[🐛 Bug]: network.onResponseCompleted does not return full response body content

[dineshkumar-kanniyammal]

Description

When intercepting and continuing responses with Selenium BiDi network.onResponseCompleted, the response body content is not fully available. Instead, it only returns the length (e.g., Optional[1088]) instead of the actual response JSON/text.

1. I am using Selenium BiDi with Firefox and trying to capture the response body content.
2. The onResponseCompleted event gives me responseDetails.getResponseData().getContent(), but instead of the actual response payload (JSON/text), it shows only the size of the content as Optional[1088].
3. This makes it impossible to parse or log the actual API response.

Reproducible Code

FirefoxOptions options = new FirefoxOptions();
options.setBrowserVersion("140.0");
options.setCapability("webSocketUrl", true);
WebDriver driver = new FirefoxDriver(options);

Network network = new Network(driver);
network.addIntercept(new AddInterceptParameters(InterceptPhase.RESPONSE_STARTED));

network.onResponseCompleted(responseDetails -> {
 System.out.println("Response Url"+ responseDetails.getResponseData().getUrl());
 System.out.println("Response Content "+responseDetails.getResponseData().getContent().toString());

network.continueResponse(new ContinueResponseParameters(responseDetails.getRequest().getRequestId()));});

 BrowsingContext browsingContext = new BrowsingContext(driver, driver.getWindowHandle());
 browsingContext.navigate("https://reqres.in/api/users?page=2",ReadinessState.COMPLETE);

Debugging Logs

Response Url https://reqres.in/api/users?page=2
Response Content Optional[1088]
Aug 26, 2025 4:44:14 PM org.openqa.selenium.bidi.Connection send
INFO: -> {
  "method": "network.continueResponse",
  "id": 7,
  "params": {
    "request": "20"
  }
}

[selenium-ci]

@dineshkumar-kanniyammal, thank you for creating this issue. We will troubleshoot it as soon as we can.

Selenium Triage Team: remember to follow the Triage Guide

[navin772]

Hi @dineshkumar-kanniyammal as per the BiDi spec, this is the intended behaviour.

The spec mentions network.ResponseContent Type as:

network.ResponseContent = {
    size: js-uint
}

which means only the size field is included in the response and not the actual content. I agree that the naming is a bit deceptive.

There are some new BiDi commands that were added in the spec like network.addDataCollector and network.getData which can help retrieve response data but it's new and currently not supported by the stable browsers (Firefox 143 supports it) nor implemented in selenium as of now.