Custom software development Your business application in production in 4 weeks
You need a custom business application, without waiting six months or committing a six-figure budget. With our AI-First Delivery method, AI writes the code and our engineers and AI PhDs review and validate it: your custom software is in production in 4 weeks, from €20,000 excl. VAT, and you own its source code.
4wks
Delivery time
€20kexcl. VAT
Starting budget
3-5x
More features
Day 1
In production from delivery
The journey at a glance
From your idea to your software
in production
A complete offer, sold as one package. Phase 2 starts as soon as Phase 1 ends.
Your need
A business application, an internal tool, a client portal… A need that no off-the-shelf software really covers.
Phase 1 — In production
From €20,000 excl. VAT
AI develops. Our engineers validate. Your software is deployed and used by your teams by the end of this phase.
Phase 2 — Consolidation
Fixed fee or subscription
Security hardening, testing, monitoring and enhancements: as a €20k to €40k excl. VAT fixed fee, or as a 2-to-3-year subscription.
4 wks
software in production
3-5x
more features
100%
source code delivered
÷280
AI cost, 2022 to 2024
The problem
Traditional software development can no longer keep up with the speed of AI
6 months and a six-figure budget
Custom software development done the traditional way means €80,000 to €150,000 and 6 months before seeing the first screen. Often, the need has changed by then.
The SaaS tool pile-up
Rather than custom software, many stack 5 or 10 tools. Result: fragmented data, low adoption, and an annual bill that explodes.
No-code that doesn't hold up
Make, n8n, Zapier… Teams don't adopt them. Everyone ends up with their own little tool on the side and industrialization becomes impossible.
Phase 1 — Your software in production (from €20,000 excl. VAT)
AI develops your software.
Our engineers validate it.
All the code of your custom business application is generated by AI. Each task is assigned to the best-performing model for the specialty: front-end, back-end, AI services, data, DevOps. Our engineers and AI PhDs orchestrate, review every line and guarantee production-ready software in 4 weeks.
Discovery & Architecture
Business workshops recorded and transcribed by AI. The specifications and technical architecture are generated automatically from your real needs. AI produces the project structure, our experts validate business coherence.
- Business workshops facilitated and transcribed by AI
- Automatically generated specifications
- Technical architecture produced by AI, validated by our experts
- Task breakdown by AI specialty
AI-First Development
AI develops the entire software. Each component is assigned to the best-performing model for the task: front-end, back-end, AI services, data, DevOps. Our engineers supervise, review code and guarantee deliverable quality.
- Source code entirely generated by AI
- Intelligent assignment: the right model for each task
- Parallel multi-agent development
- Code review and validation by our engineers
Production deployment
Your software is deployed to production and immediately used by your teams. It's a real functional internal product, not a mockup. Phase 2 takes over to consolidate and evolve it.
- Functional software deployed to production
- Team training
- Functional and technical documentation
- Phase 2 launch (consolidation & enhancements)
Phase 2 — Consolidation & Evolution
Your software is in production.
We help it grow.
As soon as Phase 1 ends, your software is deployed and in use. Phase 2 takes over immediately to secure it, enrich it and evolve it. Two options are available: a consolidation fixed fee, or a subscription that bets on the continuous decline of intelligence costs.
Fixed fee
€20k to €40k excl. VATOur web engineers consolidate the code, secure the application and bring it to industrial-grade production. The software is delivered turnkey.
- Security audit and vulnerability fixes
- Automated testing and code coverage
- Industrial-grade deployment and monitoring
- Sovereign hosting if required
- Final source code delivery
Subscription
Over 2 to 3 yearsConsolidation is spread over time as a monthly subscription. You benefit from software that improves every month, with a predictable budget and a reasoned bet on declining intelligence costs.
- Hosting, maintenance and support included
- Progressive and continuous security hardening
- New features every month
- Intelligence costs drop: you get more each month for the same price
- No heavy upfront investment: the equivalent of software leasing
Why subscription
Betting on the decline of
intelligence costs
According to the Stanford AI Index, the inference cost of a GPT-3.5-level model fell more than 280-fold between November 2022 and October 2024. Nothing suggests this trend is reversing. By subscribing today, each month you buy more value for the same budget.
In practice: new features every month, progressive security hardening, and software that evolves continuously — without one-off reinvestment. The equivalent of software leasing where each payment funds more than the last.
“By subscribing today, the client will buy significantly more for the euros invested than what they could have bought yesterday.”
“Tomorrow, we become so good and it becomes so much cheaper in terms of intelligence that we can make enhancements automatically.”
Typical timeline
Phase 1 — Software in production in 4 weeks (from €20,000 excl. VAT)
Phase 2 — Monthly subscription over 2-3 years
Hosting + maintenance + security + feature enhancements included
Comparison
The equivalent of a six-figure project,
delivered in 4 weeks
Timeline
Initial budget
Features delivered
Risk
Why it works
The advantages of the
AI-First Delivery Framework
Fast time to production
Custom software in production in 4 weeks, where a traditional project takes 6 months.
AI develops, our engineers validate
All code is generated by the best-performing AI models for each task. Our engineers supervise, review and guarantee quality.
A single business application
Replaces the pile-up of disparate tools (CRM, Excel, SaaS tools) with a single custom business application tailored to your processes.
