diff --git a/SECURITY.md b/SECURITY.md
index e42e3113b..28b1201f3 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -71,6 +71,8 @@ The data proxies under `server/providers/` are written so the browser cannot tur
 - **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`). **Limit: this gate does not survive DNS rebinding in the `HOST=0.0.0.0` mode.** By default Vite's host check (`allowedHosts`) rejects a rebinding `Host` before any handler runs, and the gate is defense in depth behind it. The LAN opt-in turns that host check off, so an attacker-controlled name that resolves to the operator's address yields a page whose `Origin` and `Host` agree and whose `Sec-Fetch-Site` is a truthful `same-origin`; all three checks pass. In that mode protection rests on the operator's network, not on `Origin`/`Host` agreement (see Network exposure below).
+- **Full Content-Security-Policy.** The dev and preview servers send a real CSP (`script-src 'self' 'unsafe-eval' blob:`: no inline script and no script from any other origin; `blob:` covers the object URLs Cesium's bundled workers bootstrap through in the built app), 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/build/embed-framing.js b/build/embed-framing.js
index 2a34e115a..95e182365 100644
--- a/build/embed-framing.js
+++ b/build/embed-framing.js
@@ -11,6 +11,15 @@
 
 const FRAMING_HEADERS = new Set(['x-frame-options', 'content-security-policy']);
 
+/** The directives of a CSP header value, minus any frame-ancestors rule. */
+function withoutFraming(value) {
+  return String(value ?? '')
+    .split(';')
+    .map((directive) => directive.trim())
+    .filter(Boolean)
+    .filter((directive) => !/^frame-ancestors\b/i.test(directive));
+}
+
 /** Whether a request is for an embed-mode document. */
 export function isEmbedDocumentRequest(url) {
   let parsed;
@@ -43,8 +52,13 @@ export function embedFramingPlugin({
       res.setHeader = (name, value) => {
         const key = String(name).toLowerCase();
         if (!FRAMING_HEADERS.has(key)) return setHeader(name, value);
-        if (key === 'content-security-policy' && !anywhere)
-          return setHeader(name, policy);
+        if (key === 'content-security-policy') {
+          // Keep every other directive of the server's policy (script-src,
+          // connect-src, ...) and only swap the framing rule.
+          const kept = withoutFraming(value);
+          const next = anywhere ? kept : [...kept, policy];
+          return next.length ? setHeader(name, next.join('; ')) : res;
+        }
         return res;
       };
       if (!anywhere) setHeader('Content-Security-Policy', policy);
diff --git a/build/vite.js b/build/vite.js
index bd18aece9..4af19e42e 100644
--- a/build/vite.js
+++ b/build/vite.js
@@ -3,6 +3,40 @@ import cesium from 'vite-plugin-cesium';
 import { embedFramingPlugin } from './embed-framing.js';
 import { panelBuildPlugin } from './panel.js';
 
