I ran into the same headache—writing an OpenAPI spec and then keeping a separate GitBook in sync felt like twice the work. We ended up trying Apidog, and the biggest win was treating the spec itself as the single source of truth: push an updated spec and the interactive docs (with request/response samples, code snippets, etc.) update automatically. It checks most of the boxes you listed:

Imports/exports OpenAPI smoothly

Markdown + syntax-highlighted code samples

Interactive “try it” UI out of the box

Git sync + CLI for CI/CD deploys

Setup was basically “import spec → tweak theme → done,” and maintenance has been minimal since. Might be worth a look if you want to stop maintaining docs separately from your API specs.

Try https://voiden.md/

As per your needs it's: - Markdown (everything in markdown, including testing and specing APIs) - Let's you write your docs in markdown around the API you're designing/testing - Git-based (in-app terminal) - Code samples supported throug markdown

Plus offline, no login, no lock in, no telemetry.

It's early days so a tad rough around the edges still, but feels like the most natural way of handling APIs I ever used till date.