— Premium Advisory Tech Copmpagny · Paris

We advise on Complex Systems Architecture
& Technology Strategy.

Vesperian architects modern agentic infrastructure for enterprises that intend to lead. We work with a small number of clients each year. On purpose.

Complex Systems Assessment, End-to-end Agentic Systems Architecture, Strategic technical leadership, Targeted Architecture Review, Strategic Technology Advisory.

We not only deliver decks and align your teams. We also deliver working agentic systems, deployed in your environment, owned by your team.

01 — Flagship

Complex Systems Assessment

35–60k€

In-depth architectural diagnostic of complex, strategic or aging information systems. We analyze your current architecture across business, technical and organizational dimensions, and deliver a clear target architecture with a prioritized roadmap. Ideal before major transformations, replatforming, or when architecture becomes a bottleneck. We use AI for AI retro-documentation and retro-engineering.

Complex system

02 — Flagship

Agentic Shift Assessment.™

35–60k€

Complete transition from conversational AI experiments to real production-grade agentic systems. We design the complete architecture, orchestration layers, agent collaboration patterns, governance model and execution roadmap.

Agentic

03 — Recurring

Fractional Chief Architect / CTO

Rate on demand

Part-time strategic technical leadership. We join your team 2 to 3 days per week to guide major technical decisions, architecture direction and transformation programs with an external, experienced perspective.

Part-time strategic technical leadership / CTO

04 — Flash

Targeted Architecture Review

12–20k€

Focused 2-to-4-week deep-dive on a specific architectural challenge — whether it's integration strategy, data platform modernization, frontend/backend decoupling, sovereignty options, or security architecture.

Architecture review

05 — Flash

Strategic Technology Advisory

8–15k€

High-impact executive workshops to support critical technology decisions. Tech trends / R&D, Build vs Buy analysis, technology stack evaluation, AI opportunity assessment, or sovereign cloud strategy.

Strategic tech advisory
34

Complex systems delivered

25

Years of experience

13

Years at OCTO Technology leading Software Engineering practice

100%

Production deployments

Built by people who have shipped Complex Systems and Agentic Architectures.

We are a small team of former CTOs, architects and engineers. We've built Complex Systems and Architectures, shipped agents. We work with a tight roster of clients — not because we have to, but because great AI work demands real depth.

Antoine Chantalou

Founder, Vesperian

With over 13 years at OCTO Technology, he led the Tech Trends program, analyzing emerging technology shifts for large organizations. Specialized in Complex Systems Architecture & Technology Strategy, he helps companies master their most strategic and challenging technical environments. His approach combines deep technical expertise with a clear strategic vision, covering business, architecture, and organizational dimensions simultaneously.

ACH

Systems built to change industries.

View all projects →
01 2025

Agentic Workflow System

Project Athena

Agentic Systems Architecture

02 2025

AI Architecture & Design

Project Helios

Complex Systems Assessment

03 2024

Enterprise Integration

Project Orion

Strategic Technology Advisory

A process designed for precision.

01 — Fullstack scoping

We map your landscape & design target solution

Across three critical dimensions: Business (Vision, high-value use cases, KPIs), Architecture (Target agentic architecture, orchestration and technical stacks), Organization.

02 — Engineer

We build with precision.

Iterative agentic development with full transparency. You see the system evolve. Nothing is a black box. Every decision is explained.

03 — Deploy

We hand over with confidence.

Production deployment, documentation, and knowledge transfer. Your team owns what we've built. We stay until they do.

Words from the teams we've built with.

We think in public.

Agentic AI

May 2025

The agentic shift is here. Most companies aren't ready.

Strategy

April 2025

Why most AI proofs of concept fail — and how to fix them

Engineering

March 2025

Designing for uncertainty: principles for production AI systems

Let's build something that lasts.

We take on a limited number of engagements each year. If you need help on Complex Systems Architecture, Technology Strategy, Agentic Systems, Sovereignty — we'd like to hear from you.

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Response within 48 hours · Paris, working globally