  We study the entanglement transition in monitored Brownian SYK chains in the
large-$N$ limit. Without measurement the steady state $n$-th R\'enyi entropy is
obtained by summing over a class of solutions, and is found to saturate to the
Page value in the $n\rightarrow 1$ limit. In the presence of measurements, the
analytical continuation $n\rightarrow 1$ is performed using the cyclic
symmetric solution. The result shows that as the monitoring rate increases, a
continuous von Neumann entanglement entropy transition from volume-law to
area-law occurs at the point of replica symmetry unbreaking.
