Agent goes to sleep during long independent actions, resumes only on user input

Description

Starting with Opus 4.6, when Claude Code is executing a long, independent action (e.g., a multi-step task via a subagent), the process can silently stall. The status line text (the rotating activity indicators like "blooping", "thinking", etc.) disappears, indicating the agent has gone idle.

The agent remains in this state indefinitely — in one case for approximately 30 minutes — until the user types something. At that point, Claude responds with something like "oh, I seem to have gotten interrupted" and continues as if nothing happened.

Steps to Reproduce

1. Start a long-running independent action in Claude Code (e.g., a complex multi-file task)
2. Leave Claude Code running without user interaction
3. Observe the status line activity text disappearing
4. Wait — the agent does not resume on its own
5. Type anything — the agent "wakes up" and continues

Expected Behavior

Long-running actions should complete without requiring user input to keep them alive. The status line should remain active while work is in progress.

Environment

• Claude Code with Opus 4.6