Better development with AI: a look back at a concrete experiment
On February 5, SNCF Connect & Tech was at the Cantine X French Tech Nantes to share the Spec-Driven Development (SDD) experiment, its practical lessons, the methods tested and the vision for moving from trial to standard practice.

Faced with the rise of generative AI tools, SNCF Connect & Tech is exploring new practices to make software development more predictable and robust.
At this meeting organized with La Cantine, Emmanuel Cordente, CTO at SNCF Connect & Tech shared his feedback on an internal Spec-Driven Development experiment, alongside Julien Landuré CTO at TechTown and Florian Perréon, CTO at Guest Suite.
A context of transforming uses
The AI program run by SNCF Connect & Tech aims to support all the company's business lines. After deploying development assistants, the team observed the limits of the vibe coding model: variability in results, a complex context to maintain in exchanges with the I, and the need for clear documentation to stabilize delivery. It is in this context that documentation once again becomes the source of truth.
We've shifted into a mode where documentation has once again become the center... In other words, the real source of truth, and the only source of truth.
EmmanuelCordente
CTO, SNCF Connect & Tech
This realisation naturally led to SDD, which structures development around solid specifications before utilising AI agents.
“The important thing is to contextualise AI in order to obtain deterministic results, relying on standards and documentation that enable code agents to be consistent with the existing base, while keeping an eye on product security and quality,” Julien Landuré, CTO at Tech Town.
SDD experimentation at SNCF Connect & Tech
The experimentation lasted five weeks, divided into two phases: two weeks dedicated to product and specifications, and three weeks to implementation. During the first two weeks, a product owner/developer duo worked side by side, isolated, to refine the product vision and build useful documentation before any code generation.
This atypical approach favors monitoring, tool evaluation and iteration, but how do you do this when the ecosystem is in perpetual motion? For Emmanuel Cordente: "In a world where every new product is presented as revolutionary, you have to test it to really understand what it can contribute."
Continuing experimentation
Although tangible gains have already been made, the project has yet to be validated for widespread use. The experiment has shown that it is possible to accelerate delivery while producing a high-quality documentary heritage, useful for on-boarding new collaborators and improving testing and maintenance. However, the adaptability of the model to other projects and to the specific needs of different teams needs to be confirmed.
"The long-term goal is to move these approaches from the IA program to standard engineering practice. This ambition marks the transition from an isolated test to a lasting transformation of practices", Emmanuel Cordente.
Discover the replay of the meeting at La Cantine de Nantes
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