V26.5.1 Path re-open after using pathfinder tool
The steps you were taking when you experienced the issues:
1. pen tool to do a open path
2. close the path using "add to shapes" in pathfinder
3 use pen tool to start a new point, the previous closed shape will reopen and join the new point
Your expected result :
using pen tool to start a new point should give a single point, not joining the previous closed shape
the closed shape should remain closed
I often interrupt path editing by pressing the "esc" key.
In this case, We can press esc key before apply pathfinder.
Thanks for raising this up!
I confirm this.
Disabling Rubber Band for Pen in Preferences > Selection & Anchor Display does not help.
The bug is pretty old and is reproducible since at least CS4 (but is absent in CS2), right after Pathfinder Unite/Add learnt to close opened paths.
A known workaround is to deselect the closed object before you start to draw a new path.