  We report muon spin rotation ($\mu$SR) and magnetization measurements under
pressure on Fe$_{1+\delta}$Se$_\mathrm{1\text{-}x}$S$_\mathrm{x}$ with x
$\approx 0.11$.Above $p\approx0.6$ GPa we find microscopic coexistence of
superconductivity with an extended dome of long range magnetic order that spans
a pressure range between previously reported separated magnetic phases. The
magnetism initially competes on an atomic scale with the coexisting
superconductivity leading to a local maximum and minimum of the superconducting
$T_\mathrm{c}(p)$. The maximum of $T_\mathrm{c}$ corresponds to the onset of
magnetism while the minimum coincides with the pressure of strongest
competition. A shift of the maximum of $T_\mathrm{c}(p)$ for a series of single
crystals with x up to 0.14 roughly extrapolates to a putative magnetic and
superconducting state at ambient pressure for x $\geq0.2$.
