Introducing Muse Code and Muse Spark 1.2

<p><strong><a href="https://research.meta.ai/blog/introducing-muse-code-and-muse-spark-1-2">Introducing Muse Code and Muse Spark 1.2</a></strong></p> Yet more evidence that the most important characteristic of any model these days is long-sequence agentic tool calling. Meta shipped their own coding agent as part of getting that to work!</p> <blockquote> <p>Muse Spark 1.2 is a coding-focused update to Muse Spark 1.1, with improvements in code generation, complex debugging, codebase understanding, and end-to-end developer workflows. In Muse Spark 1.2, we significantly scaled up training compute on coding tasks while expanding training environment diversity. The model also maintains its strength in other key areas like general agents. [...]</p> <p>We co-trained Muse Spark 1.2 with Muse Code to ensure the model exhibits its best performance and coding usability when paired together. The training included rejection sampled harness trajectories and recipe optimizations for goals, compaction, and subagents, alongside the integration of the Muse Code toolset to maximize harness compatibility. [...]</p> <p>Muse Spark 1.2 was extensively trained on long-horizon coding tasks, including whole-repository generation, large end-to-end projects, and auto-research.</p> </blockquote> <p>Here's a pelican riding a bicycle SVG <a href="https://tools.simonwillison.net/markdown-svg-renderer#url=https%3A%2F%2Fgist.github.com%2Fsimonw%2Fce974a21202b0595e36ec2a5ddb51480">produced by Muse Spark 1.2</a>:</p> <p><img alt="Cartoon illustration of a white pelican with an orange beak riding a red bicycle against a pale blue sky with clouds and a green strip of grass below. The pelican wears a small yellow helmet that looks a bit like it belongs to a Roman centurion, has rosy cheeks, and its orange webbed feet rest on the yellow pedals." src="https://static.simonwillison.net/static/2026/muse-spark-1.2.png" /></p> <p>You can see the <a href="https://simonwillison.net/2026/Jul/9/muse-spark-1-1/">Spar