Mintplex-Labs/anything-llm · warning

Key cannot start with 'system.'

Error message

Key cannot start with 'system.'

What it means

Keys starting with 'system.' are reserved for the system-defined expansion namespace; custom variables may not shadow them. As with 'user.', a dotted key is rejected earlier by the character-set check, so this guard is defense-in-depth for the reserved namespace in the current validation order.

Solutions

1. Pick a key outside the reserved namespace, e.g. 'app_version' instead of 'system.version'
2. Use underscores for pseudo-namespacing: 'system_date' still starts with 'system_' not 'system.' and passes - prefer a clearer distinct name like 'runtime_date'
3. Document reserved prefixes for your team so they are not attempted

Example fix

// before
SystemPromptVariables.create({ key: 'system.date', value: '2026-01-01' }); // reserved prefix

// after
SystemPromptVariables.create({ key: 'fallback_date', value: '2026-01-01' });

const RESERVED_PREFIXES = ['user.', 'system.'];

function usesReservedPrefix(key) {
  return typeof key === 'string' && RESERVED_PREFIXES.some((p) => key.startsWith(p));
}

if (usesReservedPrefix(key)) {
  return res.status(400).json({ error: 'Keys may not start with user. or system.' });
}

try {
  await SystemPromptVariables.create({ key, value });
} catch (err) {
  if (/cannot start with/.test(err.message)) {
    return res.status(400).json({ error: 'Reserved namespace; rename the key' });
  }
  throw err;
}

When it happens

Trigger: Attempting to define 'system.prompt' or 'system.date' as a custom variable; copying a built-in template placeholder verbatim as a key when creating a variable.

Common situations: Trying to override built-in system expansion values; importing variable sets from other tools that use dotted system namespaces.

Related errors

• Key cannot start with 'user.'
• Key is required
• Key must be a string
• Key must be at least 3 characters
• Key must be less than 255 characters

AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18). Data as JSON: /api/errors/9055d63728da0b1e. Report an issue: GitHub.

Appendix: source

Thrown at server/models/systemPromptVariables.js:367

  /**
   * Internal function to check if a variable key is valid
   * @param {string} key
   * @param {boolean} checkExisting
   * @returns {Promise<boolean>}
   */
  _checkVariableKey: async function (key = null, checkExisting = true) {
    if (!key) throw new Error("Key is required");
    if (typeof key !== "string") throw new Error("Key must be a string");
    if (!/^[a-zA-Z0-9_]+$/.test(key))
      throw new Error("Key must contain only letters, numbers and underscores");
    if (key.length > 255)
      throw new Error("Key must be less than 255 characters");
    if (key.length < 3) throw new Error("Key must be at least 3 characters");
    if (key.startsWith("user."))
      throw new Error("Key cannot start with 'user.'");
    if (key.startsWith("system."))
      throw new Error("Key cannot start with 'system.'");
    if (checkExisting && (await this.get(key)) !== null)
      throw new Error("System prompt variable with this key already exists");

    return true;
  },
};

module.exports = { SystemPromptVariables };

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