Sphinx 9: "Uncaught ReferenceError: ChineseStemmer is not defined"

[hugovk]

Describe the bug

The CPython docs built with:

• Python 3.13.2
• Sphinx 9.0.4
• zh-cn or zh-tw

Enter anything in the search box, for example python and click the search button or press enter.

Takes you to a search page like /search.html?q=python

But it shows "Searching..." with no results.

The browser console shows:

language_data.js:13 Uncaught ReferenceError: ChineseStemmer is not defined
    at language_data.js:13:18
(anonymous) @ language_data.js:13
searchtools.js:304 Uncaught ReferenceError: Stemmer is not defined
    at Object._parseQuery (searchtools.js:304:21)
    at Object.query (searchtools.js:462:16)
    at Object.performSearch (searchtools.js:298:35)
    at HTMLDocument.init (searchtools.js:238:23)

Downgrading to sphinx<9 (8.2.3) fixes it.

How to Reproduce

git clone https://github.com/python/python-docs-zh-tw.git
cd python-docs-zh-tw
make all  # this will clone cpython to ../cpython
python -m http.server -d ../cpython/Doc/build/html

Environment Information

Platform:              darwin; (macOS-15.7.1-arm64-arm-64bit-Mach-O)
Python version:        3.14.2 (v3.14.2:df793163d58, Dec  5 2025, 12:18:06) [Clang 16.0.0 (clang-1600.0.26.6)])
Python implementation: CPython
Sphinx version:        9.0.4
Docutils version:      0.22.4
Jinja2 version:        3.1.6
Pygments version:      2.19.2

Sphinx extensions

Additional context

No response