How to prevent Vue extension from "fixing" my code?

I'm experiencing an issue where "unreachable code" in a Vue/TypeScript file is automatically deleted on save. (A pretty shocking behaviour, often I'm temporarily adding a "return false" early in a function during debugging, I'd never expect the rest of the function body to be deleted!)

Through a process of elimination I have discovered that disabling either the "Vue - Official" or built-in "TypeScript and JavaScript Language Server" extension disables the behaviour, so presumably they are collectively the culprit.

I have found a way to prevent this by adding this to my settings.json:

"editor.codeActionsOnSave": {
    "source.fixAll": "false"
},

But this is a big hammer to use. I would like to disable this just for the Vue extension.

I can't find any proper documentation on editor.codeActionsOnSave but from various references around the place, I'd expect this to work:

  "editor.codeActionsOnSave": {
    "source.fixAll": "explicit",
    "source.fixAll.vue": "never",
  },

or

"source.fixAll.typescript": "never",

however, it does not. The source.fixAll setting by itself works, but source.fixAll.vue does not seem to have any effect, whether or not source.fixAll is present (and same for typescript).

How can I achieve this?

Also, ideally, how can I disable just this one specific behaviour, without disabling other code fixes from the Vue extension?

EDIT

Hmm, "source.fixAll.ts": "never" does work, but I'm still wondering: is it the TypeScript extension itself that is doing the heavy-handed "fixing", or something else? How can I find the real culprit?

By enabling logging for the TS Server, I see this:

Info 790  [11:36:27.518] response:
    {"seq":0,"type":"response","command":"getCodeFixes","request_seq":20,"success":true,"body":[{"fixName":"fixUnreachableCode","description":"Remove unreachable code","changes":[{"fileName":"[redacted]]","textChanges":[{"start":{"line":86,"offset":1},"end":{"line":89,"offset":1},"newText":""}]}]}]}
Info 791  [11:36:27.624] request:
    {
      "seq": 21,
      "type": "request",
      "command": "updateOpen",
      "arguments": {
        "changedFiles": [
          {
            "fileName": "[redacted]]",
            "textChanges": [
              {
                "newText": "",
                "start": {
                  "line": 86,
                  "offset": 1
                },
                "end": {
                  "line": 89,
                  "offset": 1
                }
              }
            ]
          }
        ],
        "closedFiles": [],
        "openFiles": []
      }
    }

I think this means the TS extension itself is the one doing the "fixing"?