Today marks the unveiling of GPT-5-Codex—a refined derivative of GPT-5, meticulously tailored for agentic coding inside Codex. Sculpted through training steeped in authentic, real-world engineering undertakings, GPT-5-Codex thrives equally in brisk, conversational problem-solving as it does in relentless, solitary marathons across sprawling, intricate projects.

Codex Evolution: From Tool to Teammate

Since the initial debut of Codex CLI in April and Codex web in May, the platform has undergone a steady metamorphosis into an ever more competent partner. A fortnight ago, Codex was consolidated into a singular, seamless experience tethered to a ChatGPT account, empowering developers to drift fluidly between local and cloud environments without forfeiting context.

Now Codex resides wherever the craft unfolds—in your console, your IDE, the web, GitHub, and even within the ChatGPT iOS enclave.

GPT-5-Codex: Built for Complex Engineering

This incarnation of GPT-5 is honed specifically for agentic software engineering within Codex. Its curriculum includes:

• Crafting full-fledged projects from scratch
  
• Adding features and automated tests
  
• Debugging deep-rooted flaws
  
• Performing large-scale refactors
  
• Conducting meticulous code reviews

Performance and Efficiency

On SWE-bench Verified tasks (n=500), GPT-5-Codex demonstrated heightened accuracy and superior results in refactoring. It dynamically allocates its reasoning—swift with minor queries, relentless with monumental ones.

• Efficiency gains: At the lowest usage percentile, GPT-5-Codex consumed 93.7% fewer tokens than GPT-5.
  
• Deep reasoning: At the top percentile, it doubled its reasoning time to ensure depth and quality.
  

In rigorous trials, it independently sustained seven-hour coding marathons, iterating, debugging, and delivering successful builds.

Code Review Mastery

GPT-5-Codex excels in code review—not as a static analyzer but as an intelligent reviewer that:

• Traverses codebases and dependencies
  
• Executes code and test suites
  
• Aligns pull request intentions with actual implementations
  

Its reviews are sharper and more impactful, with fewer irrelevant comments and greater emphasis on high-priority flaws.

Front-End and Cloud Capabilities

Beyond backend refactoring, Codex shines in front-end engineering—building refined desktop apps and optimised mobile sites.

• Accepts screenshots and design artefacts
  
• Iterates with visual feedback
  
• Delivers progress reports in real-time
  

Its cloud infrastructure enhancements reduce task completion times by 90%, including caching containers, pre-setting environments, and autonomously fetching dependencies.

Codex CLI: Revamped for Developers

The Codex CLI has been rebuilt with agentic workflows in mind:

• Attach and share images like wireframes or diagrams
  
• Automatic progress tracking with to-do lists
  
• Enhanced terminal UI with simplified approval modes
  
• Long-session optimisation with conversation state compaction
  

IDE Extension: Seamless Local & Cloud Integration

The IDE extension embeds Codex directly into environments like VS Code and Cursor. Developers enjoy:

• Shorter prompts with richer context
  
• Faster completions
  
• Smooth transitions between local and cloud tasks

Security and Trust Measures

Safety remains central to Codex’s design.

• Sandboxed environments are by default with restricted network access
  
• Configurable security policies for domains and commands
  
• Full transparency with logs, citations, and test outputs
  

Like GPT-5, this model is classified as High capability in sensitive domains, with safeguards applied rigorously.

Pricing and Availability

Codex is bundled with ChatGPT Plus, Pro, Business, Edu, and Enterprise plans.

• Plus/Edu/Business: Suited for focused weekly sessions
  
• Pro: Enables full project-level workloads
  
• Enterprise: Pooled credit systems for scalability and cost alignment
  

API integration for GPT-5-Codex is also on the horizon.

Conclusion: Codex as a True Partner

Codex is crystallising into the developer’s envisioned ally—nimble, resilient, and seamlessly integrated. It is no longer just a tool but a teammate for ambitious engineering pursuits, balancing precision, creativity, and endurance.

The era of collaborative coding is not ahead—it is already here, embodied in GPT-5-Codex.