[Bug] WebBridge session tabs get reaped after ~30s idle (MV3 service worker suspension)

Product

Kimi WebBridge browser extension + local daemon

Environment

• OS: Windows 11
• Browser: Google Chrome (latest stable)
• Extension version: v1.11.6
• Daemon version: v1.11.6
• Driving agent: Hermes Agent (drives the daemon at 127.0.0.1:10086 via the official kimi-webbridge skill)

Issue

When a task pauses for more than ~30 seconds between WebBridge commands (e.g. an agent doing short browser steps interspersed with longer reasoning/file work), the session tab context is lost. The next command fails with:

session "xxx" tab was closed — navigate first to recreate
find_tab: No tab with given id <id>

Root cause: Chrome terminates Manifest V3 extension service workers after ~30 seconds of idle (documented in Chrome's Service Worker Security FAQ). The WebBridge extension keeps session tab state in its service worker; when Chrome suspends the worker, the active tabs' handles are lost, and the daemon reports "tab was closed".

The daemon log shows the expected 30s connect/disconnect cycle:

[ws] hello from extension v1.11.6 (daemon v1.11.6)
[ws] extension connected
[ws] extension disconnected    # repeats every ~30s

Impact

• Intermittent automation (any flow with >30s gaps between browser actions, e.g. agent reasoning between steps) repeatedly fails with "tab was closed".
• find_tab(active:true) borrowing a user-viewed tab works, but session-owned tabs (navigate newTab) are lost and must be re-created, re-opening duplicate tabs each time.

Suggested fix

Keep the service worker alive while a task is active by periodically calling an extension API (e.g. chrome.runtime.getPlatformInfo() every 20–30s) or using chrome.alarms — the standard workaround for MV3 idle termination. Alternatively, persist or re-attach tab handles on worker wake-up.

Steps to reproduce

1. Install WebBridge extension v1.11.6 + daemon v1.11.6 in Chrome on Windows.
2. navigate newTab to any URL (returns a tabId).
3. Wait >30 seconds without sending any command.
4. Send snapshot / evaluate → error: session "..." tab was closed — navigate first to recreate.

Start by locating the extension's Manifest V3 service-worker entry point and the session tab-handle state, then reproduce the issue with navigate newTab, a wait longer than 30 seconds, and snapshot or evaluate. Trace the connect/disconnect cycle and determine whether the chosen keepalive or re-attachment approach preserves session-owned tabs; done means those commands continue working after the idle gap without opening duplicate tabs.