Astra, Fable 5.1, Muse Spark 1.3, and Gemini 3.8 Now Live

This week saw four giants release new models, with access varying significantly depending on programs and user profiles. Across the board, capabilities for agentic flows and cybersecurity are being highlighted. Here’s an overview of the availability and the technical promises announced.

Access and availability vary by programs and profiles

GPT-6 Astra is being deployed to individuals with access to Daybreak, a system intended for verified enterprise clients and cybersecurity practitioners. OpenAI also plans to open it up to Plus, Pro, and Business subscribers in the coming days. On the Anthropic side, Fable 5.1 is available to the general public, while Mythos remains limited to the company’s trusted access programs. At Meta, Muse Spark 1.3 is offered in Muse Code as well as through the company’s model API. Google is distributing Gemini 3.8 Flash to businesses, consumers, and developers in its products, while 3.8 Flash Cyber is only accessible to participants of the Fairwind Program, announced on the same day as these models.

Claimed capabilities: agentic, security, and coding at the forefront

For GPT-6 Astra, OpenAI highlights multi-step agentic flows, scientific research, and financial modeling, claiming it has a much better grasp of computer usage. According to the company, this is its most powerful model to date, and it ranks first in many areas according to various benchmarks. Anthropic reports significant gains over previous versions, claiming to set a new standard for coding, knowledge work, and long-term problem-solving, with a specific point: with low to medium effort, Fable 5.1 would deliver performance close to Fable 5 at a much lower cost. At Meta, Muse Spark 1.3 is announced with enhanced reasoning and increased collaboration, posing clarification questions and verifying its actions in agentic flows. Google describes Gemini 3.8 as bringing next-generation intelligence for agentic and cybersecurity applications. Overall, the announcements emphasize agentic use cases.

Overview of this week's launches by player

Four players presented new offerings this week. OpenAI unveiled GPT-6 Astra, the only model in this release that is not an “.x” update. Anthropic released Fable 5.1 and Mythos 5.1. Meta launched Muse Spark 1.3. Google introduced Gemini 3.8 Flash and 3.8 Flash Cyber, continuing from Gemini 3.7 Flash released on August 13. In the background, ChatGPT 5.6, Astra's predecessor, was launched in July with a focus on computer usage.