Mozilla names Mistral Small 4 as the model coming to the Firefox Smart Window beta, and opens the beta to France

Sources: primary, discussion
Summary: The announcement describes a partnership with Mistral and states that Mistral Small 4 is coming to the Smart Window beta for users in the United States and Canada, which puts a model identifier on the beta the 2026-09-16 digest recorded as missing. It also states Mozilla is expanding Smart Window beta access and French-language support to Firefox users in France, calls France the first new market with official French-language support, and says additional European expansion is planned later this year. Mozilla says it evaluated the model on multilingual performance and publishes no result, and the post gives no ship date and no rollout mechanism.
Why it matters: An independent browser is putting a second vendor's model behind its assistant rather than one default, and the terms of that choice are stated in the announcement rather than inferred from the product.
Follow-up: Track the ship date for Mistral Small 4 and whether Mozilla publishes the multilingual evaluation.