Background sub-agents silently blocked by permission prompts

Bug

When a background sub-agent (launched via the Agent tool with run_in_background: true) tries to use a tool that requires permission approval, the permission prompt is either:

• Not visible to the user (since the agent is in the background)
• Auto-denied

This causes the sub-agent to silently fail on that action with no way for the user to approve it retroactively.

Reproduction

1. Launch a background sub-agent that needs to call an MCP tool (e.g., agora_send_message)
2. The sub-agent polls and reads data fine (read tools are allowed)
3. When it tries to send/write via an MCP tool, permission is denied
4. The sub-agent logs "Still blocked on send permissions" and continues in a read-only loop
5. The user never sees the permission prompt or has no way to approve it

Expected behavior

Background sub-agents should either:

• Inherit the parent agent's already-granted permissions
• Queue permission requests for the user to approve asynchronously
• Allow pre-authorizing specific tools when launching a background agent
• Surface the permission prompt to the user even though the agent is in the background

Environment

• Claude Code v2.1.79
• macOS Darwin 25.3.0
• MCP server tools (agora)