Huawei Mate 60 OTG to a 1 TB stick, unplugged at 61%
Huawei Mate 60, HarmonyOS 4.2.0. The first OTG plug registered as charging only. After switching the USB mode to file transfer, the volume appeared in the document tree. Azalea used OpenDocumentTree and persisted the URI permission. A control run that skipped persist kept the profile after a process kill but listed nothing.
The stick is a dual-head metal key. Phone side USB-C. exFAT. Engine extra mode=bridge.
Why 3.3 MB/s
OTG plus SAF round trips are slower than desktop path mode. 8,241 × 3.41 MB ≈ 28.10 GB stills, 118 × 72.4 MB ≈ 8.54 GB video. Video bursts hit 18 MB/s; tiny JPEGs pulled the average down.
The yank
Notification showed about 5,100 / 8,359 when the stick came out. Foreground service reported detach. After replug and a refresh on the profile screen, the job continued from the index. Twelve .<name>.<n>.tmp files sat on disk; the app treated them as disposable and rewrote the logical keys. No half objects under the real names.
One still was named 新建 文本文档.JPG (copied from Windows). Trailing spaces are eaten on exFAT. The escaped physical name kept the key stable.