Microsoft open-sources Fabric-RLM: LLMs write code to recursively chew through big data

adnan_hashmi · x · 2026-09-26

Sandeep Pawar of Microsoft's Fabric CAT team open-sourced Fabric-RLM, a Python library implementing the Recursive Language Model (RLM) in Microsoft Fabric, tackling the pain of large CSVs, wide Excel files and PDF batches that don't fit in context — or answers you can't verify.

Built on MIT's RLM paper (Alex Zhang, Tim Kraska, Omar Khattab) and DSPy's RLM module: instead of stuffing everything into the prompt, the model writes Python, runs it in a subprocess inside your notebook session, inspects results, fixes its own code and recurses. Users supply a plain-English task, inputs (Lakehouse files, Delta tables, semantic models, CSVs...) and an output contract of fields and types. The author spent 5 months on it.

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