Mintplex-Labs/anything-llm · warning

Key must be at least 3 characters

Error message

Key must be at least 3 characters

What it means

Validation rule in SystemPromptVariables._checkVariableKey: the proposed variable key is shorter than the required 3-character minimum, which is treated as too short to be a meaningful, unambiguous substitution key.

Source

Thrown at server/models/systemPromptVariables.js:363

      console.error("Error in expandSystemPromptVariables:", error);
      return str;
    }
  },

  /**
   * 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 };

View on GitHub (pinned to 3aec848f28)

Solutions

1. Expand the abbreviation to at least 3 characters ('id' -> 'user_id')
2. When generating keys from codes, add a fixed prefix ('x_a')
3. Validate minimum length in the UI before submission

Example fix

// before
SystemPromptVariables.create({ key: 'id', value: '123' }); // throws

// after
SystemPromptVariables.create({ key: 'user_id', value: '123' });

const MIN_KEY_LEN = 3;

if (typeof key !== 'string' || key.length < MIN_KEY_LEN) {
  return res.status(400).json({ error: `Key must be at least ${MIN_KEY_LEN} characters` });
}

try {
  await SystemPromptVariables.create({ key, value });
} catch (err) {
  if (/at least 3 characters/.test(err.message)) {
    return res.status(400).json({ error: 'Key too short; expand the abbreviation' });
  }
  throw err;
}

When it happens

Trigger: Using short abbreviations ('id', 'ui', 'x') as keys; keys built from single-letter flags; trimmed input that collapsed to one or two characters.

Common situations: Compact internal naming conventions colliding with the minimum; forms where the user typed a very short identifier; programmatic keys derived from enum codes like 'A' or 'OK'.

Related errors

• Key must be less than 255 characters
• Key is required
• Key must be a string
• Key must contain only letters, numbers and underscores
• Key cannot start with 'user.'

AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18). Data as JSON: /api/errors/454b693443038b3d. Report an issue: GitHub.