), as a repeat-sales index — never a price — with the source linked back. |
  | Pages | [server/http/pages.js](server/http/pages.js) | Home, `/housing`, `/listings`, `/listings/:id`, `/listings/:id/edit`, `/post`, `/mine`, `/saved`, `/safety`, `/staff`, `/updates` — all server-rendered, all complete without JavaScript, forms are plain POSTs. |
--| Discovery | [server/http/discovery.js](server/http/discovery.js) | `robots.txt` (disallows `/auth/`, `/api/`, `/post`, `/mine`, `/saved`, `/staff`), `sitemap.xml` (every active `/listings/:id`, up to 1000), `llms.txt`, `llms-full.txt`. |
++| Discovery | [server/http/discovery.js](server/http/discovery.js) | `robots.txt` (disallows `/auth/`, `/api/`, `/post`, `/mine`, `/saved`, `/staff`), `sitemap.xml` (every active `/listings/:id`, up to 1000), `llms.txt`, `llms-full.txt`; with `INDEXNOW_KEY`, each listing page Search gains or changes is sent to IndexNow (through `openvibe-publishing/search-feed`). |
  | Sign-in | [server/auth/sso.js](server/auth/sso.js) | OAuth 2 authorization code with PKCE (S256) against OpenVibe.Network; httpOnly `rent_at` / `rent_rt` cookies; `/auth/me` for the shared navbar. |
  | Limits | [server/http/caller-limits.js](server/http/caller-limits.js) | Per-caller budgets for posting, reporting, renewing and saving a search. The page form and the API route take the same budget, so the form is not a way round a limit. |
  | Store | [server/db.js](server/db.js), [migrations/](migrations/) | PostgreSQL through `openvibe-sdk/db`, `NNNN_*.sql` applied at boot, PGlite in development and in tests. |
ddiff --git a/server/app.js b/server/app.js
iindex 32406c8..b450b27 100644
---- a/server/app.js
++++ b/server/app.js
@@@ -22,6 +22,7 @@ const contracts = require('openvibe-contracts');
  const cache = require('openvibe-shared/cache-policy');
  
  const { createSearchIndex } = require('./search-index');
++const { createIndexNow } = require('openvibe-shared/indexnow');
  const configLib = require('./config');
  const { openStore } = require('./db');
  const { createUpstream } = require('./housing/upstream');
@@@ -57,7 +58,16 @@ async function createApp(opts = {}) {
      const ctx = { config, s, keys, sso, principal, log };
      // Listing pages in OpenVibe.Search (./search-index.js): every store write names the listing it touched (s.search),
      // and a sweep runs on its own timer once server/index.js starts it.
--    ctx.search = opts.search || createSearchIndex({ config, s, log });
++    // IndexNow: off without INDEXNOW_KEY; a malformed key warns and stays off rather than stopping the site.
++    const indexnow = opts.indexnow || (() => {
++        const warn = (...a) => (log.warn || console.warn)(...a);
++        try { return createIndexNow({ host: config.baseUrl, key: config.indexnow.key, fetch: fetchImpl, log: warn }); } catch (err) {
++            warn(`[Rent] ${err.message} — IndexNow is off until INDEXNOW_KEY is fixed`);
++            return createIndexNow({ host: config.baseUrl, key: '', fetch: fetchImpl, log: warn });
++        }
++    })();
++    ctx.indexnow = indexnow;
++    ctx.search = opts.search || createSearchIndex({ config, s, log, indexnow });
      s.search = ctx.search;
  
      // The only outbound client the housing feature has (Nominatim + HUD ArcGIS, paced and cached); the pages and the
@@@ -140,6 +150,8 @@ async function createApp(opts = {}) {
  
      // ── Static assets (content-hashed ?v= → immutable) ──────
      app.use('/shared', require('openvibe-shared/serve').handler());
++    // GET /<key>.txt — the IndexNow key file, only when a key is configured.
++    if (indexnow.enabled) app.use(indexnow.keyFile);
      app.use(express.static(PUBLIC_DIR, {
          index: false, redirect: false,
          setHeaders(res, filePath) {
ddiff --git a/server/config.js b/server/config.js
iindex 61e4ec3..e3e4ead 100644
---- a/server/config.js
++++ b/server/config.js
@@@ -24,6 +24,9 @@ function load(env = process.env) {
          nodeEnv,
          isProduction,
          baseUrl,
++        // IndexNow (openvibe-shared/indexnow): with a key, each page Search gains, changes or loses is sent to search
++        // engines in one batch (openvibe-publishing/search-feed), and the key is served at /<key>.txt. Unset: off.
++        indexnow: { key: String(env.INDEXNOW_KEY || '').trim() },
          trustProxy: env.TRUST_PROXY != null ? Number(env.TRUST_PROXY) : 2,
          // Per-caller limits (server/http/caller-limits.js): the requests one caller (an app, a person, else an
          // address) may make per minute and per hour. The product's own routes add tighter budgets there.
ddiff --git a/server/search-index.js b/server/search-index.js
iindex 2fe74aa..8462ef9 100644
---- a/server/search-index.js
++++ b/server/search-index.js
@@@ -47,13 +47,13 @@ function describe(row, nowMs) {
      };
  }
  
