Sleight of Handheld: T-Mobile Appears, Disappears from Windows Phone 7 Launch Agenda

When it debuts on October 11, Microsoft’s new Windows Phone 7 OS will be available on devices from T-Mobile, as well as AT&T.

And that’s official.

Moments ago, the carrier–whose name was mysteriously removed from a Windows Phone 7 launch event invitation earlier today–confirmed its participation in next week’s WP7 festivities. “T-Mobile has indicated support for Windows Phone 7 and will announce details of our Windows Phone 7 offering on Oct. 11,” the company said in a statement.

Thank God for that. Because with Microsoft’s now-you-see-it, now-you-don’t invitations, it was getting difficult to tell.

This morning the agenda for Microsoft’s Windows Phone 7 worldwide launch event read:

T-Mobile reps will be present for device showing and their service offering discussion / Microsoft developer architect will demonstrate Windows Phone 7 applications

But after word of T-Mobile’s inclusion in the event spread, Microsoft removed the carrier’s name, changing the text to:

We will present a Windows Phone 7 device / Microsoft developer architect will demonstrate Windows Phone 7 applications

It’s not clear why Microsoft (MSFT) changed the text, though I imagine AT&T (T)–the company’s “premier partner” for the WP7 launch–couldn’t have been too happy sharing billing with a rival carrier.