Vanna AI vs Wren AI

Verdict

Vanna AI and Wren AI are the two genuinely open-source options in AI analytics assistants, and both can run entirely self-hosted with a local LLM so no query text has to leave your infrastructure. They get to a correct query in different ways. Vanna is retrieval-augmented: you "train" it by feeding schema definitions, documentation, and example question/SQL pairs, and at query time it retrieves the most relevant context and asks an LLM to write SQL from it — accuracy is a direct function of how much and how well-curated that training set is. Wren AI instead asks you to write a Modeling Definition Language (MDL) file up front — tables, joins, and business metrics defined once — and compiles every question against that governed model rather than raw schema plus retrieved examples.

In practice: Vanna is faster to get a first answer out of, because a handful of example queries is enough to start. Wren AI takes more upfront investment to define the MDL, but the result is a portable, inspectable semantic layer that stays consistent as more people ask questions, closer in spirit to what a dedicated semantic layer product offers.

Choose Vanna AI if

• You want to start fast with a lightweight, example-driven training set rather than a full model definition.
• Your use case is closer to a single engineering team's internal tool than an organization-wide, governed data-access layer.
• You want the flexibility to swap in any hosted or local LLM via Ollama without being tied to a specific model.

Choose Wren AI if

• You want a governed semantic layer — Wren's MDL — that AI agents (and other tools) query consistently, not just an LLM prompted with retrieved examples.
• You're comfortable investing the setup time to define tables, joins, and metrics once, in exchange for more consistent answers later.
• You want an embeddable API and dbt integration in the same open-source-rooted platform, with a hosted Cloud tier available if you later want a UI.

The honest caveat

Neither tool is free once you count engineering time: self-hosting either one means someone owns deployment, and Wren AI's MDL in particular is real modeling work, not a configuration checkbox. Both also sell a hosted commercial tier (Vanna Cloud; Wren AI Cloud and Enterprise Plus) that trades that maintenance cost for a subscription — worth comparing against your own build-vs-buy math before committing to the self-hosted route. See text-to-SQL and retrieval-augmented generation for the underlying techniques.