Choosing a custom software development agency is a bit like choosing a surgeon: the degree isn't enough, you want to know how many similar operations they've performed. In 2026, the French market has hundreds of agencies all promising the same thing. I've evaluated dozens of them for my own clients and for GoLive Software. Here are the 7 criteria that separate serious agencies from quote factories.
- 🎯 Verifiable specialisation: a generalist agency delivers generic products, every single time.
- ⚠️ Team transparency: knowing who actually codes your product changes everything about the outcome.
- 💡 AI integrated into the workflow: in 2026, a developer without AI ships half as fast.
- 📊 Day rates and hidden costs: the first quote never tells the whole truth.
1. Domain specialisation, not a generalist portfolio
The first instinct when looking for a custom software agency is to check the portfolio. That's necessary, but not sufficient. What really matters is the depth of expertise in your specific industry.
Why does a generalist agency cause problems?
João Nina Matos, a Portugal-based agency founder, puts it bluntly: a generalist development agency invariably ends up in what he calls "MVP hell." It churns through small custom projects for different clients, never building on any sector expertise. Every new project starts from scratch, timelines blow up, and quality stays mediocre.
According to Sortlist's 2026 ranking, the top French software development agencies all show clear vertical focus (healthcare, e-commerce, manufacturing, finance). Andersen, for instance, claims 2,000 IT projects over 19 years, spread across specific sectors: financial services, healthcare, logistics. That concentration is no accident.
When I evaluate an agency for a client, I ask one simple question: "Show me three projects similar to mine, with client names and measurable results." If the answer stays vague, I move on.
2. Transparency about who actually writes the code
Many agencies sell a brilliant technical director during the pitch, then hand the development work to junior profiles or subcontractors. This is the most expensive trap on the market.
How do you verify who will work on your project?
Jakob Wolitzki, who runs a development agency of nearly 30 people, admits he made this mistake himself: trusting too much without checking. A poorly supervised developer caused what he describes as a "catastrophic outcome" on two projects simultaneously. His lesson after 5 years of running an agency: validate the work before it's too late.
Ask for the CVs of the developers assigned to your project. Insist on joining the first sprints to observe actual velocity. If the agency refuses transparency, that is a major red flag.
At GoLive Software, I systematically share the LinkedIn profiles of the developers working on a project, along with their recent GitHub contributions. A client who knows their team makes better decisions, and the team feels a stronger sense of ownership.
3. The tech stack and architecture decisions
Custom software built on an obsolete or poorly mastered framework is technical debt by design. The agency must justify every technical choice based on your needs, not its habits.
What technical signals should you check before signing?
Yield Studio, which positions itself as France's top custom software agency for SMEs and mid-market companies, lists over 40 technologies and frameworks covered (React, Vue.js, Angular, PHP, Node.js, Python, .NET). That versatility is a good sign, provided it comes with a reasoned recommendation for your specific project.
Ask these three questions: which database and why? Which front-end framework and why? What deployment strategy (containers, serverless, PaaS)? If the answers are "we always do it this way," walk away. A good architect adapts the stack to the context.
I've seen poorly scoped SaaS projects cost twice as much in refactoring six months after launch. The initial stack choice determines total cost of ownership over 3 to 5 years.
4. The project management process
Nearly every agency claims to be "agile." Very few actually are. The real test is the frequency of deliveries and transparency on progress.
How do you tell real agile from a sales pitch?
A genuinely agile process means 1- to 2-week sprints with a working demo at the end of each sprint. Not a PowerPoint deck, not a status email: a staging environment where you can click around and test.
Anakeen, a custom development specialist with over 20 years of experience, makes an essential point in their guide: having a detailed specification document doesn't mean running a waterfall cycle. The best agencies combine rigorous functional scoping with iterative delivery. Yield Studio reports a client retention rate of 96%, a number that speaks volumes about the ability to deliver value consistently.
My personal criterion: if I can't test a working feature within the first 15 days of development, the process is broken. It's that simple.
5. Code ownership and reversibility
This is the criterion everyone forgets when signing, and everyone regrets when switching agencies. Who owns the source code? Can you leave without losing your investment?
What contract clauses should you absolutely require?
Three non-negotiable elements must appear in your contract. Full transfer of intellectual property upon delivery. Source code deposited in a repository you control (GitHub, GitLab). And a reversibility clause requiring the agency to provide technical documentation and access credentials in the event of termination.
OpenStudio, an agency specialising in open source, illustrates this well: by using open-source technologies as a foundation, they mechanically reduce the risk of vendor lock-in. This is an advantage I systematically recommend to my clients.
The true cost of custom software includes this reversibility. Without it, you don't own software, you're renting a trap.
6. AI integration in the development workflow
In 2026, a custom software agency that doesn't use AI in its development process ships more slowly and probably at lower quality than one that has integrated it. This is no longer a luxury, it's a standard.
