Z.ai
GLM-5.3 Flash Instant
A smaller, lower-cost GLM model that reads text and images, for coding and agent work such as browser and computer use. Answers without a reasoning phase.
- Context window
- 1M tokens
- Accepts
- Text and images
- Input per 1M tokens
- $0.20
- Output per 1M tokens
- $0.50
Send your first request
Set LYCEUM_API_KEY to your API key, then run this request. Usage is billed to your account.
- Base URL
https://api.lyceum.technology/openai/v1- Model ID
z-ai/glm-5.3-flash-instant- Request fields
model, messages, stream, max_tokens, tools, tool_choice
Documented request fields for this endpoint. See the documentation for model-specific controls and limits.
app.py · Install openai and set LYCEUM_API_KEY
import os
from openai import OpenAI
client = OpenAI(
api_key=os.environ["LYCEUM_API_KEY"],
base_url="https://api.lyceum.technology/openai/v1",
)
response = client.chat.completions.create(
model="z-ai/glm-5.3-flash-instant",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)app.ts · Install openai and set LYCEUM_API_KEY in Node.js
import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.LYCEUM_API_KEY,
baseURL: "https://api.lyceum.technology/openai/v1",
});
const response = await client.chat.completions.create({
model: "z-ai/glm-5.3-flash-instant",
messages: [{ role: "user", content: "Hello!" }],
});
console.log(response.choices[0]?.message.content);Terminal · Set LYCEUM_API_KEY in your terminal
curl https://api.lyceum.technology/openai/v1/chat/completions \
-H "Authorization: Bearer $LYCEUM_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "z-ai/glm-5.3-flash-instant",
"messages": [
{"role": "user", "content": "Hello!"}
]
}'What it costs
You pay only for the tokens you use.
Token pricing
| USD per million tokens | |
|---|---|
| Input | $0.20 |
| Cached input | $0.05 |
| Output | $0.50 |
No base fee. Caching applies only where listed. Check the model's processing region before sending data.
The model in detail
Checked against the sources below. Anything they don't state is left out.
Capabilities
- Input and output
- Text and images in, text out
- Context window
- 1M tokens
- Reasoning
- Disabled
- Tool calling
- Supported
Architecture and licence
- Total parameters
- 320B
- Active parameters
- 18B
- Architecture
- Mixture of experts
- Licence
- MIT
- Released
- 26 August 2026
Availability
- API model ID
z-ai/glm-5.3-flash-instant- Provider
- Z.ai
- Processing region
- EU-hosted
- Input and output types: official model card, checked 10 September 2026.
- Capabilities and request fields: Lyceum API documentation, checked 9 September 2026.
- Parameters, licence and release date: Z.ai’s own sources, including its model card and announcement, checked 29 September 2026.
Common questions about GLM-5.3 Flash Instant
Short answers about the model ID, price, limits and behaviour.
What is the model ID for GLM-5.3 Flash Instant?
Use z-ai/glm-5.3-flash-instant as the model value. The OpenAI-compatible base URL is https://api.lyceum.technology/openai/v1. You authenticate with your Lyceum API key as a Bearer token.
How much does GLM-5.3 Flash Instant cost?
GLM-5.3 Flash Instant costs $0.20 per 1M input tokens, $0.05 per 1M cached input tokens and $0.50 per 1M output tokens. Prices are in US dollars. Billed per token. No base fee.
What is the context window of GLM-5.3 Flash Instant?
GLM-5.3 Flash Instant has a 1M tokens context window. One request can generate up to 65,536 tokens and run for up to 300 seconds. Set stream: true for long outputs.
Does GLM-5.3 Flash Instant reason before it answers?
Only briefly, and it shows today. GLM-5.3 Flash Instant is GLM-5.3 Flash without a separate reasoning phase, at the same price, but its answer still starts with a short line of working that ends with a </think> tag. Drop everything up to and including that tag, or use GLM-5.3 Flash with reasoning on. We're fixing it.
Does GLM-5.3 Flash Instant support tool calling?
Yes. Send tools in the standard OpenAI format. Automatic tool calls, parallel calls and tool-result round trips work.
Does GLM-5.3 Flash Instant support prompt caching?
Yes, and it is automatic. When requests share an identical start, the cached part is billed at $0.05 per 1M tokens instead of $0.20. Keep the stable part of your prompt at the front. A cache hit is best effort, so read usage.prompt_tokens_details.cached_tokens, which is missing on a miss.
Where does GLM-5.3 Flash Instant run, and is my data kept?
GLM-5.3 Flash Instant runs on EU-hosted infrastructure. Prompts and outputs are processed, not stored, and never used for training.
How do I call GLM-5.3 Flash Instant with the OpenAI SDK?
Point the OpenAI SDK at https://api.lyceum.technology/openai/v1, use your Lyceum API key and set model="z-ai/glm-5.3-flash-instant". Chat completions, streaming, tool calling and usage accounting work as they do with OpenAI.
Behaviour notes follow the Lyceum API documentation, checked 6 October 2026.
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