Native AI scalability
A single, clean database enables native AI agents that perfectly understand your company's context.
Controlled risk
In production in 4 weeks, then continuous consolidation and evolution. No 6-month tunnel before seeing a screen.
Vendor independence
Standardized architecture, interchangeable AI models, source code delivered. It's your software.
Our philosophy
We're replacing
ourselves
Our consulting business will be transformed by AI. We'd rather be the ones leading this transformation than the ones suffering it. The AI-First Delivery Framework was born from this conviction: if AI can develop complete software, we should let our clients benefit now.
Every piece of software we deliver is living proof that the approach works. We apply to ourselves what we recommend to our clients.
“Clients want hyper-fast return on investment. Nobody cares how it's made as long as the deliverable is there and it's faster.”
“You have to accept that sometimes it's not 100% pixel-perfect. It does the job, it's great, it's incredibly fast. Design gets refined in Phase 2.”
“Our job will be replaced by AI, so we're trying to replace ourselves. At least that way, we have the next move.”
In full transparency
What Phase 1 delivers.
What Phase 2 reinforces.
Phase 1 — Your software in production
- Real, working software, deployed and used by your teams
- 3 to 5x more features than classic development at the same budget
- Source code entirely generated by AI and reviewed by our engineers
- A clean data foundation for deploying AI natively
Phase 2 — Consolidation & enhancements
- Complete security hardening and vulnerability audit
- Visual refinements and polished user experience
- Automated testing and industrial-grade code coverage
- New features (every month with the subscription) and change management support
FAQ
Have doubts?
That's normal.
How much does custom software development cost?
Phase 1, which puts your software into production in 4 weeks, starts at €20,000 excl. VAT; the price then depends on the complexity of the integrations with your information system, the number of users and the security requirements. For phase 2 you choose between two options: a consolidation fixed fee of €20k to €40k excl. VAT, or a monthly subscription over 2 to 3 years that includes hosting, maintenance, security hardening and enhancements. For comparison, a custom project run the traditional way costs €80,000 to €150,000 and takes 6 months.
How long until my business application is in production?
4 weeks for phase 1: one week of requirements gathering and architecture, two weeks of development, one week of production deployment and team training. This timeline requires an available business point of contact and quick access to your data; it holds because we deliver the core of the need, not the entire scope imagined in the first workshop. For software subject to regulatory certification, such as a medical device, this timeline makes no sense and we say so upfront.
What kinds of custom business applications do you build?
Sales and quoting tools for complex quotes, internal CRMs for sales cycles that off-the-shelf CRMs handle poorly, project management tools where AI agents prepare status reports and follow-ups, contract analysis platforms, or applications that replace an Excel file that has become critical. The common thread: know-how specific to your company that no vendor will ever model for you. For a standard process such as payroll or general accounting, off-the-shelf software remains the right answer.
Does AI really develop the entire software?
Yes. AI generates all the source code — front-end, back-end, database, AI services. Our engineers and AI PhDs orchestrate the models, review the code and validate every deliverable. It's this combination that enables delivering in 4 weeks what takes 6 months with a traditional approach.
Our business has complex calculation rules. AI will hallucinate.
Strict business rules are hard-coded via classic algorithms. AI is used to analyze, extract and structure data — not to guess regulations or do math. Every critical rule is verifiable and deterministic.
Will AI send errors or wrong quotes to my clients?
No. The delivered software is designed so your teams keep control. AI prepares the work — drafts, extractions, analyses — and a human validates sensitive actions. This validation loop is natively built into the architecture.
Will my confidential data train public models?
If sovereignty is a critical concern, the application is disconnected from public AIs and connected to our own inference APIs: open-weight models served by our own GPU servers, in colocation in France with a French operator. In this mode, no request ever goes to ChatGPT, Claude or Gemini. Your data stays your data.
Who owns the source code, and what happens if JustAI disappears?
You own the source code; it is delivered to you with functional and technical documentation. The architecture is standardized: another team can take over the software, and you just change the API URL to switch from one AI provider to another without losing your interface or data.
What happens after go-live: maintenance, enhancements?
Phase 2 starts as soon as phase 1 ends, in one of two forms. With the fixed fee (€20k to €40k excl. VAT), our engineers consolidate the code, audit security, add automated tests and monitoring, then deliver the software turnkey with the final source code. With the 2-to-3-year subscription, hosting, maintenance, support, continuous security hardening and new features every month are included: the software keeps evolving with your needs.
Fixed fee or subscription: how to choose for phase 2?
The fixed fee suits you if you want consolidated software, delivered turnkey for a fixed amount. The subscription, which we recommend, spreads consolidation over 2 to 3 years with no heavy upfront investment, and funds continuous enhancements. It rests on a measured trend: the cost per unit of intelligence is falling fast, and our deliberately cautious working assumption is a fivefold drop every year. At a constant budget, each month therefore buys more development.
Why not use no-code or tools like Make / n8n?
These tools aren't user-friendly enough for internal adoption. Everyone ends up with their own little tool on the side, and industrialization becomes impossible. Custom software shared by the whole company is simpler, more powerful, and it's yours.
Ready to see your idea take shape
in 4 weeks?
Tell us about your project. We'll honestly tell you if the AI-First approach is right — or not.