diff --git a/services/code-server.nix b/services/code-server.nix
index 3dea158..37f64e3 100644
--- a/services/code-server.nix
+++ b/services/code-server.nix
@@ -23,5 +23,16 @@
 
     # Make the claude CLI available in code-server's integrated terminal.
     environment.systemPackages = [ pkgs.claude-code ];
+
+    # Patch the Claude Code extension to add crossorigin="anonymous" to its
+    # stylesheet link — required for Firefox due to stricter CORS handling.
+    # Idempotent: sed won't match after the first apply.
+    system.activationScripts.claude-code-firefox-fix.text = ''
+      for f in /home/fred/.local/share/code-server/extensions/anthropic.claude-code-*/extension.js; do
+        [ -f "$f" ] && ${pkgs.gnused}/bin/sed -i \
+          's|<link href="${q}" rel="stylesheet">|<link href="${q}" rel="stylesheet" crossorigin="anonymous">|' \
+          "$f"
+      done
+    '';
   };
 }