Documentation rots when it lives outside the change that invalidates it, and 2026's tooling made the alternative practical: docs versioned with code, reviewed in the same pull request, and deployed by the same pipeline. The shift is cultural more than technical — docs become part of the definition of done.
Co-locate with the code
Documentation stored beside the service it describes, reviewed in the same pull request, stays synchronized with reality by construction. Docs in a separate system drift the moment the first unreviewed change ships.
Generate the mechanical parts
API references, configuration tables, and command help should be generated from source. Generated sections never disagree with the code, which frees human writing for the why rather than the what.
Measure staleness
Track when each document was last touched alongside the code it covers. A dashboard of aging docs turns vague unease about documentation into a prioritized list you can actually work through.
The mechanics that make it stick
Keep docs in the repository next to what they describe, write them in lightweight markup reviewed alongside code changes, and generate the parts that are derivable — API references from OpenAPI specs, command help from parsers, architecture diagrams from code where tooling allows. Review becomes the enforcement point: a pull request that changes behavior without updating its documentation gets the same comment any other gap would receive.
Writing docs people actually use
Code-as-docs culture needs editorial standards or it produces noise: docs should answer the question a new engineer will type into search, include runnable examples tested in CI, and be pruned when they stop earning visits. The most telling metric is search queries with no results — those are the docs you owe. Pair generated reference material with short handwritten guides that explain intent, because nobody learns a system from signatures alone.
Key takeaways
- Docs live in the repo and are reviewed in the same PR.
- Generate the derivable; handwrite the why and the runnable example.
- Zero-result search queries are your documentation backlog.
Final thoughts
Documentation as code succeeds because it inherits the discipline already applied to everything else in the repository — review, versioning and CI — and the teams that adopt it report the familiar onboarding question becoming rare.