Hey, thanks for the detailed write-up. The root cause looks right. Missing NSLocalNetworkUsageDescription in Info.plist and com.apple.security.network.client in the entitlements does break access to RFC-1918 addresses on Sequoia.
This is a known issue. We already have a fresh thread with the same report from today: Integrated terminal cannot access local network devices on macOS — missing NSLocalNetworkUsageDescription. We’ve filed it internally. The upstream fix in VS Code (PR #308457) landed in 1.116.0, and Cursor is currently on 1.105.1. We’ll pull it in after our next base update. I can’t share an ETA for the fix yet.
I’m going to close this thread as a duplicate. Please follow that other thread and I’ll post there when we have an update.