realtime.signal_stream

The single/_chirp/livemerge stream for signals.

One framework route, auto-registered at freeze when any signal exists, returns anEventStreamwhose generator merges every signal source + every imperativeapp.emitinto one typed update stream. The SSE boundary frames each update as a named event for htmx 2 or as an unnamed targeted<hx-partial>for htmx 4.

Two producer paths feed the one stream:

1. Push / derived —emit() (and the derived cascade) fan a markerChangeEventonto the bus. The merge generator drains the bus, reads the latest cached value, renders it, and yields one typed update.
2. Async sources — a@app.signal(source=...)async generator is pumped by a per-source background task that callsregistry.emitfor each yielded value, so it rides the exact same bus + cache path (coalescing-latest, derived cascade, render isolation) as push emits.

Render happens inrender_for_emit() inside the per-event boundary (oneNonereturn skips that event); a render failure never kills the shared connection. Reading the latest cached value on drain gives coalescing-latest semantics for free — a bus drop under back-pressure is reconciled by the next read.