Inputs not readonly during file upload

[bkilshaw]

Environment

• Elixir version (elixir -v): 1.18.2
• Phoenix version (mix deps): 1.7.21
• Phoenix LiveView version (mix deps): 1.0.11
• Operating system: MacOS 15.5
• Browsers you attempted to reproduce this bug on (the more the merrier): Chrome
• Does the problem persist after removing "assets/node_modules" and trying again? Yes/no: N/A

Actual behavior

We have a form that accepts a file and uploads it directly from the browser to a third party. The uploader looks like so:

Uploaders.GoogleCloud = function (entries, onViewError) {
  entries.forEach((entry) => {
    let xhr = new XMLHttpRequest();
    xhr.open("PUT", entry.meta.url, true);

    xhr.setRequestHeader("Content-Type", entry.file.type);

    xhr.upload.addEventListener("progress", (event) => {
      if (event.lengthComputable) {
        let pct = Math.round((event.loaded / event.total) * 100);
        if (pct < 100) entry.progress(pct);
      }
    });

    xhr.onerror = () => {
      entry.error();
    };

    xhr.onload = () => {
      if (xhr.status === 200 || xhr.status === 201) {
        entry.progress(100);
      } else {
        entry.error();
      }
    };

    onViewError(() => xhr.abort());

    xhr.send(entry.file);
  });
};

In my live view I have:

# In my mount
allow_upload(:insight_file,
   accept: ["video/*"],
   max_file_size: @max_file_size,
   max_entries: 1,
   auto_upload: false,
   external: &presign_upload/2
)

defp presign_upload(_entry, socket) do
   {:ok, %{"id" => media_id, "url" => url}} =
      Mux.create_direct_upload_url([])

   {:ok, %{uploader: "GoogleCloud", key: media_id, url: url}, socket}
end

When the user clicks save the file begins to upload but the inputs are not put in readonly.

If I put a Process.sleep(5_000) in my handle_event("save", _, _) then the inputs are disabled while the handle_event processes, but not during the file upload that happens first.

Expected behavior

The inputs should be readonly during the file upload.