  (Mini) split supersymmetry explains the observed Higgs mass and evades
stringent constraints, while keeping good features of TeV-scale supersymmetry
other than the little hierarchy problem. Such scenarios naturally predict
thermal wino dark matter whose mass is around $3 \, {\rm TeV}$. Its
non-perturbatively enhanced annihilation is a promising target of indirect
detection experiments. It is known that identifying the smallest halos is
essential for reducing an uncertainty in interpreting indirect detection
experiments. Despite its importance, the smallest halos of thermal wino dark
matter have not been well understood and thus are investigated in this work. In
particular, we remark on two aspects: 1) the neutral wino is in kinetic
equilibrium with primordial plasma predominantly through inelastic processes
involving the slightly heavier charged wino; and 2) the resultant density
contrast shows larger powers at dark acoustic oscillation peaks than in cold
dark matter, which is known as an overshooting phenomenon. By taking them into
account, we provide a rigorous estimate of the boost factor. Our result
facilitates accurately pinning down thermal wino dark matter through vigorous
efforts in indirect detection experiments.