+/**
+ * Content-Security-Policy for every document the dev/preview server serves.
+ * 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. `blob:` is required in the built app: Cesium's
+ * bundled workers bootstrap through `importScripts(blob:...)`, which a worker
+ * checks against script-src (the dev server loads them by URL instead).
+ * Widen any other directive only for a real violation.
+ */
+export const BROWSER_CSP = [
+  "default-src 'self'",
+  "script-src 'self' 'unsafe-eval' blob:",
+  "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' blob: data: 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('; ');
+
+/** Response headers shared by the dev and preview servers. */
+export const BROWSER_HEADERS = Object.freeze({
+  'X-Frame-Options': 'DENY',
+  'Content-Security-Policy': BROWSER_CSP,
+});
+
 /** Build browser assets with explicit inputs; never load environment or providers. */
 export function createBrowserViteConfig({
   plugins = [],
@@ -46,13 +80,15 @@ export function createBrowserViteConfig({
       fs: {
         deny: ['.env', '.env.*', '*.{crt,pem}', '**/.git/**', '**/ENVIRONMENT'],
       },
-      // These headers protect the document containing Provider Settings.
-      // Embed-mode documents are framable instead; see embed-framing.js.
-      headers: {
-        'X-Frame-Options': 'DENY',
-        'Content-Security-Policy': "frame-ancestors 'none'",
-      },
+      // These headers protect the document containing Provider Settings and
+      // give the whole page a real Content-Security-Policy (BROWSER_CSP).
+      // Embed-mode documents are framable instead: embed-framing.js rewrites
+      // only the frame-ancestors directive and keeps the rest of the policy.
+      headers: BROWSER_HEADERS,
     },
+    // The preview server serves the same documents, so it carries the same
+    // framing + CSP hardening (one constant, no drift).
+    preview: { headers: BROWSER_HEADERS },
     define: {
       'import.meta.env.GOOGLE_MAPS_API_KEY': JSON.stringify(googleApiKey),
       'import.meta.env.CESIUM_ION_TOKEN': JSON.stringify(cesiumToken),
diff --git a/scripts/format-scope.json b/scripts/format-scope.json
index a0a7820a9..5cd8ad77c 100644
--- a/scripts/format-scope.json
+++ b/scripts/format-scope.json
@@ -76,6 +76,7 @@
   "server/providers/places/routes.js",
   "src/data/placeProviderPayloads.js",
   "src/tooling/placeProviders.test.mjs",
+  "server/providers/common/same-site.js",
   "server/providers/space.js",
   "server/providers/space/celestrak.js",
   "server/providers/space/launch-library.js",
diff --git a/scripts/package-boundaries.json b/scripts/package-boundaries.json
index a880f5596..efcf4c507 100644
--- a/scripts/package-boundaries.json
+++ b/scripts/package-boundaries.json
@@ -74,6 +74,8 @@
       "server/providers/common/http.js",
       "scripts/google-server-key.mjs",
       "src/data/placeProviderPayloads.js",
+      "server/providers/common/same-site.js",
+      "src/localRequestGate.mjs",
       "src/data/routeSteps.js",
       "src/sources/httpBody.js",
       "src/sources/rateLimit.js"
@@ -287,6 +289,8 @@
       "src/loadingFeedback.js",
       "src/data/installationFeedback.js",
       "src/voice/voiceCost.js",
+      "server/providers/common/same-site.js",
+      "src/localRequestGate.mjs",
       "src/voice/actionSchemas.js",
       "server/providers/openai/toolDescriptions.js",
       "src/sources/rateLimit.js"
diff --git a/server/providers/common/same-site.js b/server/providers/common/same-site.js
new file mode 100644
index 000000000..11e9d37b4
--- /dev/null
+++ b/server/providers/common/same-site.js
@@ -0,0 +1,43 @@
+import { admitSameSiteRequest } from '../../../src/localRequestGate.mjs';
+
+/**
+ * Cross-site request gate for cost-bearing and log endpoints. Feeds the
+ * request to the pure, unit-tested `admitSameSiteRequest` and answers 403
+ * itself when the request is refused. Returns true when it has already
+ * responded (the caller returns); false when the handler should continue.
+ * Refuses cross-site browser requests (foreign or opaque Origin, a
+ * Sec-Fetch-Site other than same-origin/none, or reverse-proxy headers) while
+ * keeping loopback non-browser tools and the HOST=0.0.0.0 LAN opt-in working.
+ * @param {import('node:http').IncomingMessage} req
+ * @param {import('node:http').ServerResponse} res
+ * @returns {boolean} True when a 403 was sent.
+ */
+export function admitSameSite(req, res) {
+  const verdict = admitSameSiteRequest({
+    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;
+}
+
+/**
+ * Wrap a middleware handler so cross-site requests are refused with 403
+ * before the handler runs. Loopback tools and same-origin browser requests
+ * pass straight through.
+ * @param {(req: import('node:http').IncomingMessage, res: import('node:http').ServerResponse, next?: Function) => unknown} handler
+ * @returns {(req: import('node:http').IncomingMessage, res: import('node:http').ServerResponse, next?: Function) => unknown}
+ */
+export function sameSiteGated(handler) {
+  return (req, res, next) => {
+    if (admitSameSite(req, res)) return undefined;
+    return handler(req, res, next);
+  };
+}
diff --git a/server/providers/openai.js b/server/providers/openai.js
index 5dd03db5c..e5d84e0a9 100644
--- a/server/providers/openai.js
+++ b/server/providers/openai.js
@@ -2,6 +2,7 @@ import { defaultSourceRoot } from './common/source-root.js';
 import { handleHudSummary } from './openai/hud-summary.js';
 import { createDebugLogHandler } from './openai/debug-log.js';
 import { createRealtimeTokenHandler } from './openai/realtime.js';
+import { sameSiteGated } from './common/same-site.js';
 
 /**
  * Vite plugin: OpenAI Realtime ephemeral client secret.
@@ -15,16 +16,20 @@ function openAiRealtimeProxy({
   realtime = {},
 } = {}) {
   function install(middlewares) {
-    middlewares.use('/api/openai/hud-summary', handleHudSummary);
+    // Cost-bearing and log endpoints refuse cross-site browser requests
+    // (see server/providers/common/same-site.js and SECURITY.md).
+    middlewares.use('/api/openai/hud-summary', sameSiteGated(handleHudSummary));
 
     middlewares.use(
       '/api/realtime/debug-log',
-      createDebugLogHandler({ sourceRoot }),
+      sameSiteGated(createDebugLogHandler({ sourceRoot })),
     );
 
     middlewares.use(
       '/api/realtime/token',
-      createRealtimeTokenHandler({ ...realtime, annotationGuidance }),
+      sameSiteGated(
+        createRealtimeTokenHandler({ ...realtime, annotationGuidance }),
+      ),
     );
   }
 
