# GLM 5.3 Flash API

Z.ai's fast multimodal model for coding and long-horizon agent work, with a 1M context. Always the latest version, now 0828.

Model id: `z-ai/glm-5.3-flash`. Page: https://openscale.so/models/glm-5.3-flash

## Price per 1M tokens (USD)

| Mode | Input | Cached input | Output |
| --- | --- | --- | --- |
| Standard | $0.12 | $0.024 | $0.40 |

20% off the list price of $0.15 input, $0.03 cached input and $0.50 output.

## Specs

- Context length: 1,048,576 tokens
- Max output: 131,072 tokens per request
- Output speed: 100+ tokens per second
- Rate limits: 100 requests and 10,000,000 tokens per minute per API key
- Text and image input, text output.
- Tool calling (tool_choice: auto).
- JSON mode (response_format json_object).
- Always reasons; the reasoning is returned as reasoning. Reasoning effort: low, high, max.

## Versions

| Model id | Version | Released | Behavior |
| --- | --- | --- | --- |
| `z-ai/glm-5.3-flash` | 0828 | 28 Aug 2026 | Moves to each new tested version |
| `z-ai/glm-5.3-flash-0828` | 0828 | 28 Aug 2026 | Never changes |

## Quick start

### curl

```bash
curl https://api.openscale.so/v1/chat/completions \
  -H "Authorization: Bearer $OPENSCALE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "z-ai/glm-5.3-flash",
    "messages": [{"role": "user", "content": "Explain what a token is in one sentence."}]
  }'
```

### OpenAI SDK (Python)

```python
import os
from openai import OpenAI

client = OpenAI(
    base_url="https://api.openscale.so/v1",
    api_key=os.environ["OPENSCALE_API_KEY"],
)

response = client.chat.completions.create(
    model="z-ai/glm-5.3-flash",
    messages=[{"role": "user", "content": "Explain what a token is in one sentence."}],
)
print(response.choices[0].message.content)
```

### Anthropic SDK (Python)

```python
import os
from anthropic import Anthropic

client = Anthropic(
    base_url="https://api.openscale.so/anthropic",
    api_key=os.environ["OPENSCALE_API_KEY"],
)

message = client.messages.create(
    model="z-ai/glm-5.3-flash",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Explain what a token is in one sentence."}],
)
print(next(block.text for block in message.content if block.type == "text"))
```

## Set up a coding agent

- [Claude Code](https://openscale.so/setup/claude-code.md)
- [Codex](https://openscale.so/setup/codex.md)
- [OpenCode](https://openscale.so/setup/opencode.md)
- [OpenClaw](https://openscale.so/setup/openclaw.md)
- [Cline](https://openscale.so/setup/cline.md)
- [GitHub Copilot](https://openscale.so/setup/copilot.md)
- [DeepSeek Harness](https://openscale.so/setup/deepseek-harness.md)
- [Hermes](https://openscale.so/setup/hermes.md)
- [Kilo Code](https://openscale.so/setup/kilo-code.md)
- [Pi](https://openscale.so/setup/pi.md)
- [Zed](https://openscale.so/setup/zed.md)
- [Factory Droid](https://openscale.so/setup/droid.md)

API reference: https://openscale.so/docs. Live model catalog: https://api.openscale.so/v1/models.

## FAQ

### How much does the GLM 5.3 Flash API cost?

$0.12 per 1M input tokens, $0.024 per 1M cached input tokens and $0.40 per 1M output tokens. That is 20% off the list price of $0.15, $0.03 and $0.50. You pay only for the tokens you use, from prepaid credit.

### Is the GLM 5.3 Flash API OpenAI compatible?

Yes. Point any OpenAI SDK at https://api.openscale.so/v1 and use the model id z-ai/glm-5.3-flash, with Chat Completions or Responses. Anthropic SDKs work too, at https://api.openscale.so/anthropic.

### What is the context length of GLM 5.3 Flash?

1,048,576 tokens in total, input and output together, with up to 131,072 tokens of output per request.

### How fast is GLM 5.3 Flash on OpenScale?

100+ tokens per second of output, a floor under the measured median.

### Which GLM 5.3 Flash version does the API serve?

z-ai/glm-5.3-flash always serves the latest version we have tested, now 0828. To stay on one version, call a pinned id: z-ai/glm-5.3-flash-0828. Pinned ids never change, and every version has the same price.

### Can I use GLM 5.3 Flash in a coding agent?

Yes. OpenScale has a tested setup for 12 coding agents, including Claude Code, Codex, OpenCode, OpenClaw. One API key works for every agent.

### What are the rate limits for GLM 5.3 Flash?

100 requests and 10,000,000 tokens per minute for each API key. Need more? Email hello@openscale.so.

### How do I start?

Create an account, add credit and create an API key. New accounts get free credit to try it.