Can't read response content in devtools.network.onRequestFinished callback

[Wang Dàpéng]

I'm trying to inspect the response of ChatGPT SSE api with this code:

chrome.devtools.network.onRequestFinished.addListener((request) => {
  const headers = request.response.headers;
  const header = headers.find((header) => header.name === "content-type");
  if (header?.value.includes("text/event-stream")) {
    request.getContent((content, encoding) => {
      log(JSON.stringify({ content, encoding }));
    });
  }
});

But content is always null.

You can reproduct it with this repo: https://github.com/wong2/sse-inspector

Install the extension, send message in chat.openai.com

[wOxxOm]

Do you see a non-empty response for this exact request in devtools UI? If not, the site may be using a WebSocket connection.

[Wang Dàpéng]

The devtools UI also shows empty response, but I can explain it.

This is because ChatGPT web app is not using the built-in `EventSource` api to send SSE requests, instead it's using the `fetch` api, so devtools does not parse the response.

Does request.getContent have the same behavior as devtools UI?

But claude.ai have a different behavior...I can get the content with the above code, but the devtools UI is also empty.

[wOxxOm]

Indeed, chrome.devtools API is using the same backend as devtools itself, so a matching behavior is what I'd expect here as well.