kovidgoyal/kitty · warning

Malformed OSC 5522: metadata is not key=value pairs

Error message

Malformed OSC 5522: metadata is not key=value pairs

What it means

An OSC 5522 clipboard control sequence's metadata section could not be split into key=value records; kitty logs and drops the whole message.

Source

Thrown at kitty/clipboard.py:399

        self.osc52_in_flight_write_requests: dict[ClipboardType, WriteRequest] = {}
        self.granted_passwords: dict[str, GrantedPermission] = {}

    def parse_osc_5522(self, data: memoryview) -> None:
        from .notifications import sanitize_id

        idx = find_in_memoryview(data, ord(b';'))
        if idx > -1:
            metadata = str(data[:idx], 'utf-8', 'replace')
            epayload = data[idx + 1 :]
        else:
            metadata = str(data, 'utf-8', 'replace')
            epayload = data[len(data) :]
        m: dict[str, str] = {}
        for record in metadata.split(':'):
            try:
                k, v = record.split('=', 1)
            except Exception:
                log_error('Malformed OSC 5522: metadata is not key=value pairs')
                return
            m[k] = v
        typ = m.get('type', '')
        try:
            m = {k: decode_metadata_value(k, v) for k, v in m.items()}
        except Exception as e:
            log_error(f'Malformed OSC 5522: could not decode a metadata value. Error: {e}')
            if typ in ('wdata', 'walias') and self.in_flight_write_request is not None:
                self.abort_write_request(self.in_flight_write_request, 'EINVAL')
            return
        if typ == 'read':
            try:
                mime_types = tuple(strict_base64_decode(epayload).decode('utf-8').split())
            except Exception as e:
                log_error(f'Malformed OSC 5522: read request payload is not valid base64 encoded UTF-8. Error: {e}')
                return
            rr = ReadRequest(
                is_primary_selection=m.get('loc', '') == 'primary',

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Fix the client to use '=' between key and value, ':' between records
2. Send well-formed OSC 5522: metadata records like type=wdata:loc=clipboard

Example fix

# before
\x1b]5522;type:wdata\x1b\\
# after
\x1b]5522;type=wdata\x1b\\

def valid_meta(metadata: str) -> bool:
    return all('=' in rec for rec in metadata.split(':'))

When it happens

Trigger: parse_osc_5522 receives metadata where a record lacks '=' (e.g. 'type:wdata' instead of 'type=wdata'), so record.split('=',1) fails to unpack.

Common situations: Hand-rolled clients or probes of the kitty clipboard protocol using ':' as the kv separator instead of '='; truncated sequences.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Malformed OSC 5522: could not decode a metadata value. Error
• Clipboard alias request has no MIME type, aborting the write
• not a valid file descriptor number: %#v
• %s
• %s is not valid MIME alias specification

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/146033bfb0fe3a8d. Report an issue: GitHub.