ANS × DSFR Design System
Nobody asked me to choose between two design systems. It was the real question all along.
- Role
- UI / Product designer, consulting and systems
- Period
- 2025 → 2026
- Context
- French Digital Health Agency (ANS), via Atos / Eviden
- Tools & stack
- DSFR 1.14.x · JSON design tokens · AI-assisted generation · Open source (ansforge)
Mandate
The agency maintained its own design system; the State mandates the DSFR for every public digital service. A consulting-and-systems mission: define how the ANS carries both.
Challenge
Refuse the choice between conformance and identity. Rewriting a full system on top of the DSFR would have doubled maintenance and broken native accessibility at every upstream release.
Solution
An additive theming layer: the DSFR core stays untouched, the ANS identity overlays through 138 two-mode semantic tokens. Technical core open source (ansforge).
Results
A themed system that follows DSFR updates painlessly, and above all a durable criterion: knowing when to theme, and when to stay pure DSFR.
The full story, decision by decision
The agency historically maintained its own design system. In parallel, the State mandates the DSFR for every public digital service. Two systems, one agency. The brief said “install the DSFR”; the real question was: what do you do with the agency’s identity when the State imposes its own? What was needed was a bridge, not a binary choice.
The answer: an additive theming layer. The DSFR stays untouched as the base; the ANS identity is overlaid through tokens and an isolated extension, with a correspondence table guiding migration component by component from the legacy system. The technical core is open source (the ansforge organisation). The most durable output is not a CSS file: it is the criterion that says when to theme, and when not to.
The decisions
Additive over replacement
Rewriting a full design system on top of the DSFR would have doubled maintenance and broken native accessibility at every upstream release. The position held: never touch the DSFR core; overlay through tokens and a dedicated stylesheet. Conformance still comes for free, updates stay painless, and every themed component must justify itself by a real identity need.
Generate tokens with AI, validate with judgment
AI accelerates the combinatorial part: producing and mapping dozens of DSFR-compatible JSON token variants. It does not replace judgment: every batch goes through human validation on contrast (RGAA thresholds), brand fidelity, cross-component coherence and accessibility non-regression. A generated token can be pretty and non-conformant.
Knowing when not to theme
When the certification e-service arrived, the theming tool existed, and the answer was not to use it: pure DSFR, because a sovereign service must be recognised as a State site, not an agency brand. A tool you don’t know when to use is just a gadget; the mission delivered the criterion.