diff --git a/api/config/sandbox.cfg b/api/config/sandbox.cfg
index b9f7ce60..5e64c247 100644
--- a/api/config/sandbox.cfg
+++ b/api/config/sandbox.cfg
@@ -52,6 +52,28 @@ mount {
     mandatory: false
 }
 
+# Read-only configuration for native document tools. fontconfig loads its
+# configuration from /etc/fonts, so font matching inside the jail has no
+# configuration without it. Debian's LibreOffice ships
+# /usr/lib/libreoffice/share/registry/main.xcd as a symlink into
+# /etc/libreoffice and aborts at startup when that link dangles. Neither path
+# holds executables or secrets; both are optional for images without them.
+mount {
+    src: "/etc/fonts"
+    dst: "/etc/fonts"
+    is_bind: true
+    rw: false
+    mandatory: false
+}
+
+mount {
+    src: "/etc/libreoffice"
+    dst: "/etc/libreoffice"
+    is_bind: true
+    rw: false
+    mandatory: false
+}
+
 # Static /etc/hosts so "localhost" resolves for tool-call-server connections.
 # Uses inline content instead of bind-mounting the host's /etc/hosts, which
 # in Kubernetes leaks pod name, internal IP, and deployment metadata.