Overview
- Photon reported that Macs left running continuously hit a precise uptime threshold that stops the system from making new TCP connections.
- Impacted machines still reply to ping, open connections never time out, and temporary network ports get used up until nothing new can connect.
- Photon traced the trigger to a 32‑bit TCP timestamp in the XNU kernel that wraps back to zero in a way that conflicts with RFC 7323.
- The issue is most likely to affect Macs used for server‑like or AI workloads that run for weeks without a restart, while everyday users who reboot for updates may never see it.
- TidBITS notes the failure may surface gradually with light use or after sleep delays it, there is no public Apple fix yet, and Photon recommends a reboot and is testing a non‑restart workaround.