Internship
AI-Assisted Legacy Code Migration Research
Investigating how AI tools and LLM's can support developers when migrating legacy applications to modern technology stacks.
Information
Role
Front-end developer
Duration
3 months
Company
Sweet Mustard
Technologies
React, Java, Ruby on rails
Year
2026
Introduction
During my internship, I researched how modern AI tools can assist developers in migrating legacy software systems to newer technology stacks. The goal was to evaluate and validate the effectiveness, limitations, and practical applications of AI throughout the migration process.
Challenges
- Use of outdated technologies.
- Understanding complex legacy code with limited documentation.
- Maintaining functional equivalence during migration.
- Verifying the correctness of AI-generated implementations.
Goals
- Analyze current AI tools for software migration.
- Identify migration tasks where AI provides value.
- Evaluate strengths and weaknesses of AI-generated solutions.
- Develop guidelines for developers using AI during migrations.
Research approach
During the internship, we evaluated a variety of AI-assisted software modernization approaches. Rather than relying on a single tool or workflow, we experimented with different techniques to understand their strengths, limitations, and suitability for legacy code migration. We used a real legacy codebase as experimental subject rather than creating simplified examples.
Technologies & tools
Legacy Technologies
'%3e%3cpath%20d='M81.127%2067.3824C81.127%2067.3824%2089.4583%2066.6683%2089.4583%2055.9091C89.4583%2045.1499%2079.3656%2044.1501%2079.3656%2044.1501H61.1797V78.094H70.3202V69.9056L78.223%2078.094H91.7434L81.127%2067.3824ZM77.6041%2060.4318H70.3202V52.6718H77.6517C77.6517%2052.6718%2079.6988%2053.4335%2079.6988%2056.528C79.6988%2059.6224%2077.6041%2060.4318%2077.6041%2060.4318ZM112.024%2044.3882H102.741C96.1233%2044.3882%2093.8857%2050.3867%2093.8857%2053.2431V78.094H103.169V72.1431H111.881V78.094H120.879V53.2431C120.879%2046.0068%20114.309%2044.3882%20112.024%2044.3882ZM111.881%2062.5265H103.122V54.2904C103.122%2054.2904%20103.122%2052.4338%20106.026%2052.4338H109.215C111.786%2052.4338%20111.834%2054.2904%20111.834%2054.2904V62.5265H111.881ZM125.116%2044.3882H134.78V78.094H125.116V44.3882ZM148.348%2069.3819V44.3882H138.732V69.3819V78.094H148.348H161.345V69.3819H148.348ZM164.535%2069.4771V78.094H180.102C183.292%2078.094%20188.767%2075.7612%20188.957%2069.2391V65.9066C188.957%2060.3365%20184.387%2057.0517%20180.102%2057.0517H172.342V53.0527H187.719V44.3882H172.961C169.152%2044.3882%20164.059%2047.5302%20164.059%2053.3859V56.3852C164.059%2062.2408%20169.105%2065.2401%20172.961%2065.2401C183.673%2065.2877%20170.39%2065.2401%20180.293%2065.2401V69.4295L164.535%2069.4771Z'%20fill='%23CC0000'/%3e%3cpath%20d='M3.57468%2078.0464H41.1843C41.1843%2078.0464%2033.9956%2045.2451%2057.7991%2031.9627C62.9883%2029.4396%2079.5079%2020.0134%20106.549%2040.0083C107.406%2039.2942%20108.215%2038.7229%20108.215%2038.7229C108.215%2038.7229%2083.4593%2014.0149%2055.8948%2016.7761C42.0412%2018.0139%2024.9979%2030.6297%2015.0004%2047.2922C5.00289%2063.9547%203.57468%2078.0464%203.57468%2078.0464ZM81.9359%2019.4421L82.1263%2016.2524C81.6979%2016.0144%2080.5077%2015.4431%2077.5084%2014.5862L77.318%2017.7282C78.889%2018.2519%2080.4125%2018.8232%2081.9359%2019.4421ZM77.4132%2029.5348L77.2228%2032.534C78.7938%2032.5816%2080.3649%2032.7721%2081.9359%2033.1053L82.1263%2030.1537C80.5077%2029.8204%2078.9366%2029.63%2077.4132%2029.5348ZM59.7986%2014.6814H60.2747L59.3225%2011.7773C57.8467%2011.7773%2056.3233%2011.8726%2054.7523%2012.063L55.6568%2014.8718C57.0374%2014.729%2058.418%2014.6814%2059.7986%2014.6814ZM62.0837%2032.2008L63.1787%2035.4857C64.5593%2034.8192%2065.9399%2034.2479%2067.3205%2033.8194L66.2732%2030.6773C64.6545%2031.1534%2063.2739%2031.6771%2062.0837%2032.2008ZM40.4701%2019.6801L38.3278%2016.3952C37.1377%2017.0141%2035.8999%2017.6806%2034.6145%2018.4423L36.8044%2021.7