MSSQL extension fails to authenticate against Azure Synapse Serverless despite valid credentials

[DantasB]

Title
MSSQL extension fails to authenticate against Azure Synapse Serverless (both ATTACH and SECRET methods)

---

Description

I'm trying to connect DuckDB's MSSQL extension to Azure Synapse Serverless SQL pool, but authentication consistently fails, even though the same credentials work with pyodbc.

I tested both connection methods:

• ATTACH with connection string
• CREATE SECRET + ATTACH

Both approaches fail with the same authentication error.

---

Environment

• DuckDB version: 1.4.4
• Platform: arm
• Extension: mssql (installed via community)
• Target: Azure Synapse Serverless SQL pool

---

Steps to reproduce (ATTACH)

conn.execute(f"""
ATTACH 'Server=<host>,1433;
Database=<database>;
User Id=<user>;
Password=<password>;'
AS mssql (TYPE MSSQL);
""")

---

Steps to reproduce (SECRET)

conn.execute("""
CREATE SECRET darling_synapse_mssql (
    TYPE mssql,
    host '<host>',
    port 1433,
    database '<database>',
    user '<user>',
    password '<password>'
);
""")

conn.execute("""
ATTACH '' AS mssql (TYPE MSSQL, SECRET darling_synapse_mssql);
""")

conn.execute("""
SELECT * FROM mssql_scan('mssql', 'SELECT TOP 10 * FROM dbo.GoldVessel');
""")

---

Observed behavior

Both approaches fail with:

[MSSQL STORAGE] ValidateConnection: authentication FAILED - raw: Authentication failed: No LOGINACK token in response, translated: Authentication failed for user 'sqladminuser' - check username and password

---

Expected behavior

The connection should succeed, as the same credentials work correctly using pyodbc:

import pyodbc

conn = pyodbc.connect(
    "DRIVER={ODBC Driver 18 for SQL Server};"
    "SERVER=<host>;"
    "DATABASE=<database>;"
    "UID=<user>;"
    "PWD=<password>;"
)

---

Additional context

• Endpoint used: <workspace>-ondemand.sql.azuresynapse.net (Synapse Serverless)

• Authentication: SQL authentication (username/password)

• Password includes special characters (tested with escaping and without issues in pyodbc)

• Firewall/network verified (connection works via pyodbc)

• Issue reproduced across:

  • macOS (ARM)
  • Docker (linux_amd64)

---

Question

Is Azure Synapse Serverless officially supported by the MSSQL extension?
If not, are there known limitations or plans to support it?

---

[VGSML]

Thanks for asking, I have tested with Azure SQL and Fabric Warehouse, this works through entra id and sql server auth. I will check with Synapse, but it could be some problems with metadata reading for catalog integration.

[DantasB]

Thanks for helping @VGSML! Yeah, i tried to disable the catalog integration also but still failed.

If you have any updates or if you wanna test something else, please let me know how could I help you!