upstash/context7 · error · Error

Unterminated TOML basic string in MCP args

Error message

Unterminated TOML basic string in MCP args

What it means

A double-quoted string in the MCP args array was opened but never closed before the end of the file — the scanning loop ran off the end without finding a closing quote.

Source

Thrown at packages/cli/src/setup/toml-editor.ts:69

      continue;
    }
    if (escape !== "u" && escape !== "U") {
      throw new Error(`Unsupported TOML escape \\${escape}`);
    }

    const width = escape === "u" ? 4 : 8;
    const hex = source.slice(index, index + width);
    if (!new RegExp(`^[0-9A-Fa-f]{${width}}$`).test(hex)) {
      throw new Error(`Invalid TOML Unicode escape \\${escape}${hex}`);
    }
    const codePoint = Number.parseInt(hex, 16);
    if (codePoint > 0x10ffff || (codePoint >= 0xd800 && codePoint <= 0xdfff)) {
      throw new Error(`Invalid TOML Unicode code point U+${hex}`);
    }
    value += String.fromCodePoint(codePoint);
    index += width;
  }
  throw new Error("Unterminated TOML basic string in MCP args");
}

function parseTomlLiteralString(source: string, start: number): TomlStringToken {
  const endQuote = source.indexOf("'", start + 1);
  if (endQuote === -1) throw new Error("Unterminated TOML literal string in MCP args");
  const value = source.slice(start + 1, endQuote);
  if (value.includes("\n") || value.includes("\r")) {
    throw new Error("Multiline strings are not supported in MCP args");
  }
  return { value, start, end: endQuote + 1 };
}

function parseTomlStringArray(
  source: string,
  start: number
): { tokens: TomlStringToken[]; end: number } {
  if (source[start] !== "[") throw new Error("Expected a TOML array for MCP args");

View on GitHub (pinned to edc9eeb77b)

Solutions

1. Add the missing closing double quote on the same line
2. Ensure plain ASCII quotes (" not \u201c/\u201d)
3. Validate the TOML with a linter/editor before saving

Example fix

// before
args = ["--api-key
// after
args = ["--api-key"]

const openQuotes = (line.match(/(^|[^\\])"/g) ?? []).length;
if (openQuotes % 2 !== 0) throw new Error('Unterminated basic string');

function lineHasBalancedQuotes(line: string): boolean {
  return ((line.match(/"/g) ?? []).length) % 2 === 0;
}

catch (e) { if (/Unterminated TOML basic string/.test(e.message)) { /* add closing quote, re-run */ } throw e; }

When it happens

Trigger: args = ["--flag missing closing quote, or the closing quote was deleted/turned into a smart quote by an editor.

Common situations: Manually editing args and deleting a quote; rich-text editors converting " to curly quotes; truncated file from a failed write.

Related errors

• Unterminated TOML literal string in MCP args
• Expected a comma or closing bracket in MCP args
• Unterminated TOML array in MCP args
• Multiline strings are not supported in MCP args
• Unsupported TOML escape \\${escape}

AI-assisted analysis of upstash/context7@edc9eeb77b (2026-08-28). Data as JSON: /api/errors/e6289e3aaa17b633. Report an issue: GitHub.