Z.ai open-sources ‘Ox Alpha’ model as GLM-5.3-Flash
Z.ai Co. today released the code for GLM-5.3-Flash, a large language model that is ten times more cost-efficient than its predecessor.
The algorithm made its original debut last week under the codename Ox Alpha. LLM marketplace operator OpenRouter Inc. launched a free hosted version of Ox Alpha and didn’t disclose its developer, which drew a significant amount of industry attention. Users soon started speculating that Z.ai is the model’s creator.
GLM-5.3-Flash features a mixture of experts architecture with 320 billion parameters. It activates 18 billion parameters to answer prompts. Users requests can include a 1 million tokens worth of text, images and video while GLM-5.3-Flash’s responses contain up to 131,072 tokens.
The model features a different architecture than Z.ai’s earlier LLMs. One of the biggest changes is in its attention mechanism, a component that analyzes user prompts and extracts the most important details. It identifies those key details by breaking down each prompt into tokens and comparing them against each other.
