Thank you for looking into this. I found the cause. Running systemextensionsctl list revealed an active Network Extension: com.sentinelone.network-monitoring (SentinelOne EDR agent, version 25.3.4/8365) — [activated enabled] This is corporate endpoint security software (SentinelOne), installed as part of my company's device management policy. I disabled this Network Extension and the issue is immediately and fully resolved. curl, git pull, and ssh all connect normally now, with no other changes made.