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GLM-5.3 Flash API

The GLM-5.3 Flash API: Z.ai's low-cost GLM for coding and agents, 60% below Z.ai's list price

Price per 1M tokens60%off

Input: $0.06~~$0.15~~
Output: $0.20~~$0.50~~
Cached input: $0.006

Get your API key Try it in the playground

Model IDglm-5.3-flash

chat.py

from openai import OpenAI
client = OpenAI(
    base_url="https://api.zurelay.com/v1",
    api_key="YOUR_ZURELAY_KEY",
)
stream = client.chat.completions.create(
    model="glm-5.3-flash",
    messages=[{"role": "user", "content": "Explain quicksort in two sentences."}],
    stream=True,
)
for chunk in stream:
    if chunk.choices:
        print(chunk.choices[0].delta.content or "", end="")

Base URL https://api.zurelay.com/v1. Works with any OpenAI SDK. Chat API docs

Context window: 1M tokens
Max output: 128K tokens
Reasoning: low · high · max
Input: Text
Released: Aug 26, 2026
Status: Operational

Pricing

GLM-5.3 Flash API pricing. A fraction of the list price.

Pay as you go from prepaid credit, with no subscription. Top up from $10. Requests that fail are never billed.

Rate	Zurelay	Z.ai list	You save
Input per 1M tokens	$0.06	~~$0.15~~	60%off
Output per 1M tokens	$0.20	~~$0.50~~	60%off
Cached input per 1M tokens	$0.006	—	—

One rate at every prompt length, up to the full 1M context window. Streaming, tool calls and structured outputs cost nothing extra.

Savings calculator

Move the sliders to your monthly usage.

Input tokens per month50M

Output tokens per month10M

Zurelay

$5.00

Z.ai list price

$12.50

You save every month$7.50

$90.00 a year

Overview

What is GLM-5.3 Flash?

GLM-5.3 Flash is Z.ai's low-cost GLM, with 18B of its 320B parameters active per token. Z.ai says it outperforms GLM-5.2 and approaches Claude Opus 4.8 on coding and agent benchmarks. The Zurelay GLM-5.3 Flash API serves it through one OpenAI-compatible endpoint with a 1M-token context window, at 60% below Z.ai's list price.

Z.ai released GLM-5.3 Flash on August 26, 2026, as a smaller, cheaper sibling of its GLM-5.3 flagship. The GLM-5.3 Flash API on Zurelay takes text and writes text, with a 1M-token context window and up to 128K output tokens per request. Z.ai built it for coding and agent work: long tool-calling runs, frontend and game code, and office and research workflows. On Zurelay the model ID is glm-5.3-flash, and it costs $0.06 per 1M input tokens and $0.20 per 1M output tokens.

It has its own base model, trained on a new 30T-token corpus, with 320B total parameters and 18B active per token. It is also the first GLM to combine sparse and linear attention, which Z.ai says cuts attention compute by 3.0 times and the KV cache by 4.4 times against GLM-5.3, so long prompts stay cheap to serve. The weights are on Hugging Face under the MIT license.

Z.ai reports that GLM-5.3 Flash consistently outperforms GLM-5.2 across six coding and agent benchmarks, often by a wide margin: 63.4 against 46.2 on DeepSWE v1.1 and 48.8 against 26.2 on AutomationBench. On Z.ai's in-house Code Bench at max effort it nearly matches Claude Opus 4.8, 29.0 against 29.5. Z.ai also reports a score of 57 on the Artificial Analysis Intelligence Index, a level it says used to cost about ten times as much.

Reasoning is always on. Z.ai's API takes a reasoning_effort of low, high or max, with max as the default and the setting Z.ai recommends, and thinking can't be switched off. The model supports function calling, structured JSON output, streaming and context caching. You pay $0.06 per 1M input tokens and $0.20 per 1M output tokens, against Z.ai's list price of $0.15 and $0.50, with cached input at $0.006.

Strengths

Where GLM-5.3 Flash shines. And what teams build with it.

Near-Opus coding scores

On Z.ai's in-house Code Bench at max effort it scores 29.0 against 29.5 for Claude Opus 4.8, and it beats GLM-5.2 at every effort level.

A big step past GLM-5.2

Z.ai reports it ahead of GLM-5.2 on all six of its coding and agent benchmarks: 63.4 against 46.2 on DeepSWE v1.1 and 48.8 against 26.2 on AutomationBench.

Cheap long context

Hybrid sparse and linear attention cuts attention compute by 3.0 times and the KV cache by 4.4 times against GLM-5.3, across a 1M-token window.

MIT-licensed weights

The weights are open under MIT, so you can build on Zurelay today and self-host the same model later if you need to.

Use cases

Coding agents on a budget
Run long tool-calling loops that read code, edit files and run tests, at about a tenth of GLM-5.3's list price.
Frontend and game code
Write web pages, interfaces, games and 3D scenes from a written spec, then iterate on the code with test results and error messages.
Office and finance work
Plan research and analysis, call tools and review the results. Z.ai built it for office documents and financial research workflows.
Long-document work
Put whole codebases, contracts or report sets into the 1M-token window and ask across all of them at once.

