GLM-5.3-Flash or Muse Spark Open: which to choose?

What are we comparing?

GLM-5.3-Flash and Muse Spark Open are two open-weight models that you can install on your own servers, one from Zhipu AI (Z.ai), the other from Meta. GLM-5.3-Flash was released on September 18, 2026, Muse Spark Open on 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-5.3-Flash scores 71.9 out of 100 and Muse Spark Open 75.2. Muse Spark Open leads by 3.3 points.

On the 4 benchmarks reported for both, GLM-5.3-Flash wins 2 times and Muse Spark Open 2:

• GPQA Diamond (PhD-level science questions): GLM-5.3-Flash 90.2%, Muse Spark Open 88.6%
• OTIS Mock AIME (competition mathematics problems): GLM-5.3-Flash 93.9%, Muse Spark Open 98.1%
• FrontierMath (very hard research-level mathematics): GLM-5.3-Flash 55.8%, Muse Spark Open 69.8%
• APEX-Agents (professional tasks carried out by an agent): GLM-5.3-Flash 52.8%, Muse Spark Open 33.4%

Budget

GLM-5.3-Flash costs $0.30 per million input tokens and $1.05 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 $0.008 with GLM-5.3-Flash versus $0.034 with Muse Spark Open. GLM-5.3-Flash is 4.2 times cheaper, a gap that adds up quickly over 1,000 tasks: $25.43 difference.

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

Features and limits

Muse Spark Open reads more in one go: 1,048,576 tokens of context (roughly 1,573 pages), versus 1,000,000 for GLM-5.3-Flash.

Reasoning mode: GLM-5.3-Flash yes, Muse Spark Open yes. Tool calling: GLM-5.3-Flash yes, Muse Spark Open yes. Image input: GLM-5.3-Flash yes, Muse Spark Open yes.

Both publish their weights: you can host them yourself.

In short

Our reading of the data:

• Choose GLM-5.3-Flash for a lower cost.
• Choose Muse Spark Open for a higher capability index.

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