frequent msgs from accountsd and assistantd wanting to use login keychain

To stop accountsd and assistantd from repeatedly asking to use your login keychain, the issue is usually caused by your login password and keychain password being out of sync, or iCloud Keychain sync issues.

Resync Your Keychain Password

If you recently changed your Mac login password, your login keychain password may still be set to your old password.

• Open the Keychain Access app (search for it in Spotlight).
• When prompted, select the option to open it.

• In the left sidebar, right-click (or Control-click) the login keychain.
• Select Change Password for Keychain “login”.
• Enter your old Mac login password first, and then enter your new Mac login password so they match.

More info on that: Keychain Access User Guide for Mac - Apple Support

Kill Hanging Keychain Processes via Terminal

You can force background system daemons to restart and clear stuck prompts. 

• Open Terminal from Spotlight or Applications > Utilities.
• Type the following command and press return

sudo killall -kill accountsd assistantd

• Type your Mac administrator password (it will not show on screen as you type) and press return, then restart your Mac. 

Toggle iCloud Keychain

Resetting the iCloud sync connection often clears stubborn credential loops.

• Go to System Settings (or System Preferences) and click on your Apple ID / Name at the top of the sidebar.
• Select iCloud > Passwords & Keychain 

• Turn off "Sync this Mac" / iCloud Keychain.
• Restart your iMac.
• Return to System Settings and turn on iCloud Keychain again.

Check Keychain Auto-Lock Settings

If your keychain locks itself too aggressively, background system services will trigger a prompt every time they try to reach it.

• Open Keychain Access.
• Right-click the login keychain and choose Change Settings for Keychain “login”.
• Uncheck Lock after [X] minutes and Lock when sleeping if you prefer it to stay unlocked while logged in, then click Save