diff --git a/SECURITY.md b/SECURITY.md
index 64689ca..4a03863 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -28,7 +28,7 @@ These are designed to be used directly in the browser (like a Mapbox public toke
 1. **Google Maps API key** — loads Photorealistic 3D Tiles directly and powers GEV place search. **Restrict it** (HTTP referrer + API restriction to the required Google APIs) in the Google Cloud Console. An unrestricted key in a public deployment can be abused and billed to you.
 2. **Cesium ion token** (`CESIUM_ION_TOKEN`, optional — for ion-hosted Google Photorealistic 3D Tiles, Bing world imagery, and world terrain) — used as `Cesium.Ion.defaultAccessToken` client-side. Use a public **`assets:read`** token with **URL restrictions** for any hosted deployment. The Community plan has eligibility and usage limits; a public token is not a secret, but it can still consume the account's quota.
 
-> The Vite `define` block in `vite.config.js` controls exactly what reaches the client: only these two keys plus two non-secret CCTV feature flags. Everything else stays server-side.
+> The Vite `define` block in `vite.config.js` controls exactly what reaches the client: only these two keys. Everything else stays server-side.
 
 Never commit real keys. `.env` is gitignored; only `.env.example` (placeholder names) is tracked. On macOS `dev-fresh.sh` can read keys from the Keychain; plain Vite uses env vars or a local `.env`, and Pinokio uses its ignored app `ENVIRONMENT` file.
 
@@ -52,6 +52,8 @@ The data proxies in `vite.config.js` are written so the browser cannot turn the
 - **Sanitized errors** — internal error details are not echoed back to clients.
 - **Coalesced OAuth refresh** and cached successful responses only (OpenSky).
 - **Redacted debug logging.** The voice debug log (`.gev-logs/`, gitignored) strips API keys, bearer tokens, client secrets, and image data URLs before writing.
+- **Cross-site gate on cost/log endpoints.** The cost-bearing (`/api/realtime/token`, `/api/openai/hud-summary`, `/api/google/nearby-places`) and log (`/api/realtime/debug-log`) endpoints refuse cross-site browser requests: a foreign or opaque `Origin`, a `Sec-Fetch-Site` other than `same-origin`/`none` (this is what blocks an `<img>`/navigation that carries no `Origin`), or any reverse-proxy/CDN forwarding header returns `403`. Non-browser loopback tools (the repo QA harnesses POST the token endpoint with no `Origin`) and the explicit `HOST=0.0.0.0` LAN opt-in keep working — the gate deliberately does not require a loopback remote address; that stricter requirement belongs only to the credential panel (`admitKeySetupRequest`).
+- **Full Content-Security-Policy.** The dev and preview servers send a real CSP (`script-src 'self' 'unsafe-eval'`: no inline script and no script from any other origin), alongside the existing `X-Frame-Options: DENY` and `frame-ancestors 'none'`. `'unsafe-eval'` stays because Knockout, bundled inside Cesium's widgets package, resolves the global object with `eval` at load time and the globe does not initialize without it; styles permit `'unsafe-inline'` and Google Fonts because Vite's dev client injects `<style>` elements.
 
 ## Network exposure — the operator threat model
 
diff --git a/src/keySetupCore.mjs b/src/keySetupCore.mjs
index 030565a..6cc8082 100644
--- a/src/keySetupCore.mjs
+++ b/src/keySetupCore.mjs
@@ -101,6 +101,17 @@ const LOCAL_HOSTNAMES = new Set(['localhost', '127.0.0.1', '::1', '[::1]']);
 /** Socket addresses that count as this machine. */
 const LOOPBACK_ADDRESSES = new Set(['127.0.0.1', '::1', '::ffff:127.0.0.1']);
 
