cablecat 0.2.0

TUI inspector for USB-C cables, eMarkers, and Power Delivery.

CableCat

CableCat is a terminal inspector for USB-C ports, cables, eMarkers, USB Power Delivery, data speed, DisplayPort Alt Mode, USB4, and Thunderbolt-related state.

It opens as a TUI by default and gives each USB-C port a readable diagnosis: what is connected, what the OS can observe, what the cable or partner appears to declare, and which details are unavailable.

Install

CableCat is distributed through PyPI.

pipx install cablecat

You can also use uv or pip:

uv tool install cablecat
python -m pip install cablecat

Quick Start

Open the inspector:

cablecat

Export a machine-readable snapshot:

cablecat --json

Include raw OS observations:

cablecat --json --raw

Refresh snapshots continuously:

cablecat --watch --json

What CableCat Shows

CableCat is designed to answer practical questions quickly:

• Is this port empty, charging, carrying USB data, running DisplayPort Alt Mode, or doing several things at once?
• What USB speed is currently observable, such as High Speed, SuperSpeed, or SuperSpeed+?
• What USB-PD source power profiles are visible, and what is the advertised max?
• Was an eMarker observed, and what cable capabilities can be decoded from it?
• Is the connected partner likely a display, hub, peripheral, charger, AMA, or another PD product type?
• Which USB devices are attached below the port?
• Which facts are observed, decoded, inferred, unknown, or unavailable?

The TUI keeps the port list on the left and a readable diagnosis on the right. The detail tabs expose overview, attached devices, decoded PD/VDO fields, raw OS properties, and warnings.

Important Limits

CableCat is read-only. It does not:

• sniff USB-PD traffic;
• send Discover Identity or other active PD messages;
• load a helper driver;
• claim to verify cable electrical quality.

CableCat reports declared capabilities and OS-observed state. A cable can claim support for a speed or current rating and still fail a real signal-integrity or power test. Use a hardware tester when you need electrical validation.

On macOS, some eMarker information may only appear when the system decides it needs it, such as for cables above 3A, USB4, or Thunderbolt scenarios. When the OS does not expose a field, CableCat marks it as unavailable instead of guessing.

Platform Support

Current CableCat focuses on Apple Silicon macOS 14+.

Platform	Status
macOS 14+ arm64	Supported first. Uses a bundled Swift/IOKit probe.
Linux	Adapter placeholder only. Future target: /sys/class/typec.
Windows	Adapter placeholder only. Future target: UCSI, SetupAPI, or WMI.

CLI Reference

cablecat                 # open the TUI
cablecat --json          # print normalized JSON
cablecat --json --raw    # include raw OS probe data
cablecat --watch --json  # stream refreshed JSON snapshots
cablecat --version       # print version
cablecat --help          # show all options

The JSON output contains stable high-level sections for diagnosis, capabilities, decoded PD/VDO fields, and raw observations when requested.

Development

CableCat uses Python for the CLI/TUI and decoding layers, plus a SwiftPM-built macOS dynamic library for the IOKit probe.

Common commands:

make test
make build
make push

make build runs:

.venv/bin/python -m build --outdir dist

On macOS arm64, python -m build invokes the Hatchling build hook, builds libCableCatMacOSProbe.dylib with SwiftPM, and includes it in the wheel at:

cablecat/native/macos/libCableCatMacOSProbe.dylib

The resulting macOS wheel is tagged like:

py3-none-macosx_14_0_arm64

License And Prior Art

CableCat is licensed under GPL-3.0-only.

WhatCable is useful prior art for product behavior and presentation, but CableCat does not copy WhatCable implementation code. CableCat treats WhatCable's public repository only as a behavioral reference because its license note describes mixed MIT/proprietary source boundaries.