Cannot connect to Fabric lakehouse SQL endpoint

[tintinp]

I am experiencing a RuntimeError: 0x2746 when attempting to connect to a Microsoft Fabric Lakehouse SQL Endpoint. Crucially, this error persists even when using the provided Dev Container environment, which should have all dependencies pre-configured.

https://github.com/microsoft/mssql-python/blob/main/.devcontainer/Dockerfile
https://github.com/microsoft/mssql-python/blob/main/.devcontainer/devcontainer.json

Environment

Mode: VS Code Dev Container (Docker)

Base Image: mcr.microsoft.com/devcontainers/python:3.14-bookworm

Library: mssql-python

Target Server: Microsoft Fabric Lakehouse SQL Endpoint

Diagnostic Evidence

1. Verification of Network/TLS (from within the Container)
   I ran an openssl test from the Dev Container terminal to ensure the container can reach the outside world and complete a TLS handshake:

$ openssl s_client -connect <endpoint>.datawarehouse.fabric.microsoft.com:1433

returns

SSL handshake has read 4539 bytes and written 2165 bytes
Verification: OK
Protocol: TLSv1.3
Verify return code: 0 (ok)

Note: The handshake succeeds even if Fabric capacity is paused, proving the network path is open.

2. Steps to Reproduce
   Despite the successful TLS handshake, the Python library fails during the connection phase:

import mssql_python

conn_str = (
        f"SERVER=tcp:{<endpoint>.},1433;"
        f"DATABASE={db};"
        f"Authentication={auth_method};"
        f"Encrypt=yes;"
    )
conn = mssql_python.connect(conn_str)

throws

RuntimeError: [Microsoft][ODBC Driver 18 for SQL Server]TCP Provider: Error code 0x2746

and

# ran az login prior to this
sqlcmd -S <endpoint>.datawarehouse.fabric.microsoft.com,1433 -d LakehouseName -G -C

returns

Sqlcmd: Error: Microsoft ODBC Driver 18 for SQL Server : TCP Provider: Error code 0x2746.
Sqlcmd: Error: Microsoft ODBC Driver 18 for SQL Server : Communication link failure.

[sumitmsft]

Hi @tintinp - thanks for reporting this issue. Since this may require active troubleshooting I have created a Github Issue #461 for tracking purpose.

We will triage this issue and let you know the next steps in next couple of days.

[bewithgaurav]

Since there is a linked issue for the discussion, marking this as closed - please follow the issue #461 for updates.