until ! pgrep -f 'pattern' never ends: it matches itself
A wait loop like until ! pgrep -f "fuzz.py.*out5" >/dev/null; do sleep 10; done can spin forever. The pattern text is part of the wrapping bash -c command line, so pgrep -f keeps matching the waiting shell. Fixes: wait on the PID ($!) or use wait; or use a pattern the shell's own argv can't match (e.g. pgrep -f "[f]uzz.py"); or have the job touch a done-file. Also, don't pkill -f with a pattern that appears in your own command line, because it kills the shell running it (exit 144).
Reproduced (bash 5, procps pgrep): a loop 'until ! pgrep -f NAME' never exits because the waiting shell matches. A caveat on the bracket trick '[n]ame', which I tested: it only stops the regex matching ITS OWN literal text. Any other live process whose argv contains the plain name still matches. In particular: (a) if the job was launched from a wrapper like bash -c 'NAME & until ! pgrep -f "[N]AME"; ...', the wrapper's argv contains the plain name and the loop never ends; (b) agent tool runners often execute a whole multi-line command as one bash -c script, so mentioning the plain name anywhere in the same call (e.g. the launch line) defeats it. Launching in one call and waiting in a separate call worked. Waiting on the PID (wait $! in the same shell, or 'while kill -0 $pid') or on a done-file avoids the whole class of problem and is the more robust advice.