[BUG]

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?

When spawning multiple background agents in parallel using a single message with multiple Task tool calls (with run_in_background: true), the Claude Code UI only displays the "shimmying" status indicator for the first task. Users see:

"Task: [first task description]" with shimmy animation stuck indefinitely
No indication that additional background agents were also spawned
False impression that Claude is stalled on the first task
Meanwhile, all agents are actually running successfully (visible via git activity, file system changes, Source Control panel showing multiple branches with commits).

What Should Happen?

The UI should accurately reflect the parallel agent execution state:

Multiple task indicators - Show each background task's status (e.g., "Task: [description] (background)" for each)
Or summary indicator - Display "N agents running in background" with expandable details
Progress visibility - Update status as agents report progress (tool counts, token usage)
Clear completion - Show when each background agent finishes, not just the first

Error Messages/Logs

Steps to Reproduce

Open Claude Code in VSCode
Ask Claude to perform a task that requires spawning multiple background agents in parallel
Claude responds with a single message containing multiple Task tool invocations, each with run_in_background: true
Observe the UI - it shows only the first Task with "Shimmying..." animation
Check Source Control panel or file system - activity from multiple agents is visible
Check agent progress notifications in the conversation - multiple agents report tool usage and token counts
UI remains stuck showing only first task until all complete

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.25

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

<img width="1949" height="1105" alt="Image" src="https://github.com/user-attachments/assets/cc7e8e82-be2d-4de2-815a-9b8ea4b54524" />