Cowork sessions crash with 1M context error — auto-compaction regression (tengu_slate_siskin disabled)

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?

Cowork sessions consistently crash after ~10 minutes with a 1M context error. The auto-compaction that used to work in cowork has stopped working entirely.

Last month, cowork sessions showed a "compacting" message periodically during long runs — this kept memory under control and sessions completed successfully. That compacting behaviour no longer happens in cowork, causing the session to fill up and crash.

The regular Claude Code side window (Chrome extension) still compacts fine. Only cowork is broken.

After investigation, the root cause was identified: the feature flag tengu_slate_siskin is set to "enabled": false in ~/.claude.json. This flag controls auto-compaction for cowork agents. It was previously enabled (compacting was working), but something on Anthropic's server side disabled it for this account.

Confirmed account-specific: Checked with ~10 other Claude users — none of them experience this issue. Their cowork sessions compact normally. This is not a global issue — it is specific to this account.

Reinstalling the app did not fix it — the broken flag is pushed from Anthropic's servers on login, so local reinstalls have no effect.

Account ID: 66db580b-2e7f-4a33-afc2-b5d3611df8e5

What Should Happen?

Cowork should auto-compact during long sessions, exactly as it did last month. The "compacting" message should appear periodically and the session should complete without hitting the 1M context limit. Users should not be asked to pay for usage credits to work around a bug introduced by a server-side change.

Error Messages/Logs

API Error: Usage credits required for 1M context · turn on usage credits at claude.ai/settings/usage, or use --model to switch to standard context

Steps to Reproduce

1. Open Claude (desktop app)
2. Start a cowork session with any long-running task
3. Let it run for ~10 minutes
4. Session crashes with: "API Error: Usage credits required for 1M context"
5. No "compacting" message appears at any point during the session

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — worked approximately few days ago

Claude Code Version

2.1.160 (Claude Code)

Platform

Other

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

• OS: Windows
• Claude app version: 2.1.160
• The flag tengu_slate_siskin in ~/.claude.json is "enabled": false on this account.
• Reinstalling the Claude app does not fix it — the broken flag is re-pushed from Anthropic servers on login.
• The autoCompactThreshold: 0.7 workaround in ~/.claude/settings.json does not help cowork sessions specifically.
• Requested fix: Re-enable tengu_slate_siskin for account ID 66db580b-2e7f-4a33-afc2-b5d3611df8e5