[Bug]: Hidden preview tabs report available:true but every automation call fails (No target available / Execution context was destroyed) #24353

Area

apps/desktop (collaborative browser / preview automation)

Steps to reproduce

1. In one thread, have an agent open several background preview tabs with preview_open (open:false, profile default) on logged-in web apps, for example a Coolify dashboard with /terminal and a Next.js app.
2. Let the thread idle for a few hours. The tabs stay hidden and are never shown.
3. Call preview_status for one of these tabs, then preview_evaluate or preview_snapshot.

Expected behavior

One of two things:

• The automation reattaches to the tab, or reloads it, and the call works.
• preview_status reports the tab as not automatable, for example available:false with a reason such as "tab suspended/detached, reopen it". The call then fails fast with that reason.

Actual behavior

preview_status reports the tab as available: true and loading: false with title: null. Every automation call then fails:

• preview_evaluate: cdpSession.send: Protocol error (Runtime.evaluate): No target available
• preview_snapshot: page.evaluate: Execution context was destroyed, most likely because of a navigation., repeatedly, although no navigation is happening.

Observed effects:

• All 4 old hidden tabs in the thread were in this state at the same time.
• A fresh preview_open with reuseExistingTab:false in the same profile works immediately, with cookies and logins intact. Only the old tabs are broken.
• One fresh tab on a page with a websocket terminal (xterm.js) went bad within minutes. preview_snapshot and preview_evaluate timed out after 15 s. preview_open with tabId and open:true, to reveal it, then hung for 660000 ms before timing out.

Why it matters: an agent cannot tell "tab detached" from "page broken" or "logged out". Our agent concluded that the user's session had expired and twice asked the user to log in again. The user was in fact logged in the whole time.

Impact

Major degradation or frequent failure

Version or commit

0.0.46-nightly.20261015.3171

Environment

macOS 26.6.2, T3 Code (Nightly) desktop, Claude agent provider (Opus 5.5)

Logs or stack traces

preview_status(tab_5) -> {"available":true,"visible":false,"title":null,"loading":false,"control":{"owner":"unclaimed","generation":0}}
preview_evaluate(tab_5) -> Preview automation evaluate failed: cdpSession.send: Protocol error (Runtime.evaluate): No target available
preview_snapshot(tab_5) -> Preview automation snapshot failed: page.evaluate: Execution context was destroyed, most likely because of a navigation.
preview_snapshot(tab_1j, fresh) -> Preview automation snapshot timed out after 15000ms.
preview_open(tab_1j, open:true) -> Preview automation open timed out after 660000ms.

Workaround

Open a new tab with preview_open (reuseExistingTab:false) and stop using the old one.

Possibly related, not duplicates: #15579 (hidden webviews stay alive), #23015 (all automation times out on Windows unattended).