AI in September 2026: 7 new models at a glance

September was one of the busiest months of the year in AI: five major labs shipped new flagships or cheaper “fast” models within a few weeks of each other. The common theme is clear: models that run longer, more complex tasks on their own, at lower prices.

In brief

• Claude Opus 5.5 (Anthropic, Sep 22): Anthropic’s new flagship, now $4 input / $20 output per million tokens.
• GPT-6 Astra (OpenAI, Sep 3): OpenAI’s new-generation top model, strongest in computer use and software engineering.
• GPT-6 Sol and Luna (OpenAI, Sep 22): lighter, cheaper siblings of Astra.
• Gemini 3.8 Flash (Google, Sep 2): a new version of Google’s fast, low-cost workhorse.
• Muse Spark 1.3 (Meta, Sep 2): Meta’s agent- and coding-focused update.
• Grok 4.7 (SpaceXAI, Sep 21): a bigger base model at the same price.
• Open models: DeepSeek V4.1 Flash, Kimi K3 and Qwen3.8-Max keep the open-weight front busy.

In independent tests Claude Opus 5.5 currently leads, followed by Claude Fable 5.1 and GPT-6 Astra. See the live ranking on our AI Models page.