Grapefruit

Custom AI Development

Custom AI development: from proof of concept to production

Grapefruit builds custom AI applications that run in production: generative AI features inside your products, fine-tuned models that write in your brand's voice, and forecasting or prediction tools. We start with an evaluated prototype on your data, then build, integrate, secure and operate the system, and hand you the code.

Signs you need this

  • Off-the-shelf AI tools do not know your products, your data or your tone of voice
  • A proof of concept impressed in a demo but nobody measured its accuracy
  • You need AI inside an existing product, portal or app, not another standalone tool
  • Security requires the system to run in your own cloud tenant
  • You want to own the model, prompts and code rather than rent a black box

What you get

  • Evaluated prototype

    A working proof of concept on your data with an evaluation set, accuracy and hallucination report and a go/no-go recommendation.

  • Model selection and fine-tuning

    The right model per task, and fine-tuning on your content where a general model is not good enough, as we did for UNTOLD's newsletters.

  • Application and integration

    AI features built into your web platform, app or internal tools, with the UX that makes people actually use them.

  • Secure deployment

    Deployment in your cloud tenant or an agreed EU region, access control, logging, cost controls and a documented data flow.

  • Monitoring and handover

    Dashboards for quality, cost and usage, re-evaluation on model updates, and full handover of code, prompts and evaluation sets.

Our method

How we deliver: Discover, Pilot, Scale, Operate

A go/no-go gate between every phase. You fund the next step only when the previous one has earned it.
  1. 011 week

    Discover

    Frame the use case, users and data, agree success metrics and build the evaluation set before writing code.

    • Use case brief
    • Evaluation set
    • Success metrics
  2. 023 to 4 weeks

    Pilot

    Prototype on your data in your tenant, compare models, measure accuracy and cost, and decide go or no-go with evidence.

    • Working prototype
    • Test report
    • Production estimate
  3. 032 to 6 months

    Scale

    Production architecture, integration, guardrails, human review, security testing, AI Act documentation and launch.

    • Production system
    • Documentation pack
    • Team training
  4. 04Ongoing

    Operate

    Monitoring, evaluation re-runs on model updates, model and prompt upgrades, and cost optimisation.

    • Monthly quality and cost report

Ways to start

Most teams start with the AI Prototype Sprint

Fixed scope, clear deliverables, and no obligation to continue.
  1. Fixed scope3 to 4 weeks

    AI Prototype Sprint

    A working AI prototype on your own data in 4 weeks, so you decide with evidence, not slides.

    • Use case framing, evaluation set and success metrics agreed up front
    • Working prototype in your cloud tenant (assistant, agent, content model or document extraction)
    • Accuracy and hallucination test report
    • Security and data flow note
    Plan a prototype sprint
  2. Project2 to 6 months

    AI Solution Build

    From validated prototype to a production AI system your team trusts and runs.

    • Architecture and secure deployment in your cloud tenant
    • Evaluation suite, guardrails and human-in-the-loop design
    • Integration with your systems, monitoring and cost controls
    • EU AI Act documentation pack
    Start a project
  3. OngoingOngoing, monthly

    AI Operations Partner

    Your AI keeps working, stays compliant and keeps improving.

    • Monitoring and evaluation re-runs on every model update
    • Prompt and model upgrades, cost optimisation
    • EU AI Act and GDPR documentation upkeep
    • Quarterly use-case review
    Book a 30-min call
  4. Fixed scope2 to 3 weeks

    Technical & Platform Audit

    Know the real state of your platform before you invest in it.

    • Code quality and architecture review
    • Performance (Core Web Vitals) and security surface review
    • CMS and stack fitness, GDPR and cookie compliance
    • AI readiness of your data and APIs
    Request a technical audit

FAQ

Custom AI Development: questions buyers ask

Should we fine-tune a model or use retrieval over our documents?

Use retrieval when the model needs facts that change, such as policies, products or prices. Fine-tune when it needs a style or a task pattern, such as writing in your brand voice. UNTOLD's newsletters used fine-tuned models for tone. Many systems combine both, and the prototype shows which one pays off.

Who owns the code and the model?

You do. Code, prompts, fine-tuning data, evaluation sets and documentation are yours and handed over. Fine-tuned models live in your account with the model provider or in your cloud, so you are not dependent on us to keep using them.

How do you prevent hallucinations in production?

We cannot promise zero errors, so we measure them. Every system has an evaluation set of real cases run before launch and after every model update, plus guardrails, source citations where facts matter, and human review where mistakes are costly.

Is our data used to train public AI models?

No. We use enterprise API terms or models deployed in your cloud, where your data is not used to train the provider's models. Where fine-tuning is needed, the resulting model is private to your account. Data flows are documented and covered by a data processing agreement.

What drives the cost of a custom AI project?

Integration work and data preparation, more than the model itself. Other drivers are the number of users and languages, security requirements such as on-premises deployment, and the level of human review. We measure these in the prototype so the production estimate is based on evidence.

How fast can we see something working?

A prototype takes 3 to 4 weeks. For UNTOLD, a first version of the newsletter model was ready in 1 week with one AI engineer and one copywriter. Production timelines of 2 to 6 months depend mostly on integrations and approvals.

Which AI models do you work with?

We are model-agnostic and pick per use case based on quality, cost, language support and data residency, including commercial models such as the GPT family and open-weight models when they must run in your own infrastructure.

Start with the AI Prototype Sprint

A working AI prototype on your own data in 4 weeks, so you decide with evidence, not slides. 3 to 4 weeks, fixed scope, no obligation to continue.

We reply within 1 business day, usually the same day. Not ready to talk? Take the free AI assessment.