Compare GPT-5.3-Codex vs. SWE-2

GPT-5.3-Codex is a next-generation AI agent built to expand Codex beyond code writing into full-spectrum professional execution. It unifies advanced coding intelligence with reasoning, planning, and computer-use capabilities. The model delivers faster performance while handling more complex workflows across development environments. GPT-5.3-Codex can autonomously iterate on large projects while remaining interactive and steerable. It supports tasks such as debugging, deployment, performance optimization, and system monitoring. The model demonstrates state-of-the-art results across real-world coding benchmarks. It also excels at web development, generating production-ready applications from minimal prompts. GPT-5.3-Codex understands intent more effectively, producing stronger default designs and functionality. Its agentic nature allows it to operate like a collaborative teammate. This makes it suitable for both individual developers and large teams.

SWE-2 is a software engineering model from Cognition built for agentic coding tasks that require strong performance at lower computational and monetary cost. It is post-trained from the Kimi K3 base model and extends Cognition’s earlier SWE-1.7 training approach with a new reinforcement learning method for jointly optimizing multiple reasoning-effort settings. Medium, high, and maximum effort modes provide different tradeoffs between speed, cost, exploration, and verification depending on task complexity. The model is trained to inspect only the parts of a codebase that are likely to matter, helping it reach implementation faster and reduce unnecessary exploration. SWE-2 can generate and modify code, run tests, analyze repositories, work through terminal tasks, and verify whether implementations satisfy user requirements. Cognition also reports improvements in end-to-end test creation, regression detection, instruction following, and re-deriving conclusions when challenged. Its training process incorporates cost-aware rewards, length-weighted reward baselines, expanded reinforcement learning environments, and hardened verifiers intended to improve both efficiency and reliability. SWE-2 is positioned as a cost-efficient alternative to larger frontier coding models while remaining competitive on software engineering benchmarks such as FrontierCode, DeepSWE, and Terminal-Bench. The model is available in Devin Desktop and Devin CLI and is being introduced to additional Cognition products including Devin Web and Fusion.