HTTP headers

The two halves only meet on redirect following, through these headers:

Header	Direction	Set by	Read by
Turbo-Frame	request	Turbo, on frame requests: the id of the frame	TurboManager, the turbo_frame filter, TurboHandler
X-Turbo-Request-Id	request	Turbo 8+, on its fetch requests (Turbo 7 does not send it)	TurboManager::isTurboRequest(), for DELETE redirects
Turbo-Frame-Follow-Redirect	request	TurboHandler, value 1, for frames with data-turbo-follow-redirect	TurboManager::followTurboFrameRedirect(), TurboFrameListener
Turbo-Location	response	TurboFrameListener, on a 204 replacing a redirect: the original Location	TurboHandler, which calls onRedirect

Any backend can drive TurboHandler by answering Turbo-Location, and any client can use TurboFrameListener by following it: see Without @silarhi/turbo.