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claude-code - 💡(How to fix) Fix ANTHROPIC_DEFAULT_*_MODEL env vars from settings.json injected in OAuth mode but BASE_URL is not, causing tool failures with third-party API model names [1 participants]

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anthropics/claude-code#48365•Fetched 2026-04-16 07:02:16
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When using Claude Code via the desktop app (OAuth authentication), environment variables from ~/.claude/settings.json's env field are partially respected in an inconsistent way:

  • ANTHROPIC_DEFAULT_HAIKU_MODEL → is injected and used by internal tools (e.g. WebFetch)
  • ANTHROPIC_BASE_URL → is not used (overridden by OAuth routing)

This causes tools like WebFetch/WebSearch to fail when the user has configured third-party API model names that are only valid on their custom BASE_URL.

Root Cause

When using Claude Code via the desktop app (OAuth authentication), environment variables from ~/.claude/settings.json's env field are partially respected in an inconsistent way:

  • ANTHROPIC_DEFAULT_HAIKU_MODEL → is injected and used by internal tools (e.g. WebFetch)
  • ANTHROPIC_BASE_URL → is not used (overridden by OAuth routing)

This causes tools like WebFetch/WebSearch to fail when the user has configured third-party API model names that are only valid on their custom BASE_URL.

Code Example

"env": {
     "ANTHROPIC_BASE_URL": "https://third-party-api.example.com",
     "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-4-5-20251001-custom"
   }
RAW_BUFFERClick to expand / collapse

Summary

When using Claude Code via the desktop app (OAuth authentication), environment variables from ~/.claude/settings.json's env field are partially respected in an inconsistent way:

  • ANTHROPIC_DEFAULT_HAIKU_MODEL → is injected and used by internal tools (e.g. WebFetch)
  • ANTHROPIC_BASE_URL → is not used (overridden by OAuth routing)

This causes tools like WebFetch/WebSearch to fail when the user has configured third-party API model names that are only valid on their custom BASE_URL.

Steps to Reproduce

  1. Set in ~/.claude/settings.json: 
    "env": {
  "ANTHROPIC_BASE_URL": "https://third-party-api.example.com",
  "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-4-5-20251001-custom"
}
  2. Log in via OAuth in the desktop app's Code feature
  3. Use WebFetch or WebSearch tool

Expected Behavior

Either:

  • OAuth mode ignores ALL env vars that depend on BASE_URL (including model name overrides), OR
  • OAuth mode respects BASE_URL and routes tool sub-calls accordingly

Actual Behavior

WebFetch reads ANTHROPIC_DEFAULT_HAIKU_MODEL = claude-haiku-4-5-20251001-custom but routes to Anthropic's official API (via OAuth), which doesn't recognize the third-party model name:

There's an issue with the selected model (claude-haiku-4-5-20251001-custom)

Environment

  • Claude Code version: 2.1.109
  • Platform: Windows 11
  • Auth mode: OAuth (desktop app)

extent analysis

TL;DR

To fix the inconsistent environment variable handling, consider modifying the OAuth authentication flow to respect the ANTHROPIC_BASE_URL environment variable or adjusting the tool configuration to use the official API model names.

Guidance

  • Verify that the ANTHROPIC_BASE_URL environment variable is correctly set in the ~/.claude/settings.json file and that it is not being overridden by any other configuration settings.
  • Check if the OAuth authentication flow can be modified to respect the ANTHROPIC_BASE_URL environment variable, allowing tools like WebFetch and WebSearch to route sub-calls accordingly.
  • Consider adding a fallback or default behavior for tools that rely on the ANTHROPIC_DEFAULT_HAIKU_MODEL environment variable, in case the custom model name is not recognized by the official API.
  • Review the documentation for the Claude Code desktop app and OAuth authentication to ensure that environment variables are being handled as expected.

Example

No code snippet is provided as the issue is related to configuration and authentication flow.

Notes

The issue seems to be specific to the OAuth authentication mode in the desktop app, and the fix may require modifications to the authentication flow or tool configuration. Further investigation is needed to determine the root cause and the most suitable solution.

Recommendation

Apply a workaround by adjusting the tool configuration to use official API model names or modifying the OAuth authentication flow to respect the ANTHROPIC_BASE_URL environment variable, as the issue is likely related to the inconsistent handling of environment variables in the OAuth mode.

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#api#embedding generation#cache error#pipeline error#environment variable

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claude-code - 💡(How to fix) Fix ANTHROPIC_DEFAULT_*_MODEL env vars from settings.json injected in OAuth mode but BASE_URL is not, causing tool failures with third-party API model names [1 participants]