GPT-5.6 Luna Max vs Muse Spark Open compared

On the headline score, OpenAI's GPT-5.6 Luna (Max) and Meta's Muse Spark Open (Xhigh) are almost level. Time to first token is the standout number here: 0.94 seconds for Muse Spark Open, 108 seconds for GPT-5.6 Luna Max. Everything below is read from the benchmark, price and speed data in Franklin AI's catalogue; nothing here comes from a hands-on test.

Muse Spark Open is the faster writer

GPT-5.6 Luna Max generates about 125 tokens per second and Muse Spark Open about 207 tokens per second. On long outputs, that is a real advantage for Muse Spark Open. The wait for the first token averages 108 seconds on GPT-5.6 Luna Max against 0.94 seconds on Muse Spark Open. GPT-5.6 Luna Max waits 115 times as long before its first token. Waits that long are felt on every chat-style request, though they matter less for batch jobs.

For a 1,500-token response, first token plus generation comes to roughly 2.0 minutes on GPT-5.6 Luna Max and 8.2 seconds on Muse Spark Open.

The headline benchmark

The catalogue puts GPT-5.6 Luna Max at 23.8 and Muse Spark Open at 24.9 on its intelligence index. It is a small margin for an index that averages many evaluations.

For context, that places GPT-5.6 Luna Max 70th and Muse Spark Open 68th out of 109 scored models still on offer.

For coding or maths work specifically, the catalogue has no dedicated index on either side yet.

Generation gap

GPT-5.6 Luna Max came first, on July 9, 2026; Muse Spark Open followed on October 15, 2026.

Cost: GPT-5.6 Luna Max is cheaper

Per million tokens, GPT-5.6 Luna Max charges $0.20 for input and $1.20 for output, while Muse Spark Open charges $1.25 and $4.25. That makes GPT-5.6 Luna Max's output 72% cheaper.

For a sample workload of 1 million input tokens and 200,000 output tokens, GPT-5.6 Luna Max would cost $0.44 and Muse Spark Open $2.10, a difference of $1.66. Scale it up to a chat app with 50,000 sessions of 800 input and 300 output tokens and the bill is $26.00 for GPT-5.6 Luna Max against $114 for Muse Spark Open.

Score per dollar

Per point of intelligence index, GPT-5.6 Luna Max costs $0.019 of blended price per million tokens and Muse Spark Open $0.080. GPT-5.6 Luna Max delivers each index point for 76% less; whether Muse Spark Open's extra 1.1 points are worth the premium depends on how often your tasks need them.