diff --git a/image-recipe/configs/nginx-archipelago.conf b/image-recipe/configs/nginx-archipelago.conf
index 37a98f97..983ca9cd 100644
--- a/image-recipe/configs/nginx-archipelago.conf
+++ b/image-recipe/configs/nginx-archipelago.conf
@@ -35,9 +35,37 @@ server {
     }
 
     # AIUI SPA (Chat mode iframe) — SPA fallback for client-side routing
+    #
+    # /aiui/-scoped CSP (AIUI-04, D-19 unaffected — this is a build-time/
+    # runtime property, not a repository-location one): this header governs
+    # ONLY the document served from this location (it replaces, not adds to,
+    # the site-wide policy above — nginx add_header does not inherit from
+    # the previous level once the current level declares its own, same as
+    # the Cache-Control line below already does at this location). Its
+    # connect-src is scoped to the AIUI path prefix, so AIUI's own
+    # JavaScript is browser-prevented from issuing a same-origin fetch to
+    # /rpc/v1 with the ambient session cookie. This makes AIUI-04's
+    # "sandboxed by construction" an enforced boundary rather than the
+    # code-discipline convention the old proxy comment further down
+    # mistakenly implied. It does NOT split AIUI onto a different origin —
+    # DOM, storage, and cookies are still shared with the rest of the site;
+    # only what this policy polices (script/style/connect/etc. sources) is
+    # restricted. The residual risk (a browser that ignores or partially
+    # enforces CSP) is named, not silently assumed away, in 13-AI-SPEC.md
+    # §6 and mitigated by G-B3's rate limit on assistant.chat (13-12).
     location /aiui/ {
         try_files $uri $uri/ /aiui/index.html;
         add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob:; font-src 'self' data:; media-src 'self' blob: data:; connect-src $scheme://$host:*/aiui/ blob: data:; frame-ancestors 'self'; base-uri 'self'; form-action 'self';" always;
+    }
+
+    # AIUI's own JS reaching a paid/relay path directly (openrouter was
+    # deleted outright in 13-02 — no proxy_pass to openrouter.ai survives
+    # anywhere in this config) must not silently 200 via the SPA catch-all
+    # below. Explicit here rather than bolted onto 13-02 after the fact
+    # (13-02's Task 3 checkpoint, operator-accepted 2026-08-03).
+    location /aiui/api/openrouter/ {
+        return 404;
     }
 
     # AIUI assets fallback — AIUI may reference /assets/ without /aiui/ prefix
@@ -956,10 +984,24 @@ server {
     }
 
     # AIUI SPA (Chat mode iframe) — SPA fallback for client-side routing
+    #
+    # /aiui/-scoped CSP — see the HTTP server block above for the full
+    # rationale (AIUI-04, D-19 unaffected). Both server blocks must carry
+    # this header — a change applied to only one leaves AIUI's JS able to
+    # reach /rpc/v1 with the ambient session cookie on whichever block
+    # actually serves the request, same class of gap as T-13-15.
     location /aiui/ {
         try_files $uri $uri/ /aiui/index.html;
         add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: blob:; font-src 'self' data:; media-src 'self' blob: data:; connect-src $scheme://$host:*/aiui/ blob: data:; frame-ancestors 'self'; base-uri 'self'; form-action 'self';" always;
     }
+
+    # AIUI's own JS reaching a paid/relay path directly must not silently
+    # 200 via the SPA catch-all below — see the HTTP server block above.
+    location /aiui/api/openrouter/ {
+        return 404;
+    }
+
     # See the HTTP server block above for the full rationale: re-pointed to
     # the session-gated Rust daemon (T-13-08/T-13-09), OpenRouter relay
     # deleted outright (T-13-10). Both server blocks must carry this fix —
diff --git a/neode-ui/src/views/Chat.vue b/neode-ui/src/views/Chat.vue
index e486fa7b..58c72865 100644
--- a/neode-ui/src/views/Chat.vue
+++ b/neode-ui/src/views/Chat.vue
@@ -30,7 +30,17 @@
       </div>
     </Transition>
 
-    <!-- AIUI iframe — on mobile, leave room for close bar + tab bar at bottom -->
+    <!-- AIUI iframe — on mobile, leave room for close bar + tab bar at bottom.
+         No `sandbox` attribute: it was considered and rejected for this
+         phase (AIUI-04, 13-RESEARCH.md Open Question 2). `allow-scripts`
+         together with `allow-same-origin` is the well-known escape pattern,
+         and dropping `allow-same-origin` moves AIUI to an opaque origin,
+         breaking its storage and its origin-checked postMessage bridge — a
+         change bigger than this phase budgeted. The enforced boundary
+         instead is the /aiui/-scoped Content-Security-Policy (nginx) plus
+         the node-side rate limit (G-B3, 13-12); the residual risk (a
+         browser that ignores or partially enforces CSP) is named in
+         13-AI-SPEC.md §6, not silently assumed away. -->
     <iframe
       v-if="aiuiUrl"
       ref="aiuiFrame"
@@ -38,6 +48,7 @@
       :title="t('chat.aiAssistant')"
       class="chat-iframe chat-iframe-mobile"
       allow="microphone"
+      referrerpolicy="no-referrer"
       style="background: transparent"
     />