v155 · extensions · developer tool

Graceful degradation playbook

Chrome 155 gives extension developers something they never had: a deterministic moment to fall back. Pick the capability you were using chrome.debugger for; get the restricted-environment alternative, the manifest permissions it needs, and the attach-rejection handler that catches the two stable error strings — copy-ready.

1 · What were you attaching a debugger for?

2 · The code to ship

manifest + fallback


    

      
      
    

  


  

    
3 · The attach handler every debugger extension needs now

    
async function attachOrFallback(tabId) {
  try {
    await chrome.debugger.attach({ tabId }, "1.3");
    return { mode: "debugger" };
  } catch (e) {
    // Chrome 155+ deterministic policy rejections:
    if (e.message === "Host access is restricted by policy." ||
        e.message === "Screenshot capture is restricted by policy.") {
      return { mode: "restricted", reason: e.message };
    }
    throw e; // real failures (bad tab, already attached...) still surface
  }
}

    
Pre-155 there was nothing reliable to catch here — attach succeeded and commands failed later, one by one. Watch that difference in the simulator.

  


  
see also