Muse Spark 1.3

What is disclosed

The latest Muse Spark in Meta's API is version 1.3.¹¹1Meta, Meta Model API documentation, models list, read 29 September 2026. https://dev.meta.ai/docs/models Meta released it on 2 September 2026.²²2Meta, "Introducing Muse Spark 1.3", 2 September 2026. https://research.meta.ai/blog/introducing-muse-spark-1-3 The first Muse Spark, a closed reasoning model from Meta Superintelligence Labs, came out on 8 April 2026.³³3Meta, "Introducing Muse Spark", 8 April 2026. https://ai.meta.com/blog/introducing-muse-spark-msl/

Meta has not published a parameter count for any version. It has not said whether the model is a mixture of experts, and the weights are not public.¹¹

In April Meta called the first release "a natively multimodal reasoning model", with tool use and visual chain of thought.³³ It claimed the capabilities of Llama 4 Maverick with "over an order of magnitude less compute".³³

The context window is 1,048,576 tokens. No maximum output is published.¹¹ Input can be text, images, video or PDF files, and output is text.¹¹ Audio is listed too, with a footnote: audio understanding "is currently not fully supported".¹¹

What is new

The documentation describes 1.3 as tuned for agentic workflows. Versions 1.2 and 1.1 are still listed, as older models.¹¹

According to the launch post, 1.3 "takes fewer turns where not needed and is less verbose". Meta engineers compared it with 1.2 and counted about 20% fewer tool calls and about 25% fewer tokens.²²

With 1.3, a "max reasoning" setting reached Muse Code and the Meta Model API.²² The API page recommends it for challenging reasoning and agentic tasks.⁴⁴4Meta, Muse Spark page of the Meta Model API, prices per million tokens, read 29 September 2026. https://dev.meta.ai/models/muse-spark. Arithmetic: 4.25 / 0.20 = 21.25.

The post's roadmap includes "the Muse Spark open weights release" and gives no date.²² One open model distilled from Muse Spark already exists, Muse Glimmer 30B.⁵⁵5Meta Superintelligence Labs, Muse Glimmer model card, August 2026, which calls the model "distilled from Muse Spark". https://huggingface.co/meta-models/Muse-Glimmer-30B

Using it

Version 1.3 has two ids in the API. They differ in price and in what Meta does with the traffic.⁴⁴

muse-spark-1.3 costs $1.25 per million input tokens and $4.25 per million output tokens. Meta says traffic on it is not used to improve its products.⁴⁴

Traffic on the other id, muse-spark-1.3-contributor, is used to improve Meta's products. Its output costs $0.20 per million tokens, about 21 times less (4.25 / 0.20). Input costs $0.10.⁴⁴

Cached input costs $0.15 per million tokens on the standard id and $0.002 on the contributor one.⁴⁴