qmk/qmk_firmware

[Bug] Cannot release a 2 key combo on a single key release

Open

#26041 opened on Feb 28, 2026

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bughelp wanted

Description

Describe the Bug

I made a simple combo that sends X when both A & D are pressed.

enum combos {
  C_AD
};

const uint16_t PROGMEM combo_AD[] = {KC_A, KC_D, COMBO_END};

combo_t key_combos[] = {
  [C_AD] = COMBO(combo_AD, KC_X),
};

I cannot get the combo to release if only A or D is released using process_combo_key_release from the docs. It will release only once both A and D have been released.

This is what I have tried:

bool process_combo_key_release(uint16_t combo_index, combo_t *combo, uint8_t key_index, uint16_t keycode) {
    return true;
}

as well as:

bool process_combo_key_release(uint16_t combo_index, combo_t *combo, uint8_t key_index, uint16_t keycode) {
    switch (combo_index) {
        case C_AD:
            switch(keycode) {
                case KC_A:
                    unregister_code(KC_X);
                    break;
                case KC_D:
                    unregister_code(KC_X);
                    break;
            }
            return true; //release combo
    }
    return false;
}

Keyboard Used

royal_kludge/rk61

Link to product page (if applicable)

No response

Operating System

No response

qmk doctor Output

Is AutoHotKey / Karabiner installed

  • AutoHotKey (Windows)
  • Karabiner (macOS)

Other keyboard-related software installed

No response

Additional Context

No response

Contributor guide

Tech stack
c
Domain
desktop
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
Understanding of QMK combo systemC programming basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the combo release logic in `quantum/process keycode/process combo.c`. The issue reports that `process combo key release` is not working as expected when only one key of a two key combo is released. Check the `process combo key release` callback implementation and the default combo release behavior. Consider testing with a minimal keymap to isolate the issue. Look for any recent changes to combo handling in the git history. The reporter provided code snippets; verify if the callback is correctly invoked and if the `return true` correctly forces release.