[BUG] Chrome extension: permanent disconnect after CDP operations — 6 months unfixed, 7+ closed issues, root cause identified with proposed fix

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

Why this is filed as a new issue

This bug has been reported 7+ times over 6 months and auto-closed every time — none were fixed. All prior issues are now locked. This consolidation includes a root cause analysis at the extension code level and a proposed 30-line fix.

Prior issues (all closed, none resolved):

• #15463 — Chrome native host enters zombie state (root, NOT_PLANNED)
• #15743 — Extension disconnects during screenshot/JS operations (dupe of #15463)
• #24217 — Extension doesn't reconnect after native messaging disconnect (NOT_PLANNED)
• #25518 — Debugger detaches on complex pages (NOT_PLANNED)
• #28013 — Permanent disconnect after screenshot/scroll (dupe, our root cause analysis)
• #42223 — (different bug, correctly duped)

Multiple users across all platforms (macOS, Linux, Windows) confirm this is still broken.

What's Wrong?

The Chrome extension permanently disconnects after CDP-based operations (screenshot, scroll, coordinate click). Once disconnected, it enters an infinite exponential backoff reconnection loop and never recovers. Only a full Chrome restart resolves it.

Stable tools (content script API): navigate, read_page, find, form_input, javascript_tool — all work reliably.

Unstable tools (debugger/CDP API): screenshot, scroll, coordinate-based left_click, gif_creator export — trigger permanent disconnect.

Root Cause (Extension Code Level)

Examined extension source at ~/.config/google-chrome/Default/Extensions/fcoeoabgfenejglbffodgkkbkcdhcgfn/1.0.59_0/. Three compounding bugs:

Bug 1: Missing chrome.debugger.onDetach listener

The extension registers chrome.debugger.onEvent but never registers chrome.debugger.onDetach. Zero references to onDetach in the entire extension codebase.

When Chrome detaches the debugger mid-operation (page navigation, iframe changes, resource pressure), the extension doesn't know. The next sendCommand fails with "Detached while handling command."

Bug 2: sendCommand retry gap

The retry logic handles "debugger is not attached" (pre-command check) but NOT "Detached while handling command" (mid-command failure). Different error strings, only the first is caught.

Bug 3: Native messaging port has zero reconnection logic

port.onDisconnect clears state but never attempts reconnection. Once the port drops (from the error cascade of Bug 1+2), the connection is permanently dead.

The Cascade

1. Page.captureScreenshot on complex page takes 20s+
2. Chrome detaches debugger mid-operation (no onDetach listener)
3. CDP response arrives with "Detached while handling command"
4. sendCommand retry doesn't match this error string → unhandled
5. Error propagates, native messaging port disconnects
6. onDisconnect fires → state cleared → no reconnection
7. All subsequent tool calls fail permanently

Proposed Fix (~30 lines across 3 locations)

Fix 1 — Add onDetach listener:

chrome.debugger.onDetach.addListener((source, reason) => {
  const tabId = source.tabId;
  // Mark debugger as detached, reject pending promises, clean up CDP state
});

Fix 2 — Extend sendCommand retry:

const msg = error.message.toLowerCase();
if (msg.includes("not attached") || msg.includes("detached")) {
  await this.attachDebugger(tabId);
  continue; // retry
}

Fix 3 — Add reconnection to onDisconnect:

port.onDisconnect.addListener(() => {
  const error = chrome.runtime.lastError?.message;
  port = null; connected = false;
  if (error?.includes("native messaging host not found")) return;
  const delay = Math.min(3000 * Math.pow(2, reconnectAttempt++), 60000);
  setTimeout(() => connectToNativeHost(), delay);
});

Environment

• Chrome: 133+ (tested on Linux, reports confirm macOS and Windows)
• Claude Code: 2.1.83+
• Extension: 1.0.59+
• Confirmed across native messaging AND WebSocket bridge paths

Impact

Browser automation is Claude Code's differentiator over other AI coding tools. This bug makes CDP-based operations (screenshot, scroll, coordinate actions) unreliable to unusable. Multiple users (#24217, #25518, #28013) have reported it as "extension is unusable."

The fix is small, backward-compatible, and addresses the root cause rather than working around symptoms. Happy to submit a PR if the extension source is available.