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. $0.12 input, $0.024 cached input and $0.40 output per 1M tokens, with a 1,048,576 tokens context.

GLM 5.3 Flash price per 1M tokens

GLM 5.3 Flash price in USD per 1M tokens
ModeInputCached inputOutput
Standard$0.12$0.024$0.40

Prices are USD per 1M tokens, 20% off the list price of $0.15 input, $0.03 cached input and $0.50 output. Cached input is a prompt prefix the model has seen before, which agents resend on every turn. You pay only for the tokens you use. Compare it with every model on OpenScale.

Specs

GLM 5.3 Flash specs
SpecValue
Model idz-ai/glm-5.3-flash
DeveloperZ.ai
Context length1,048,576 tokens
Max output131,072 tokens per request
Output speed100+ tokens per second
Rate limit100 requests and 10M tokens per minute per 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

z-ai/glm-5.3-flash always serves the latest version we have tested, now 0828. Pinned ids never change. Every version has the same price.

GLM 5.3 Flash versions
Model idVersionReleasedBehavior
z-ai/glm-5.3-flash082828 Aug 2026Moves to each new version
z-ai/glm-5.3-flash-0828082828 Aug 2026Never changes

Call GLM 5.3 Flash from your code

Use any OpenAI SDK with the base URL https://api.openscale.so/v1, or any Anthropic SDK with https://api.openscale.so/anthropic. Set your API key as OPENSCALE_API_KEY.

curl
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)
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)
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"))

Every parameter, streaming and errors are in the API reference.

Use GLM 5.3 Flash in your coding agent

Each guide is a tested setup that keeps your existing configuration. Select z-ai/glm-5.3-flash as the model.

Or pick your agent and copy one setup prompt on the agent setup page.

Questions

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.

Create an account to get an API key. Plain Markdown version of this page: /models/glm-5.3-flash.md.