What causes "${context} returned a malformed message." in jackwener/OpenCLI?

Inspect the in-page evaluate script for the context named in the error and coerce its message to a string (String(msg) or err.message)

jackwener/OpenCLI · error · CommandExecutionError

${context} returned a malformed message.

Error message

${context} returned a malformed message.

What it means

requirePostActionResult checks the optional `message` field of a browser result: if the key exists and the value is neither null nor a string, the helper throws this error naming the failing context. The library enforces that any message attached to a post-action result is a string so downstream column output never receives a non-string value.

Source

Thrown at clis/twitter/post.js:50

            throw new CommandExecutionError(`Not a valid file: ${absPath}`);
        }
        return absPath;
    });
}

function isUnsupportedInsertTextError(err) {
    const msg = err instanceof Error ? err.message : String(err);
    const lower = msg.toLowerCase();
    return lower.includes('unknown action') || lower.includes('not supported') || lower.includes('inserttext returned no inserted flag');
}

function requirePostActionResult(value, context) {
    const result = unwrapBrowserResult(value);
    if (!result || typeof result !== 'object' || Array.isArray(result) || typeof result.ok !== 'boolean') {
        throw new CommandExecutionError(`${context} returned a malformed result.`);
    }
    if (Object.prototype.hasOwnProperty.call(result, 'message') && result.message != null && typeof result.message !== 'string') {
        throw new CommandExecutionError(`${context} returned a malformed message.`);
    }
    if (Object.prototype.hasOwnProperty.call(result, 'error') && result.error != null && typeof result.error !== 'string') {
        throw new CommandExecutionError(`${context} returned a malformed error.`);
    }
    return result;
}

function validateSubmitStatusPair(result) {
    if ((result.id && !result.url) || (!result.id && result.url)) {
        throw new CommandExecutionError('Twitter post completion returned only one of id/url.');
    }
    if (!result.id && !result.url) return;
    if (typeof result.id !== 'string' || !/^\d+$/.test(result.id)) {
        throw new CommandExecutionError('Twitter post completion returned a malformed status id.');
    }
    if (typeof result.url !== 'string') {
        throw new CommandExecutionError('Twitter post completion returned a malformed status url.');
    }

View on GitHub (pinned to 49907e53dc)

Solutions

Inspect the in-page evaluate script for the context named in the error and coerce its message to a string (String(msg) or err.message)
If using a modified/forked post.js, revert to returning message as a plain string
Clear browser extensions that might alter evaluate return values and retest

Example fix

// before (in-page script)
return { ok: false, message: { code: 7, text: 'composer not found' } };
// after
return { ok: false, message: 'composer not found (code 7)' };

Defensive patterns

Strategy: validation

Validate before calling

function hasValidMessage(r) { return !('message' in (r || {})) || r.message == null || typeof r.message === 'string'; }
if (raw && !hasValidMessage(raw)) throw new Error('message must be a string');

Type guard

function hasStringMessage(v) { return v == null || typeof v !== 'object' || !('message' in v) || v.message == null || typeof v.message === 'string'; }

Try / catch

try {
  return requirePostActionResult(await page.evaluate(script), context);
} catch (e) {
  if (String(e.message).endsWith('returned a malformed message.')) console.warn('in-page script message field not a string; check script return');
  throw e;
}

Prevention

Always return message as a plain string from in-page scripts
Use err.message, not the Error object, in catch blocks
Avoid structured payloads in the message field

When it happens

Trigger: An in-page script (from focusComposer, verifyComposerText, insertComposerText, waitForImageUpload, upload, or clickResult) returns { ok: true, message: <non-string> } — e.g. message set to an object, number, boolean, or the result of JSON.parse of an object instead of a string.

Common situations: Custom-modified or forked browser scripts returning structured message payloads instead of strings; a page.evaluate returning a DOM error object placed into `message`; refactoring the in-page script so `message` becomes an Error instance rather than Error.message.

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/34904288570e819d. Report an issue: GitHub.