kovidgoyal/kitty · warning · SystemExit

Unknown action: {action}

Error message

Unknown action: {action}

What it means

After successfully loading libsystemd, sd_bus_default_user() failed to connect to the systemd user bus (kitty/systemd.c:91). The negative return is a -errno style code converted via strerror. kitty's systemd integration (used for scoped notifications) is disabled for the session.

Source

Thrown at kittens/choose_fonts/backend.py:229

def main() -> None:
    setup_debug_print()
    cache: dict[FaceKey, RenderedSampleTransmit] = {}
    for line in sys.stdin.buffer:
        cmd = json.loads(line)
        action = cmd.get('action', '')
        if action == 'list_monospaced_fonts':
            opts = create_default_opts()
            send_to_kitten({'fonts': create_family_groups(), 'resolved_faces': resolved_faces(opts)})
        elif action == 'read_variable_data':
            ans = []
            for descriptor in cmd['descriptors']:
                ans.append(get_variable_data_for_descriptor(descriptor))
            send_to_kitten(ans)
        elif action == 'render_family_samples':
            opts, family_key, dpi_x, dpi_y = opts_from_cmd(cmd)
            send_to_kitten(render_family_sample(opts, family_key, dpi_x, dpi_y, cmd['width'], cmd['height'], cmd['output_dir'], cache))
        else:
            raise SystemExit(f'Unknown action: {action}')


def query_kitty() -> dict[str, str]:
    import subprocess

    ans = {}
    for line in subprocess.check_output([kitten_exe(), 'query-terminal']).decode().splitlines():
        k, sep, v = line.partition(':')
        if sep == ':':
            ans[k] = v.strip()
    return ans


def showcase(family: str = 'family="Fira Code"', sample_text: str = '') -> None:
    q = query_kitty()
    opts = Options()
    opts.foreground = to_color(q['foreground'])
    opts.background = to_color(q['background'])

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Verify XDG_RUNTIME_DIR is set and /run/user/$(id -u)/bus exists.
2. Ensure the systemd user session is running: systemctl --user status; if dead, restart login session or enable lingering: loginctl enable-linger $USER.
3. Check DBUS_SESSION_BUS_ADDRESS is unset or valid for the user bus.
4. If you don't need systemd notifications, ignore the message.

Example fix

# before: launched kitty via ssh without user bus
# after
export XDG_RUNTIME_DIR=/run/user/$(id -u)
loginctl enable-linger $USER  # then re-login

test -S "$XDG_RUNTIME_DIR/bus" && echo user-bus-ok || echo no-user-bus

When it happens

Trigger: kitty startup when the user session has no user bus: XDG_RUNTIME_DIR not set, /run/user/$UID not mounted, running outside a systemd user session (plain startx, some SSH or container setups), or DBUS_SESSION_BUS_ADDRESS pointing somewhere invalid.

Common situations: Starting kitty from a non-systemd session (cv/lightdm without user lingering), inside containers, over SSH without a user bus, or after systemd --user crashed.

Related errors

• This must be run as kitten choose-files
• Pipe to kitten was broken while sending data to it
• {val} is not a valid layout
• Unknown command in session file: {cmd}
• failed to export interface: %s at object path: %s with error

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/1a05cf002c69aee4. Report an issue: GitHub.