Multiple routers¶

RouterVersioner(
    app=app,
    routers=[users_router, products_router],
    version_format=VersionFormat.SEMVER,
).versionize()

Both routers are versioned together, sharing the same prefix tree, so this is the way to split a versioned API across modules without creating a second RouterVersioner.

Sharing one app across several RouterVersioner instances only makes sense for one reason: mixing version_format values, SemVer for one group of routes and CalVer for another, on the same app. Splitting modules that share a version_format doesn't need a second instance; pass them all to one RouterVersioner via routers=[...] instead (see multi_router_app.py). If you do share an app across instances, one rule is enforced: every instance needs its own prefix_format/latest_prefix. Two instances that resolve to the same prefix would otherwise overwrite each other's docs/openapi routes at the same path; this raises RuntimeError. /versions (see Version discovery) doesn't need this coordination: every instance's contribution is aggregated into the same endpoint automatically.

For modules that genuinely don't need to coordinate at all, mount them as separate FastAPI sub-applications instead (see Reverse proxy and sub-apps).