Problem

When a Mac sleeps with Hermes Desktop open, the WebSocket connection drops. The TUI gateway parks the session but reaps it after only 20 seconds (HERMES_TUI_WS_ORPHAN_REAP_GRACE_S). On wake, Desktop holds a stale runtime session ID — any action (send message, interrupt) 404s with "session not found".

The Desktop frontend already has retry logic (use-prompt-actions.ts:667-686) that catches the 404, calls session.resume to re-register, and retries once. This means the team already knows this race exists — but the grace window is still far too short for real-world sleep durations (minutes to hours).

Steps to Reproduce

1. Open Hermes Desktop with an active session
2. Close the MacBook lid (sleep) for >20 seconds
3. Wake the Mac
4. Try to send a message in the existing session
5. Observe "session not found" error (may recover via retry, may not)

Root Cause

tui_gateway/server.py:146-162:

_WS_ORPHAN_REAP_GRACE_S = 20.0  # default

This grace was designed to prevent leaked _SlashWorker processes from browser refreshes (#38591), not to handle sleep/wake. For sleep/wake, 20s is effectively instant.

Environment

• Hermes Desktop (Electron) on macOS
• Gateway: embedded TUI gateway
• Reproducible: every sleep/wake cycle >20s