Citation discipline — the verbatim-substring contract

Every Forum Atlas paragraph is a contract: the model claims something, the Citation Validator agent confirms that the claim's quoted excerpt is a verbatim substring of a retrieved source chunk, and only then does the paragraph persist with citation rows.

This is the right answer to the problem that has dogged generative AI in serious-tool contexts since 2023: paraphrases that drift from the source, fabricated quotes that look plausible, citations to documents that don't exist. The verbatim-substring contract makes that class of failure impossible — if the model can't quote, the paragraph renders "insufficient evidence" and the brief still delivers.

The matcher normalizes whitespace but doesn't lowercase or strip punctuation. $1.2B doesn't match $1.2 billion. The model is expected to quote source text exactly. The check itself runs inside our pipeline as a Postgres function, citation_verbatim_matches().