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CrossPoint-based fork

SUMI

v0.6.3 · X4 (X3 partial)

Offline apps, dictionary & Lua plugins

X3 partial support X4 supported Risk: Medium

Best for: Tinkerers who want a do-it-all offline device, plus the most genuine “plugin” story in the scene.

Open the flasher GitHub repo & releases

What SUMI adds

  • A sandboxed Lua plugin system: drop .lua files into /custom/ on the SD card and they become launchable apps. The only genuine on-device scriptable plugins in the scene.
  • ~20 built-in apps: chess, sudoku, notes, even a Game Boy emulator (“SumiBoy”).
  • A StarDict dictionary with fuzzy matching for offline word lookup; reading stats and achievements.
  • BLE 5.0 page-turner remotes and keyboards work (one of the few custom firmwares that keeps Bluetooth).
  • Offline-first by design (no WiFi at all). Built on Papyrix + CrossPoint; full on X4, partial on X3 (B&W reading works, grayscale still uses the X4 path).
SUMI firmware running on an Xteink pocket e-reader
SUMI’s home screen — the signature sumi-e ink-art border, with Files and Menu controls.

How to install SUMI

via web flasher

SUMI runs on the Xteink X4 (X3 partial). The install is 3 steps via web flasher, start to finish:

  1. 1

    Connect an unlocked X3/X4 by USB-C in Chrome or Edge and wake it.

  2. 2

    Open sumi.page/flasher and pick your model.

  3. 3

    Flash, then reboot (Reset, hold Power 3–5s). Books and dictionaries go on the SD card.

First flash? The mechanics are the same across every fork. Compare the five flashing methods on the directory, or follow the step-by-step flash CrossPoint without panicking guide.

SUMI safety: locked units & reverting

SUMI is a medium-risk flash. Settle two things before you touch the flasher: whether your Xteink shipped locked, and how you'd get back.

Locked devices & SUMI

Unlocked X4 (X3 partial). Flash over USB-C at sumi.page/flasher; SUMI ships no Unlocker or SD-update path, so it isn’t for locked units.

Not sure if your unit is locked? Read the locked-device safety brief, or the full locked vs unlocked buying guide.

How to revert SUMI

On an unlocked Xteink you have three ways back:

  1. 1Re-flash stock. The same web flasher offers official Xteink firmware.
  2. 2Restore a backup. “Write full flash from file” brings back the exact prior state, if you saved one first.
  3. 3Swap boot partition. A quick rollback at xteink.dve.al/debug.

On a locked unit there is no USB safety net. That is why locked devices stick to CrossPoint/CrossInk.

The one caveat: Offline by design — no WiFi transfer, so load books via SD card or the flasher’s file tools. X3 support is partial (grayscale artifacts). A younger project than CrossPoint, and quieter lately: the last release (v0.6.3) landed in May 2026.

Other Xteink firmware

Full directory →

Not sure SUMI is the right pick? Take the 30-second firmware chooser.

CrossPoint Reader

The main community firmware

The default: best all-round reader

Full guide

CrossInk

Typography + reading stats fork

Reading stats, Bionic Reading, glyph fixes

Full guide

Papyrix

More formats, one binary for both devices

FB2 / Markdown / HTML, multi-script

Full guide

CrossPet

Gamified reading + Vietnamese

Vietnamese UI + gamified virtual pet & games

Full guide

Microreader

Deliberately minimal, EPUB-only

Minimal, distraction-free EPUB-only

Full guide

AvesO3

For AO3 fanfiction readers

AO3 fanfiction workflow

Full guide

SUMI details verified August 11, 2026 against its GitHub repo, README and releases. PocketInk is independent and not affiliated with Xteink. Firmware names and versions change quickly — check the repo for the latest.