# GLM 5.1

Z.AI's long-horizon coding model. GLM 5.1 works autonomously on a single task for over eight hours, planning, executing, and self-correcting to deliver complete engineering-grade output.

- **Model ID:** `zai/glm-5.1`
- **Type:** chat
- **Providers:** zai, novita
- **Context window:** 204,800
- **Maximum output tokens:** 131,072
- **Pricing:** $1.38/1M input tokens, $4.4/1M output tokens
- **Canonical page:** https://vercel.com/ai-gateway/models/glm-5.1

## Supported parameters

Detailed capability metadata has not been reported for this model.

## Example

```ts
import { streamText } from 'ai'

const result = streamText({
  model: 'zai/glm-5.1',
  prompt: 'Why is the sky blue?'
})
```

## About

GLM 5.1 builds on the GLM-5 generation with a significant jump in coding capability, released April 7, 2026. Where GLM-5 introduced multiple thinking modes and agentic workflows, GLM 5.1 pushes the autonomy envelope: it sustains focus on one task for over eight hours, continuously planning, writing code, running tests, and improving its own output without human intervention.

The model targets long-horizon tasks that earlier models struggle with. Multi-file refactors, end-to-end feature implementation, and large-scale codebase migrations benefit from the extended autonomous execution window. Rather than handing back partial results for human review at each step, GLM 5.1 completes the full loop and delivers finished, tested code.

GLM 5.1 supports a context window of 204.8K tokens and max output of 131.1K tokens. Through AI Gateway, it shares the same unified API, built-in observability, and provider routing as other Z.AI models.

## What to consider

GLM 5.1 excels when given a well-defined task with clear acceptance criteria. Provide a detailed specification, relevant file paths, and expected behavior so the model can plan its autonomous execution effectively.

Tasks running for hours consume tokens proportionally. Monitor usage through AI Gateway's observability tools and set budget limits for extended runs.

Despite autonomous self-correction, review the final output before merging into production. Treat GLM 5.1 as a thorough junior engineer who still needs a code review.

## When to use

### Best For

- **Large-scale refactors** spanning dozens of files where sustained context and iterative testing matter
- **End-to-end feature implementation** from spec to tested, working code with minimal human checkpoints
- **Codebase migrations** that require hours of methodical file-by-file changes
- **Complex bug investigations** where the model autonomously traces root causes across a large codebase
- **Autonomous coding agents** that need a model capable of multi-hour independent operation

### Consider Alternatives When

- Your tasks complete in under a few minutes. GLM-5 or GLM-5-Turbo handle short-horizon coding at lower cost
- You need vision or multimodal input. GLM-5V-Turbo combines coding with screenshot and GUI understanding
- Interactive pair-programming is the workflow. GLM-4.7-Flash provides fast responses for real-time back-and-forth
- Budget is the primary constraint. GLM-5-Turbo offers GLM-5-class capability at reduced per-token cost for shorter tasks

## Best for

- **Large-scale refactors:** Dozens of files where sustained context and iterative testing matter
- **End-to-end feature implementation:** Spec to tested, working code with minimal human checkpoints
- **Codebase migrations:** Hours of methodical file-by-file changes
- **Complex bug investigations:** The model autonomously traces root causes across a large codebase
- **Autonomous coding agents:** A model capable of multi-hour independent operation

## Consider alternatives

- **Short-horizon tasks:** GLM-5 or GLM-5-Turbo handle coding tasks completing in minutes at lower cost
- **Vision or multimodal input:** GLM-5V-Turbo combines coding with screenshot and GUI understanding
- **Interactive pair programming:** GLM-4.7-Flash provides fast responses for real-time back-and-forth workflows
- **Budget-constrained workloads:** GLM-5-Turbo offers GLM-5-class capability at reduced per-token cost for shorter tasks

## Frequently asked questions

### How long can GLM 5.1 work on a single task?

Over eight hours of continuous autonomous operation. It plans, executes, tests, and iterates on its own output throughout that window.

### How does GLM 5.1 differ from GLM-5?

GLM-5 introduced multiple thinking modes and agentic workflows for general-purpose reasoning. GLM 5.1 builds on that foundation with a specific focus on long-horizon coding tasks, sustaining autonomous operation for hours rather than minutes.

### What is the context window for GLM 5.1?

204.8K tokens.

### What is the pricing for GLM 5.1?

Check the pricing panel on this page for today's numbers. AI Gateway tracks rates across every provider that serves GLM 5.1.

### How do I access GLM 5.1 through AI Gateway?

Use the `zai/glm-5.1` model identifier with your AI Gateway API key. No separate Z.AI account is needed. BYOK is also supported.

## Links

- [Model page](https://vercel.com/ai-gateway/models/glm-5.1)
- [AI Gateway documentation](https://vercel.com/docs/ai-gateway)


If you encounter incorrect information, can’t find what you need, need a capability Vercel doesn’t currently offer, or have any other feedback to report, please do it by following the instructions at https://vercel.com/feedback.md.