[Bug] ECONNRESET on Wi-Fi at MTU 1500; connections succeed at MTU ≤1492 (path MTU/ICMP suspected)

Bug Description
Claude Code intermittently fails with "API Error: Connection dropped (ECONNRESET)" on my home connection (Movistar, Spain, Wi-Fi mesh), and a VPN removes it. Root cause isolated: a path MTU problem toward 160.79.104.10. With the Wi-Fi interface at MTU 1500, 3 to 8 of 40-52 fresh TLS connections succeeded; at MTU 1492, 1480, 1460, 1440 and 1400, 10 of 10 succeeded every time. A-B-A on the same Wi-Fi-only path, VPN off: 1500 (8/52), 1400 (40/40), 1500 (3/40). So full-size 1500-byte packets are dropped without a working ICMP "fragmentation needed". Claude Code 2.1.294, macOS 26, Max 20x. Related: anthropics/claude-code#94225 (a user in Poland found the same threshold), support conversation 215475788280207. Request id: 8dc5ace8-1362-4c11-9306-dd5d2496a1c9. Please route to the networking team to check MSS clamping / ICMP handling for the 160.79.104.0/24 prefix at the edge. Note: another Mac on the same Wi-Fi mesh works at MTU 1500, so a client-side factor is not ruled out.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.295
• Feedback ID: 785ccde7-669e-4f94-b1fb-9c577a8fe1ee