Setup:

• Claude Code authenticated via Anthropic OAuth/SSO (Team Plan)
• ANTHROPIC_BASE_URL=https://api.portkey.ai
• ANTHROPIC_CUSTOM_HEADERS=x-portkey-api-key: <key>
• No ANTHROPIC_API_KEY set (as per your OAuth docs)
• Config follows: https://portkey.ai/docs/integrations/libraries/claude-code-anthropic#max-plan-/-anthropic-oauth-enterprise

Issue:
Mid-session, Claude Code starts returning auth errors requiring re-login. Running /login or claude auth status shows we're still authenticated, but all API requests are rejected. Restarting the session doesn't fix it — only unsetting ANTHROPIC_BASE_URL resolves the issue.

Hypothesis:
When the OAuth bearer token is refreshed mid-session, the new token may not be forwarded correctly through the Portkey gateway, causing Anthropic to reject subsequent requests.

Expected behavior:
Portkey should transparently forward the OAuth bearer token (including refreshed tokens) to Anthropic on each request.