Feature Request: Provide TaskOutput tool access to sub-agents

Summary

Sub-agents spawned via the Task tool cannot efficiently wait for background processes because they lack access to the TaskOutput tool that the orchestrator has.

Problem Description

Orchestrator capabilities:

• Can run Bash({ command: "...", run_in_background: true })
• Can efficiently block with TaskOutput({ task_id: "...", block: true, timeout: 600000 })
• Gets notified when task completes

Sub-agent capabilities:

• Can run Bash({ command: "...", run_in_background: true })
• Receives task ID and output file path
• Cannot use TaskOutput - tool is not available
• Must read output file directly via Read tool
• No way to block/wait for task completion

Impact

Sub-agents working on tasks that require long-running processes (>10 minute timeout) are forced into inefficient patterns:

1. Polling loops - Repeatedly sleep and check output file, wasting turns and context
2. Orchestrator management - Have orchestrator manage background tasks, but this pollutes orchestrator context (defeating the purpose of sub-agents)
3. Foreground only - Limit all work to ≤10 minutes (the max timeout parameter)

Verified Behavior

Tested with general-purpose sub-agent (which has Tools: *):

• Confirmed TaskOutput is not in their tool set
• They have TaskCreate/TaskGet/TaskUpdate/TaskList (task tracking, unrelated)
• They successfully used Read to get output file contents
• No blocking mechanism available

Suggested Enhancement

Provide sub-agents access to TaskOutput tool, allowing them to:

TaskOutput({ task_id: "abc123", block: true, timeout: 600000 })

This would enable sub-agents to efficiently handle long-running operations without:

• Wasting context on polling loops
• Requiring orchestrator intervention
• Being limited to 10-minute foreground operations

Environment

• Claude Code CLI
• macOS