GLM-5.1 vs Muse Spark Open

The match-up at a glance

This comparison pits two open-weight models that you can install on your own servers against each other: GLM-5.1 and Muse Spark Open, one from Zhipu AI (Z.ai), the other from Meta. The first dates from April 7, 2026, the second from October 15, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

Which one is more capable?

On our capability index, GLM-5.1 scores 70.9 out of 100 and Muse Spark Open 75.2. Muse Spark Open leads by 4.3 points.

On the 4 benchmarks reported for both, GLM-5.1 wins 2 times and Muse Spark Open 2:

• GPQA Diamond (PhD-level science questions): GLM-5.1 89.9%, Muse Spark Open 88.6%
• OTIS Mock AIME (competition mathematics problems): GLM-5.1 93.3%, Muse Spark Open 98.1%
• FrontierMath (very hard research-level mathematics): GLM-5.1 36.8%, Muse Spark Open 69.8%
• APEX-Agents (professional tasks carried out by an agent): GLM-5.1 40.9%, Muse Spark Open 33.4%

Which one costs less?

GLM-5.1 costs $0.90 per million input tokens and $3.59 per million output tokens; Muse Spark Open costs $1.25 and $4.25.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.025 with GLM-5.1 versus $0.034 with Muse Spark Open. GLM-5.1 is 1.3 times cheaper, a gap that adds up quickly over 1,000 tasks: $8.4 difference.

Run the numbers with your own volumes in the agent cost calculator.

Context and capabilities

Muse Spark Open reads more in one go: 1,048,576 tokens of context (roughly 1,573 pages), versus 200,000 for GLM-5.1.

Reasoning mode: GLM-5.1 yes, Muse Spark Open yes. Tool calling: GLM-5.1 yes, Muse Spark Open yes. Image input: GLM-5.1 no, Muse Spark Open yes.

Both publish their weights: you can host them yourself.

In short

Our reading of the data:

• Choose GLM-5.1 for a lower cost.
• Choose Muse Spark Open for a higher capability index, a larger context window, a more recent release and image input.

This verdict relies on public figures; it does not replace a trial on your own tasks.