What is GLM-5.3-Flash?

GLM-5.3-Flash is an efficiency-focused multimodal AI model from Z.ai that combines advanced reasoning, coding, agentic execution, and visual intelligence. It is the first GLM-5-series model designed with native multimodal capabilities, allowing it to work directly with both textual and visual inputs. The architecture uses 320 billion total parameters while activating only 18 billion at a time, significantly reducing the amount of computation required for inference. A hybrid attention design blends linear attention for local information with sparse attention for retrieving important context from much larger inputs. Z.ai also uses technologies such as IndexPool and Manifold-Constrained Hyper-Connections to improve memory efficiency, latency, and model scaling. The model can operate with context windows of up to one million tokens, making it suitable for large repositories, lengthy documents, extended agent sessions, and complex multimodal workflows. GLM-5.3-Flash was trained on a 30-trillion-token multimodal corpus intended to strengthen reasoning across code, images, interfaces, documents, spreadsheets, presentations, and other business artifacts. In software development scenarios, the model can visually inspect rendered applications, evaluate its own output, and iteratively correct layout, functionality, or interaction issues. Z.ai’s reported benchmark results show large improvements over GLM-5.2 in areas such as software engineering and automation, while placing GLM-5.3-Flash close to leading frontier systems on several coding and agentic evaluations. Before its formal release, the model was anonymously tested under the name ox-alpha on OpenCode and OpenRouter, where Z.ai says it became one of the most widely used models during its testing period. GLM-5.3-Flash is available through Z.ai’s API and coding products as well as through downloadable weights on Hugging Face, with deployment support for SGLang, vLLM, and TokenSpeed.

Pricing

Price Starts At:
$0.15 per 1M tokens (input)
Price Overview:
Input: $0.15 per 1M tokens
Output: $0.50 per 1M tokens
Cached input: $0.03 per 1M tokens

Integrations

Offers API?:
Yes, GLM-5.3-Flash provides an API

Screenshots and Video

GLM-5.3-Flash Screenshot 1

Company Facts

Company Name:
Z.ai
Date Founded:
2019
Company Location:
China
Company Website:
z.ai

Product Details

Deployment
SaaS
Training Options
Documentation Hub
Support
Web-Based Support

Product Details

Target Company Sizes
Individual
1-10
11-50
51-200
201-500
501-1000
1001-5000
5001-10000
10001+
Target Organization Types
Mid Size Business
Small Business
Enterprise
Freelance
Nonprofit
Government
Startup
Supported Languages
English

GLM-5.3-Flash Categories and Features

GLM-5.3-Flash Customer Reviews

Write a Review
  • Reviewer Name: A Verified Reviewer
    Position: Developer
    Has used product for: Free Trial
    Uses the product: Daily
    Org Size (# of Employees): 100 - 499
    Ease Of Use
    Cost
    Would you Recommend to Others?
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    GPT-5.3-Flash Review

    Date: Aug 24 2026
    Summary

    Updating my review now that Ox Alpha was revealed to be GPT-5.3-Flash. GPT-5.3-Flash feels like one of the more interesting stealth model launches because it combines huge context, strong developer buzz, and serious agentic-coding positioning. If the eventual creator backs up the early hype with transparency, reliability, and clear commercial terms, this could become a major model for developers and AI power users.

    Positive

    What makes it exciting is that it seems built for the exact workloads developers care about right now: long-horizon coding, complex reasoning, big-context analysis, and agentic workflows. A million-token context window is especially useful if you want to drop in a large repo, long spec, research corpus, or messy project history and have the model reason across it.

    Negative

    I would treat it as something exciting to test, not something to blindly trust with sensitive work.

    Read More...
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