kovidgoyal/kitty · error

Failed to read from session file, ignoring: {default_session

Error message

Failed to read from session file, ignoring: {default_session}

What it means

kitty could not open/read the configured session file (default_session or --session argument). It logs and falls back to an empty default session (one tab, first enabled layout).

Source

Thrown at kitty/session.py:352

                session_path = args.session.session_path
            else:
                if args.session == '-':
                    f = sys.stdin
                else:
                    f = open(resolve_custom_file(args.session))
                with f:
                    session_data = f.read()
                    session_path = f.name
            yield from parse_session(session_data, opts, environ=environ, session_arg=session_arg, session_path=session_path)
            return
    if default_session and default_session != 'none' and not getattr(args, 'args', None):
        session_arg = session_arg_to_name(default_session)
        try:
            with open(default_session) as f:
                session_data = f.read()
                session_path = f.name
        except OSError:
            log_error(f'Failed to read from session file, ignoring: {default_session}')
        else:
            yield from parse_session(session_data, opts, session_arg=session_arg, session_path=session_path)
            return
    ans = Session()
    current_layout = opts.enabled_layouts[0] if opts.enabled_layouts else 'tall'
    ans.add_tab(opts)
    ans.tabs[-1].layout = current_layout
    if args is not None:
        ans.os_window_class = args.cls
        ans.os_window_name = args.name
        ans.os_window_title = args.title
    if special_window is None:
        cmd = args.args if args and args.args else resolved_shell(opts)
        from kitty.tabs import SpecialWindow

        cwd: str | None = args.directory if respect_cwd and args else None
        special_window = SpecialWindow(cmd, cwd_from=cwd_from, cwd=cwd, env=env_when_no_session, hold=bool(args and args.hold))
    ans.add_special_window(special_window)

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Use an absolute path for the session file in kitty.conf
2. If relative, place it in the kitty config directory where kitty resolves relative paths
3. Verify with: test -r /path/to/session.file && kitty --session /path/to/session.file

Example fix

# before (relative, wrong dir)
session startup.session

# after
session /home/user/.config/kitty/startup.session

import os
p = '/abs/path/to/session.file'
assert os.path.isfile(p) and os.access(p, os.R_OK), f'bad session file: {p}'

def is_readable_session(path: str) -> bool:
    import os
    return os.path.isfile(path) and os.access(path, os.R_OK)

When it happens

Trigger: open(default_session) raises OSError — file missing, unreadable permissions, or a directory — inside create_sessions.

Common situations: Relative path resolved differently than expected (session paths in kitty.conf are relative to config dir), moved/renamed file, or permission issues.

Related errors

• This should be run as kitten broadcast
• No option named: {k}
• No custom kitten named {kitten} found
• Not a number: {x} with error: {e}
• Not a valid unit: {x}. Allowed units are: {default_unit}, {"

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/5267bb98e3b1e598. Report an issue: GitHub.