Corne (crkbd) — Reference Keyboard (Not Chosen)

What it is

The Corne, by Japanese designer foostan, is the single most popular small split keyboard in the custom mechanical-keyboard community as of 2026. Two halves connected by TRRS, 3×6 column-staggered alpha keys per side, 3 thumb keys per side, 42 keys total. Two switch variants: Corne Cherry (MX-compatible) and Corne Chocolate (Kailh Choc v1/v2). Current v4 PCB ships with hotswap sockets, optional OLED + RGB. Firmware support: QMK (canonical), ZMK (wireless variant).

It is the keyboard the Ferris Sweep was designed in dialog with — David Barr’s Sweep is “Corne minus one column and one thumb,” sized down from 42 keys to 34. Anyone evaluating a small split in 2026 looks at the Sweep and the Corne side-by-side.

How it compares to the Ferris Sweep

Property	Corne	Ferris Sweep	KN-86 chose
Key count	42	34	Sweep — closer to the canonical 31-key target; 8 fewer keys to give homes to
Columns per side	6	5	Sweep — pinky-outer column dropped; less pinky strain
Thumb keys per side	3	2	Sweep — one fewer thumb but operator still has 4 thumbs total; KN-86 uses 4 cleanly (EVAL/LSHFT/0/TERM per ADR-0031 §3.1)
Hotswap	v4 yes	current rev yes	Tie
OLED option	yes	yes (skipped for KN-86)	Tie
Trackpoint option	community add-on (crkbd-trackpoint)	first-party holykeebs option	Sweep — first-party trackpoint integration is cleaner
Switch family	MX (Cherry) or Choc (Chocolate)	Choc only	Sweep — matches KN-86 Choc v1 commitment
Community size	7.5k stars / 1.1k forks	smaller (no central GitHub repo; David Barr’s design under various forks)	Corne wins on absolute community size; Sweep wins on “small enough to know every quirk”
Sourcing	Many vendors (splitkb, Beekeeb, KeyHive, holykeebs, Little Keyboards)	holykeebs primarily; some boutique	Tie at hobbyist scale
First release	2018 (foostan)	2020 (David Barr)	Both well-established
License	CC-BY-4.0 + MIT	open-source hardware (David Barr’s design)	Both open

Why we chose Sweep over Corne

Documented in keyboard-decision.md and ADR-0031. The short version:

1. Key count match. 34 ≈ 31 (canonical KN-86) is a closer match than 42; fewer “what goes here?” decisions.
2. Pinky kindness. Sweep drops the outer pinky column. KN-86’s pinky-bottom slots are explicitly reserved as v2 spares (ADR-0031 §4.3); Corne would force assigning meaning to keys we’d be happier leaving empty.
3. First-party holykeebs trackpoint integration. trackpoint-module.md commits 2× trackpoint for KN-86; holykeebs’ Sweep + trackpoint config is shipping-product. Corne+trackpoint is community-add-on (joh/crkbd-trackpoint) — proven but less first-party-clean.
4. The 3-thumb Corne benefit doesn’t apply. KN-86’s thumb-cluster bindings (EVAL, LSHFT, 0, TERM) fit cleanly in 4 thumbs total. A 5th and 6th thumb (the Corne’s extra) would either go unbound or get arbitrary assignments.

Why Corne is useful even though we didn’t pick it

• Cross-check for build patterns. Two trackpoints on a split is a non-default config. The joh/crkbd-trackpoint repo + the broader Corne-trackpoint community is the reference for “how does QMK PS/2-mouse + split-transport actually work in practice?” Worth reading during firmware bring-up.
• The known-EMI issue. Corne v4 boards have documented EMI susceptibility (connectivity disruption near mobile devices). Worth checking whether holykeebs’ modified-diode Sweep PCB has the same issue. Bring-up validation task.
• Community keymap repository. QMK’s keyboards/crkbd/keymaps/ directory has hundreds of community keymaps. Useful patterns to mine (layer organization, tap-dance idioms, combo macros) even though our 34-key layout is in keyboards/ferris/sweep/.
• Larger build-tutorial corpus. Corne tutorials on YouTube outnumber Sweep tutorials roughly 10:1. Anyone learning to solder hot-swap sockets on a small split will get more reps from Corne content — the technique transfers losslessly to Sweep.

What we explicitly do NOT borrow

• 42 keys. Sweep’s 34 is enough; adding 8 more would dilute the “every keycap is a domain vocabulary token” doctrine (sinclair-zx-spectrum.md).
• Cherry MX option. KN-86 commits to Choc v1 per ADR-0024. No MX path.
• 3-thumb-per-side ergonomics. Two thumbs is enough for our 4 thumb verbs.
• ZMK wireless variant. KN-86 is wired-only — internal USB-C through the hub IC (ADR-0018 §5).

Notes

• Cross-link ferris-sweep.md — the chosen keyboard.
• Cross-link keyboard-decision.md — the Sweep-over-custom + Sweep-over-Corne decision.
• Cross-link trackpoint-module.md — the 2× trackpoint commitment + Corne+trackpoint community cross-reference.
• Cross-link ADR-0031 — formal Sweep adoption.
• Original Corne repo: github.com/foostan/crkbd. Read the build guide even if not building one — it’s the gold standard for small-split build documentation.