How does AI change agency productivity in 2026?
Jakob Wolitzki measured it in his own agency: adopting Cursor boosted his team's productivity by 30 to 40%, verified through time tracking and task management in ClickUp. That's consistent with what I see at GoLive Software, where our Vietnamese developers use Claude Code and Cursor daily.
The Syntec Numérique barometer confirms that generative AI adoption has been accelerating across French IT services firms since mid-2025. The question is no longer "does the agency use AI?" but "how, and on which tasks?"
An agency that hasn't formalised its AI usage in 2026 probably has a cultural problem with technology.
Ask the question directly: what AI tools do your developers use? How do you measure the productivity gain? If the answer is vague, the integration is cosmetic. On ai-first.fr, I regularly document how AI actually fits into the daily work of technical teams.
7. The pricing model and hidden costs
The last criterion, and often the trickiest. The posted day rate represents only a fraction of the real cost of a custom software project.
Should you go with fixed-price or time-and-materials?
Each model has its pitfalls. Fixed-price is reassuring on budget but incentivises the agency to deliver the bare minimum. Time-and-materials offers more flexibility but can spiral if the scope isn't locked down. Here's what I see in the field as of June 2026:
| Criterion | Traditional IT firm | Local FR agency | Freelancer | Structured offshore |
|---|---|---|---|---|
| Average day rate | €450-700/day | €500-900/day | €300-600/day | €150-350/day |
| Team transparency | Low | Good | Full | Variable |
| Scalability | Strong | Limited | None | Strong |
| Quality commitment | Contractual | Reputation-based | Variable | Depends on structure |
| AI integration | Slow | In progress | Fast | Fast |
SOURCE: field estimates by GoLive Software · Updated 06/2026
My advice: ask for a detailed line-by-line quote. If the agency can't break costs down between design, development, testing, and deployment, the estimate is a rough guess. Also check what's included in post-delivery maintenance. A development contract with a traditional IT services firm can hide 18 to 22% annual turnover on the team, based on my own observations.
"The lowest price is almost never the best choice. The best value comes from senior teams, well-tooled, in competitive geographies."
Vincent Roye, June 2026
I see it every week: a small senior team in Vietnam, assisted by AI, delivers as fast as a French team that costs twice as much. The key variable isn't location, it's technical competence and management rigour. My model at GoLive rests on this equation: skilled Vietnamese developers, augmented by AI, to ship fast and ship well.
These 7 criteria won't guarantee your project will succeed. But they eliminate 80% of the agencies that would waste your time and money. If a custom software agency passes all 7 filters, you've found a serious partner. The rest, regardless of their sales pitch, don't deserve your trust.
Frequently asked questions
What budget should you plan for custom software in 2026?
A functional MVP costs between €15,000 and €60,000 depending on complexity. A full business application with integrations, testing, and deployment falls between €50,000 and €200,000. These ranges vary significantly depending on the team's geography and the level of polish expected.
How long does it take to build custom software?
An MVP can be delivered in 6 to 12 weeks if the agency works in short sprints. A complete product takes 4 to 9 months. The determining factor isn't team size, it's the clarity of the functional scope at the outset and the client's responsiveness on approvals.
What's the difference between a custom software agency and an IT services firm?
An agency specialises in designing and delivering finished products. An IT services firm (known as an ESN in France, formerly SSII) primarily provides technical staff on a time-and-materials basis. Some IT services firms also deliver fixed-price projects, but their business model is built on volume of billable days, not on the quality of the delivered product.
Can an offshore agency deliver serious business software?
Yes, provided the team is structured with French-speaking technical management and formalised quality processes. The country doesn't determine code quality. Developer competence, specification clarity, and project management rigour are the real success factors.
Should you require a prototype before starting full development?
It's strongly recommended. A clickable prototype (interactive mockup or minimal MVP) lets you validate the UX and user flows before investing in development. The best agencies build this phase into their methodology, typically for a cost of €3,000 to €8,000.
Vidéos YouTube
- From Custom Software Agency to AI Systems (Amazon Data + MCP) · Jakob Wolitzki
- A los 22 años comencé una agencia de software. Esto fue lo que pasó 5 años después · Jakob Wolitzki
- Your software development agency will fail if you don't learn this fast enough · João Nina Matos
- Software Agencies! This is the best way to get clients in 2026 · Jayant Padhi
Articles & ressources
- Agence de développement logiciels sur mesure · openstudio.fr
- Les 10 meilleures agences de développement de logiciel en France · sortlist.fr
- Agence n°1 de Logiciel Sur-Mesure pour PME & ETI · yieldstudio.fr
- Développement logiciel sur mesure : guide pour réussir · anakeen.com
- Agence de Développement Logiciel Sur Mesure · andersenlab.fr
