BUG: boolean operations for Index return np.array instead of Index

[sam-s]

Pandas version checks

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• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
s = pd.Series([3,5,8], name="s")
i = pd.Index([3,5,8], name="i")
assert isinstance((s + 5), pd.Series)
assert isinstance((s == 5), pd.Series)
assert isinstance((i + 5), pd.Index)
assert isinstance((i == 5), pd.Index)

Issue Description

Operating on a Series returns a Series, but adding a number to an Index return an Index while testing for something in an Index returns an np.array.

Expected Behavior

Expected: no errors.
Actual: the last assert fails.

Installed Versions

INSTALLED VERSIONS

commit : 9c8bc3e
python : 3.13.5
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19045
machine : AMD64
processor : Intel64 Family 6 Model 85 Stepping 7, GenuineIntel
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : English_United States.1252

pandas : 2.3.3
numpy : 2.3.3
pytz : 2025.2
dateutil : 2.9.0.post0
pip : 25.2
Cython : None
sphinx : None
IPython : 9.6.0
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.14.2
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : 2025.9.0
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : 6.0.2
matplotlib : 3.10.7
numba : None
numexpr : None
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : None
pyreadstat : None
pytest : None
python-calamine : None
pyxlsb : None
s3fs : 2025.9.0
scipy : 1.16.2
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : 2.0.2
xlsxwriter : None
zstandard : None
tzdata : 2025.2
qtpy : None
pyqt5 : None

[linicole74]

take

[linicole74]

oh take is gone now, I would like to work on this issue

[rhshadrach]

Thanks for the report, what is your use case where you'd like this to return an Index?

A Boolean index is generally not all that useful. Typically when one does index == 5, it's to be used as e.g. a mask and not as an index itself. It seems to me Index would be the wrong result here.

[sam-s]

index has a name - carried over from the i argument. numpy array does not.
basic interface consistency requires returning the same kind of object.