In at least SDL Tridion 2011, Content Manager Explorer and Template Builder run against the current, even if minor, version of a template. Publishing will use the last major, checked-in, template version.

For Template Building Blocks (TBBs):

How do the following publishing contexts* affect TBB versions?

• Template Builder
• CME Preview
• Session Preview
• Publish

This would mainly be for DWT TBBS and C# TBB fragments. I'm not sure how we'd create a minor version of a TBB that's part of an assembly (it that possible with TcmUploadAssembly?).

For Session Preview

Also, which version of a template should Session Preview use?

Background: in older versions of Tridion, we had to check in (at least) legacy templates to see changes in CME Preview (update, Save & Close, then see changes). Now we can simply Save then check, but I'm not sure for XPM... yet (update follows). :-)

Update: Changing markup in a DWT without publishing does show in Session Preview. If viewing as the user that made the DWT edit, I see the latest template, even if it's a minor version. However, viewing as another user, I only see the last major version.

In other words, if viewing the page as the same user, we can edit a DWT, save, and then immediately see changes in Experience Manager's Session Preview without checking in. Feel free to clarify or add more; I'll also this as a community answer.