  Multi-wavelength polarimetry and radio observations of Swift J1727.8-1613 at
the beginning of its recent 2023 outburst suggested the presence of a bright
compact jet aligned in the north-south direction, which could not be confirmed
without high angular resolution images. Using the Very Long Baseline Array and
the Long Baseline Array, we imaged Swift J1727.8-1613, during the
hard/hard-intermediate state, revealing a bright core and a large, two-sided,
asymmetrical, resolved jet. The jet extends in the north-south direction, at a
position angle of $-0.60\pm0.07\deg$ East of North. At 8.4 GHz, the entire
resolved jet structure is $\sim110 (d/2.7\,\text{kpc})/\sin i$ AU long, with
the southern approaching jet extending $\sim80 (d/2.7\,\text{kpc})/\sin i$ AU
from the core, where $d$ is the distance to the source and $i$ is the
inclination of the jet axis to the line of sight. These images reveal the most
resolved continuous X-ray binary jet, and possibly the most physically extended
continuous X-ray binary jet ever observed. Based on the brightness ratio of the
approaching and receding jets, we put a lower limit on the intrinsic jet speed
of $\beta\geq0.27$ and an upper limit on the jet inclination of $i\leq74\deg$.
In our first observation we also detected a rapidly fading discrete jet knot
$66.89\pm0.04$ mas south of the core, with a proper motion of $0.66\pm0.05$ mas
hour$^{-1}$, which we interpret as the result of a downstream internal shock or
a jet-ISM interaction, as opposed to a transient relativistic jet launched at
the beginning of the outburst.
