"dev" environment broken with Safari/GNOME Web: Shows sequence of numbers instead of page

[luator]

Describe the bug
Running reflex run (or explicitly reflex run --env dev), the page doesn't load with Safari and GNOME Web browser. Instead a long sequence of comma-separated numbers is shown in plain text:

60,33,68,79,67,84,89,80,69,32,104,116,109,108,62,60,104,116,109,108,32,108,97,110,103,61,34...

To Reproduce

uv venv
. ./venv/bin/activate
uv pip install reflex
uv reflex init  # use defaults to get a basic example app
uv reflex run
# or
uv reflex run --env dev

Expected behavior
The page of the example app created by reflex init should load.

Screenshots

Specifics (please complete the following information):

• Python Version: 3.14.0
• Reflex Version: 0.9.10.post1
• OS: Ubuntu 24.04.4
• Browser (Optional): GNOME Web (but a colleague has the same behaviour with Safari on Mac)

Additional context
Only the "dev" environment is affected. "preview" and "prod" work as expected.

[linear-code]

ENG-12228

[FarhanAliRaza]

#7048
The solution of this being worked on will be fixed in next release. Hopefully today.