GPT-5.1 Codex Max Now Available in Microsoft Foundry Models

Microsoft has announced the general availability of OpenAI's GPT-5.1-Codex-Max in Microsoft Foundry Models, marking a significant milestone for enterprise developers seeking advanced AI-powered coding capabilities. This release represents a leap forward in agentic coding technology, combining OpenAI's most powerful coding model with Microsoft's enterprise-grade infrastructure to deliver unprecedented capabilities for software development at scale.

Understanding GPT-5.1-Codex-Max

GPT-5.1-Codex-Max represents OpenAI's new frontier agentic coding model, designed specifically for long-running, project-scale work with enhanced reasoning and token efficiency. Unlike traditional coding assistants that struggle with context retention across extended sessions, this model was purpose-built to handle complex engineering tasks that span hours or even days of development work.

The model is the first natively trained to operate across multiple context windows through a process called compaction, allowing it to work coherently over millions of tokens in a single task. This breakthrough enables developers to tackle project-scale refactors, deep debugging sessions, and multi-hour agent loops without losing track of earlier steps or context.

The compaction system automatically condenses information as sessions approach context limits, freeing space to continue tasks without interrupting progress. This technical innovation solves one of the most significant limitations of previous AI coding models, which would lose coherence or require manual intervention when context windows filled up.

Benchmark Performance and Real-World Capabilities

GPT-5.1-Codex-Max delivered impressive results on industry-standard benchmarks, achieving 77.9% on SWE-Bench Verified, 79.9% on SWE-Lancer IC SWE, and 58.1% on TerminalBench 2.0. These scores significantly exceed the regular GPT-5.1-Codex model, which scored 73.7%, 66.3%, and 52.8% respectively on the same benchmarks.

SWE-Bench Verified represents the gold standard for evaluating AI coding capabilities, testing models on real-world software engineering tasks from actual GitHub repositories. The near-80% success rate demonstrates that GPT-5.1-Codex-Max can independently solve the vast majority of real coding challenges that human developers face daily.

The model was trained on real-world software engineering tasks including PR creation, code review, frontend coding, and Q&A. This practical training approach ensures the model understands not just syntax and algorithms but the entire development workflow from planning through implementation to documentation.

Notably, GPT-5.1-Codex-Max is the first model OpenAI has trained to operate in Windows environments, addressing a significant gap in previous AI coding tools that often struggled with Windows-specific development patterns, file systems, and toolchains.

Microsoft Foundry Integration

Microsoft Foundry represents a unified platform where businesses can confidently choose the right model for every job, backed by enterprise-grade reliability. The platform brings together leading AI models from OpenAI, Anthropic, xAI, Black Forest Labs, Cohere, Meta, Mistral, and Microsoft's own innovations under a single, coherent infrastructure.

GPT-5.1-Codex-Max is available through Microsoft Foundry and accessible in Visual Studio Code via the Foundry extension. This integration enables developers to access frontier AI capabilities directly within their familiar development environments without switching contexts or managing separate AI subscriptions.

The Foundry platform provides enterprise-grade features critical for business adoption: built-in security, comprehensive observability tools, governance frameworks for responsible AI deployment, and seamless integration with existing development workflows. Organizations can manage model access, monitor usage, and enforce policies across their entire development organization from a single administrative interface.

Pricing and Availability

The model is available through the API with competitive pricing of $1.25 per million input tokens and $10 per million output tokens, matching GPT-5's pricing structure. This pricing represents exceptional value given the model's superior capabilities, making advanced AI coding accessible to organizations of all sizes.

Access follows a registration-based model. Organizations must apply and receive approval based on Microsoft's eligibility criteria before deploying GPT-5.1-Codex-Max. This controlled rollout ensures responsible deployment while allowing Microsoft to provide appropriate support as enterprises integrate the technology into critical development workflows.

GitHub Copilot users with Pro, Pro+, Business, and Enterprise subscriptions can access GPT-5.1-Codex-Max through public preview. Developers can select the model directly from the Copilot Chat model picker in Visual Studio Code, GitHub.com, GitHub Mobile, and the Copilot CLI, providing multiple access points for different development scenarios.

Enterprise Use Cases and Applications

The combination of GPT-5.1-Codex-Max with Microsoft Foundry enables powerful enterprise applications that were previously impractical or impossible. Multi-agent coding workflows allow teams to automate repetitive tasks across microservices while maintaining shared context for seamless collaboration. The model can coordinate changes across dozens of microservices, ensuring consistency and preventing integration issues.

Enterprise application modernization becomes dramatically more efficient. Organizations with legacy .NET or Java applications can leverage GPT-5.1-Codex-Max to refactor monolithic architectures into cloud-native microservices. The model understands both legacy patterns and modern best practices, generating migration paths that preserve business logic while adopting contemporary approaches.

Complex debugging sessions benefit from the model's ability to maintain context across extended investigations. Developers can work with GPT-5.1-Codex-Max to trace issues through multiple layers of abstraction, examine log files spanning hours of operation, and correlate symptoms across distributed systems without losing track of investigation threads.

