diff --git a/frontend/Dockerfile b/frontend/Dockerfile
index a65170e..63fc677 100644
--- a/frontend/Dockerfile
+++ b/frontend/Dockerfile
@@ -25,4 +25,11 @@ FROM nginx:1
 COPY --from=build-stage /app/frontend/dist/ /usr/share/nginx/html
 
 COPY ./frontend/nginx.conf /etc/nginx/conf.d/default.conf
+COPY ./frontend/nginx-security-headers.conf /etc/nginx/security-headers.conf
+# The CSP's connect-src names the API when the bundle calls it on another
+# origin (https://api.x and wss://api.x); empty, nginx proxies it on this one.
+ARG VITE_API_URL
+RUN api="${VITE_API_URL%/}"; \
+    sed -i "s|__API_ORIGINS__|${api:+ $api $(echo "$api" | sed 's/^http/ws/')}|" \
+      /etc/nginx/security-headers.conf
 COPY ./frontend/nginx-backend-not-found.conf /etc/nginx/extra-conf.d/backend-not-found.conf
diff --git a/frontend/index.html b/frontend/index.html
index f78a925..9e53cfe 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -11,7 +11,9 @@
     <link rel="manifest" href="%BASE_URL%manifest.webmanifest" />
     <link rel="apple-touch-icon" href="%BASE_URL%apple-touch-icon.png" />
     <title>Fluksio</title>
-    <!-- Set the theme class before first paint so the app never flashes light. -->
+    <!-- Set the theme class before first paint so the app never flashes light.
+         The CSP admits this script by its hash (nginx-security-headers.conf):
+         change the script and that hash changes with it. -->
     <script>
       (() => {
         try {
diff --git a/frontend/nginx-security-headers.conf b/frontend/nginx-security-headers.conf
new file mode 100644
index 0000000..2684c91
--- /dev/null
+++ b/frontend/nginx-security-headers.conf
@@ -0,0 +1,14 @@
+# Security headers. Included at server level and again in every location with
+# an add_header of its own, since nginx drops the inherited ones there.
+#
+# script-src: the bundle, plus the theme script inline in index.html by its
+# hash. Edit that script and this hash must change with it (sha256 of the text
+# between the tags, base64), or the app paints light-then-dark again.
+# style-src 'unsafe-inline': Monaco, Radix's scroll lock and the toasts insert
+# <style> elements at runtime, which no hash can name.
+# img/frame-src take any http(s): a camera stream or website widget points
+# wherever its dashboard says. connect-src is this origin plus the API's when
+# the bundle calls one elsewhere; the Dockerfile fills that in.
+add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'sha256-FpmE/jXgh7LaQmoMHvqlYVa3hl7+cMNkDN2fSejs9So='; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob: http: https:; media-src 'self' blob:; font-src 'self'; connect-src 'self'__API_ORIGINS__; worker-src 'self'; frame-src http: https:; frame-ancestors 'self'; object-src 'none'; base-uri 'self'; form-action 'self'" always;
+add_header X-Content-Type-Options "nosniff" always;
+add_header Referrer-Policy "strict-origin-when-cross-origin" always;
diff --git a/frontend/nginx.conf b/frontend/nginx.conf
index 12ec6eb..7690ac0 100644
--- a/frontend/nginx.conf
+++ b/frontend/nginx.conf
@@ -24,6 +24,8 @@ server {
     text/css
     text/plain;
 
+  include /etc/nginx/security-headers.conf;
+
   location / {
     root /usr/share/nginx/html;
     index index.html index.htm;
@@ -35,6 +37,7 @@ server {
   # on every reload.
   location /assets/ {
     root /usr/share/nginx/html;
+    include /etc/nginx/security-headers.conf;
     add_header Cache-Control "public, max-age=31536000, immutable";
   }
 
@@ -42,6 +45,7 @@ server {
   # assets, so a stale copy pins the browser to the previous build.
   location = /index.html {
     root /usr/share/nginx/html;
+    include /etc/nginx/security-headers.conf;
     add_header Cache-Control "no-cache";
   }
 
diff --git a/frontend/src/components/Dashboard/widgets.tsx b/frontend/src/components/Dashboard/widgets.tsx
index c8d779b..d549ae7 100644
--- a/frontend/src/components/Dashboard/widgets.tsx
+++ b/frontend/src/components/Dashboard/widgets.tsx
@@ -474,8 +474,12 @@ function EmbedWidget({ widget }: WidgetProps) {
     <iframe
       src={url}
       title={widget.title || url}
-      // Same-origin is deliberately withheld: the page keeps its own storage
-      // and cookies only by being another origin, which it is.
+      // `allow-same-origin` keeps the page in its own origin, with the
+      // cookies and storage most sites will not start without: the demo's
+      // weather map renders an unstyled list without it. That is safe only
+      // while the page *is* another origin. One served from this app's own
+      // origin would run as the app, scripts and all, and could read the
+      // session.
       sandbox="allow-scripts allow-popups allow-forms allow-same-origin"
       referrerPolicy="no-referrer"
       loading="lazy"
diff --git a/frontend/src/lib/zodConfig.ts b/frontend/src/lib/zodConfig.ts
new file mode 100644
index 0000000..e2ae419
--- /dev/null
+++ b/frontend/src/lib/zodConfig.ts
@@ -0,0 +1,12 @@
+/**
+ * Zod without its `eval` probe.
+ *
+ * Zod compiles a faster object parser with `new Function` where it can, and
+ * finds out by trying once. Under the CSP (`frontend/nginx-security-headers.conf`)
+ * that try is reported as a violation on every page, although Zod catches it
+ * and falls back. `jitless` skips the probe and goes straight to the fallback.
+ * Imported first in `main.tsx`, since a schema built before it would probe.
+ */
+import { z } from "zod"
+
+z.config({ jitless: true })
diff --git a/frontend/src/main.tsx b/frontend/src/main.tsx
index e4d0115..d410ff3 100644
--- a/frontend/src/main.tsx
+++ b/frontend/src/main.tsx
@@ -1,3 +1,5 @@
+// First: it configures Zod before any module builds a schema.
+import "./lib/zodConfig"
 import {
   MutationCache,
   QueryCache,