GLM-5.1, the Zhipu AI (Z.ai) model in numbers

GLM-5.1 at a glance

GLM-5.1 is a language model from Zhipu AI (Z.ai), released on April 7, 2026. That makes it 6 months old as of October 22, 2026. It is an open-weight model: you can host it yourself on infrastructure you control, and 55 API providers listed on models.dev also offer it. It has a reasoning mode: it can "think" before answering, which helps with multi-step problems but uses more tokens, and therefore more money.

We file it under open-weight models (68 models in this category on the site).

Measured performance

According to results published by Epoch AI (checked on October 22, 2026), GLM-5.1 has a capability index of 70.9 out of 100, computed on 5 benchmarks from our basket.

It is not among the top 30 of the weekly ranking.

• GPQA Diamond (PhD-level science questions): 89.9% — the best tracked model, Gemini 4 Argon, reaches 96.4%
• OTIS Mock AIME (competition mathematics problems): 93.3% — the best tracked model, GPT-5.5 Pro, reaches 100%
• FrontierMath (very hard research-level mathematics): 36.8% — the best tracked model, GPT-6 Astra, reaches 93.7%
• SWE-bench Verified (fixing real software bugs): 74.2% — the best tracked model, Claude Opus 4.7, reaches 83.5%

What it can do

Its context window reaches 200,000 tokens, roughly 300 pages of text at 500 words per page: enough for a long report or several contracts at once. A single answer can run to 131,072 tokens.

It accepts as input: text.

It can call tools (functions, APIs) and return structured JSON output, which makes it a possible foundation for an AI agent.

The weights are published on Hugging Face (zai-org/GLM-5.1): 753.9 billion parameters, mit license and 598,053 downloads over the last 30 days. See also our list of open-source models.

How much does GLM-5.1 cost?

GLM-5.1 costs $0.90 per million input tokens and $3.59 per million output tokens (developer's price, checked on October 22, 2026).

In practice, an agent task that reads 20,000 tokens and writes 2,000 costs about $0.025, or $25.1 for 1,000 such tasks.

That is 3.6 times the median output price of open-weight models ($1).

Tokens read back from cache cost $0.19 per million, which helps an agent that keeps resending the same context.

To estimate your own budget, use the agent cost calculator.

Who is it for?

Given its category, GLM-5.1 is mainly aimed at projects where you want control over your data or hosting, or want to adapt the model to your field.

Before adopting it, test it on your own examples: benchmarks measure standard tasks, not your job.

What could replace it?

In the same category, the models closest to GLM-5.1 are:

• GLM-5.2 (Zhipu AI (Z.ai), index 70.5)
• GLM-5.3-Flash (Zhipu AI (Z.ai), index 71.9) — see the comparison
• DeepSeek V4 Pro 0813 (DeepSeek, index 72.2) — see the comparison
• Qwen3.6 27B (Alibaba Cloud (Qwen), index 72.2) — see the comparison