Legacy software modernisation is the work of making an old app safe to change again — current frameworks, a build that runs, tests around the flows that matter — without stopping releases. For most UK and EU teams the right first move is to stabilise, not rewrite. This guide explains how to decide, what a code audit should cover, and what ships in the first month. CodeLoop Studio is a studio in Sarajevo that takes over and modernises Flutter, React Native, native and Next.js apps for UK / EU teams.
| Fact | Detail |
|---|---|
| Who | CodeLoop Studio — studio in Sarajevo, Bosnia and Herzegovina; no London or Berlin office |
| For | UK / EU teams with an existing Flutter, React Native, native iOS/Android or Next.js app |
| First deliverable | Code audit + freeze + one release you are willing to sign |
| Rewrite policy | Only with a product reason, written in the audit |
| After modernisation | Maintenance: OS and store updates, dependency upgrades, crash triage |
| Working hours | CET/CEST overlap with UK and DACH |
| Language | English-language delivery |
| Verify | Clutch · case studies on our work |
What legacy software modernisation actually means
An app becomes “legacy” when change is risky: the framework or SDK is years behind, the build only works on one laptop, there are no tests around the flows that make money, one person knows where secrets live, or a store policy deadline is about to pull the listing. Modernisation is restoring the ability to ship — not a redesign of every screen, not a new brand, and not a six-month rewrite sold as progress.
UK and EU product teams usually need the app to keep serving users while the foundation catches up. That is why we start with access, a build that runs, and a freeze of the next honest release. The commercial path is legacy software takeover.
Stabilise, refactor or rewrite — how to decide
The decision is a product decision written after an audit, not a sales preference. Use the table below as a shortlist filter; the audit fills in the reasons.
Stabilise when…
The product still ships or can ship after a short restore. Users need OS and store updates more than a new architecture. The stack can support the next slice once the build and signing are boring again.
Refactor when…
Core flows work, but the code is hard to change safely. You need tests, module boundaries, and dependency upgrades without stopping the release train.
Rewrite only when…
The platform or architecture cannot support the next product need — and that reason is written in the audit. A rewrite without a frozen v0 is how calendars disappear.
| Situation | Stabilise | Refactor | Rewrite |
|---|---|---|---|
| App ships, but the build is fragile | ✓ | ||
| Framework/SDK two or more major versions behind | ✓ then upgrade | ✓ | |
| Core flows work, code is hard to change | ✓ | ||
| Platform or architecture cannot support the next product need | ✓ (with a written reason) | ||
| Nobody has repo or store access | First recover access |
What a modernisation code audit covers
Before anyone promises a modern stack, recover the truth: repository access, store accounts, backend and secrets ownership, whether the app builds and signs in CI, framework and dependency versions, crash and ANR data, tests on the flows that make money, security and personal-data handling, and who still knows the system. The output is a written report and a proposed first slice — not a redesign deck.
The commercial checklist for what the code audit contains lives on the takeover hub. We will not invent a rescue gallery of unnamed clients.
The first month: what ships first
Freeze what is in and out of the next release. Fix the build and CI so releases are boring. Ship one release the client is willing to sign. Then upgrade frameworks and SDKs in steps — not a big-bang weekend. Feature work returns after the foundation can take it. Durations depend on access and debt; the plan is written after the audit, not guessed from a blog post.
Modernising Flutter and React Native apps
Flutter
Typical work is SDK upgrades, null-safety leftovers, replacing abandoned packages, and keeping platform channels honest for device APIs. We already ship Flutter products end to end — see Flutter app development — and we will not force a Flutter rewrite of a healthy native app for a blog post.
React Native
Version upgrades, the New Architecture when libraries allow, and replacing abandoned native modules are the usual path. Public case studies on this site are mostly Flutter and native; React Native takeovers and extensions are a real engagement model — details on React Native app development and the takeover hub.
Maintenance after modernisation
Once the app builds and ships again, keep it alive: OS and store updates, dependency upgrades, crash triage, and small features on a monthly cadence inside your repo and store accounts. Scope is agreed in writing. Commercial path: legacy app takeover. Checklist essay: taking over a legacy project.
FAQ
Making an existing app safe to change again — current frameworks and SDKs, a working build and release pipeline, and tests around critical flows — while it keeps serving users.
Stabilise first in most cases. Rewrite only when the product needs something the current architecture cannot support; a code audit should give that reason in writing.
It depends on the size of the app, how far behind the framework is and whether the build works today. After the audit we give a written plan with the first release and the next steps.
Yes. CodeLoop Studio takes over Flutter, React Native, native and Next.js codebases after a code audit and continues development for UK / EU teams from our studio in Sarajevo.
Yes — OS and store updates, dependency upgrades, crash triage and small features, with monthly scope agreed in writing.
Have an app nobody wants to touch? Send us repo access details and the next release you need — we reply with a written audit plan.
Get a written estimate