Meta ships Muse Spark 1.3 for agentic coding

On 2 Sep 2026 Meta’s developer docs listed Muse Spark 1.3 as the latest Spark coding model, described as trained for agentic workflows and optimized for competitive coding. The drop landed on Hacker News and follows the Aug Muse Spark 1.2 contributor-tier OpenRouter listing. Meta frames Spark as a coding-focused line rather than a general chat model; no separate blog post with benchmarks accompanied the catalog update.