linshenkx/prompt-optimizer · error · VariableExtractionParseError

variables[${index}] is not a valid object.

Error message

variables[${index}] is not a valid object.

What it means

While validating each entry of the variables array, entry at position ${index} is null, a primitive, or otherwise not an object. Each extracted variable must be an object with name/value/position fields, so normalization aborts on the first malformed entry and reports its index.

Source

Thrown at packages/core/src/services/variable-extraction/service.ts:211

    if (!data || typeof data !== 'object') {
      throw new VariableExtractionParseError('Extraction result is not a valid object.');
    }

    // 验证 variables 字段
    if (!Array.isArray(data.variables)) {
      throw new VariableExtractionParseError('Extraction result must have a "variables" array.');
    }

    // 验证 summary 字段
    if (typeof data.summary !== 'string') {
      throw new VariableExtractionParseError('Extraction result must have a "summary" string.');
    }

    // 标准化每个变量
    const variables: ExtractedVariable[] = data.variables.map((variable: any, index: number) => {
      // 验证必需字段
      if (!variable || typeof variable !== 'object') {
        throw new VariableExtractionParseError(`variables[${index}] is not a valid object.`);
      }

      if (typeof variable.name !== 'string' || !variable.name.trim()) {
        throw new VariableExtractionParseError(`variables[${index}] is missing a valid "name" field.`);
      }

      if (typeof variable.value !== 'string') {
        throw new VariableExtractionParseError(`variables[${index}] is missing a valid "value" field.`);
      }

      if (!variable.position || typeof variable.position !== 'object') {
        throw new VariableExtractionParseError(`variables[${index}] is missing a valid "position" object.`);
      }

      if (typeof variable.position.originalText !== 'string') {
        throw new VariableExtractionParseError(
          `variables[${index}].position is missing a valid "originalText" field.`
        );

View on GitHub (pinned to 3e677b1d9f)

Solutions

1. Log the raw variables array to see the actual shape at the failing index.
2. Fix the prompt/template to require each entry be an object like {name, value, position}.
3. Add a pre-normalization filter/mapper converting shorthand entries: strings -> {name: s, value: '', position: {start: 0, end: 0}}.
4. Switch to a model with stronger instruction-following.

Example fix

// before
return this.normalizeExtractionResponse(parsed);

// after
parsed.variables = parsed.variables.map(v => typeof v === 'string' ? { name: v, value: '', position: { start: 0, end: 0 } } : v).filter(Boolean);
return this.normalizeExtractionResponse(parsed);

const allVariablesAreObjects = (vars: unknown[]): boolean =>
  vars.every(v => !!v && typeof v === 'object' && !Array.isArray(v));

try {
  await extractionService.extract({ modelKey, content });
} catch (e) {
  if (e instanceof VariableExtractionParseError && /is not a valid object/.test(e.message)) {
    // filter/map string entries to objects, then retry
  }
  throw e;
}

When it happens

Trigger: The LLM's variables array contains a null, a string (e.g. just the variable name), or a number at the reported index. Reached via extract() when the model emits a heterogeneous or degenerate array.

Common situations: Model emits variables as a plain string array ("variables": ["user.name", "date"]) instead of objects; model inserts null placeholders; mixed-quality output from a weak model; prompt example showed a shorthand format.

Related errors

• variables[${index}] is missing a valid "name" field.
• variables[${index}] is missing a valid "value" field.
• Extraction result must have a "variables" array.
• Extraction result must have a "summary" string.
• Invalid import data format

AI-assisted analysis of linshenkx/prompt-optimizer@3e677b1d9f (2026-08-27). Data as JSON: /api/errors/b70b9915fc9369b6. Report an issue: GitHub.