+/**
+ * Reverse-proxy / CDN forwarding headers. Their presence means the request did
+ * not originate on this machine, whatever its socket says. Shared with the
+ * cost/log endpoint gate in localRequestGate.mjs so there is one definition.
+ */
+export const PROXY_SIGNALS = Object.freeze([
+  'forwarded', 'via', 'x-forwarded-for', 'x-forwarded-host',
+  'x-forwarded-port', 'x-forwarded-proto', 'x-real-ip',
+  'cf-connecting-ip', 'cf-ray',
+]);
+
 /** Parse an exact local request authority from a Host header. */
 function localAuthority(hostHeader, protocol) {
   const raw = String(hostHeader || '').trim().toLowerCase();
@@ -200,7 +211,6 @@ export function admitKeySetupRequest({
   // on this machine, whatever its socket says. Refuse them outright as defense
   // in depth — the shipped tunnel (Pinokio) is force-closed at boot, so these
   // only appear when someone has deliberately fronted the dev server.
-  const PROXY_SIGNALS = ['forwarded', 'via', 'x-forwarded-for', 'x-forwarded-host', 'x-forwarded-port', 'x-forwarded-proto', 'x-real-ip', 'cf-connecting-ip', 'cf-ray'];
   if (PROXY_SIGNALS.some((name) => String(proxyHeaders[name] || '').trim() !== '')) {
     return { ok: false, status: 403, error: 'Provider Settings does not answer proxied requests' };
   }
diff --git a/src/localRequestGate.mjs b/src/localRequestGate.mjs
new file mode 100644
index 0000000..ef2246d
--- /dev/null
+++ b/src/localRequestGate.mjs
@@ -0,0 +1,107 @@
+/**
+ * Same-site request gate for the cost-bearing and log endpoints.
+ *
+ * The credential panel has its own stricter gate (`admitKeySetupRequest` in
+ * keySetupCore.mjs): loopback socket + local Host + exact Origin + JSON
+ * Content-Type. The four endpoints here — `/api/realtime/token` (mints an
+ * OpenAI Realtime token = spends money), `/api/openai/hud-summary` (OpenAI
+ * spend), `/api/google/nearby-places` (Google spend), and
+ * `/api/realtime/debug-log` (appends to a local JSONL) — were previously
+ * ungated, so a hostile web page open in the same browser could reach them
+ * cross-site: a `fetch` carries a foreign `Origin`, and an `<img>`/navigation
+ * carries NO `Origin` at all but does carry `Sec-Fetch-Site: cross-site`.
+ *
+ * This module is the pure core that refuses those shapes while keeping the
+ * documented `HOST=0.0.0.0` LAN opt-in and non-browser loopback tools (the two
+ * repo QA harnesses POST the token endpoint from Node with no Origin) working.
+ * It deliberately does NOT require a loopback remote address (that belongs only
+ * to the credential panel), the presence of an `Origin`, or a JSON
+ * Content-Type. It touches nothing but its arguments, so every refusal below is
+ * pinned by a unit assertion.
+ */
+import { PROXY_SIGNALS } from './keySetupCore.mjs';
+
+/**
+ * Compute a request's own authority (an origin string) from its protocol and
+ * Host header. Unlike the credential-panel gate's localhost-restricted
+ * `localAuthority`, this returns whatever Host the request actually carries —
+ * the LAN opt-in serves a non-loopback Host to LAN browsers, and a same-origin
+ * fetch from such a page must still match. Malformed/missing input yields null.
+ * @param {string} hostHeader e.g. `req.headers.host`
+ * @param {string} protocol `http:` or `https:`
+ * @returns {string|null}
+ */
+function requestAuthority(hostHeader, protocol) {
+  const raw = String(hostHeader || '').trim().toLowerCase();
+  const scheme = String(protocol || '').toLowerCase();
+  if (!raw || !['http:', 'https:'].includes(scheme) || /[\s/?#@]/.test(raw)) return null;
+  try {
+    return new URL(`${scheme}//${raw}`).origin;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Decide whether a request to a cost-bearing/log endpoint is same-site enough
+ * to admit. Pure: no I/O, no globals.
+ *
+ * Policy, in order:
+ *  1. any reverse-proxy / CDN signal header present (PROXY_SIGNALS) → 403;
+ *  2. `Sec-Fetch-Site` present and not `same-origin` / `none` → 403 (this is
+ *     what blocks `<img src=...>` and cross-site navigation, which carry no
+ *     Origin but do carry `Sec-Fetch-Site: cross-site`);
+ *  3. `Origin` present must exactly equal the request's own authority computed
+ *     from protocol + Host — the same exact-origin comparison the credential
+ *     gate uses (no userinfo, no path/search/hash). The literal string `null`
+ *     is an opaque origin (sandboxed iframe / `data:` URL) and is refused;
+ *  4. otherwise ok. Non-browser loopback tools and the LAN opt-in (which may
+ *     carry neither `Origin` nor `Sec-Fetch-Site`) pass here.
+ *
+ * @param {{method?: string, hostHeader?: string, protocol?: string, origin?: string, secFetchSite?: string, proxyHeaders?: Record<string,string>}} req
+ * @returns {{ok: true} | {ok: false, status: 403, error: string}}
+ */
+export function admitSameSiteRequest({
+  method,
+  hostHeader,
+  protocol = 'http:',
+  origin,
+  secFetchSite,
+  proxyHeaders = {},
+} = {}) {
+  // (1) A request carrying reverse-proxy / CDN forwarding headers did not
+  // originate on this machine, whatever its socket says.
+  if (PROXY_SIGNALS.some((name) => String(proxyHeaders[name] || '').trim() !== '')) {
+    return { ok: false, status: 403, error: 'Proxied requests are not accepted' };
+  }
+  // (2) The browser tells us when a request is cross-site. `none` is a typed
+  // URL / bookmark; `same-origin` is the app itself. Anything else (cross-site,
+  // same-site but cross-origin) is refused.
+  const site = String(secFetchSite || '').trim().toLowerCase();
+  if (site !== '' && site !== 'same-origin' && site !== 'none') {
+    return { ok: false, status: 403, error: 'Cross-site requests are not accepted' };
+  }
+  // (3) If Origin is present it must exactly equal the request's own authority.
+  if (origin !== undefined && origin !== null && origin !== '') {
