Swift discovered GRB050128 with the Burst Alert Telescope and promptly pointed its narrow field instruments to monitor the afterglow .
X–ray observations started 108 s after the trigger time .
The early decay of the afterglow is relatively flat with a temporal decay modeled with a power law with index \sim - 0.3 .
A steepening occurs at later times ( \sim 1500 s ) with a power law index of \sim - 1.3 .
During this transition , the observed X–ray spectrum does not change .
We interpret this behaviour as either an early jet break or evidence for a transition from the fast cooling regime to the slow cooling regime in a wind environment .