OpenAI

GPT-5.4 is OpenAI's frontier large language model featuring advanced reasoning and extended long-context capabilities. It offers tiered pricing at $2.50/$15 per million input/output tokens for standard usage, with rates doubling to $5/$22.50 per million tokens above the 272K token threshold. Designed for enterprise and developer use cases requiring large context windows and high-throughput inference.

ChatGPT is OpenAI's flagship conversational AI assistant, layered on top of their GPT and o-series models to deliver capabilities far beyond raw model access — including web browsing, code execution (Advanced Data Analysis), image generation via DALL-E, file and document analysis, memory, persistent Projects, and a GPT Store for specialised agents. Launched in November 2022, it triggered a mainstream AI adoption wave and remains the most widely used AI assistant globally. It supports agentic workflows through tool use, Operator-style task execution, and integrations, making it a true agent platform rather than just a model interface.

OpenAI Codex is a cloud-based software engineering agent capable of autonomously completing coding tasks such as writing features, fixing bugs, running tests, and navigating codebases — operating in isolated sandboxes in parallel. It is available as both a cloud agent integrated into ChatGPT and an open-source CLI tool (Codex CLI), competing directly with Claude Code, Devin, and similar agentic coding products. The agent is powered by codex-1, a model fine-tuned for agentic software engineering tasks.

Codex CLI is OpenAI's open-source command-line coding agent that runs directly in the terminal, capable of reading and writing files, executing shell commands, and performing multi-step coding tasks autonomously. It supports multiple approval modes (suggest, auto-edit, full-auto) and acts as an MCP client, integrating with a growing ecosystem of tools and servers. Originally launched in April 2025, it received a major model upgrade to GPT-5.2-Codex in December 2025 and expanded to a desktop app in February 2026.