Re-resolve the NanoKVM USB stick when it moves to another port

[thirteen37]

Problem

Connecting to a NanoKVM USB device failed with "Could not find USB video capture device … It may have been unplugged" while the stick sat there working fine.

Device.videoDeviceUniqueID and serialDevicePath both persist a USB location, not device identity:

• a UVC uniqueID embeds the locationID it enumerated at
• /dev/cu.usbserial-NNNN encodes the same thing

Move the stick to a different port and both saved values dangle. Confirmed against the hardware — the saved entry pointed at 0x1120000345f2131 / /dev/cu.usbserial-1140, the stick now enumerates as 0x2120000345f2131 / /dev/cu.usbserial-2140:

AVCaptureDevice(uniqueID: "0x1120000345f2131") -> nil
open("/dev/cu.usbserial-1140")                 -> -1 errno=2 No such file or directory

Fix

Re-resolve both identifiers against what is actually attached, before opening anything.

• Camera — falls back to the single attached device sharing the saved uniqueID's VID/PID tail (345f2131 = MACROSILICON MS2131).
• Serial — falls back to the port hanging off that camera's parent hub. On a NanoKVM-USB the capture chip and the CH340 are two functions behind the stick's own hub, so the pairing is exact rather than a guess.

Ambiguity (two identical sticks attached) still fails, now with an error telling you to re-select in Edit Device.

USBLocationID carries the locationID arithmetic as pure functions so it is testable without hardware. USBSerialPort now reports the locationID that the IOKit parent walk was already positioned to read.

Verification

Feeding the resolvers the actual stale values from devices.json recovers the current device:

saved video : 0x1120000345f2131
saved serial: /dev/cu.usbserial-1140
resolved video : 0x2120000345f2131
resolved serial: /dev/cu.usbserial-2140

Confirmed working end-to-end against the stick by @thirteen37.

7 new unit tests. KVMCore package, macOS and iPadOS suites all pass.

Also

Corrects a stale claim in CLAUDE.md: the macOS app is not sandboxed — the App Sandbox was dropped to get raw /dev/cu.* access, and device.camera is the only entitlement.

Not included

The session re-resolves on every connect rather than writing the resolved values back, so Edit Device still shows the old ID as "(not connected)" until you re-pick. Connecting works regardless.

🤖 Generated with Claude Code

https://claude.ai/code/session_013CARgLMkYsjjJYFysqzWih