Service
Fixed Price Software Development
From discovery through to production, every engagement is scoped, quoted, and delivered at a fixed price. Whether you need to validate an idea, build an MVP, modernise a legacy system, or get a board-ready due diligence report — we deliver in weeks, not months.
The Guarantee
If we don't deliver to the agreed spec, you don't pay. Simple. Every engagement has clear deliverables, acceptance criteria, and a single fixed price — agreed before we write a line of code.
Fixed Price
No timesheets, no hourly billing, no scope creep. You know the cost before we start.
Clear Scope
Detailed spec with acceptance criteria. We both know exactly what “done” looks like.
Money Back
If the deliverables don't meet the agreed spec, you get a full refund. We carry the risk.
How We Engage
Every customer's situation is different. These are the engagement types we offer — each one scoped independently, priced upfront, and delivered to a clear spec.
Discovery & Proposal
The starting point for every engagement
- We scope, estimate, and propose before a line of code is written
- For legacy systems: fixed-price discovery phase with codebase access
- Output: detailed spec, acceptance criteria, and a single fixed price
Rapid Prototype
2–5 days, validate before you commit
- Working prototype to test assumptions and gather early feedback
- Non-production — focused on UX, UI, and concept validation
- De-risks the full build before the big spend
MVP Build
Production-grade delivery in weeks
- Full-stack delivery: frontend, backend, infrastructure, deployment
- Built to extend — no rewrite needed when you scale
- CI/CD, automated testing, and documentation from day one
Post-MVP Milestones
Ongoing feature delivery against a live product
- Each milestone is a new fixed-price engagement with clear scope
- Continuous delivery against a prioritised backlog
- Same guarantees — fixed price, clear spec, money back
Legacy Refactor & Migration
Old tech to modern stack, incrementally
- Any language, any platform — we assess what you have and plan the path
- Incremental migration, not big-bang rewrites
- Data migration with validation, rollback, and zero downtime
API & Integration Builds
Connect your systems, build partner APIs
- Third-party platform integration and custom API development
- System-to-system connectivity and data synchronisation
- Documented, versioned, and production-ready
AI Agents & Automation
Intelligent workflows that work with your data
- Bespoke AI agents, LLM integration, and RAG pipelines
- Process automation that eliminates manual, repetitive work
- Built with guardrails — reliable, auditable, and safe
Technical Due Diligence
For VC, PE, and M&A transactions
- Architecture, code quality, security, scalability, and IP assessment
- Board-ready report with RAG-rated findings and recommendations
- AI/ML claims validation and technology risk quantification
Security Assessments
Infrastructure, application, and policy
- ISO 27001, Cyber Essentials, and GDPR alignment review
- Vulnerability assessment and penetration testing coordination
- Prioritised remediation roadmap with severity-rated findings
What We Work With
Technology-agnostic. We work across languages, frameworks, and platforms.
How It Works
We carry the delivery risk, so we control the delivery process. We can't commit to a fixed price if we're bottlenecked by processes outside our control. Code review? Absolutely — at milestone sign-off, or monitored along the way. But not as a gate on every commit.
Discovery
We resolve all design decisions, scope, and acceptance criteria upfront — so the build is completely de-coupled from your team. For greenfield projects, we scope from your brief. For legacy systems, we run a fixed-price discovery phase — typically a few days — with access to your codebase to map the landscape first. All code access is demonstrably deleted afterwards.
Prototype
Where appropriate, we build a working prototype to validate the approach before committing to the full build. You see something real before the big spend.
Build milestones
The build is split into milestones, each with a concrete delivery. You see working software at each stage — not just at the end.
Productionisation
Final hardening — extended testing, security controls, deployment, and documentation. Full source code and IP handed over. You own everything, no lock-in.
Warranty & beyond
Every delivery includes a warranty period — bugs against the agreed spec are fixed at no cost. After that, ongoing support is either a new fixed-price engagement or rolls into a Fractional CTO retainer.
Why Mangrove
- AI-native engineering — we use AI throughout our development process, delivering faster without compromising quality
- Security built in — with 20+ years in cybersecurity, security is part of the architecture, not an afterthought
- Full ownership — you get the source code, documentation, and complete IP. No vendor lock-in
- Production-grade from day one — CI/CD, automated testing, infrastructure as code, and security scanning on every project
Have a project in mind?
Send us your spec or idea. We'll come back with a clear scope and fixed-price proposal — no obligation.