[BUG] Interactive mode fails with ECONNRESET while -p (print) mode works fine

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?

Interactive mode fails with ECONNRESET while -p (print) mode works fine

Environment

• Claude Code version: 2.1.39 (also reproduced on 2.1.34)
• OS: macOS (Apple Silicon)
• Node: v20.12.2
• Bun: (bundled with Claude Code)
• Auth method: OAuth (Claude Pro subscription)

Description

Interactive mode consistently fails with Unable to connect to API (ECONNRESET) on every attempt. Print mode (claude -p) works perfectly every time, from any directory. This has been verified across two Claude Code versions (2.1.34 and 2.1.39).

Steps to Reproduce

1. Authenticate via claude login (succeeds)
2. Run claude -p "hi" → works, returns response
3. Run claude (interactive mode), type anything → fails with ECONNRESET after a few seconds

❯ hello
  ⎿  Unable to connect to API (ECONNRESET)
     Retrying in 20 seconds… (attempt 6/10)

Key Diagnostic Findings

Network is not the issue

• curl to api.anthropic.com works (TLS, streaming, authenticated — all fine)
• bun -e "fetch('https://api.anthropic.com/v1/messages'...)" works, including streaming via ReadableStream
• All relevant Anthropic endpoints resolve and respond (api.anthropic.com, statsig.anthropic.com, console.anthropic.com)

Auth is not the issue

• OAuth token is present in macOS Keychain under Claude Code-credentials
• Token has valid scopes: user:inference, user:mcp_servers, user:profile, user:sessions:claude_code
• Token is not expired
• MCP server connections authenticate and connect successfully during interactive startup (Craft and Vercel MCP servers connect fine in the same session that fails to send messages)
• -p mode works with the same token

Debug log comparison

Both -p and interactive mode show identical auth logging:

[API:request] Creating client, ANTHROPIC_CUSTOM_HEADERS present: false, has Authorization header: false
[API:auth] OAuth token check starting
[API:auth] OAuth token check complete

In -p mode, the request succeeds. In interactive mode, it immediately fails:

[ERROR] API error (attempt 1/11): undefined Connection error.

The only observable difference in the logs is the billing header:

• -p mode: cc_entrypoint=sdk-cli
• Interactive mode: cc_entrypoint=cli

Telemetry also fails

The 1P event logging also fails with ECONNRESET in interactive mode, suggesting it's not limited to the messages API endpoint:

[ERROR] 1P event logging: 33 events failed to export (code=ECONNRESET, The socket connection was closed unexpectedly.)

Not directory-specific

Fails from /tmp, ~, ~/Code, ~/Desktop — all directories. The -p mode works from all of these.

What I've ruled out

• ❌ DNS issues (all endpoints resolve)
• ❌ TLS issues (TLSv1.3 handshake completes)
• ❌ Router/ISP blocking (curl streaming test works)
• ❌ Proxy settings (no HTTP_PROXY/HTTPS_PROXY set)
• ❌ Bun networking (standalone Bun fetch + streaming works)
• ❌ Stale API key in env (removed, confirmed clean)
• ❌ Zombie processes / file lock contention (killed all, no change)
• ❌ MCP server interference (no local MCP config; cloud MCP servers actually connect fine)
• ❌ Hooks (disabled all hooks, no change)
• ❌ Version-specific regression (same on 2.1.34 and 2.1.39)
• ❌ macOS firewall (not enabled)

Expected Behavior

Interactive mode should connect to the API the same way -p mode does.

Workaround

claude -p "prompt" works reliably as a non-interactive alternative.

What Should Happen?

Interactive mode should connect to the API the same way -p mode does.

Error Messages/Logs

Steps to Reproduce

1. Authenticate via claude login (succeeds)
2. Run claude -p "hi" → works, returns response
3. Run claude (interactive mode), type anything → fails with ECONNRESET after a few seconds

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.39 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This report was created by Claude. I spent two hours debugging with it earlier (via web). Super frustrating to have Claude just stop working.