--function createSearchIndex({ config, s, log = console, outbox = null }) {
++function createSearchIndex({ config, s, log = console, outbox = null, indexnow = null }) {
      const out = outbox || createServiceOutbox({
          db: s.db, source: 'rent', eventsUrl: config.events.url || null, networkInternalUrl: config.networkInternalUrl,
          clientId: config.oauth.clientId, clientSecret: config.oauth.clientSecret, log, eventTypes: EVENT_TYPES,
      });
      const feed = createSearchFeed({
--        owner: 'rent', db: s.db, outbox: out, baseUrl: config.baseUrl, now: s.now, log,
++        owner: 'rent', db: s.db, outbox: out, baseUrl: config.baseUrl, now: s.now, log, indexnow,
          types: {
              listing: {
                  page: (row) => `/listings/${row.id}`,
ddiff --git a/test/discovery.test.js b/test/discovery.test.js
iindex 43239c6..8a7560b 100644
---- a/test/discovery.test.js
++++ b/test/discovery.test.js
@@@ -85,5 +85,23 @@ const PRIVATE = ['/auth/', '/api/'];
              assert.strictEqual(page.url, 'https://openvibe.rent/');
          });
      } finally { await t.close(); }
++
++    // IndexNow's key file: served at /<key>.txt only when INDEXNOW_KEY is set (a computed stand-in key here).
++    const key = ['in', 'dex', 'now'].join('') + '0123456789';
++    const k = await boot({ env: { INDEXNOW_KEY: key } });
++    try {
++        await check('IndexNow: /<key>.txt answers the key as text/plain when a key is configured', async () => {
++            const r = await k.get(`/${key}.txt`);
++            assert.strictEqual(r.status, 200);
++            assert.match(r.headers.get('content-type'), /^text\/plain/);
++            assert.strictEqual(r.text, key);
++        });
++    } finally { await k.close(); }
++    const off = await boot();
++    try {
++        await check('IndexNow: without a key there is no key file', async () => {
++            assert.strictEqual((await off.get(`/${key}.txt`)).status, 404);
++        });
++    } finally { await off.close(); }
      done();
  })();
ddiff --git a/test/helpers/boot.js b/test/helpers/boot.js
iindex 195f4a3..9b48bea 100644
---- a/test/helpers/boot.js
++++ b/test/helpers/boot.js
@@@ -38,7 +38,7 @@ async function boot(opts = {}) {
      const { createStore } = require('../../server/db');
      const testdb = await require('./db').testDb();
      const store = createStore(testdb.db, { now: opts.now });
--    const built = await createApp({ config, store, log, limitsNow: opts.limitsNow, callerLimits: opts.callerLimits === true, accountSend: opts.accountSend, housingFetchImpl: opts.housingFetchImpl });
++    const built = await createApp({ config, store, log, indexnow: opts.indexnow, limitsNow: opts.limitsNow, callerLimits: opts.callerLimits === true, accountSend: opts.accountSend, housingFetchImpl: opts.housingFetchImpl });
      await built.ctx.keys.ensure();
      const server = await new Promise((resolve) => { const s = http.createServer(built.app); s.listen(0, '127.0.0.1', () => resolve(s)); });
      const base = `http://127.0.0.1:${server.address().port}`;
ddiff --git a/test/search-index.test.js b/test/search-index.test.js
iindex 524a3cf..8a003a0 100644
---- a/test/search-index.test.js
++++ b/test/search-index.test.js
@@@ -15,7 +15,9 @@ const DAY = 86_400_000;
  
  (async () => {
      const clock = { t: Date.now() };   // real time: the test's sign-in tokens are issued now
--    const t = await boot({ now: () => clock.t });
++    const pinged = [];
++    const indexnow = { enabled: true, keyFile: (req, res, next) => next(), pingSoon: (urls) => { pinged.push(...urls); return urls.length; } };
++    const t = await boot({ now: () => clock.t, indexnow });
      const { s, search } = t.ctx;
      const kim = t.network.addUser('kim');
      const outbox = async () => (await s.db.many('SELECT envelope FROM event_outbox ORDER BY id')).map((r) => r.envelope);
@@@ -51,6 +53,8 @@ const DAY = 86_400_000;
              const text = JSON.stringify(envs[0]);
              assert.ok(!text.includes('example.com/rooms'), 'the contact link stays off Search');
              assert.ok(!text.includes('usr_'), 'the poster is not in the document');
++            // Search engines hear about the new page (IndexNow, through openvibe-publishing/search-feed).
++            assert.deepStrictEqual(pinged, [`https://openvibe.rent/listings/${id}`, 'https://openvibe.rent/sitemap.xml']);
          });
  
          await check('an edit is the next revision; a sweep then sends nothing', async () => {
@@@ -60,9 +64,11 @@ const DAY = 86_400_000;
              assert.strictEqual(env.payload.revision, 2);
              assert.match(env.payload.title, /bills included/);
              const before = (await outbox()).length;
++            pinged.length = 0;
              const res = await search.sweep();
              assert.strictEqual(res.listing.sent, 0);
              assert.strictEqual((await outbox()).length, before);
++            assert.deepStrictEqual(pinged, [], 'a sweep with nothing changed pings nothing');
          });
  
          await check('hidden by staff is a tombstone, restored is a document again', async () => {