Created attachment 259476 [details] Screenshot of assertion in Inspector^2 I was not able to reproduce this reliably, but I did get a screenshot with some relevant state. It appears that in some cases, we may try to show a script resource (load triggered via SourceMap) in a call frame before that script has been loaded from the backend. I don't really understand what SourceCodeTextEditor can assume in _populateWithScriptContent(). In my understanding, a script will not be associated with a resource until the DebuggerManager receives the parser notification (scriptDidParse) and makes a new WebInspector.Script. But in this case, it has nothing, and this is a normal call frame whose resource has a source map. Joe, does anything stand out to you? The call stack may provide some extra clues. Unfortunately I didn't save the Inspector's debugger call frames it was trying to show.
<rdar://problem/22363055>