What causes "${context}: malformed evaluate payload" in jackwener/OpenCLI?

Check the evaluate callback returns a plain object (e.g. return { ok: true, data }) rather than a raw value or nothing.

jackwener/OpenCLI · error · CommandExecutionError

${context}: malformed evaluate payload

Error message

${context}: malformed evaluate payload

What it means

requireObjectEvaluateResult unwraps a payload returned from a browser page.evaluate() call and enforces that it is a plain object. If the in-page script returned undefined, null, an array, or a primitive, the library throws this CommandExecutionError with the given context label, because evaluate results that fail to serialize (e.g. returning a DOM node or function) come back as undefined.

Source

Thrown at clis/douyin/_shared/evaluate-result.js:13

import { CommandExecutionError } from '@jackwener/opencli/errors';

export function unwrapEvaluateResult(payload) {
  if (payload && !Array.isArray(payload) && typeof payload === 'object' && 'session' in payload && 'data' in payload) {
    return payload.data;
  }
  return payload;
}

export function requireObjectEvaluateResult(payload, context) {
  const result = unwrapEvaluateResult(payload);
  if (!result || Array.isArray(result) || typeof result !== 'object') {
    throw new CommandExecutionError(`${context}: malformed evaluate payload`);
  }
  return result;
}

View on GitHub (pinned to 49907e53dc)

Solutions

Check the evaluate callback returns a plain object (e.g. return { ok: true, data }) rather than a raw value or nothing.
Log the raw payload before requireObjectEvaluateResult to see what the page actually returned.
Verify the page is still on the expected URL and not redirected/login-gated before evaluating.
Fix the in-page extraction script if Douyin DOM/JS changes made it return early.

Example fix

// before
const payload = await page.evaluate(() => document.querySelector('.x')?.innerText);
const obj = requireObjectEvaluateResult(payload, 'extract');
// after
const payload = await page.evaluate(() => ({ text: document.querySelector('.x')?.innerText ?? null }));
const obj = requireObjectEvaluateResult(payload, 'extract');

Defensive patterns

Strategy: type-guard

Validate before calling

if (payload === undefined) console.error('evaluate returned undefined — non-serializable return or page navigated away');

Type guard

function isObjectPayload(v: unknown): v is Record<string, unknown> {
  return typeof v === 'object' && v !== null && !Array.isArray(v);
}
if (!isObjectPayload(raw)) throw new Error('unexpected evaluate payload');

Try / catch

try {
  const obj = requireObjectEvaluateResult(payload, 'extract');
} catch (e) {
  if (String(e.message).endsWith('malformed evaluate payload')) {
    console.error('page.evaluate must return a plain object; check the in-page script and current URL');
  }
  throw e;
}

Prevention

Always return plain objects from page.evaluate callbacks
Never return DOM nodes, functions, or class instances from evaluate
Check page.url() matches the expected host before evaluating
Wrap in-page extraction in try/catch that returns { ok:false, error } instead of undefined

When it happens

Trigger: A page.evaluate() callback returns undefined (functions/DOM nodes don't serialize), returns null, an array, or a primitive instead of an object; the page navigated mid-evaluate so the script never completed.

Common situations: Douyin page DOM changed so the extraction script hits an early return; returning a non-serializable value from evaluate; script error swallowed and resolved with undefined; calling on a page that redirected away from creator.douyin.com.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/4c3b318db94030ec. Report an issue: GitHub.