The best text-to-SQL tool for Postgres routes to SQL you already trust.

A text-to-SQL tool writes new SQL every turn. You cannot audit what you did not write. The model reads your prompt, reads your schema, writes a new SELECT, runs it. Every turn is a coin-flip on whether the SQL is correct.

Chion inverts that with a verified SQL agent: it routes your question to a query your team already wrote, reviewed, and trusted. If a verified query matches the intent, the agent executes it deterministically and returns the result. Only when no verified query matches does the agent fall back to generation, and even then, it generates inside a typed SQL contract bound to your schema.

The verified library compounds with every question your team asks. The text-to-SQL prompt resets every turn.

Schema hallucination. The model invents column names that look right but do not exist (customer_lifetime_value when the real column is ltv_usd). Runs in dev, fails in prod, takes an hour to debug.

Join drift. The model picks a join key that is correct for one question and wrong for the next (user_id vs account_id vs customer_id) and you only notice when the numbers do not tie out to last quarter’s report.

Aggregation errors. AVG of pre-computed ratios, SUM across snapshot tables, COUNT DISTINCT on a column that has nulls. Plausible-looking numbers, wrong math, decisions made on top of them.

A verified SQL agent avoids these by routing to pre-verified queries instead of regenerating SQL each turn: typed contract enforcement at L1 + L2.

A verified SQL agent helps wherever your team has analytical patterns that repeat. Revenue by segment, retention by cohort, funnel conversion by source: anything you have written more than twice belongs in the verified library. The agent owns the library; your team owns the queries.

It does not help for genuinely novel questions a verified library cannot answer. For those, the agent falls back to generation under a typed contract: slower than a text-to-SQL tool, but the output is contract-bound to read-only SELECT and your RLS-aware schema. You can also ship the result back into the library as a verified skill, so the next person asking it gets the verified path.

Pick a SQL agent when your analytical work compounds. Pick a text-to-SQL tool when it does not.

Pick a verified SQL agent when: your team has 50+ SQL queries already written; analysts are tired of rewriting variations; you need an audit trail; you want answers your security team can sign off on; you want the same SQL working tomorrow that worked today.

Pick a text-to-SQL tool when: you have no SQL library to compile; the volume is low enough that fresh-generation works; you are prototyping and need answers in five minutes; auditability is not a hard requirement; your data is small enough that occasional regeneration errors do not matter.

The two are not mutually exclusive. Many teams run both: a verified SQL agent for production workflows, a text-to-SQL tool for exploration. The choice is which one anchors your daily analytics work.

Chion runs every SQL through two validator layers before execution. Layer 1 enforces read-only SELECT: INSERT, UPDATE, DELETE, DROP, ALTER are rejected at the parser, in code, not in the LLM. Layer 2 binds the SQL to a typed contract: only columns your role can see, only joins your schema declares, only aggregations valid for the column types involved. The full architecture is documented under Trust & Security.

If a verified query matches the intent, the agent uses it directly; if not, it generates inside the contract, executes read-only, and surfaces the result with the SQL visible underneath. That routing-over-regeneration pattern is the core of a verified SQL agent.

Read-only SELECT. AES-256-GCM credential vault. 1,000-row cap. Immutable audit log.

AskYourDatabase. A conversational front end that fresh-generates SQL each turn and runs it free-form against your database. Chion is the AskYourDatabase alternative that routes to verified SQL and is read-only by code.

Vanna. An open-source framework that generates SQL from RAG trained on your data. You train, host, and harden it yourself. Chion is the managed Vanna alternative: verified, read-only, no self-hosting.

Julius. A general AI analyst that generates SQL from your table metadata and keeps the query out of view. Chion is the Julius alternative for teams who need to see, and trust, the SQL.

TextQL. An enterprise analyst that answers through an ontology layer you map and maintain first. The TextQL alternative that skips the ontology layer. Chion routes to SQL your analysts already verified, no mapping project required.

Same gap everywhere: SQL no one on your team authored or signed.