The r/LocalLLaMA post presents Muse Spark Open as a US model with open weights and claims a leading position among comparable models from the country. The excerpt does not name the developer, a release date, or the parameter count. It also omits the license and official benchmark scores.

Discussion around the post praises custom sglang kernels and full inference support through MLX and the major inference engines. Commenters also welcome NVFP4 weights said to have been calibrated in-house. Some users object to the safety post-training and to requests for user data before access. Others find the model smaller than expected or ask for a 27b version. Some question the use of GQA.

Benchmark reactions are mixed. Some commenters call the results respectable. Others claim Muse Spark Open is weaker than Muse Spark 1.2 or Muse Spark 1.3, and place it behind GLM 5.3 or Kimi K3. The thread provides no benchmark table to resolve those comparisons.