DESCRIBE THE BUG

The UF2 runner rejects --dev-id with a fatal error before any flashing occurs, even though the runner never uses a device serial number.

The nRF Connect VS Code extension unconditionally appends -i <serial> to west flash whenever it detects a connected Nordic device, regardless of which runner is selected. Because UF2BinaryRunner.capabilities() did not declare dev_id=True, the base-class guard in ZephyrBinaryRunner.create() aborts immediately with a fatal error.

STEPS TO REPRODUCE

1. Use a board with a UF2 bootloader and no on-board J-Link (tested: Seeed XIAO nRF52840, UF2 drive mounts at G:).
2. Add set(BOARD_FLASH_RUNNER uf2) before find_package(Zephyr ...) in CMakeLists.txt.
3. Open the project in VS Code with the nRF Connect SDK extension.
4. Put the board in UF2 bootloader mode (double-tap reset, drive appears).
5. Click Flash — the extension calls: west flash -d build -i F3ADA8E6C5AA9120

→ west aborts immediately. Nothing is copied to the drive.

RELEVANT LOG OUTPUT

west flash -d c:\mynRF\blinky\build -i F3ADA8E6C5AA9120
FATAL ERROR: uf2 doesn't support --dev-id option

IMPACT

Major – the UF2 runner is completely unusable from any IDE or tool that passes --dev-id. The only workaround is manually copying the .uf2 file in Explorer.

ENVIRONMENT

• OS: Windows 11
• Board: Seeed XIAO nRF52840 (UF2 bootloader, no on-board J-Link)
• Zephyr: reproduced on v3.7 (nRF Connect SDK v3.2.4), present in main
• West: bundled with nRF Connect SDK toolchain
• IDE: VS Code + nRF Connect SDK extension

ADDITIONAL CONTEXT

UF2BinaryRunner.capabilities() returns RunnerCaps(commands={'flash'}) without dev_id=True. The base-class guard in
ZephyrBinaryRunner.create() (core.py line 676) rejects any runner that receives --dev-id without declaring it:

if args.dev_id and not caps.dev_id:
    _missing_cap(cls, '--dev-id')

UF2 flashing is connectionless — the runner identifies the target drive via INFO_UF2.TXT using --board-id. do_create() reads only args.board_id; args.dev_id has no meaning for this transport.

Fix — declare dev_id=True and emit a warning so users know the value is accepted but has no effect on target selection:

     @classmethod
     def capabilities(cls):
-        return RunnerCaps(commands={'flash'})
+        return RunnerCaps(commands={'flash'}, dev_id=True)

     @classmethod
     def do_create(cls, cfg, args):
-        return UF2BinaryRunner(cfg, board_id=args.board_id)
+        return UF2BinaryRunner(cfg, board_id=args.board_id, dev_id=args.dev_id)

     def do_run(self, command, **kwargs):
+        if self.dev_id:
+            self.logger.warning('--dev-id %s is not used by the UF2 runner '
+                                'and will be ignored', self.dev_id)