Cowork: `RPC error: ensure user ... already exists unexpectedly` blocks new task creation

Summary

Creating a new task in Cowork fails immediately with an RPC error referencing an
orphaned sandbox user. The task never reaches the model — sending any message
(e.g. "estas ahi") returns the error before Claude responds.

Error message (shown in UI)

Algo salió mal
RPC error: ensure user: user laughing-awesome-planck already exists unexpectedly: uid=1054 gid=1054
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Environment

• Claude Code version: 2.1.111
• Platform: macOS (Darwin 25.3.0)
• Surface: Claude Code desktop app — Cowork tab
• Model selected: Opus 4.7
• Account has many existing Cowork tasks in Dispatch (10+ visible in sidebar)

Steps to reproduce

1. Open Claude Code desktop app
2. Go to Cowork → New task
3. Name it "Check agent availability"
4. Send any message (tested with "estas ahi")
5. Error appears immediately; no model response

Expected

The task should create a fresh sandbox user and route the message to Opus 4.7.

Actual

RPC fails because the sandbox user laughing-awesome-planck (uid=1054 gid=1054)
already exists from a previous task and was not cleaned up. The "Intentar
nuevamente" button reproduces the same error.

Workarounds tried

• [ ] Full app restart (Cmd+Q + relaunch)
• [ ] Renaming the task
• [ ] claude doctor

Notes

Suggests sandbox-user cleanup is not happening on task termination, so the uid
slot stays bound to a stale username and collides on the next allocation.