What Happened to OpenAI Codex?
OpenAI Codex initially launched in 2021 as a GPT-3 based language model for code generation, powering the first GitHub Copilot, but was deprecated in March 2023 as OpenAI's general-purpose models surpassed its capabilities. It was reborn in May 2025 as a distinct, cloud-based autonomous coding agent integrated into ChatGPT, offering advanced features like multi-file code execution, testing, and even web app deployment with Codex Sites by June 2026. As of August 2026, it continues to evolve with new GPT-5 series models and a token-based billing system, serving as a powerful agentic tool for developers.
Quick Answer
OpenAI Codex, first introduced in 2021 as a code-generating language model, was deprecated in March 2023. However, it was relaunched in May 2025 as an autonomous coding agent, a completely different product integrated into ChatGPT. As of August 2026, the new OpenAI Codex is a cloud-based agent that can read entire codebases, write and edit across multiple files, run tests, and even build and host web applications via 'Codex Sites'. It utilizes OpenAI's latest GPT-5 series models and operates on a token-based credit system, available through desktop apps, CLI, and VS Code extensions.
📊Key Facts
📅Complete Timeline13 events
Original OpenAI Codex Launched
OpenAI introduced Codex, a GPT-3 based language model fine-tuned on public code, capable of translating natural language into code. It became the underlying model for GitHub Copilot.
Original Codex API Deprecated
OpenAI officially deprecated the original Codex API, advising developers to migrate to its more capable general-purpose models like GPT-3.5 and GPT-4, which had surpassed Codex in coding tasks.
New OpenAI Codex (Agent) Relaunched
OpenAI relaunched 'Codex' as a completely new product: a cloud-based, autonomous coding agent integrated into ChatGPT. This agent could read repositories, write across files, run tests, and open pull requests.
Codex Available to ChatGPT Plus Users
Following its initial rollout to Pro, Business, and Enterprise users, OpenAI made the new Codex agent available to ChatGPT Plus subscribers.
Native Desktop App Launched
A native desktop application for OpenAI Codex was launched for Mac and Windows, leading to a significant increase in usage.
GPT-5.3-Codex Model Introduced
OpenAI launched GPT-5.3-Codex, a new agentic coding model that combined Codex and GPT-5 training stacks for enhanced code generation and reasoning.
Transition to Token-Based Billing
OpenAI moved Codex to a token-based credit billing system for Plus, Pro, Business, and new Enterprise plans, making costs harder to predict for users.
Six Older Codex Models Retired
OpenAI retired six older Codex models, primarily from the GPT-5.1 and GPT-5.2 generations, from the Codex platform for ChatGPT sign-in users.
GPT-5.2 and GPT-5.3-Codex Deprecation Announced
OpenAI announced the sunsetting of GPT-5.2 and GPT-5.3-Codex from ChatGPT logins by June 2, with GPT-5.5 becoming the default. API access for these models was to be blocked by June 30, 2026.
Codex Sites Launched for App Building
OpenAI introduced Codex Sites, allowing users on ChatGPT Business and Enterprise plans to build, deploy, and host entire web applications from a single prompt.
API Access Blocked for GPT-5.2 and GPT-5.3-Codex
New API requests to GPT-5.2, GPT-5.2-Codex, and GPT-5.3-Codex models were blocked, with full endpoint removal scheduled for December 31, 2026.
GPT-5.6 Sol General Availability
OpenAI's flagship GPT-5.6 Sol model, noted for its high performance in coding benchmarks, reached general availability across ChatGPT, the API, Codex, and GitHub Copilot.
Computer History Feature Integrated
OpenAI introduced 'Computer History' in the ChatGPT desktop app, allowing ChatGPT and Codex to reference user activity across apps and websites for improved context and memory. Codex maintains a separate view.
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🔍Deep Dive Analysis
OpenAI Codex has undergone a significant transformation, evolving from a specialized code-generation model to a comprehensive autonomous coding agent. Initially launched in August 2021, the first iteration of OpenAI Codex was a descendant of GPT-3, specifically fine-tuned on billions of lines of public code to translate natural language into working code. This model was instrumental in powering the early versions of GitHub Copilot, demonstrating the revolutionary potential of AI in software development.
However, this original Codex model faced deprecation on March 23, 2023. OpenAI cited that its newer, more general-purpose models, such as GPT-3.5 and GPT-4, had already surpassed Codex in coding tasks while also offering broader contextual understanding, rendering a separate specialist code model unnecessary. Developers were advised to migrate to these more capable general models.
The story of OpenAI Codex took an unexpected turn in May 2025 when OpenAI revived the name for a completely different product: an autonomous coding agent. This new Codex is a cloud-based software engineering agent integrated directly into ChatGPT, designed to handle multi-step software tasks. It can read entire repositories, write code across multiple files, run tests, and even open pull requests, operating in a sandboxed cloud environment.
Throughout 2026, this agentic Codex has seen rapid development. In February 2026, a native desktop app for Mac and Windows was launched, significantly boosting its usage. OpenAI also introduced new coding-specialized models, such as GPT-5.3-Codex on February 5, 2026, which combined Codex and GPT-5 training stacks for enhanced code generation and reasoning. On April 2, 2026, OpenAI shifted Codex's billing to a token-based credit system, impacting Plus, Pro, Business, and Enterprise users. Further model consolidations occurred, with six older Codex models (GPT-5.1 and GPT-5.2 generations) being retired for ChatGPT sign-in users on April 14, 2026, and GPT-5.2 and GPT-5.3-Codex being sunset from ChatGPT logins by June 2, 2026, with GPT-5.5 becoming the default. API access for these older models was also slated for blocking by June 30, 2026.
A significant turning point in June 2026 was the launch of 'Codex Sites,' a feature enabling users to build, deploy, and host entire web applications from a single prompt, available on ChatGPT Business and Enterprise plans. As of July 9, 2026, the flagship GPT-5.6 Sol model became generally available across OpenAI's ecosystem, including Codex. The most recent development, as of August 13, 2026, is the integration of a 'Computer History' feature, allowing ChatGPT and Codex to reference a user's activity across apps and websites for enhanced context and memory, with Codex maintaining a separate view within the ChatGPT desktop app.
In essence, the original OpenAI Codex model was superseded by more general AI, but the 'Codex' name was repurposed for a sophisticated, autonomous agent that significantly expands AI's role in the software development lifecycle. It is now a core part of OpenAI's offering for developers, distinct from GitHub Copilot which has evolved into a multi-model platform.
What If...?
Explore alternate histories. What if OpenAI Codex made different choices?