748C38.0422%2021.0131%2039.2324%2020.299%2040.4701%2019.6801ZM50.2296%2041.1033L52.5147%2044.531C53.324%2043.3408%2054.2762%2042.2459%2055.3235%2041.1509L53.1812%2037.9136C52.0863%2038.9134%2051.0865%2040.0083%2050.2296%2041.1033ZM43.3266%2056.4328L47.1827%2059.4796C47.3732%2057.6229%2047.7064%2055.7663%2048.1825%2053.9096L44.7548%2051.196C44.1359%2052.9574%2043.7074%2054.7189%2043.3266%2056.4328ZM22.4747%2033.8194L19.0946%2030.8678C17.8568%2032.058%2016.6666%2033.2481%2015.5717%2034.4383L19.2374%2037.5804C20.2371%2036.295%2021.3321%2035.0096%2022.4747%2033.8194ZM8.09735%2055.0998L2.62254%2053.1003C1.71801%2055.1474%200.718258%2057.5277%200.242188%2058.8131L5.717%2060.8126C6.33589%2059.194%207.33564%2056.8612%208.09735%2055.0998ZM42.6125%2068.525C42.7077%2071.0481%2042.9457%2073.0952%2043.1837%2074.5234L48.8966%2076.5705C48.4681%2074.7139%2048.0397%2072.6192%2047.754%2070.3816L42.6125%2068.525Z'%20fill='%23CC0000'/%3e%3c/g%3e%3cdefs%3e%3cclipPath%20id='clip0_200_12660'%3e%3crect%20width='189'%20height='96'%20fill='white'/%3e%3c/clipPath%3e%3c/defs%3e%3c/svg%3e)
Modern Stack
'/%3e%3cpath%20d='M22.2644%202.0069l-9.7253%201.9056a.3571.3571%200%2000-.2879.3294l-.5982%2010.1038c-.014.238.2045.4227.4367.3691l2.7077-.6248c.2534-.0585.4823.1647.4302.4194l-.8044%203.9393c-.0542.265.1947.4918.4536.4132l1.6724-.5082c.2593-.0787.5084.1487.4536.414l-1.2784%206.1877c-.08.387.4348.598.6495.2662L16.5173%2025%2024.442%209.1848c.1327-.2648-.096-.5667-.387-.5106l-2.787.5379c-.262.0505-.4848-.1934-.4109-.4497l1.8191-6.306c.074-.2568-.1496-.5009-.4118-.4495z'%20fill='url(%23paint1_linear)'/%3e%3cdefs%20id='defs50'%3e%3clinearGradient%20id='paint0_linear'%20x1='6.0002'%20y1='32.9999'%20x2='235'%20y2='344'%20gradientUnits='userSpaceOnUse'%20gradientTransform='matrix(.07142%200%200%20.07142%201.3398%201.8944)'%3e%3cstop%20stop-color='%2341D1FF'%20id='stop38'/%3e%3cstop%20offset='1'%20stop-color='%23BD34FE'%20id='stop40'/%3e%3c/linearGradient%3e%3clinearGradient%20id='paint1_linear'%20x1='194.651'%20y1='8.8182'%20x2='236.076'%20y2='292.989'%20gradientUnits='userSpaceOnUse'%20gradientTransform='matrix(.07142%200%200%20.07142%201.3398%201.8944)'%3e%3cstop%20stop-color='%23FFEA83'%20id='stop43'/%3e%3cstop%20offset='.0833'%20stop-color='%23FFDD35'%20id='stop45'/%3e%3cstop%20offset='1'%20stop-color='%23FFA800'%20id='stop47'/%3e%3c/linearGradient%3e%3c/defs%3e%3c/svg%3e)
AI
Our workflow typically involved:
01
Selecting a legacy feature or component.
02
Defining a target modern technology stack.
03
Using AI tools and LLM's to migrate legacy code.
04
Comparing different prompting and migration strategies.
05
Reviewing, testing, and refining the generated code.
06
Measuring maintainability, correctness, and development effort.
Results & conclusion
The research showed that AI can significantly accelerate migration-related tasks, particularly in code understanding, documentation generation, and initial code transformations. However, developer oversight remains essential for validating architectural decisions, ensuring correctness, and handling domain-specific business logic.
Personal reflection
This internship gave me insight into the challenges organizations face when modernizing software systems. I learned how AI can act as a powerful assistant rather than a replacement for developers, and I gained hands-on experience evaluating emerging AI tools in real-world software engineering scenarios.
Technical skills
- Software Migration
- Legacy System Analysis
- AI-Assisted Development
- Prompt Engineering
- Software Architecture
- Code Refactoring
Research skills
- Functional analysis
- Experiment design
- Comparative Evaluation
- Documentation
Key takeaways
AI Accelerates Migration
Speeds up repetitive migration tasks.
Human Expertise Remains Essential
Critical decisions still require developers.
Documentation Improves
AI excels at explaining and documenting legacy code.
Best Used as a Copilot
Most effective when combined with developer review.