GPT OSS 20B vs GPT 5.4

OpenAI’s 21B-parameter open-weight Mixture-of-Experts (MoE) model, released under the Apache 2.0 license. Features 3.6B active parameters per forward pass, optimized for low-latency inference and deployability on consumer or single-GPU hardware. Trained in OpenAI’s Harmony response format, it supports reasoning level configuration, fine-tuning, and agentic capabilities such as function calling and structured outputs.

GPT-5.4 is OpenAI’s newest frontier model that merges the Codex and GPT families into a single unified system. It offers a 1M+ token context window (922K input, 128K output) and supports both text and image inputs, enabling high-context reasoning, coding, and multimodal analysis in one workflow. The model brings stronger performance in coding, document understanding, tool usage, and instruction following. It’s built to be a solid default for both general tasks and software engineering—able to produce production-ready code, synthesize information from multiple sources, and handle complex multi-step workflows with fewer iterations and better token efficiency.