ConnectionRefused on MCP/larger payloads, macOS Tahoe — native 2.1.199 (related to #56242)

What's wrong

Claude Code connects and works for small prompts (e.g. "hello") but fails with Unable to connect to API (ConnectionRefused) in a retry loop on any larger request — Slack MCP integration, and /bug submission itself hangs on "Submitting report…".

Reinstall (native installer), restart, keychain unlock, CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1, and NODE_OPTIONS="--dns-result-order=ipv4first" all tried, none resolved it.

Environment

• Claude Code: native 2.1.199
• macOS: macOS 26.5.2 (25F84)
• Platform: darwin-arm64
• Auth: subscription via /login (succeeds)

Network confirmed healthy

curl -sS -I https://api.anthropic.com/v1/messages returns HTTP 405 (expected — reaches the API fine). Browser claude.ai works normally on same machine/network. Failure is isolated to the Claude Code client on larger payloads. Claude app works as expected. Just the CLI is erroring

Appears related to

• #56242
• #38977 (Tahoe/Bun HTTP client)