  Based on the experience gained during the four and a half years of the
mission, the Fermi -LAT collaboration has undertaken a comprehensive revision
of the event-level analysis going under the name of Pass 8. Although it is not
yet finalized, we can test the improvements in the new event reconstruction
with the special case of the prompt phase of bright Gamma-Ray Bursts (GRBs),
where the signal to noise ratio is large enough that loose selection cuts are
sufficient to identify gamma- rays associated with the source. Using the new
event reconstruction, we have re-analyzed ten GRBs previously detected by the
LAT for which an x-ray/optical follow-up was possible and found four new gamma
rays with energies greater than 10 GeV in addition to the seven previously
known. Among these four is a 27.4 GeV gamma-ray from GRB 080916C, which has a
redshift of 4.35, thus making it the gamma ray with the highest intrinsic
energy (147 GeV) detected from a GRB. We present here the salient aspects of
the new event reconstruction and discuss the scientific implications of these
new high-energy gamma rays, such as constraining extragalactic background light
models, Lorentz invariance violation (LIV) tests, the prompt emission mechanism
and the bulk Lorentz factor of the emitting region.
