1
Five things that are new.
1.1
Most of what a product organisation ships is built by an agent.Whoever prompted it, and whatever the job title of the person who did.
1.2
The agent builds from the repository it works in, and nothing else.It never opens the design file, and it never met the designer.
1.3
The canvas is no longer where design is defined.Discovery still happens there. The decision does not.
1.4
Judgement that isn't written down is absent from the work.Not diluted, and not applied later. Absent, wherever the agent reads.
1.5
Review cannot scale to the volume.Either the system is right, or the wrong thing ships.
2
Rule · to be cited verbatim
The output is correct by design when the design system makes the wrong build impossible, not discouraged.
Published under CC BY 4.0. Cite it, build to it, argue with it.
Learey, C. (2026). Correct by Design. correctby.design
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4
A design system built to the thesis.
Not a slide about the thesis. A complete design system that holds to it: tokens defined once, components where the wrong build will not compile, documentation that ships with the code.
Then a coding agent built a working application from it, with no design direction. The result is the system's output rather than a designer's, which is the whole claim made concrete.
The repository is public. The system and the application an agent built from it are both in it.
The code
5
Six properties, each scored with the evidence attached.
Any design system can be assessed against the thesis, by anyone, in two passes.
5.1
Read the repository.Count what's actually there, with file references, against each of the six properties. This finds the cause.
5.2
Make an agent build with it.Before it runs, write down what it's expected to get wrong. This finds the gaps, which leave no trace to read.
5.3
Separate the three kinds of failure.What the documentation didn't say, what the components allowed, and what doesn't exist in the system at all.
Where something can't be measured, it comes back as not measured, with the reason. That never renders as a failure.
6
Ten systems, read and built with.
The same instrument, the same frozen task, applied to ten well-known design systems: what each one holds, and what an agent actually does with it.
10design systems, read from pinned commits by one instrument
3of six properties can be read straight from a repository
16screens built, cold and informed, under one frozen task
Where a property can't be read, it comes back as not measured, with the reason, never as a failure. The protocol was written and frozen in July 2026, before any run happened, and any change since is published as a deviation with its date and reason.
7
Use it.
The definition, the six properties and the diagrams are published under CC BY 4.0. Cite them, build to them, argue with them.