Shared memory and context tools for agentic work.
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/*
* pollGuard — the anti-stacking heart of the status pollers.
*
* Framework-free and DOM-free (no React, no timers, no `document`) so the
* no-stack property is unit-testable deterministically — the repo's
* `liveRefreshCore` / `scanMachine` pure-core pattern. The React shells that wire
* it to `setInterval` + visibility live in useRunnerdStatus / useUniverse /
* usePresences / useMissions.
* The disease it cures: a poller that fires a fresh request every tick STACKS
* requests without bound when the server stalls (observed live: 19 pending health
* polls while the owner was SIGSTOPped). This guard makes stacking impossible —
* `begin()` hands out a fresh AbortController ONLY when none is in flight, and
* returns `null` (SKIP this tick) while one still is. `settle(controller)` frees
* the slot when THAT request finishes; `abort()` cancels the in-flight request on
* teardown and frees the slot so the guard is immediately reusable.
*/
export interface PollGuard {
/**
* Start a poll iff none is in flight. Returns a fresh `AbortController` whose
* `signal` the fetch must carry (so `abort()` can cancel it), or `null` when a
* poll is already in flight — the caller SKIPS this tick, and nothing stacks.
begin(): AbortController | null;
* Free the slot for the request `begin()` handed out. Identity-checked: a stale
* settle (from a request that was already `abort()`ed and superseded) is a no-op,
* so it can never free a newer in-flight poll's slot.
settle(controller: AbortController): void;
/** Abort any in-flight request and free the slot (teardown / disable / dep change). */
abort(): void;
/** True while a poll is in flight (a `begin()` right now would return `null`). */
readonly inFlight: boolean;
}
export function createPollGuard(): PollGuard {
let current: AbortController | null = null;
return {
begin() {
if (current !== null) return null; // in flight → skip this tick (no stacking)
current = new AbortController();
return current;
},
settle(controller) {
// Only the CURRENT request may free the slot — a stale settle from a
// superseded (aborted) request must not clear a newer poll.
if (current === controller) current = null;
abort() {
current?.abort();
current = null;
get inFlight() {
return current !== null;
};