diff --git a/server/providers/places/google.js b/server/providers/places/google.js
index 1ee83a892..f7baacc90 100644
--- a/server/providers/places/google.js
+++ b/server/providers/places/google.js
@@ -3,6 +3,7 @@ import {
   keylessGooglePlacesResponse,
 } from './google-key.js';
 import { makeOptInRateLimiter, clientKey } from '../common/rate-limit.js';
+import { admitSameSite } from '../common/same-site.js';
 import {
   projectNearbyPlaces,
   projectTextSearchPlaces,
@@ -50,6 +51,9 @@ export function googlePlacesContextProxy({
 } = {}) {
   function install(middlewares) {
     middlewares.use('/api/google/nearby-places', async (req, res) => {
+      // Gate first, like the OpenAI routes: a cross-site caller learns nothing
+      // about this endpoint's method surface.
+      if (admitSameSite(req, res)) return;
       if (req.method !== 'GET') {
         res.statusCode = 405;
         res.setHeader('Content-Type', 'application/json');
diff --git a/src/localRequestGate.mjs b/src/localRequestGate.mjs
new file mode 100644
index 000000000..0dfc0fe73
--- /dev/null
+++ b/src/localRequestGate.mjs
@@ -0,0 +1,147 @@
+/**
+ * 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.
+ */
+/**
+ * Reverse-proxy / CDN forwarding headers. Their presence means the request did
+ * not originate on this machine, whatever its socket says. Kept as this
+ * module's own list (keySetupCore.mjs carries the same nine names for the
+ * credential panel) so the gate has no imports and can sit in any package
+ * boundary.
+ */
+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',
+]);
+
+/**
+ * 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 {{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({
+  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 000000000..cb085bda7
--- /dev/null
+++ b/src/localRequestGate.test.mjs
@@ -0,0 +1,107 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { admitSameSiteRequest } from './localRequestGate.mjs';
+
+const same = {
+  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);
+});
+
+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({
+    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({
+    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({
+    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({
+    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/src/tooling/viteBuild.test.mjs b/src/tooling/viteBuild.test.mjs
index 31fe32107..a297ccdcb 100644
--- a/src/tooling/viteBuild.test.mjs
+++ b/src/tooling/viteBuild.test.mjs
@@ -1,7 +1,7 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
 import { readFileSync } from 'node:fs';
-import { createBrowserViteConfig } from '../../build/vite.js';
+import { BROWSER_CSP, createBrowserViteConfig } from '../../build/vite.js';
 import standaloneConfig, * as compatibility from '../../vite.config.js';
 import * as providers from '../../server/providers/local.js';
 
@@ -23,10 +23,18 @@ test('explicit build inputs preserve browser-only defines, plugin order and loop
   assert.ok(config.server.fs.deny.includes('**/ENVIRONMENT'));
   assert.ok(config.server.fs.deny.includes('.env.*'));
   assert.equal(config.server.headers['X-Frame-Options'], 'DENY');
-  assert.equal(
-    config.server.headers['Content-Security-Policy'],
+  const csp = config.server.headers['Content-Security-Policy'];
+  assert.equal(csp, BROWSER_CSP);
+  for (const directive of [
+    "script-src 'self' 'unsafe-eval' blob:",
+    "object-src 'none'",
+    "base-uri 'self'",
     "frame-ancestors 'none'",
-  );
+  ]) {
+    assert.ok(csp.includes(directive), directive);
+  }
+  assert.ok(!csp.includes("script-src 'self' 'unsafe-inline'"));
+  assert.deepEqual(config.preview.headers, config.server.headers);
   assert.deepEqual(config.define, {
     'import.meta.env.GOOGLE_MAPS_API_KEY': '"browser-fixture"',
     'import.meta.env.CESIUM_ION_TOKEN': '"ion-fixture"',
@@ -127,6 +135,22 @@ test('only embed-mode documents may be framed, and only by the allowed ancestors
   anywhere.setHeader('X-Frame-Options', 'DENY');
   anywhere.setHeader('Content-Security-Policy', "frame-ancestors 'none'");
   assert.deepEqual(Object.fromEntries(anywhere.headers), {});
+  // A full policy keeps its other directives; only the framing rule changes.
+  const full = "default-src 'self'; script-src 'self'; frame-ancestors 'none'";
+  const embeddedFull = response();
+  middleware({ url: '/?embed=1' }, embeddedFull, () => {});
+  embeddedFull.setHeader('Content-Security-Policy', full);
+  assert.equal(
+    embeddedFull.headers.get('content-security-policy'),
+    "default-src 'self'; script-src 'self'; frame-ancestors https://a.example",
+  );
+  const anywhereFull = response();
+  open({ url: '/?embed=1' }, anywhereFull, () => {});
+  anywhereFull.setHeader('Content-Security-Policy', full);
+  assert.equal(
+    anywhereFull.headers.get('content-security-policy'),
+    "default-src 'self'; script-src 'self'",
+  );
   const normal = response();
   middleware({ url: '/' }, normal, () => {});
   normal.setHeader('X-Frame-Options', 'DENY');