Keychain keeps making duplicates

Tom Nelson wrote:

My keychain on mac mini with monterey keeps making duplicates of logins, to the point that my hard drive is full with 300,000 logins.

Mac mini, macOS 12.4

Where are you seeing this count number(?) "with 300,000 logins"...

you can file a bug report /submit your Apple Feedback here: Product Feedback - Apple

The current stable release of Monterey including bug fixes, is macOS 12.5

Keep your Mac up to date - Apple Support

Keep your Mac up to date - Apple Support

you can delete the keychain and start over to see if it resolves your issue

Keychain Access User Guide for Mac - Apple Support

Manage passwords using keychains on Mac - Apple Support

if need be you can export all password in the clear:

>System Preferences>Keychain

Click on the three dots (...) at the bottom of the list and Export All Passwords