Yeachan-Heo/oh-my-codex · error · Error

Unsupported sandbox.md frontmatter line

Error message

Unsupported sandbox.md frontmatter line: ${trimmed}

What it means

parseSimpleYamlFrontmatter throws when a frontmatter line is neither a section header ('key:'), a nested 'key: value' pair, nor matches the /^([A-Za-z0-9_-]+):\s*(.+)\s*$/ shape. The parser supports only a tiny YAML subset, so list items, comments, multiline strings, or keys with unsupported characters make the line unparseable and it throws with the offending line included.

Solutions

1. Rewrite the offending line as 'key: value' with an alphanumeric/underscore/hyphen key.
2. Remove list items, comments, and multi-line YAML constructs from sandbox.md frontmatter.
3. Keep nesting to exactly one level under a section header like 'evaluator:'.
4. Check the exact line quoted in the error message and fix or delete it.

Example fix

# before (sandbox.md frontmatter)
evaluator:
  command: ./run.sh
  # timeout in seconds
  format: json

# after
evaluator:
  command: ./run.sh
  format: json

const FRONTMATTER_LINE = /^(?:[A-Za-z0-9_-]+:\s*(?:\S.*)?|[ \t]+[A-Za-z0-9_-]+:\s*.+)$/;

function frontmatterLinesSupported(frontmatter: string): boolean {
  return frontmatter.split(/\r?\n/).filter(l => l.trim()).every(l => FRONTMATTER_LINE.test(l));
}

const isSimpleYamlLine = (line: string): boolean =>
  /^[A-Za-z0-9_-]+:(\s+.*)?$/.test(line) || /^[ \t]+[A-Za-z0-9_-]+:\s+.+$/.test(line);

try {
  parseSandboxContract(content);
} catch (err) {
  if ((err as Error).message.startsWith('Unsupported sandbox.md frontmatter line')) {
    // the message quotes the exact offending line; simplify it to 'key: value'
  }
  throw err;
}

When it happens

Trigger: A sandbox.md frontmatter line like '- item', 'key: [a, b]', '# comment', 'key:', with unsupported characters in the key (spaces, dots), or a value line without a colon — anything the simple regex cannot match after failing the section/nested checks.

Common situations: Copying richer YAML from elsewhere (anchors, lists, quotes spanning lines) into sandbox.md; adding comments with '#'; using keys with dots or spaces expecting full YAML support.

Related errors

• sandbox.md must start with YAML frontmatter containing…
• has invalid YAML frontmatter on line
• must start with YAML frontmatter containing non-empty name…
• Invalid sandbox.md frontmatter section
• Nested sandbox.md frontmatter key requires a parent section

AI-assisted analysis of Yeachan-Heo/oh-my-codex@3ad79a8a6f (2026-08-27). Data as JSON: /api/errors/62cfde582a544efd. Report an issue: GitHub.

Appendix: source

Thrown at src/autoresearch/contracts.ts:111

function parseSimpleYamlFrontmatter(frontmatter: string): Record<string, unknown> {
  const result: Record<string, unknown> = {};
  let currentSection: string | null = null;

  for (const rawLine of frontmatter.split(/\r?\n/)) {
    const line = rawLine.replace(/\t/g, '  ');
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) continue;

    const sectionMatch = /^([A-Za-z0-9_-]+):\s*$/.exec(trimmed);
    if (sectionMatch) {
      currentSection = sectionMatch[1];
      result[currentSection] = {};
      continue;
    }

    const nestedMatch = /^([A-Za-z0-9_-]+):\s*(.+)\s*$/.exec(trimmed);
    if (!nestedMatch) {
      throw contractError(`Unsupported sandbox.md frontmatter line: ${trimmed}`);
    }

    const [, key, rawValue] = nestedMatch;
    const value = rawValue.replace(/^['"]|['"]$/g, '');
    if (line.startsWith(' ') || line.startsWith('\t')) {
      if (!currentSection) {
        throw contractError(`Nested sandbox.md frontmatter key requires a parent section: ${trimmed}`);
      }
      const section = result[currentSection];
      if (!section || typeof section !== 'object' || Array.isArray(section)) {
        throw contractError(`Invalid sandbox.md frontmatter section: ${currentSection}`);
      }
      (section as Record<string, unknown>)[key] = value;
      continue;
    }

    result[key] = value;
    currentSection = null;

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