`mypy` regression in blob SDK for `blob_name`/`container_name` properties

[kyleknap]

• Package Name: azure-storage-blob
• Package Version: 12.27.0
• Operating System:
• Python Version:

Describe the bug
In the latest version of the blob SDK, mypy is throwing errors for client properties such as blob_name and container_name. This started happening in 12.27.0.

To Reproduce
Steps to reproduce the behavior:

1. Install SDK and mypy

> uv venv -p 3.12
Using CPython 3.12.10
Creating virtual environment at: .venv
Activate with: .venv\Scripts\activate
> .\.venv\Scripts\activate
(repro-mypy-issue) > uv pip install azure-storage-blob
Resolved 12 packages in 345ms
Installed 12 packages in 239ms
 + azure-core==1.36.0
 + azure-storage-blob==12.27.0
 + certifi==2025.10.5
 + cffi==2.0.0
 + charset-normalizer==3.4.4
 + cryptography==46.0.3
 + idna==3.11
 + isodate==0.7.2
 + pycparser==2.23
 + requests==2.32.5
 + typing-extensions==4.15.0
 + urllib3==2.5.0
(repro-mypy-issue) > uv pip install mypy
Resolved 4 packages in 275ms
Prepared 2 packages in 4.36s
Installed 3 packages in 719ms
 + mypy==1.18.2
 + mypy-extensions==1.1.0
 + pathspec==0.12.1

2. Create this sample.py script:

from azure.storage.blob import BlobClient

client = BlobClient(
   "account_url",
   "container",
   "blob"
)
client.container_name
client.blob_name

3. Run mypy:

(repro-mypy-issue) > mypy .\sample.py
sample.py:8: error: "BlobClient" has no attribute "container_name"  [attr-defined]
sample.py:9: error: "BlobClient" has no attribute "blob_name"  [attr-defined]
Found 2 errors in 1 file (checked 1 source file)

4. Confirm it works on version before:

(repro-mypy-issue) > uv pip install azure-storage-blob==12.26.0
Resolved 12 packages in 35ms
Uninstalled 1 package in 30ms
Installed 1 package in 202ms
 - azure-storage-blob==12.27.0
 + azure-storage-blob==12.26.0
(repro-mypy-issue) > mypy .\sample.py
Success: no issues found in 1 source file

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @jalauzon-msft @vincenttran-msft.