[BUG] Cowork mode: MCP connectors (Asana, Google Calendar) return 403 errors despite working in Claude Chat

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?

MCP connectors (specifically Asana and Google Calendar) that work correctly in Claude Chat fail with HTTP 403 errors when used in Cowork mode.

When attempting to use any Asana or Google Calendar MCP tool in Cowork mode, every call returns:
Tool call failed: 403

The same connectors work perfectly in standard Claude Chat, suggesting the OAuth credentials are not being properly passed through in the Cowork containerized environment.

This affects both:

• Native Asana MCP tools (mcp__70413d83-a9a5-47f8-8370-f4af625dd2a9__*)
• Zapier-based Asana/Calendar tools (mcp__816e0fba-d385-4171-9ff1-0f48d617f38b__*)

What Should Happen?

MCP connectors should work identically in Cowork mode as they do in Claude Chat. The OAuth credentials should be properly passed through to the containerized Cowork environment, allowing authenticated API calls to succeed.

Error Messages/Logs

Tool call failed: 403

Example calls that fail:
- mcp__70413d83-a9a5-47f8-8370-f4af625dd2a9__asana_list_workspaces
- mcp__70413d83-a9a5-47f8-8370-f4af625dd2a9__asana_get_user
- mcp__70413d83-a9a5-47f8-8370-f4af625dd2a9__asana_search_tasks
- mcp__816e0fba-d385-4171-9ff1-0f48d617f38b__google_calendar_find_multiple_events
- mcp__816e0fba-d385-4171-9ff1-0f48d617f38b__asana_find_all_tasks_from_project

All return the same generic 403 error with no additional details.

Steps to Reproduce

1. Open Claude Chat (claude.ai) and verify Asana/Google Calendar connectors are enabled and working
2. Use an Asana tool (e.g., "Show my Asana tasks") - confirm it works
3. Start a new Cowork mode session from Claude Desktop
4. Ask Claude to use the same Asana connector (e.g., "Show my overdue Asana tasks")
5. Observe: Tool returns Tool call failed: 403

Key observation: The same MCP connectors that work in Claude Chat fail in Cowork mode, despite being the same authenticated user session.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Cowork mode (Research Preview) - January 2026

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Related issues:

• #11146 - Claude Desktop: Web session mode lacks MCP server access despite configuration (similar but distinct - that's about complete lack of access, this is about 403 auth failures)

Environment:

• Claude Desktop with Cowork mode enabled
• MCP connectors authenticated and working in Claude Chat
• macOS

Workaround attempted:

• None available - the connectors simply don't work in Cowork mode

This appears to be an OAuth credential passthrough issue specific to the Cowork containerized environment.