Do Google's AI Overviews and AI Mode keep up with Spanish rule changes? About one answer in twenty did not

We asked Google, from Spain and in Spanish, 101 questions about 28 Spanish rules: 27 that changed in 2025–2026 (minimum wage, contributions, pensions, birth leave, consumer, traffic, housing and invoicing rules) and one announced change that never happened. Each AI Overview (AIO) and AI Mode answer was judged against the consolidated law in the Boletín Oficial del Estado as in force on 2 October 2026, not against the pages it cites. There were three readings that evening (606 responses), collected through a commercial SERP API. One rule, the 2 % cap on rent updates, was re-imposed on 1 October and repealed on 2 October; we report it apart as a case study. On the other 27, an AIO appeared for 77–86 % of the queries and AI Mode always answered.

12 of 240 AIO answers (5.0 %, 95 % CI 2.9–8.5 %) and 13 of 291 AI Mode answers (4.5 %, CI 2.6–7.5 %) gave a superseded rule as current, mixed it with the current one, or stated a fixed date the law does not contain. Twenty of the 25 errors concern three rules that moved in 2026: the state register for short-term lets, which the Supreme Court annulled in May–June, still presented as mandatory; the workplace mobility-plan deadline, which a decree-law cut from 24 to 12 months, given as December 2027; and B2B e-invoicing, given calendar dates although its deadlines run from an order not yet published. In the rent-cap case study, 5 of 23 answers, 4 of them AI Mode, presented the repealed 2 % cap as law.

The BOE was cited in 5.4 % of AIO answers and 15.8 % of AI Mode answers. Forums and social networks made up 13.2 % of AIO references. A regex script flagged 31 answers (16 AIO, 15 AI Mode); an AI agent re-read every flag and every answer of the six facts whose ground truth we corrected. A blind second AI reader agreed on whether an answer was wrong with κ 0.86 (κ 0.76 over all categories). In a random sample of unflagged answers, the agent found 0 of 40 missed errors.

Our own first fact sheet had the same failure. Checking quotations in the original BOE texts missed a Supreme Court annulment and a decree-law amendment published months earlier, plus a transitional period.