  We study long-term radio/X-ray correlations in Cyg X-1. We find the
persistent existence of a compact radio jet in its soft state. This represents
a new phenomenon in black-hole binaries, in addition to compact jets in the
hard state and episodic ejections of ballistic blobs in the intermediate state.
While the radio emission in the hard state is strongly correlated with both the
soft and hard X-rays, the radio flux in the soft state is not directly
correlated with the flux of the dominant disk blackbody in soft X-rays, but
instead it is lagged by about a hundred days. We interpret the lag as occurring
in the process of advection of the magnetic flux from the donor through the
accretion disk. On the other hand, the soft-state radio flux is very tightly
correlated with the hard X-ray, 15--50 keV, flux without a measurable lag and
at the same rms. This implies that the X-ray emitting disk corona and the
soft-state jet are powered by the same process, probably magnetically.
