  We present a new scheme for tagging high-$p_{T}$ bottom and charm jets using
energetic muons. Contemporary track-based $b$ tags lose their ability to reject
light jet background as jet $p_{T}\rightarrow\mathcal{O}(\mathrm{TeV})$, where
the massive boost exposes fundamental limits in tracking resolution. For our
"$\mu_{x}$" tag, the signal efficiency and light jet rejection is robust versus
$p_{T}$. In the tested regime (jet $p_{T}\in[\mathrm{0.5,2.1}]$ TeV), $\mu_{x}$
tags $\sim14\%$ of $b$ jets, $\sim6.5\%$ of $c$ jets and $\sim0.65\%$ of light
jets. Since $\mu_{x}$ tagging should be immediately useful in a searches for
heavy resonances, we test it with a typical dijet search --- a heavy,
leptophobic $Z^{\prime}$.