Code review automation reaches new sophistication levels. The model can perform comprehensive reviews that consider security implications, performance characteristics, maintainability concerns, and alignment with organizational coding standards. These AI-assisted reviews augment human judgment rather than replacing it, catching issues that might slip through manual review while freeing developers to focus on architectural and design considerations.

Token Efficiency and Performance Improvements

Beyond raw capability improvements, GPT-5.1-Codex-Max demonstrates significant efficiency gains. The model achieves better performance using 30% fewer thinking tokens compared to GPT-5.1-Codex at the same reasoning effort level on SWE-Bench Verified. This efficiency translates directly to cost savings and faster response times for development teams.

The improved token efficiency results from more effective reasoning strategies. Rather than exploring exhaustive solution spaces or generating verbose intermediate steps, GPT-5.1-Codex-Max focuses its computational resources on the most promising approaches. This targeted reasoning reduces waste while maintaining or improving solution quality.

Adaptive reasoning capabilities allow the model to adjust its approach based on task complexity. Simple modifications receive quick, direct solutions, while complex architectural changes trigger deeper analysis and more careful planning. This dynamic adjustment optimizes the balance between speed and thoroughness across diverse development scenarios.

Security Considerations and Safeguards

GPT-5.1 Codex Max Now Available in Microsoft Foundry Models

With great capability comes significant responsibility, and OpenAI has implemented comprehensive security measures around GPT-5.1-Codex-Max. The model runs in a secure sandbox by default, with file writes limited to designated workspaces and network access disabled unless explicitly enabled by developers.

OpenAI deployed dedicated cybersecurity-specific monitoring to detect and disrupt malicious activity when GPT-5-Codex launched, and these protections extend to GPT-5.1-Codex-Max. While the company has not observed meaningful increases in scaled abuse, they continue preparing additional mitigations as agentic capabilities evolve.

The model represents OpenAI's most capable cybersecurity model deployed to date, though it does not reach High capability on Cybersecurity under the company's Preparedness Framework. This transparency about limitations helps organizations understand appropriate use cases and necessary precautions when deploying the technology.

Prompt injection risks emerge when enabling internet access or web search capabilities. Untrusted content from external sources could potentially manipulate the model's behavior. OpenAI recommends keeping Codex in restricted-access mode and carefully vetting any external data sources before integration.

Integration with Development Workflows

GPT-5.1-Codex-Max integrates seamlessly with modern development practices and toolchains. The model supports asynchronous execution for long-running tasks, maintaining state and context across multiple interactions. Developers can initiate complex refactoring operations, return hours later, and find the model has continued working while preserving full context of earlier decisions.

Multimodal capabilities enable the model to work with architecture diagrams, UI mockups, and screenshots alongside code. This visual understanding helps bridge the gap between design specifications and implementation, allowing developers to reference visual materials when describing desired functionality.

Repository-aware intelligence means the model understands entire codebases rather than working with isolated files. This holistic understanding enables cohesive refactors that maintain consistency across related modules, automated test generation that covers integration scenarios, and visual verification that proposed changes align with existing patterns.

The model supports streaming responses, function calling, and structured outputs, providing flexibility for different integration patterns. Development teams can build custom tooling that leverages GPT-5.1-Codex-Max capabilities while maintaining control over user experience and workflow integration.

The Broader Context of AI-Assisted Development

Codex usage has grown more than 10 times since the launch of GPT-5-Codex in August, with Codex models now serving trillions of tokens per week. This explosive growth demonstrates widespread developer adoption and the genuine productivity improvements AI coding assistants provide.

The release of GPT-5.1-Codex-Max represents continued evolution in this space, raising the ceiling on what's possible with AI assistance. As models become more capable at sustained, complex work, the boundary between AI assistance and AI autonomy blurs. Developers increasingly act as orchestrators and reviewers rather than writing every line of code manually.

This shift doesn't diminish the importance of human expertise but rather elevates it. Understanding architecture, making design decisions, evaluating trade-offs, and ensuring code quality remain fundamentally human responsibilities. AI tools like GPT-5.1-Codex-Max amplify these capabilities by handling implementation details, catching potential issues, and exploring alternatives that humans might overlook.

Looking Forward

The availability of GPT-5.1-Codex-Max in Microsoft Foundry Models marks an important milestone in enterprise AI adoption for software development. By combining cutting-edge AI capabilities with enterprise infrastructure, security, and governance, Microsoft and OpenAI have created a platform that organizations can confidently deploy at scale.

As development teams gain experience with these tools and best practices emerge, we can expect increasingly sophisticated applications. The future of software development likely involves tight collaboration between human developers and AI assistants, each contributing their unique strengths to create better software faster.

Conclusion

GPT-5.1-Codex-Max's arrival in Microsoft Foundry Models represents a watershed moment for enterprise software development. With its unprecedented ability to maintain context across extended tasks, superior benchmark performance, and integration with enterprise-grade infrastructure, this model offers capabilities that were science fiction just years ago. Organizations seeking to accelerate development, modernize legacy applications, or improve code quality now have access to tools that can meaningfully contribute to these goals. As AI-assisted development continues maturing, GPT-5.1-Codex-Max stands as a powerful demonstration of what's possible when cutting-edge AI research meets practical enterprise needs.