Is there anything you're doing with the *stream, After you initWithURL?
If you are taking the content from the InputStream inited with the local file, you would need to be creating a NSOutputStream to take the InputStream and redirect it to Safari. So I don't think just initWithURL: call with the url will tell you much, but the call to open the http:// url in safari will try to determine the content-type and try to output the file. But I don't think safari would be able to display the contents if it was a mulit-part mime yaml file.