+    if (origin === 'null') {
+      return { ok: false, status: 403, error: 'Opaque origins are not accepted' };
+    }
+    const authority = requestAuthority(hostHeader, protocol);
+    let parsedOrigin;
+    try {
+      parsedOrigin = new URL(String(origin));
+    } catch {
+      return { ok: false, status: 403, error: 'Unrecognized Origin refused' };
+    }
+    const exactOrigin = parsedOrigin.username === ''
+      && parsedOrigin.password === ''
+      && parsedOrigin.pathname === '/'
+      && parsedOrigin.search === ''
+      && parsedOrigin.hash === ''
+      && parsedOrigin.origin === authority;
+    if (!exactOrigin) {
+      return { ok: false, status: 403, error: 'Cross-origin requests are not accepted' };
+    }
+  }
+  return { ok: true };
+}
diff --git a/src/localRequestGate.test.mjs b/src/localRequestGate.test.mjs
new file mode 100644
index 0000000..978b1ef
--- /dev/null
+++ b/src/localRequestGate.test.mjs
@@ -0,0 +1,113 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { admitSameSiteRequest } from './localRequestGate.mjs';
+
+const same = {
+  method: 'POST',
+  hostHeader: 'localhost:4173',
+  protocol: 'http:',
+  origin: 'http://localhost:4173',
+  secFetchSite: 'same-origin',
+};
+
+test('the honest same-origin browser request is admitted', () => {
+  assert.equal(admitSameSiteRequest(same).ok, true);
+  assert.equal(admitSameSiteRequest({ ...same, method: 'GET' }).ok, true);
+});
+
+test('a cross-site Origin is refused', () => {
+  const r = admitSameSiteRequest({ ...same, origin: 'https://evil.example' });
+  assert.equal(r.ok, false);
+  assert.equal(r.status, 403);
+});
+
+test('an opaque Origin ("null") is refused even when Host would match', () => {
+  const r = admitSameSiteRequest({ ...same, origin: 'null' });
+  assert.equal(r.ok, false);
+  assert.equal(r.status, 403);
+});
+
+test('Sec-Fetch-Site cross-site without an Origin is refused (the <img> case)', () => {
+  const r = admitSameSiteRequest({
+    method: 'GET',
+    hostHeader: 'localhost:4173',
+    protocol: 'http:',
+    secFetchSite: 'cross-site',
+  });
+  assert.equal(r.ok, false);
+  assert.equal(r.status, 403);
+});
+
+test('Sec-Fetch-Site same-site (cross-origin sibling) is refused', () => {
+  const r = admitSameSiteRequest({
+    ...same,
+    origin: 'http://localhost:4173',
+    secFetchSite: 'same-site',
+  });
+  assert.equal(r.ok, false, 'same-site is not same-origin');
+  assert.equal(r.status, 403);
+});
+
+test('a reverse-proxy signal header is refused', () => {
+  for (const header of ['x-forwarded-for', 'forwarded', 'via', 'cf-connecting-ip', 'cf-ray', 'x-real-ip', 'x-forwarded-host', 'x-forwarded-port', 'x-forwarded-proto']) {
+    const r = admitSameSiteRequest({ ...same, proxyHeaders: { [header]: 'anything' } });
+    assert.equal(r.ok, false, `${header} present → refused`);
+  }
+  // An empty forwarding header is not a proxy signal.
+  assert.equal(admitSameSiteRequest({ ...same, proxyHeaders: { 'x-forwarded-for': '' } }).ok, true);
+});
+
+test('same-origin Origin with Sec-Fetch-Site same-origin is admitted', () => {
+  assert.equal(admitSameSiteRequest(same).ok, true);
+});
+
+test('no Origin and no Sec-Fetch headers (curl / Node harness) is admitted', () => {
+  const r = admitSameSiteRequest({
+    method: 'POST',
+    hostHeader: 'localhost:4173',
+    protocol: 'http:',
+  });
+  assert.equal(r.ok, true, 'non-browser loopback tools pass');
+});
+
+test('Sec-Fetch-Site none (typed URL / bookmark) is admitted', () => {
+  const r = admitSameSiteRequest({
+    method: 'GET',
+    hostHeader: 'localhost:4173',
+    protocol: 'http:',
+    secFetchSite: 'none',
+  });
+  assert.equal(r.ok, true);
+});
+
+test('a LAN remote address is irrelevant: the function takes no remoteAddress', () => {
+  // The credential-panel gate requires a loopback socket; this gate does not.
+  // Passing a LAN-shaped Host/Origin pair must still match (LAN opt-in works).
+  const lan = admitSameSiteRequest({
+    method: 'GET',
+    hostHeader: '192.168.1.5:4173',
+    protocol: 'http:',
+    origin: 'http://192.168.1.5:4173',
+    secFetchSite: 'same-origin',
+  });
+  assert.equal(lan.ok, true, 'a same-origin LAN browser request is admitted');
+});
+
+test('a cross-port or cross-scheme Origin against the same Host is refused', () => {
+  assert.equal(admitSameSiteRequest({ ...same, origin: 'http://localhost:4174' }).ok, false, 'cross-port');
+  assert.equal(admitSameSiteRequest({ ...same, origin: 'https://localhost:4173' }).ok, false, 'cross-scheme');
+  assert.equal(admitSameSiteRequest({ ...same, origin: 'http://127.0.0.1:4173' }).ok, false, 'different loopback host');
+});
+
+test('an unparseable Origin is refused', () => {
+  assert.equal(admitSameSiteRequest({ ...same, origin: 'not a url' }).ok, false);
+});
+
+test('a missing Host with a present Origin is refused (no authority to match)', () => {
+  assert.equal(admitSameSiteRequest({ ...same, hostHeader: '' }).ok, false, 'empty Host → null authority');
+  assert.equal(admitSameSiteRequest({ ...same, hostHeader: undefined }).ok, false, 'absent Host → null authority');
+});
+
+test('a foreign Host is refused when an Origin is present', () => {
+  assert.equal(admitSameSiteRequest({ ...same, hostHeader: 'evil.example:4173' }).ok, false, 'foreign Host does not match local Origin');
+});
diff --git a/vite.config.js b/vite.config.js
index 34dac52..8ba035b 100644
--- a/vite.config.js
+++ b/vite.config.js
@@ -66,6 +66,7 @@ import {
   upsertDotenvValues,
   validateKeySetupUpdates,
 } from './src/keySetupCore.mjs';
+import { admitSameSiteRequest } from './src/localRequestGate.mjs';
 import { hardenCredentialFile } from './src/keySetupHardening.mjs';
 import {
   fetchTerrainChunkWithRetry,
@@ -5054,6 +5055,33 @@ function trackBackfillProxies() {
   };
 }
 
