How much does the GLM-5.1 API cost?

GLM-5.1 costs $1.4 per million input tokens and $4.4 per million output tokens. A workload of 10M input and 1.5M output tokens per month costs about $20.60.

What is the context window of GLM-5.1?

GLM-5.1 supports a context window of 200,000 tokens (200K), with up to 128K output tokens per response.

Is GLM-5.1 open source?

Yes — GLM-5.1 is an open-weights model released under the MIT license, so it can be downloaded and self-hosted.

What are the best alternatives to GLM-5.1?

The closest alternatives by overall capability are Qwen3-Max, GPT-5.5, Gemini 3 Pro, Gemini 2.5 Pro. See the comparison pages for detailed head-to-head breakdowns.

GLM-5.1

Name: GLM-5.1
Price: 1.4 USD
Author: Z.ai (Zhipu)

Z.ai (Zhipu)·Apr 2026reasoningopen weights · MIT

GLM-5.1 is Z.ai's iteration on GLM-5 and a milestone for open weights: it took the top spot on SWE-bench Pro (58.4 vs 57.3 for Claude Opus 4.6) — the first time an open model led a major agentic-coding leaderboard outright. Independent reviews put its overall coding ability at about 95% of Opus-class models for a fraction of the running cost. Hosted pricing varies by provider; the weights remain MIT-licensed for self-hosting.

Benchmark results

No verified benchmark results tracked yet for GLM-5.1. This page is updated as official evaluations are published.

Where it shines

#1 open-weights model on SWE-bench Pro
~95% of Opus-class coding at budget prices
MIT license with broad third-party host availability

Alternatives to GLM-5.1

Qwen3-Max

Alibaba's trillion-parameter API flagship — frontier-adjacent quality with strong agentic tool use at mid-tier prices.

GPT-5.5

OpenAI's flagship reasoning model with a 1M-token context window, built for hard coding, science and long-horizon agentic work.

Gemini 3 Pro

Google's November 2025 frontier breakout — 91.9% GPQA Diamond and 37.5% HLE made it the reasoning leader of its generation.

Gemini 2.5 Pro

Google's 2025 workhorse flagship — first mainstream thinking model with a 1M context, still widely deployed.

Frequently asked questions

How much does the GLM-5.1 API cost?: GLM-5.1 costs $1.4 per million input tokens and $4.4 per million output tokens. A workload of 10M input and 1.5M output tokens per month costs about $20.60.
What is the context window of GLM-5.1?: GLM-5.1 supports a context window of 200,000 tokens (200K), with up to 128K output tokens per response.
Is GLM-5.1 open source?: Yes — GLM-5.1 is an open-weights model released under the MIT license, so it can be downloaded and self-hosted.
What are the best alternatives to GLM-5.1?: The closest alternatives by overall capability are Qwen3-Max, GPT-5.5, Gemini 3 Pro, Gemini 2.5 Pro. See the comparison pages for detailed head-to-head breakdowns.