Muse Spark 1.2 vs GPT-5.5

Muse Spark 1.2 and GPT-5.5 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Muse Spark 1.2, from Meta, has a 1,048,576-token context window, costs $1.25/1M input and $4.25/1M output tokens and scores 39.6 on the Artificial Analysis Intelligence Index.

GPT-5.5, from OpenAI, has a 1,050,000-token context window, costs from $5.50/1M input and $33.00/1M output tokens across 2 providers and scores 38.4 on the Artificial Analysis Intelligence Index.

Muse Spark 1.2 is the cheapest on input, 4.4× cheaper than the next model, GPT-5.5 has the largest context window, Muse Spark 1.2 scores highest for intelligence and GPT-5.5 leads on coding.