MemPalace/mempalace · error · ValueError

--metadata is not valid JSON: {exc}

Error message

--metadata is not valid JSON: {exc}

What it means

Raised by _parse_metadata_arg() in the CLI when the --metadata option value cannot be parsed by json.loads. The metadata option expects a raw JSON document on the command line; any JSON syntax error (trailing comma, unquoted keys, smart quotes from shell paste, unterminated string) triggers this ValueError with the underlying parser message appended.

Source

Thrown at mempalace/cli.py:1512

        raise ValueError("pass inline text or a file, not both")
    if file_arg is not None:
        if file_arg == "-":
            return _read_stdin_exact()
        return Path(os.path.expanduser(file_arg)).read_bytes().decode("utf-8")
    if inline is not None:
        return inline
    return default


def _parse_metadata_arg(raw):
    import json

    if raw is None:
        return None
    try:
        value = json.loads(raw)
    except ValueError as exc:
        raise ValueError(f"--metadata is not valid JSON: {exc}") from None
    if not isinstance(value, dict):
        raise ValueError("--metadata must be a JSON object")
    return value


def _print_event_line(event):
    target = event["to_agent"] or "*"
    corr = f" corr={event['correlation_id']}" if event["correlation_id"] else ""
    status = f" [{event['status']}]" if event["status"] else ""
    arts = f" artifacts={len(event['artifact_ids'])}" if event["artifact_ids"] else ""
    body = event["body"].replace("\n", " ")
    if len(body) > 80:
        body = body[:77] + "..."
    body = f" :: {body}" if body else ""
    print(
        f"  {event['id']}  {event['created_at']}  {event['type']}  "
        f"{event['stream']}/{event['room']}  {event['from_agent']}->{target}"
        f"{status}{corr}{arts}{body}"

View on GitHub (pinned to 06cb6987f0)

Solutions

1. Quote the JSON correctly for your shell, using single quotes outside and double quotes inside: --metadata '{"source":"cli"}'
2. Validate the string with `echo "$META" | python3 -m json.tool` or jq before running the command
3. If the metadata lives in a variable, build it with jq -n or a here-doc to guarantee valid JSON

Example fix

# before
mempalace event add ... --metadata "{'source':'cli'}"

# after
mempalace event add ... --metadata '{"source":"cli"}'

import json

# Validate before passing --metadata
try:
    json.loads(metadata_raw)
except ValueError as exc:
    raise SystemExit(f"bad --metadata JSON: {exc}")

def is_valid_metadata_json(raw: str) -> bool:
    try:
        json.loads(raw)
        return True
    except (ValueError, TypeError):
        return False

try:
    meta = _parse_metadata_arg(raw)
except ValueError as exc:
    if "not valid JSON" in str(exc):
        meta = _parse_metadata_arg(json.dumps(eval_shorthand(raw)))  # or re-prompt user
    else:
        raise

When it happens

Trigger: Passing --metadata with malformed JSON, e.g. `--metadata "{'a':1}"` (single quotes), `--metadata "{a:1}"` (unquoted key), or a value mangled by shell quoting/escaping so the string reaching the CLI is not valid JSON.

Common situations: Single-quoted Python-style dicts pasted into shell; shell interpolation stripping inner quotes; smart quotes introduced by editors/terminals; truncated JSON from variable expansion.

Related errors

• --metadata must be a JSON object
• pass inline text or a file, not both
• operator {key!r} not supported by chroma backend
• daemon is not running
• daemon is not running; job {args.job_id} is {job['state']}

AI-assisted analysis of MemPalace/mempalace@06cb6987f0 (2026-08-15). Data as JSON: /api/errors/a3496ce8dd582e0e. Report an issue: GitHub.