What if a gamma-ray burst hit the high frontier?

As Lucio says, GRBs are short. A "long duration burst" lasts a few tens
of seconds; regular ones last two seconds or less.

In addition, though I haven't looked into this deeply, I suspect that
you'd be much better off in a space habitat than you would be on Earth.
The Earth's shielding is primarily magnetic, which does nothing at all
to gamma rays. So all that's left is the shielding effect of the
atmosphere.

Space habitats, on the other hand, are likely to be relying entirely on
mass for shielding. Enough mass to knock down the constant rain of
cosmic rays to acceptable levels would -- I suspect -- do a great job of
blocking even GRBs, or at least knocking them down enough that the
damage (which depends on both intensity and duration) would be minimal.

It's an interesting question, though. Somebody should actually run the
numbers!