What prgm (Why) does gpg-agent.exe start in Windows?

In the past I installed gpg4win v3.1.3 with gpg v2.2.10 on 64bit Windows 7
Later I made a copy of the whole installation directory, then uninstalled the original gpg4win installation and moved afterwards the mentioned previous
backup to the original directory and restarted Win7.

When I investigate now the process list then after a couple of minutes I can see always a gpg-agent.exe daemon running.

This is strange since I uninstalled gpg4win (which should remove all services as well).
Furthermore I found no auto-start entry. and even worse I found no registry entry containing pattern “gpg-agent”.

So what does gpg-agent.exe start???

Why is gpg-agent.exe started at all?

Can it be that Thunderbird (With Enigmail) start it?
Or another valid, trustful program outside of gpg4win (e.g.stunnel) ?

The gpg-agent is the separated process that handles secret key access. This is because of security reasons.

Any operation of the tools “gpg, gpgsm” that requires secret key information, e.g. key listing, decryption, verification. Will automatically launch a gpg-agent if it is not running.

So something on your system is using Gpg4win / GnuPG e.g. Thunderbird with Enigmail, and that results in a started gpg-agent. It is not started by auto run or on windows login etc.