Using current Flutter master, or Dart nightly build debug sessions don't launch. It looks like we're not passing jsonrpc in the requests (this seems incorrect, but the VM may have previously been accepting it?).

[6:56:40 PM] [Observatory] [Info] [Dart] ==> {"id":"0","method":"getVersion"}
[6:56:40 PM] [Observatory] [Info] [Dart] <== {"jsonrpc":"2.0","error":{"code":-32600,"message":"Request must contain a \"jsonrpc\" key.","data":{"request":{"id":"0","method":"getVersion"}}},"id":"0"}

@devoncarew FYI - I'll work on a fix and make a patch release. Not sure if this will affect IntelliJ or others though.