AI-Assisted Application Modernization with Publicis Sapient and AWS

Generative AI is opening a practical new path for organizations that have been slowed by legacy applications, aging mainframes and hard-to-find skills. With Publicis Sapient and AWS, modernization becomes more than a long, risky translation exercise. It becomes a faster, more traceable and more maintainable transformation journey—one that combines AWS cloud and generative AI services with Publicis Sapient’s modernization accelerators, engineering expertise and human intervention.

Built on a foundation that includes Amazon Bedrock and Amazon CodeWhisperer, our approach helps organizations move from legacy code and fragmented documentation toward modern architectures, clearer specifications and better testing discipline. Instead of treating modernization as a black-box conversion effort, we use generative AI to make legacy systems understandable, actionable and ready for cloud-native evolution.

Why modernization needs a new approach

Many enterprises know their technology stack is holding them back, but traditional modernization efforts often struggle to deliver the expected speed or certainty. Outdated applications can drain budgets, lock teams into inflexible contracts and make it harder to innovate or migrate to the cloud. At the same time, organizations face a persistent skills shortage: it is increasingly difficult to find engineers who understand both legacy platforms and modern cloud-native architectures.

This creates a familiar pattern. Modernization programs move slowly, rely on incomplete documentation and carry significant delivery risk. Traditional translation tools frequently fail to capture business logic, and timelines can slip while costs rise. For organizations that need greater agility, faster product launches and stronger operational resilience, that is no longer sustainable.

How Publicis Sapient applies generative AI to modernization on AWS

Publicis Sapient uses multiple large language models, contextual knowledge and pre-built prompt libraries to amplify developer productivity across the modernization lifecycle. This is not automation for automation’s sake. It is a structured, engineering-led approach that combines AI acceleration with human oversight to improve quality, reduce effort and support better decision-making.

Our modernization process starts with understanding what the legacy application actually does. Generative AI analyzes existing codebases and helps deconstruct complex programs into clearer feature summaries, business rules and functional specifications. Context matters, so teams enrich the models with the right domain knowledge, system intent and transformation goals. Prompt libraries help standardize how modernization tasks are executed, while human experts validate outputs, refine assumptions and guide architecture decisions.

From code understanding to cloud-native delivery

One of the biggest barriers in legacy transformation is the gap between undocumented systems and future-state design. Publicis Sapient helps close that gap by turning existing code into verified specifications and generating modern software with full traceability. This is where Sapient Slingshot plays an important role.

Sapient Slingshot is designed to modernize legacy systems by converting what already exists into usable engineering intelligence. That means teams are not starting from scratch or relying solely on tribal knowledge. They can use AI-assisted outputs to understand dependencies, expose hidden business logic and define a clearer modernization path.

The value extends beyond code translation. By generating specifications, tests and structured outputs from legacy systems, organizations gain artifacts they can use throughout the migration journey—from architecture planning and sprint execution to validation and long-term maintenance. For leaders trying to move from mainframe-bound operations to cloud-native delivery, that traceability is critical.

Business outcomes that matter

AI-assisted modernization is valuable because it improves the economics and execution of change. Based on Publicis Sapient’s analysis of more than 100 end-to-end experiments using its generative AI modernization accelerators together with PSChat, Bodhi, GPT and AWS solutions, organizations may realize:

Actual outcomes vary by client context, but the direction is clear: modernization can become faster, more reliable and less labor-intensive.

There is also a strong operational case for this approach. Better specifications improve traceability. Better test generation improves confidence. Better code understanding improves maintainability. And faster migrations reduce the drag of legacy systems on business growth.

A practical example of modernization impact

For a leading benefits provider, Publicis Sapient designed a process that enabled cloud developers to use private models and LLMs to deconstruct legacy mainframe programs. Proof-of-concept results were then used to fine-tune operationalization and support iterative development in sprints.

The impact was significant. The organization achieved a migration that was three times faster and reduced effort through AI. It also created functional specifications that improved traceability and quality, while making the code easier to maintain and enhance in a modern technology stack.

Publicis Sapient has also demonstrated the ability to convert 3 million lines of COBOL into clear specifications in eight weeks—an example of how generative AI can compress one of the most time-consuming phases of modernization.

Modernization with AWS, built for enterprise scale

AWS provides the secure, scalable foundation for this work. Publicis Sapient’s partnership with AWS brings together cloud migration, modernization and generative AI capabilities in a way that helps enterprises move from experimentation to production. Amazon Bedrock and Amazon CodeWhisperer help establish the foundation for generative AI-driven engineering workflows, while the broader AWS ecosystem supports enterprise requirements for scale, security and operationalization.

Publicis Sapient’s AWS relationship is built around end-to-end transformation, not isolated tooling. That means clients can align modernization efforts with broader goals such as cloud migration, responsible AI adoption, improved engineering productivity and long-term platform resilience.

Why Publicis Sapient

Publicis Sapient brings together more than 30 years of digital business transformation experience, deep application modernization expertise and enterprise AI platforms purpose-built for real-world delivery. Our SPEED framework—Strategy, Product, Experience, Engineering, and Data & AI—helps connect modernization work to measurable business outcomes, not just technical milestones.

This is especially important for organizations that are struggling with legacy complexity but need to move decisively. Publicis Sapient combines strategy through implementation, proprietary accelerators such as Sapient Slingshot, and deep AWS partnership capabilities across cloud strategy, migration, build and security.

Start modernizing with confidence

Legacy technology should not determine the speed of your future. With Publicis Sapient and AWS, generative AI can help transform modernization from a slow, opaque process into a structured, high-velocity journey grounded in engineering rigor and human oversight.

If your organization is facing mainframe constraints, outdated applications or a shortage of legacy skills, AI-assisted modernization offers a practical way forward: understand what you have, define where you are going and accelerate the move to a cloud-native future with greater confidence.