Since at_client with PuTTY isn’t working either, that rules out the terminal and points straight at the board files in your nfed checkout. Can you run the following from your nfed directory and paste the output?
git status
git diff boards/
If there are any modifications to the board definitions (especially boards/circuitdojo/feather_nrf9151/), those would be the culprit — any board-level changes need to live in a .overlay file in your project, not in the nfed tree itself.
You can also skip the local build entirely and flash a known-good at_client binary straight from CI: grab nfed_v3.2.x_7fab730_at_client_circuitdojo_feather_nrf9151 from https://github.com/circuitdojo/nrf9160-feather-examples-and-drivers/actions/runs/25947550693, extract the zip, and flash the merged.hex inside with:
probe-rs download --chip nRF9151_xxAA --binary-format hex path/to/merged.hex
If probe-rs isn’t installed yet, see the Programming section of the docs. If input works with the CI binary but not your local build, the issue is in your environment or board files rather than the hardware.
Also worth noting: the supported way to connect and interact with the device is either the serial monitor in the VS Code extension or the zephyr-tools CLI (zephyr-tools --port <port> --follow). Other terminals (PuTTY, nRF Connect Desktop, etc.) may not behave correctly with the Feather’s RP2040 bridge.
