Turbo Frame navigation falls back to full page visit

The goal is to determine why navigation from a link inside a Turbo Frame results in a full document visit instead of a partial frame replacement.

Turbo Drive intercepts the click and expects the server HTML to include a <turbo-frame> element whose id matches the originating frame. If that element is absent or mismatched, Turbo discards the partial response and performs a full page visit. This behavior is documented for current Turbo releases, but the exact major version in use has not been confirmed, and frame semantics can differ between releases.

Because no console error is guaranteed for a missing frame target, the fallback can resemble a server error or network failure. The uncertainty is whether the response markup, the frame identifier, or Turbo configuration is responsible.

Which response attribute or markup condition triggers the full-page fallback? Does the server response need to wrap content in a <turbo-frame id="frame-id"> element matching the source frame? Can disabling Turbo on the link isolate whether Turbo Drive caused the full visit?