First what do you mean by “agents”. The only reason I ask is that term in the Atlassian world refers to licensed users of Jira Service Desk and for sure they need the ability to own issues thru closure.
Regardless, if you want to control the permissions of users in a project then you need to be using a Classic project template. You could consider migrating your issues from the NG to a Classic. Use the Search bar above and search for “migrating next-gen to classic” and you will find reference to the steps. Basically the steps are to setup your Classic project as desired to align closely to current NG and then use the bulk move issues.
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