Streaming Flight

Flight navigation resolves the whole tree before sending it. Streaming Flight sends it progressively, the same way Suspense streaming works for HTML — but over the data protocol, so client-driven navigation shows fallbacks immediately and fills them in as data resolves.

React devs: this is the RSC stream's out-of-order rows, over plain NDJSON instead of React's binary Flight wire.

PHP devs: it's the same Fiber scheduler as HTML Suspense streaming, but each chunk is a piece of the tree as data, not rendered HTML.

The protocol: NDJSON

Flight::stream() emits newline-delimited JSON:

1. The shell row — the serialized tree, with each pending Suspense boundary replaced by a placeholder ["$","div",{"id":"F:<n>"},[<fallback>]].
2. A boundary row for each boundary as it resolves, out of order: {"b": <n>, "tree": <resolved tree>}.

use Attitude\PHPX\Server\Flight;

if (Flight::wantsStream()) {           // ?__flight_stream=1 | X-Flight-Stream: 1 | Accept: application/x-ndjson
    Flight::stream($viewContent, $components);
}

A two-boundary page where the second declared boundary is faster streams like this:

["$","main",null,[["$","div",{"id":"F:0"},[["$","em",null,["load-a"]]]],["$","div",{"id":"F:1"},[["$","em",null,["load-b"]]]]]]
{"b":1,"tree":[["$","p",{"id":"done-b"},["B"]]]}
{"b":0,"tree":[["$","p",{"id":"done-a"},["A"]]]}

Boundary 1 arrives before 0 — out of order, as soon as its data is ready. Nested boundaries work too: resolving one can reveal more, which stream in turn.

The client reader

streamNavigate(url) (in examples/todo/src/client/flight.ts) reads the stream row by row:

const reader = res.body.getReader()
// first row -> build the view with fallbacks in place
root.replaceChildren(toNode(shell)); mountIslands(root)
// each later row -> patch its boundary as it arrives
slot = document.getElementById('F:' + row.b)
slot.replaceChildren(toNode(row.tree)); mountIslands(slot)

It reuses the same toNode DOM builder and mountIslands from Flight navigation, so islands inside a streamed boundary boot as soon as that boundary lands.

Relationship to the other streaming

	Transport	Chunks are
Suspense streaming	HTML + <template> swap	rendered HTML
Streaming Flight	NDJSON rows	serialized tuple trees

Both are driven by the same Fiber scheduler; they differ only in what they put on the wire and who assembles the DOM (the browser vs. the client runtime).