diff --git a/ct/t3code.sh b/ct/t3code.sh
index 13e27f4c4a..8516335084 100644
--- a/ct/t3code.sh
+++ b/ct/t3code.sh
@@ -43,6 +43,16 @@ function update_script() {
   $STD npm install -g t3@latest
   msg_ok "Updated T3 Code"
 
+  msg_info "Configuring T3 Code Service"
+  mkdir -p /etc/systemd/system/t3code.service.d
+  cat <<EOF >/etc/systemd/system/t3code.service.d/claude.conf
+[Service]
+# Allow Claude Full access mode as root inside the LXC.
+Environment=IS_SANDBOX=1
+EOF
+  systemctl daemon-reload
+  msg_ok "Configured T3 Code Service"
+
   msg_info "Starting Service"
   systemctl start t3code
   msg_ok "Started Service"
diff --git a/install/t3code-install.sh b/install/t3code-install.sh
index 97359216ff..b37afc415a 100644
--- a/install/t3code-install.sh
+++ b/install/t3code-install.sh
@@ -46,6 +46,8 @@ Type=simple
 User=root
 Environment=PATH=/usr/local/bin:/usr/bin:/bin
 Environment=T3CODE_TELEMETRY_ENABLED=false
+# Allow Claude Full access mode as root inside the LXC.
+Environment=IS_SANDBOX=1
 WorkingDirectory=/opt/t3code
 ExecStart=/usr/bin/t3 serve --host 0.0.0.0 --base-dir /opt/t3code
 Restart=on-failure
diff --git a/json/t3code.json b/json/t3code.json
index 27672d1f3d..9116fd1c8c 100644
--- a/json/t3code.json
+++ b/json/t3code.json
@@ -41,6 +41,10 @@
       "text": "Provider CLIs (Codex, Claude, Grok, OpenCode, GitHub) are included in the install. Login to the CT after creation to authenticate with these services.",
       "type": "info"
     },
+    {
+      "text": "T3 Code and its agents run as root inside the LXC. The service sets IS_SANDBOX=1 so Claude can use Full access mode without a manual environment override. This does not enable additional sandboxing: agents can modify all container data and any writable host bind mounts. Use an unprivileged container and avoid exposing sensitive host paths.",
+      "type": "warning"
+    },
     {
       "text": "Access T3 Code at http://<IP>:3773 and pair a device with the token/QR shown after install. Regenerate it with: `pct exec <CTID> -- t3 pair --base-dir /opt/t3code.`",
       "type": "info"