[BUG] Persistent ECONNRESET / "Connection lost mid-response" on all Code surfaces while raw HTTPS to api.anthropic.com is healthy (Windows 11, v2.1.229)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Since Aug 12, 2026, every Claude Code surface on this machine fails with
"Connection dropped (ECONNRESET)" and "API Error: Connection lost mid-response".
Requests that do complete take minutes — a one-word prompt reported
"Crunched for 3m 12s".

Affected: VS Code extension, Claude desktop app (Code mode), CLI interactive.
NOT affected: Cowork/Home mode on the same account, which executes server-side.

Environment: Claude Code v2.1.229, Windows 11, Node v20.14.0, PowerShell,
Claude Max plan. Reproduced on Fable 5, Opus 5, and Opus 5 1M context alike,
and on two unrelated networks.

Ruled out with measurements, not assumptions:

• Network: 0% packet loss over 50 pings, full 1500 MTU (ping -f -l 1472 passes)
• DNS + TLS to api.anthropic.com: dns 0.053s, connect 0.095s, tls 0.175s
• 60 KB POST to api.anthropic.com via curl: HTTP 401 in 0.53s
• The same 60 KB POST via bare Node.js https.request: HTTP 401, completed fine
• Long-lived SSE streams from other hosts: run for minutes uninterrupted
• Winsock LSP (third-party provider hooked into MSAFD Tcpip): bare Node passes

through it cleanly

• Antivirus: Windows Defender only, no HTTPS inspection
• Windows updates: installed AFTER onset
• Client version: problem predates v2.1.229; updating changed nothing
• VS Code: ruled out, since the desktop app Code mode fails identically
• Local config: reproduced in a clean temp directory with no MCP servers and

no CLAUDE.md, via
claude --strict-mcp-config --mcp-config empty-mcp.json

So raw HTTPS from this machine to api.anthropic.com is fast and reliable,
while actual model requests from Claude Code degrade to minutes and then reset.

Anthropic support confirmed two incidents (Aug 12 13:50-18:07 UTC and
Aug 13 14:33-16:08 UTC), both now resolved. A complete restart of VS Code,
the desktop app and all terminals after resolution, plus a fresh conversation,
changed nothing — the failure persists.

Possibly related: #83994

What Should Happen?

A trivial prompt returns within a few seconds without connection errors,
as it does in Cowork/Home mode on the same account and the same machine.

Error Messages/Logs

Connection dropped (ECONNRESET) · Retrying in 17s · attempt 6/10
API Error: Connection lost mid-response. The response above may be incomplete.
Crunched for 3m 12s

Network measurements from the same machine, same session:

$ ping -n 50 1.1.1.1
  0% loss, min 24ms / avg 50ms / max 116ms

$ ping -f -l 1472 1.1.1.1
  passes — full 1500 MTU, no fragmentation black hole

$ curl.exe -sS -o NUL -w "dns:%{time_namelookup} connect:%{time_connect} tls:%{time_appconnect} total:%{time_total}" https://api.anthropic.com/v1/messages
  dns:0.053066 connect:0.095212 tls:0.174907 total:0.216534

$ curl.exe -X POST --data-binary "@60kb.txt" https://api.anthropic.com/v1/messages
  401 0.534546

$ node nodepost.js   # same 60 KB POST, bare Node https.request
  STATUS 401
  OK, bytes: 141

Full debug log available on request.

Steps to Reproduce

1. Run claude in any directory on Windows 11 (also reproduces in the

VS Code extension and in the Claude desktop app Code mode)

1. Send any prompt, even a single word
2. The response either hangs for 3+ minutes, or fails with

"Connection dropped (ECONNRESET)" through all 10 retry attempts

Also reproduces in a clean room:
cd $env:TEMP; mkdir cc-clean; cd cc-clean
'{"mcpServers":{}}' | Out-File -Encoding ascii empty-mcp.json
claude --strict-mcp-config --mcp-config empty-mcp.json

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Code: v2.1.229

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_