What causes "browser function returned no result object" in JuliusBrussee/caveman?

Update chromedp and the browser to matched, recent versions.

browser function returned no result object

Error message

browser function returned no result object

What it means

Thrown in callOnNodeRaw when Runtime.callFunctionOn returns neither an exception nor a result object (res == nil). This is an unexpected protocol response: a successful call should always return a RemoteObject, so nil indicates the browser did not send the expected payload.

Solutions

Update chromedp and the browser to matched, recent versions.
Retry the call; transient protocol gaps during teardown often resolve.
Re-snapshot to obtain a fresh node handle before retrying.
If persistent, add logging of the raw CDP response and file an issue with browser version.

Defensive patterns

Strategy: retry

Try / catch

var out *Result
err := retry(3, backoff, func() error {
    var e error
    out, e = sess.CallOnNode(target, fn)
    if e != nil && strings.Contains(e.Error(), "returned no result object") {
        return e // retryable protocol gap
    }
    return stop(e)
})
return err

Prevention

Keep chromedp and the browser build version-matched and updated.
Avoid calling into nodes while the page/iframe is tearing down.
Monitor browser health (crash/OOM) in long sessions.
Re-snapshot rather than reusing very old node handles.

When it happens

Trigger: CDP responds with an empty/missing 'result' field: node destroyed between resolveNode and callFunctionOn returning nothing, protocol mismatch between chromedp and the browser version, or the call returned an undefined-by-protocol shape.

Common situations: Running against an older/newer Chromium than the chromedp protocol expects; flaky responses during page teardown; browser under crash/OOM pressure dropping payloads.

Related errors

AI-assisted analysis of JuliusBrussee/caveman@3ee70a1026 (2026-09-20). Data as JSON: /api/errors/e7706afabe3657ac. Report an issue: GitHub.

Appendix: source

Thrown at browse/cdp.go:418

	var exception *runtime.ExceptionDetails
	if err := chromedp.Run(ctx, chromedp.ActionFunc(func(actionCtx context.Context) error {
		obj, err := dom.ResolveNode().WithBackendNodeID(cdp.BackendNodeID(target.BackendDOMNodeID)).Do(actionCtx)
		if err != nil {
			return err
		}
		if obj == nil {
			return errors.New("resolve node returned no object")
		}
		res, exception, err = runtime.CallFunctionOn(fn).WithObjectID(obj.ObjectID).Do(actionCtx)
		return err
	})); err != nil {
		return nil, err
	}
	if exception != nil {
		return nil, errors.New("browser function threw")
	}
	if res == nil {
		return nil, errors.New("browser function returned no result object")
	}
	return res, nil
}

func jsString(s string) string {
	b, _ := json.Marshal(s)
	return string(b)
}

func DefaultUserDataDir(home string) string {
	if home == "" {
		if h, err := os.UserHomeDir(); err == nil {
			home = filepath.Join(h, ".caveman")
		}
	}
	if home == "" {
		return ""
	}

View on GitHub (pinned to 3ee70a1026)