Messages.app notification only shows contact number instead of contact names on macOS

I managed to fix this by going to System Preferences > Language & Region. I changed the default language from English (UK) to English (Canada) and quit System Preferences. I then changed the default back to English (UK) and then quit System Preferences again. I then restarted macOS.

I have absolutely no idea why that works. From the number of similar posts on the internet proposing different solutions, I suspect there are multiple possible issues leading to the same problem. However, this it worked for me on macOS Big Sur 11.0.1. Unfortunately I can't find the link describing this solution to give credit but if anyone does find it do link in.

Hope this helps you.

I did a bit of digging and uncovered a fairly unobtrusive workaround for this. YMMV, but it worked for me. Tested on macOS 11.4.

By restarting a few system agents, the bug appears to go into remission. This leads me to believe that the root cause is some sort of timing issue or race condition that happens during boot.

Until a proper fix exists, I welcome anyone to try this script (also at luckman212/imessage-number-fix)

#!/usr/bin/env bash

declare -a xpcArr=(
  gui/$UID/com.apple.AddressBook.abd
  gui/$UID/com.apple.AddressBook.AssistantService
  gui/$UID/com.apple.AddressBook.ContactsAccountsService
  gui/$UID/com.apple.AddressBook.SourceSync
  gui/$UID/com.apple.assistant_service
  gui/$UID/com.apple.assistantd
  gui/$UID/com.apple.CallHistorySyncHelper
  gui/$UID/com.apple.ContactsAgent
  gui/$UID/com.apple.iCloudNotificationAgent
  gui/$UID/com.apple.imagent
  gui/$UID/com.apple.imautomatichistorydeletionagent
  gui/$UID/com.apple.notificationcenterui.agent
  gui/$UID/com.apple.telephonyutilities.callservicesd
  gui/$UID/com.apple.usernoted
  gui/$UID/com.apple.UserNotificationCenterAgent
  user/$UID/com.apple.imdpersistence.IMDPersistenceAgent
)

for d in "${xpcArr[@]}"; do
  echo -n "restarting $d"
  read -r PID < <(launchctl kickstart -kp "$d")
  if [ -n "$PID" ]; then
    echo " ✔ [$PID]"
  else
    echo " ✘"
  fi
done