Write to Fabric OneLake from a Synapse Spark notebook

Hi Krumelur,

Thank you for reaching out to the community with your question.

At this time, writing directly from a standalone Azure Synapse Spark notebook to Microsoft Fabric OneLake (Lakehouse) using the abfss:// endpoint is not supported. While OneLake uses a similar URI format to ADLS Gen2, its authentication model is different, and tokens issued through Synapse-linked services are not recognized by Fabric. This is why the approach that works for ADLS Gen2 does not apply to OneLake.

As a supported and reliable workaround, we recommend first writing your data from Synapse Spark to a staging location in Azure Data Lake Storage Gen2. From there, you can use a Synapse pipeline with a Copy Activity to move the data into your Fabric Lakehouse. This pipeline should use a Lakehouse Linked Service configured with a service principal and certificate for secure access. This method ensures compatibility and follows Microsoft’s best practices for integrating Synapse with Fabric.

We truly appreciate your engagement in the forum and encourage you to continue sharing your experiences and questions. Your contributions help strengthen the community for everyone.

Hope my suggestion gives you good idea, if you have any more questions, please feel free to ask we are here to help you.
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Regards,

Sahasra

Community Support Team.

Hi Krumelur,

Although an access token can be successfully acquired using a certificate and service principal (via MSAL and SNI), writing data from Synapse Spark to Microsoft Fabric OneLake using the  abfss:// protocol is currently not supported. The 404 error encountered in this scenario stems from the inability of the ABFS driver within Synapse to resolve OneLake’s internal namespace, despite successful authentication.

Microsoft Fabric’s OneLake implements a virtualized filesystem abstraction that is compatible only with Microsoft-native tools such as Fabric Spark notebooks, Dataflows, and Pipelines. External Spark engines, including Synapse Spark, are not capable of interpreting OneLake paths correctly. Consequently, token-based configurations fail at the filesystem resolution stage rather than during authentication.

As of June 2025, Microsoft has not introduced support for direct data writes from Synapse Spark to OneLake. The recommended approach is to first write the data to Azure Data Lake Storage Gen2 (ADLS Gen2), and subsequently transfer it to the Lakehouse using either a Synapse pipeline Copy Activity or a Fabric Dataflow.

Hope my suggestion gives you good idea, if you have any more questions, please feel free to ask we are here to help you.
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Thank you.