→ custom AI software development services
Custom AI software development services for serious B2B teams
Bespoke business software where AI is a feature, not the product. Backend, frontend, data, integrations, mobile, ML. Includes our 3-week AI MVP path for funded founders.
Overview
How we approach this work.
Custom AI software development services from Resser cover the full build: backend, frontend, mobile, data, ML, integrations, infrastructure. AI is a feature inside a real software product, not the product itself.
We work with two kinds of teams. Mid-market companies who need bespoke software with AI features built in. Funded founders building an AI-native product from scratch who need a senior team to ship in weeks, not quarters.
Every build starts with eval and a cost model. Discovery week locks the spec. Prototype sprint produces a working slice in your environment. Hardening makes it production-grade. Then you own it.
What we build
Concrete deliverables.
Full custom AI applications
End-to-end product: frontend, backend, data, AI, integrations. Production-grade from day one.
3-week AI MVP
Funded founders and product teams: working slice in 3 weeks, eval live by week 2, deployable by week 3. We say so up front if your scope cannot fit.
AI feature engineering inside existing software
Add AI features into a SaaS, ERP, CRM, or internal tool you already run. Integrated with your data, your auth, your audit log.
Backend services and data pipelines
FastAPI, Django, Node, Go services. Postgres, Redis, Kafka, Clickhouse. ETL into vector stores for RAG.
Eval and observability tooling
We ship the eval suite and the observability dashboard alongside the AI feature. Without them, the AI is a science project, not a product.
Admin and operations tooling
Internal dashboards for prompt versioning, eval review, cost monitoring, and human-in-the-loop approval queues.
How we do it
The process, in four phases.
Discovery week (fixed price)
Spec, eval plan, cost model, timeline. Output is yours either way.
Prototype sprint (2-3 weeks)
Working slice in your environment with real integrations and a live eval suite.
Hardening (2-6 weeks)
Production patterns: eval in CI, cost telemetry, retry logic, prompt versioning, runbook.
Handover or retainer
You own the codebase, the deploy, the runbook. We stay on retainer if useful.
Stack
What we build with.
Languages
TypeScript, Python, Go, Swift, Kotlin, Rust where the bottleneck demands it.
Frameworks
Next.js 15, React 19, FastAPI, Django, Fastify, NestJS, Hono. LangGraph, Vercel AI SDK, LlamaIndex, Pydantic AI for the AI layer.
Data and ML
Postgres + pgvector, Qdrant, Pinecone, Turbopuffer. Anthropic Claude, OpenAI, open-weights via vLLM. Voyage / Cohere / OpenAI embeddings.
Eval and observability
LangSmith, Braintrust, Helicone, Promptfoo, custom eval harnesses.
Outcomes
What we ship.
Fintech compliance review software shipped end-to-end; reviewers handle each case in a fraction of the previous time.
Healthcare intake software: meaningful accuracy lift on the triage classifier with materially lower per-intake cost.
B2B SaaS AI MVP: live in 3 weeks. Converted to full build after eval cleared the success criteria.
References with names available after a scoping call.
Related services
Other places this work shows up.
FAQ
Frequently asked.
What is a 'custom AI MVP' and is it really 3 weeks?
Three weeks from kickoff to a working MVP in your environment is typical for a focused scope. The eval suite is live by week 2; the deployable slice is live by week 3. Stretch projects with custom data work or unusual integrations run 4-6 weeks. We say so on day one if the scope cannot fit in three.
How is this different from off-the-shelf AI tools?
Off-the-shelf AI tools cover generic use cases. Custom AI software is built around your data, your workflow, your existing systems, and your eval criteria. The fit and the integration are the value.
Can you take the project end-to-end or do you only do AI?
End-to-end. We ship the full software product: frontend, backend, mobile, data, integrations, AI, eval, observability, deploy. The AI is a feature inside a real product, not a standalone deliverable.
What does a typical custom AI software build cost?
An AI feature added into existing software: €10,000-€25,000. A custom AI web or mobile app: €50,000-€100,000. A full custom AI product with multiple surfaces and on-prem requirements: €100,000+.
Do you take equity or fixed-fee only?
Fixed-fee or retainer for most engagements. We have taken equity on a small number of early-stage builds when the founder and timing were right. We do not lead with equity offers.
Want to scope this for your project?
Fill the project-estimate form. We reply within one business day with a preliminary scope and a rough budget bracket.