GPT-5.1 Codex Max vs Qwen3.5-397B-A17B

GPT-5.1 Codex Max

OpenAI

GPT-5.1 Codex Max, released by OpenAI in November 2025, is an enhanced coding variant from the GPT-5.1 Codex line, designed for more complex software engineering tasks requiring additional reasoning depth. It targets large-scale code generation, automated refactoring, and sophisticated agentic development workflows.

Alibaba / Qwen

Qwen3.5-397B-A17B is a 397-billion-parameter mixture-of-experts model from Alibaba's Qwen team, released in February 2026 as the open-weight flagship of the Qwen3.5 series, featuring 17 billion active parameters per forward pass through a hybrid linear-attention and sparse-MoE architecture based on Gated Delta Networks. The model was co-trained on text, images, and video using early fusion, making it natively multimodal across a 262K token context window, while achieving significantly higher inference throughput than comparable dense models due to its sparse computation design. At release it was one of the most capable open-weight models publicly available, offered under Apache 2.0 and accessible through Alibaba's DashScope API as the Qwen3.5-Plus endpoint.