GPT-5.3 Codex

GPT-5.3 Codex is a OpenAI model available in Sim. GPT-5.3 Codex is a OpenAI model tracked in Sim. It supports a 400k token context window. Pricing starts at $1.75/1M input tokens and $14/1M output tokens. Key capabilities include Tool choice, Structured outputs, Reasoning low, medium, high, xhigh.

GPT-5.3 Codex starts at $1.75/1M input tokens, $0.175/1M cached input tokens, and $14/1M output tokens.

GPT-5.3 Codex supports a context window of 400k tokens in Sim. In an agent, this determines how much conversation history, tool outputs, and retrieved documents the model can hold in a single call.

GPT-5.3 Codex supports the following capabilities in Sim: Tool choice, Structured outputs, Reasoning low, medium, high, xhigh, Max output 128k.

Best for reasoning-heavy tasks that need more deliberate model control. When used in a Sim workflow, it can be selected in any Agent block from the model picker.