# vFunction

> vFunction is a modernization platform for large existing Java and .NET applications that gives AI coding tools such as Kiro and Claude Code the runtime architectural context, specifications, and integration tests they need to refactor and rewrite them one domain at a time.

vFunction is a modernization platform for large existing Java and .NET applications. It gives AI coding tools the context and guardrails they need to refactor, rewrite, and modernize existing systems with speed, accuracy, and control. Using runtime analysis and proprietary data science, it captures how an application actually runs in production and helps your architects define a target architecture before modernization begins. It generates a specification for each domain from the observed runtime flows, with the architectural issues found during analysis factored in, and integration tests from runtime analysis. Kiro, Claude Code, and other AI coding tools and agents receive them through vFunction's MCP server and downloadable skills and refactor and rewrite the application one domain at a time under your team's review; AWS Transform is used within the same workflow for .NET and Java upgrades. vFunction's engineers run the process with your team until your team can run it alone.

vFunction is built for applications past roughly 500,000 lines of code or 1,000 classes. It analyzes Java and .NET applications, is installed in the customer's environment, and is priced per application with no per-user fees. It is not an AI coding tool, a version upgrader, a security scanner, or a portfolio assessment tool; it is used alongside them. vFunction, Inc. is headquartered in Menlo Park, California.

## Product

- [Platform](https://vfunction.com/platform/): how vFunction gives AI coding tools runtime architectural context, specifications, and guardrails to modernize large Java and .NET applications
- [Use cases](https://vfunction.com/use-cases/): Full-Stack Windows Modernization; Modernize Large VM Apps to Containers; Power AI-Driven Development for Existing Applications
- [Full-Stack Windows Modernization](https://vfunction.com/windows-modernization/): modernizing .NET Framework applications, upgrading to .NET 10, and converting SQL Server databases to PostgreSQL, with AWS Transform and Kiro
- [Modernize Large VM Apps to Containers](https://vfunction.com/use-cases/monolith-to-microservices/): moving large Java and .NET applications from VMs into container-ready modular systems
- [vFunction on AWS](https://vfunction.com/solutions/aws/): modernizing Java and .NET applications on AWS
- [What's new in vFunction 5.0](https://vfunction.com/whats-new-vfunction-5-0/): vFunction 5.0 brings large existing Java and .NET applications into AI-driven development: evidence-backed specifications and integration tests generated from the running application, the database migrated to PostgreSQL in the same workflow, all delivered to Kiro, Claude Code, and AWS Transform.
- [Power AI-Driven Development for Existing Applications](https://vfunction.com/ai-driven-development/): AI-driven development (AI-DLC) needs specifications, a system model, and tests. vFunction generates them from your running Java or .NET application and delivers them to Kiro, Claude Code, AWS Transform, and other AI coding tools.
- [Modernize the legacy applications in your portfolio companies](https://vfunction.com/portfolio-modernization/): AI is already in your portfolio companies’ development. It stalls on the monolith each one sells. vFunction gets AI coding tools through it; AWS funds it.
- [The cost of waiting](https://vfunction.com/cost-of-waiting/): Why leaving a large existing application alone used to be the safe choice, why it isn't now, and how AI coding tools and vFunction change what modernizing costs.

## Buying and working with vFunction

- [Pricing](https://vfunction.com/pricing/): priced per application, unlimited users, available through cloud marketplaces
- [How an engagement works](https://vfunction.com/how-engagements-work/): vFunction's forward-deployed engineers modernize one large Java or .NET application with your team, in your environment, until your team can run the process alone. The six steps, what you supply, and who does what.
- [Contact](https://vfunction.com/contact/): tell vFunction about the application you have in mind
- [Customer stories](https://vfunction.com/resource-center/case-studies/)
- [Partners](https://vfunction.com/partners/): cloud providers and system integrators
- [System integrators](https://vfunction.com/partners/system-integrators/)

## Research

- [Why application modernization projects fail](https://vfunction.com/resources/report-wakefield-why-app-modernization-projects-fail/): Wakefield Research survey report
- [2025 Architecture in Software Development report](https://vfunction.com/resources/report-2025-architecture-in-software-development/)

## Recognition

- [AWS AI Software Competency](https://vfunction.com/blog/vfunction-achieves-aws-ai-software-competency/)
- [AWS Resilience Competency](https://vfunction.com/blog/aws-resilience-competency/)
- [Gartner Cool Vendor 2024](https://vfunction.com/blog/gartner-cool-vendor-2024/)

## Guides

- [Kiro for modernization: an enterprise guide](https://vfunction.com/blog/kiro-for-modernization/)
- [vFunction and AWS on full-stack Windows modernization](https://vfunction.com/blog/vfunction-and-aws-help-enterprises-tackle-full-stack-windows-modernization/)
- [LLMs vs. brownfield reality: why refactoring enterprise systems is hard](https://vfunction.com/blog/llms-vs-brownfield-reality-why-refactoring-enterprise-systems-is-hard/)
- [.NET application modernization guide](https://vfunction.com/blog/net-application-modernization-guide/)
- [AWS application modernization guide](https://vfunction.com/blog/aws-application-modernization-guide/)
- [MCP security](https://vfunction.com/blog/mcp-security-navigating-the-wild-west-of-ai-integration/)
- [Distributed monolith architecture](https://vfunction.com/blog/distributed-monolith-architecture/)
- [Static vs. dynamic code analysis](https://vfunction.com/blog/static-vs-dynamic-code-analysis/)
- [Monolith to microservices](https://vfunction.com/blog/monolith-to-microservices/)
- [Microservices architecture and design](https://vfunction.com/blog/microservices-architecture-guide/)
- [What is technical debt?](https://vfunction.com/blog/what-is-technical-debt/)
- [What is software architecture?](https://vfunction.com/blog/what-is-software-architecture/)
- [Architecture diagram basics and best practices](https://vfunction.com/blog/architecture-diagram-guide/)

## Optional

- [Blog](https://vfunction.com/blog/)
- [Newsroom](https://vfunction.com/newsroom/)
- [About vFunction](https://vfunction.com/about/)
- [Become a partner](https://vfunction.com/partners/become-a-partner/)