Google Babel is an upcoming unified messaging system set to replace Talk. We’ve covered many stories on the chat service, and some leaked source code reveals an “Upgrade” to Babel. Labeled as “DOGFOOD CONFIDENTIAL – INTERNAL ONLY”, a screenshot of source code posted by the unofficial Google Operating System blog spills the beans.

Here is what it says:

Upgrade Chat to Babel! Babel is Google’s new messenger with clients for Android, iOS, Chrome, Google+ and Gmail. Access the same conversation list from anywhere! Some of the new features: – A new, conversation-based UI – Advanced group conversations – Send pictures – Improved notifications across devices Please help us launch Babel, and send us your feedback! You can always switch back to the old chat during the dogfood.

A screenshot of the rumored web UI shows just a list of your contacts, unlike last week’s screenshots which revealed the chat interface. That screenshot looks a lot like GTalk, which is already in GMail. The difference is that there are no “call” or “video chat” buttons, casting doubt on this being the true unified messenger app we’re all expecting.

This isn’t the first time that Google Babel has appeared in Gmail. Recently, Google+ user Patric Dhawaan saw an interesting message after moving conversations to trash. Because one or more conversations were “part of a Babel chat”, they would still be available “in other Babel chat applications”.

With I/O taking place May 15-17, we’re expecting to hear official word about the unified messenger. Last week, rumors flew around that WhatsApp was in talks with Google for a $1 billion acquisition, perhaps paving the way for Babel. However, we’ve since learned WhatsApp simply isn’t interested in selling.