Muse Spark 1.3

Muse Spark 1.3 is Meta's closed-weights reasoning model for agentic and coding work, and it suits developers who want a 1 million token context from a vendor outside the usual Anthropic, OpenAI and Google trio. Meta's research post says it was released on 2 September 2026 in Muse Code and the Meta Model API, and OpenRouter listed it the same day. OpenRouter shows a context of 1,048,576 tokens, with text, image, video and file input and text output. Its price there is $1.25 per million input tokens and $4.25 per million output tokens. Meta's post names no price, so confirm it on Meta's developer page. Meta says that against Muse Spark 1.2 its engineers saw about 20 percent fewer tool calls and 25 percent fewer tokens. Those are internal comparisons, not independent tests. The post lists open weights and bigger models only as roadmap items with no date, so today it is hosted only. A max reasoning mode is offered on both Muse Code and the API. We would trial it on agent loops where token use drives cost. Figures come from Meta's research post and OpenRouter. We have not run it ourselves.