This spec explains how the new auto-complete feature will accommodate phone numbers in addition to pretty names and IM handles. We were always obsessed with the auto-complete interactions for our power users. 

This spec explained how a user would switch from IM to SMS and back during a conversation. It also showed how a user would enter a phone number for a contact if it wasn't already in the messenger system which was an important product requirement for gathering user phone numbers as a means of retention.

This spec showed how in version 2 editing phone numbers for a client can be done in a dialog instead of going to the user settings page. It also showed how a user can see the IM status of an SMS contact should they want to switch to conversing via IM instead.

This is the UI for adding a phone number to a contact via the conversation screen vs. the contact list or edit contact screen. We wanted to allow users to add numbers and edit contacts to reduce their having to visit different screens while in a conversation.

This was somewhat of an edge case but we needed address the UI for a user that had "gone mobile" a Yahoo! Messenger feature that forwarded all received IM messages to a users mobile phone. In this instance, a user cannot send the device SMS messages since they are already receiving the messages via their phone. 

This spec shows a few different use cases in the conversation view. It shows a conversation that switches mediums from IM to SMS and back. It also shows the state of a message that failed to send allowing the user to retry.