Could you please explain why this is needed?

I added that so I could run all the integration tests with a single command. I could remove it if you don't like it.

No, I do not have a strong preference about it being there - but if you decide to keep it just please add a small comment explaining why it's there so later we know :)

Maybe instead of doing one more special case here you could initialize origin inside this if statement:

if (parentContext instanceof TagContext) {
          tags.putAll(((TagContext) parentContext).getTags());
        }

This may simplify some of this code, I think - you might be able to set origin to null by default and then read it from context only if context supports this.

I considered that, but thought this would be cleaner... I'll try reimplementing and see if that works better.

Was this a bug?

No, I reordered it so it was consistent with other parts of the code... (see deletion below.)

Ah, I missed that, thanks!