diff --git a/CLAUDE.md b/CLAUDE.md
index bb66f92..01e59be 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -108,6 +108,39 @@ installs over Phase 1's without an uninstall and drill progress survives.
 - `android/app/src/main/java/dev/ncode/sp404layers/MainActivity.java` — inset bridge
 - `android/app/src/main/AndroidManifest.xml` — `android:screenOrientation="portrait"`
 
+## Device notes (TCL 50 PRO NXTPAPER 5G, Android 16 / API 36)
+
+**adb needs a udev rule.** The phone is USB `1bbb:0c01`. Ubuntu's
+`android-sdk-platform-tools-common` matches vendor *and* product, and lists only
+older TCL products, so nothing matched and the device node stayed `root:root`.
+Fixed with a vendor-wide rule (product IDs change with USB mode):
+
+```
+echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="1bbb", MODE="0660", GROUP="plugdev", TAG+="uaccess"' \
+  | sudo tee /etc/udev/rules.d/51-android-tcl.rules
+sudo udevadm control --reload-rules && sudo udevadm trigger
+```
+
+It lives in `/etc/udev` so apt upgrades don't overwrite it. The `uaccess` tag
+grants the logged-in session access, so no logout is needed.
+
+**A blank grey window means the screen was off when the app started.** TCL's
+`AppBootManagerService` refuses to let the app bind the WebView's sandboxed
+renderer process while the display is dozing:
+
+```
+W/AppBootManager: Type[TYPE_SERVICE];Result[false];
+  Target[org.chromium.content.app.SandboxedProcessService0];
+  Caller[dev.ncode.sp404layers];Reason[screen_off & caller care]
+E/cr_ChildProcessConn: Failed to establish the service connection.
+```
+
+With no renderer the page never parses, so there is no crash, no JS error, an
+empty `document.title`, and DevTools `Runtime.evaluate` hangs. The failure is
+sticky for the life of the process — reopening from Recents keeps the grey
+window. Wake and unlock the phone first, then `am force-stop` and relaunch.
+This is an OEM policy, not an app bug, and it only bites when launching over adb.
+
 ## Gotchas
 
 - The reference's multitouch relies on `touch-action:none` on `.unit` plus