Consider the following cell contents:

#!groovy
// @LogService log
log.info("Hello, World!")

This will throw:

javax.script.ScriptException: groovy.lang.MissingPropertyException: No such property: log for class: Script1

SciJava script parameters are required to be at the very beginning of the script.
Maybe the shebang (#!groovy) line can be stripped from the script before handing it to the ScriptService to allow proper input harvesting?

(Tested with scijava-jupyter-kernel 0.3.1-0 on Windows.)