[BUG] Task Tool Fails with OAuth Authentication Error for Max Subscription Users

Task Tool Fails with OAuth Error for Max Subscription Users

Description

The Task tool consistently fails with an OAuth authentication error when attempting to use any subagent type (code-reviewer, debugger, security-auditor, general-purpose, test-runner). This occurs despite having valid Max subscription credentials and an active session.

Error Message

API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is currently not supported."}}

Environment

• Claude Code Version: Current (as of 2025-08-17)
• Subscription Type: Max
• Operating System: Linux 5.15.167.4-microsoft-standard-WSL2 (WSL2)
• Authentication Method: OAuth (Max subscription)
• Session State: Active and authenticated

Steps to Reproduce

1. Have an active Max subscription
2. Authenticate successfully with Claude Code
3. Attempt to use any Task tool with subagents:

``javascript
Task(subagent_type="general-purpose", prompt="Any prompt")
``

1. Receive OAuth authentication error consistently

Expected Behavior

Task tool should execute successfully with Max subscription OAuth authentication, as documented in the agent workflow documentation.

Actual Behavior

All Task tool invocations fail immediately with OAuth authentication error, making agent-based workflows non-functional for Max subscription users.

Additional Context

• Credentials file exists and contains valid OAuth tokens at ~/.claude/.credentials.json
• Token expiry verified as valid (not expired)
• Other tools (Bash, Read, Write, etc.) work correctly
• WebFetch also fails with the same OAuth error
• Manual fallback commands work as expected

Verification Performed

{
  "credentialsExist": true,
  "subscriptionType": "max",
  "tokenExpired": false,
  "otherToolsWorking": true
}

Impact

This issue prevents Max subscription users from utilizing the agent-based workflow system, requiring manual fallback execution for all agent operations. This significantly impacts productivity and workflow automation capabilities.

Related Issues

• Similar to #2542, #1484, #597, #3498 but specifically affects Task tool functionality

Suggested Priority

High - Core functionality broken for paying Max subscription users