Get started

Call GLM-5.3 Flash in three steps.

No waitlist and no new SDK. If your code already talks to OpenAI, it already talks to Zurelay.

1
Create a key
Sign up, add credit and create an API key. Set a monthly budget or a rate limit per key if you like.
Get your API key
2
Point your SDK at Zurelay
Change the base URL. Everything else in your code stays the same.
https://api.zurelay.com/v1
3
Use glm-5.3-flash
Send chat completions as usual. Streaming, tool calls and usage reporting work as you expect.
glm-5.3-flash

Works with the tools you already use

Compare

Similar models. All on the same key.

73%off

GLM-5.3

$0.38 / $1.21 per 1M tokens

Pick GLM-5.3, Z.ai's larger text-only flagship, for the hardest coding and security work; it scores 66.9 on DeepSWE v1.1 against 63.4.

GLM-5.3 API

53%off

Qwen 3.8 Flash

$0.07 / $0.22 per 1M tokens

Pick Qwen 3.8 Flash for Alibaba's low-cost open-weight model when you also need image and video input.

Qwen 3.8 Flash API

90%off

DeepSeek V4 Flash

$0.03 / $0.12 per 1M tokens

Pick DeepSeek V4 Flash for an even cheaper reasoning model with a 1M-token context, and compare the two on your own evals.

DeepSeek V4 Flash API

FAQ

GLM-5.3 Flash API questions.

Anything else? Ask our team and we’ll answer by email.

How much does the GLM-5.3 Flash API cost?

GLM-5.3 Flash costs $0.06 per 1M input tokens and $0.20 per 1M output tokens on Zurelay, with cached input at $0.006. Z.ai's list price is $0.15 input and $0.50 output, so you save 60%. One rate applies at every prompt length.

Is there a cheaper GLM-5.3 Flash API than Z.ai's?

Yes. Zurelay serves the same glm-5.3-flash model at 60% below Z.ai's list price. You pay from prepaid credit for the tokens you use, with no subscription or coding plan.

How do I call the GLM-5.3 Flash API with the OpenAI SDK?

Install the official OpenAI SDK, set the base URL to https://api.zurelay.com/v1 and use your Zurelay API key. Then pass model "glm-5.3-flash" to chat.completions.create. Z.ai recommends temperature 1, top_p 0.95 and a reasoning_effort of max.

What is the GLM-5.3 Flash context window?

GLM-5.3 Flash has a 1M-token context window and writes up to 128K output tokens per request. On Zurelay it takes text input and returns text.

Can GLM-5.3 Flash read images on Zurelay?

Not on Zurelay yet. Z.ai's own API takes images and video, but Zurelay serves GLM-5.3 Flash for text only, and a request with an image is turned away with a clear error before anything is billed. For images and video at a similar price, use Qwen 3.8 Flash.

What is GLM-5.3 Flash best at?

Coding and agent work: long tool-calling runs, frontend and game development and 3D scenes. Z.ai also built it for office documents and financial research, and reports it ahead of GLM-5.2 across six coding and agent benchmarks.

How is GLM-5.3 Flash different from GLM-5.3?

GLM-5.3 is Z.ai's larger, text-only flagship and scores higher on DeepSWE v1.1, 66.9 against 63.4. GLM-5.3 Flash is a smaller model with 18B active parameters, and Z.ai lists it at about a tenth of GLM-5.3's price. Both have a 1M-token context, 128K output and always-on reasoning at low, high or max.

Does the GLM-5.3 Flash API support streaming and per-key limits?

Yes. Set stream: true to receive tokens as they are generated, and add stream_options.include_usage to get token counts in the final chunk. You can give each Zurelay API key its own monthly budget and requests-per-minute cap. Failed requests are retried on another route and never billed.

Is GLM-5.3 Flash on Zurelay the same model Z.ai serves?

Yes. Requests go to glm-5.3-flash itself. Zurelay doesn't swap in a smaller or substitute model. Only smart routing, which you turn on yourself, can answer with a close alternative when the model is down, and the x-zurelay-model header names the model that answered. Output is sampled, so wording varies from run to run, just as it does on Z.ai's own API. Zurelay is an independent service and is not affiliated with Z.ai.

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GLM-5.3 Flash API

GLM-5.3 Flash API pricing. A fraction of the list price.

What is GLM-5.3 Flash?

Where GLM-5.3 Flash shines. And what teams build with it.

Near-Opus coding scores

A big step past GLM-5.2

Cheap long context

MIT-licensed weights

Coding agents on a budget

Frontend and game code

Office and finance work

Long-document work

Call GLM-5.3 Flash in three steps.

Create a key

Point your SDK at Zurelay

Use glm-5.3-flash