Context: the content script file in my MV3 extension is injected into every page as such via the manifest.json:

  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/contentScript.js"
      ],
      "match_origin_as_fallback": true,
      "match_about_blank": true,
      "all_frames": true,
      "run_at": "document_idle"
    }
  ],

When the extension is first installed, I additionally run the following via the background.js to inject the script into existing tabs:

chrome.scripting.executeScript({ files: ['js/contentScript.js',], target: { tabId: 123, allFrames: true }, })

When a user takes some action on the page, like keydown or mouse click, the content script file sends a message using chrome.runtime.sendMessage, which is received by a background.js file using chrome.runtime.onMessage.addListener((msg, sender) => { }).

Problem: I have noticed the sender.tab value is often undefined for many of my extension users. When I try to access its id, I get an error: “Cannot read properties of undefined (reading ‘id’)”. I have been unable to reproduce this issue on my own. I have checked that this specific message is only sent by the content script (not by the offscreen document, for example)

Question: In what particular cases will the sender.tab value be undefined when sending this message from the content script?