[BUG] Cowork scheduled tasks fail when Slack is the first (or only) connector called

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?

Scheduled tasks in Cowork fail with a Slack authentication error when Slack is the first (or only) connector called in the task. The session cannot complete the Slack OAuth flow in a non-interactive/automated context.

Tasks that call other connectors first (e.g. Jira, Google Calendar) and then call Slack work correctly — Slack authenticates successfully when it is not the first connector invoked.

What Should Happen?

Scheduled tasks should be able to authenticate and use the Slack
connector as the first (or only) connector, without requiring a
prior call to another connector to "warm up" the session.

Error Messages/Logs

The Slack connector requires authentication and this is a non-interactive scheduled task session, so I cannot access the Slack tools right now.
Scheduled task failed: the Slack connector is not authenticated in this session. Priscila needs to re-authorize the Slack connector in her claude.ai connector settings for the daily briefing to run.
---

The Slack connector requires authentication that can't be completed in this automated session. The scheduled task cannot run because the Slack tools need to be re-authorized.
Please re-authorize the Slack connector in your Claude connector settings, and the next scheduled run should work normally.
Scheduled task failed: the Slack MCP server requires re-authentication. No channels were read and no digest was sent. The user needs to re-authorize the Slack connector in their settings.

Steps to Reproduce

1. Open Cowork and create a new scheduled task via "New task → Configure manually"
2. Set the instructions to call only Slack tools (e.g. slack_read_channel followed by slack_send_message)
3. Schedule it to run on weekdays at a specific time
4. Wait for the scheduled run → task fails with authentication error

Workaround: Prepend any other connector call (e.g. Google Calendar list_events) as the first step before any Slack tool call → task succeeds

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

N/A - Cowork (claude.ai)

Platform

Other

Operating System

macOS

Terminal/Shell

Other

Additional Information

Slack connector works normally in interactive Claude.ai sessions
Re-authorizing the Slack connector does not fix the issue for scheduled runs
Only tasks using exclusively the Slack connector are affected
Tasks using Slack after other connectors (Jira, Google Calendar) work correctly — suggesting a session warm-up issue with the Slack OAuth flow in automated contexts
The issue is not limited to scheduled runs — manually triggering the same task also fails with the same authentication error, confirming the problem is tied to the Cowork task session itself, not the scheduling mechanism

<img width="467" height="202" alt="Image" src="https://github.com/user-attachments/assets/7e79d428-568d-42a8-8d6c-f1ebdb4ff058" />