[BUG] Interactive mode ignores ANTHROPIC_BASE_URL, connects directly to api.anthropic.com

[markarranz]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• I can reproduce this bug consistently

Bug Description

Interactive mode (claude) makes a direct connection to api.anthropic.com on startup, ignoring the ANTHROPIC_BASE_URL environment variable. Print mode (claude -p) correctly respects ANTHROPIC_BASE_URL.

This prevents running Claude Code interactively in environments where direct internet access is blocked and API traffic must route through a proxy (e.g., Kubernetes pods with iptables egress rules, corporate networks with API gateways).

Steps to Reproduce

1. Set ANTHROPIC_BASE_URL to a local proxy endpoint:

   export ANTHROPIC_BASE_URL=http://localhost:8081/anthropic
   export ANTHROPIC_API_KEY=sk-ant-...

2. Block direct egress to api.anthropic.com (e.g., via iptables or firewall)

3. Run claude -p "hi". This works; the request goes through the proxy.

4. Run claude (interactive). This fails with:

   Unable to connect to Anthropic services
   Failed to connect to api.anthropic.com: ECONNREFUSED
   

Expected Behavior

Interactive mode should route all traffic (including startup org/auth/telemetry calls) through ANTHROPIC_BASE_URL when set, the same way print mode does.

Environment

• Claude Code v2.1.80
• Linux (Ubuntu 24.04 container in Kubernetes)
• ANTHROPIC_BASE_URL set and verified working with -p mode

Context

We run Claude Code inside isolated Kubernetes agent pods where iptables rules block all external egress from the agent user, forcing traffic through a sidecar proxy. The proxy handles credential injection and policy enforcement. Print mode works perfectly through this setup, but interactive mode bypasses ANTHROPIC_BASE_URL for what appears to be an initial org lookup or auth validation call.

[markarranz]

Resolved with environment variables:

CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1
CLAUDE_CODE_SKIP_FAST_MODE_NETWORK_ERRORS=1

These prevent the startup connections (autoupdater, Sentry, Statsig, org-status check) that bypass ANTHROPIC_BASE_URL. Interactive mode now works correctly behind a proxy with iptables-based network isolation.

[github-actions]

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