+/**
+ * Cross-site request gate for the cost-bearing and log endpoints. Mirrors the
+ * credential-panel `admit` helper (below) but feeds the request to the pure,
+ * unit-tested `admitSameSiteRequest` in src/localRequestGate.mjs. Returns true
+ * when it has already responded 403 (caller returns); false when the request is
+ * admitted and the handler should continue. Refuses cross-site browser requests
+ * (foreign/opaque Origin, or Sec-Fetch-Site other than same-origin/none, or
+ * reverse-proxy headers) while keeping loopback non-browser tools and the LAN
+ * opt-in working.
+ */
+const admitSameSite = (req, res) => {
+  const verdict = admitSameSiteRequest({
+    method: req.method,
+    hostHeader: req.headers?.host,
+    protocol: req.socket?.encrypted ? 'https:' : 'http:',
+    origin: req.headers?.origin,
+    secFetchSite: req.headers?.['sec-fetch-site'],
+    proxyHeaders: req.headers || {},
+  });
+  if (verdict.ok) return false;
+  res.statusCode = verdict.status;
+  res.setHeader('Content-Type', 'application/json');
+  res.setHeader('Cache-Control', 'no-store');
+  res.end(JSON.stringify({ error: verdict.error }));
+  return true;
+};
+
 /**
  * Vite plugin: OpenAI Realtime ephemeral client secret.
  *
@@ -5069,6 +5097,7 @@ export function openAiRealtimeProxy() {
         res.end(JSON.stringify({ error: 'Method not allowed' }));
         return;
       }
+      if (admitSameSite(req, res)) return;
 
