[BUG] VS Code extension: focus loop between visible Claude tabs still present in 2.1.280 (up to 3,600 webview_focused/s)

What happened

With several Claude Code tabs visible side by side (4 editor groups, one Claude tab each), keyboard focus ping-pongs between the Claude tabs on its own. The selected chat keeps jumping and typed text lands in the wrong session.

This is the same bug as #71809 and bugs 1 and 3 of #79770. Both were auto-closed as stale, but it still happens on 2.1.280.

Evidence from the extension log

Each loop shows as a burst of {"type":"webview_focused"} requests in Claude VSCode.log. One day on one machine:

| Window (ext host) | Burst | Events | Peak |
|---|---|---|---|
| exthost2 | 12:37:43–12:38:17 | 4,410 | 190/s |
| exthost3 | 15:00:12–15:01:10 | ~8,000 | 3,623/s |
| exthost6 | 15:14:52–15:24:28 | ~20,000 | 274/s |
| exthost8 | 15:29:24–15:30:11 | ~7,400 | 447/s |

A calm window logs single-digit webview_focused events per hour.

Likely cause

In webview/index.js, several window focus listeners move focus into the chat input when the webview gets focus, for example:

window.addEventListener("focus",()=>{z.notifyWebviewFocused(),T("window")})
// and
K0=()=>{setTimeout(Z1,0)}; window.addEventListener("focus",K0)   // Z1 -> input.focus() when activeElement is body

These run in every visible Claude webview, not only the active one. When VS Code regains OS focus (Alt-Tab back) or a tab closes and reveals a Claude panel, two or more visible webviews each re-focus themselves and keep re-triggering each other.

Suggested fix

Only the active panel should re-focus its input on window focus. Alternatively, ignore programmatic focus that arrives within a short time of a sibling panel's focus (re-entrancy guard or debounce).

Workaround

A tiny local extension that, on window.onDidChangeWindowState blur with 2+ Claude tabs visible, parks focus on workbench.action.focusStatusBar, then refocuses the Claude group after the window regains focus. Keeping only one Claude tab visible also avoids it.

Environment

• Extension: anthropic.claude-code 2.1.280 (linux-x64, Remote-SSH)
• VS Code: 1.138.0, Windows 11 client, Linux server
• claudeCode.preferredLocation: panel, 4 Claude tabs in 4 editor groups

window.addEventListener("focus",()=>{z.notifyWebviewFocused(),T("window")})        // T -> setTimeout(... Z.emit(""))
X1=()=>{if(!document.activeElement||document.activeElement===document.body)P0()},K0=()=>{setTimeout(X1,0)};
window.addEventListener("focus",K0)