We predict and analyze boundary-driven exceptional
points in semi-infinite Hermitian photonic waveguide
lattices with a side-coupled defect. The exceptional
points arise from coherent reflections at the lattice termination,
which induce strong memory effects in the
defect dynamics. Using an exact analytic approach, we
derive the defect’s non-Markovian memory kernel, revealing
the trajectories and coalescence conditions of
the resonances, which can be precisely tuned by the
defect position and the coupling strength. Our results
provide a simple and experimentally accessible platform
for exploring memory-enabled non-Hermitian physics
in Hermitian photonic lattices.