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I have a small bit of code in which I'm using a proxy:

function proxy(initial) {
  const {attach, stream} = makeProxy();
  return [stream.startWith(initial), attach];
}

export default function flatScan(f, initial) {
  return stream => {
    const [proxyState$, fulfill] = proxy(initial);
    const state$ = most.just(proxyState$).join(); // prevent proxy disposal bug
    const initialize = (x, state) => f(state, x, state$);
    const nextState$ = sample(initialize, stream, state$)
      .join()
      .thru(fn$ => sample((fn, state) => fn(state), fn$, state$))
      .startWith(initial)
      .multicast();
    fulfill(nextState$);
    return state$;
  };
}

Notice the commented line where I'm wrapping the proxy stream in another stream and then flattening it again. If I don't do this, and a second observer attaches to the proxy before the previous observer has disposed itself, then the original observer will still try to call dispose as it should, but the proxy will continue emitting events to that observer's sink, even after disposal. Somehow wrapping the proxy in another dummy operator solves the problem.

If you need an active use case in order to figure this out, let me know and I'll help you set up a working copy of my project so you can see it happening.

I've tried several ways to close the cycle with Proxy and they all seem to result in a stack overflow. Perhaps this sets up an infinite loop in the stream control logic?

This example counts to 5 the hard way, but it's a good example of the process I'm trying to model (shutting down a harmonic oscillator when it comes to rest). y$ emits a single true when the accumulated sum reaches 15. Closed-loop this would shut x$ down.

When the attach line is commented out you can see this in the console log. When it not commented out Chrome just sits there for a few seconds until devtools disconnects. I presume this crash is from the stack filling up with an endless stream of handshaking.

import { proxy }     from 'most-proxy'
import { periodic }  from 'most'

const trigger$ = periodic(1000, 1)
  .scan( (s, t) => s + t, 0)
  .take(10)

const { stream: yProxy$, attach: attachY } = proxy()

const x$ = trigger$.until(yProxy$)

const y$ = x$
  .scan( (s, x) => s + x, 0 )
  .map( sum => sum >= 15)
  .filter( b => b )
  .skipRepeats()

attachY(y$)

x$.observe( x => console.log(x))
y$.observe( x => console.log(x))

[edit] - Perhaps some sort of air-gap or break in the handshaking protocols is needed in the proxy stream to make the stream graph appear acyclic to the scheduler?

Released code works fine, but when I downloaded the repo (to update the most version number in package.json) and ran npm install I got a whole bunch of errors like this:

node_modules/most/type-definitions/most.d.ts(7,72): error TS2304: Cannot find name 'Promise'.