       const apiKey = process.env.OPENAI_API_KEY;
       const keyless = keylessHudSummaryResponse(apiKey);
@@ -5131,6 +5160,7 @@ export function openAiRealtimeProxy() {
         res.end(JSON.stringify({ error: 'Method not allowed' }));
         return;
       }
+      if (admitSameSite(req, res)) return;
 
       try {
         const body = await readRequestBody(req, REALTIME_DEBUG_LOG_MAX_BYTES);
@@ -5156,6 +5186,7 @@ export function openAiRealtimeProxy() {
         res.end(JSON.stringify({ error: 'Method not allowed' }));
         return;
       }
+      if (admitSameSite(req, res)) return;
 
       // Opt-in per-IP throttle (GEV_RATELIMIT_OPENAI_PER_MIN). No-op when unset.
       if (!enforceOptInRateLimit(openAiRateLimiter(), req, res)) return;
@@ -5400,6 +5431,7 @@ export function googlePlacesContextProxy() {
         res.end(JSON.stringify({ error: 'Method not allowed', places: [] }));
         return;
       }
+      if (admitSameSite(req, res)) return;
 
       // Keyless place context has no provider cost, so it resolves before the
       // paid-endpoint limiter can consume or exhaust quota (mirrors the HUD
@@ -7721,6 +7753,32 @@ function keySetupEndpoint() {
   };
 }
 
+/**
+ * Content-Security-Policy applied to every document the dev/preview server
+ * serves. Held in one constant so dev and preview cannot drift. No inline
+ * script and no foreign script origin is permitted. 'unsafe-eval' is required:
+ * Knockout (bundled inside @cesium/widgets) resolves the global object with
+ * `(0, eval)("this")` at module load, and without it the Cesium widget never
+ * initializes (verified in headless Chrome). It also covers Cesium's WASM
+ * decoders. Widen any other directive only if a real violation appears.
+ */
+const LOCAL_CSP = [
+  "default-src 'self'",
+  "script-src 'self' 'unsafe-eval'",
+  "style-src 'self' 'unsafe-inline' https://fonts.googleapis.com",
+  "font-src 'self' data: https://fonts.gstatic.com",
+  "img-src 'self' data: blob: https:",
+  "media-src 'self' blob: https:",
+  "connect-src 'self' https: wss: ws:",
+  "worker-src 'self' blob:",
+  "child-src 'self' blob:",
+  "manifest-src 'self'",
+  "object-src 'none'",
+  "base-uri 'self'",
+  "form-action 'self'",
+  "frame-ancestors 'none'",
+].join('; ');
+
 /**
  * Main Vite configuration factory.
  *
@@ -7781,7 +7839,15 @@ export default defineConfig(({ mode }) => {
       // serves, which is what makes that attack impossible rather than unlikely.
       headers: {
         'X-Frame-Options': 'DENY',
-        'Content-Security-Policy': "frame-ancestors 'none'",
+        'Content-Security-Policy': LOCAL_CSP,
+      },
+    },
+    // The preview server serves the same documents, so it carries the same
+    // framing + CSP hardening (one LOCAL_CSP constant, no drift).
+    preview: {
+      headers: {
+        'X-Frame-Options': 'DENY',
+        'Content-Security-Policy': LOCAL_CSP,
       },
     },
     // Expose selected API keys to the browser via import.meta.env.*