File size: 5,270 Bytes
c453128 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 | /**
* SingleTabGate — allow only ONE live AgentGUI tab/window per browser.
*
* Two open copies of the app are actively harmful, not just wasteful: each
* desk's live activity stream is a single server-side queue, so two activity
* WebSockets steal alternating tokens from each other (fragmented chat), and
* two FloorManagers patrol/audit/nudge the same desks concurrently.
*
* Mechanism: the Web Locks API. The first tab acquires an exclusive lock and
* holds it for its lifetime (auto-released by the browser on close/crash).
* Any later tab fails the `ifAvailable` probe, renders a blocking overlay
* instead of the app, and queues a waiting lock request — so it activates
* automatically the moment the holder goes away. "Use here instead" broadcasts
* a takeover: the holder releases its lock (unmounting the app and closing all
* its WebSockets) and shows a "moved to another tab" screen.
*
* Browsers without `navigator.locks` (non-secure contexts, very old engines)
* skip gating entirely — same behavior as before this component existed.
*/
import { useEffect, useRef, useState, type ReactNode } from "react";
const LOCK_NAME = "agent-gui-single-tab";
const TAKEOVER_CHANNEL = "agent-gui-tab-takeover";
type GateStatus = "pending" | "active" | "blocked" | "deactivated";
const hasLocks = typeof navigator !== "undefined" && "locks" in navigator;
export default function SingleTabGate({ children }: { children: ReactNode }) {
const [status, setStatus] = useState<GateStatus>(hasLocks ? "pending" : "active");
// Resolving this promise releases the held lock (lets another tab take over).
const releaseRef = useRef<(() => void) | null>(null);
useEffect(() => {
if (!hasLocks) return;
const abort = new AbortController();
const bc = new BroadcastChannel(TAKEOVER_CHANNEL);
let dead = false;
// Queue for the lock. Granted immediately if free; otherwise this waits
// until the current holder closes or releases, then activates this tab.
navigator.locks
.request(LOCK_NAME, { signal: abort.signal }, async () => {
if (dead) return;
setStatus("active");
await new Promise<void>((resolve) => { releaseRef.current = resolve; });
})
.catch(() => { /* request aborted on unmount */ });
// If someone else already holds the lock, our request above is parked in
// the queue — flip to the blocked overlay (never downgrade an active tab).
navigator.locks.query().then((state) => {
if (dead) return;
if (state.held?.some((l) => l.name === LOCK_NAME)) {
setStatus((s) => (s === "pending" ? "blocked" : s));
}
}).catch(() => {});
bc.onmessage = (e) => {
// Another tab requested takeover. Only the holder reacts: release the
// lock (the waiter is granted next) and go passive. BroadcastChannel
// never echoes to the sender, so the taker can't deactivate itself.
if (e.data === "takeover" && releaseRef.current) {
releaseRef.current();
releaseRef.current = null;
setStatus("deactivated");
}
};
return () => {
dead = true;
abort.abort();
releaseRef.current?.(); // StrictMode remount / real unmount: free the lock
releaseRef.current = null;
bc.close();
};
}, []);
if (status === "active") return <>{children}</>;
if (status === "pending") return null; // lock grant resolves in microseconds
const blocked = status === "blocked";
return (
<div style={{
height: "100vh", display: "flex", flexDirection: "column",
alignItems: "center", justifyContent: "center", gap: 14,
background: "var(--bg)", color: "var(--text)", textAlign: "center", padding: 24,
}}>
<div style={{ fontSize: 42 }}>{blocked ? "🔒" : "👋"}</div>
<div style={{ fontSize: 18, fontWeight: 600 }}>
{blocked
? "AgentGUI is already open in another tab or window"
: "This session moved to another tab"}
</div>
<div style={{ color: "var(--text-dim)", maxWidth: 440, fontSize: 13, lineHeight: 1.5 }}>
{blocked
? "Running two copies splits the live agent streams between them and " +
"doubles manager patrols, so only one tab can be active at a time. " +
"Close the other tab to continue here, or take over now."
: "Another tab took over this AgentGUI session. Reload to claim it back."}
</div>
{blocked ? (
<button
onClick={() => {
// The waiting lock request from the effect is already queued; the
// holder releases on this message and we activate automatically.
const c = new BroadcastChannel(TAKEOVER_CHANNEL);
c.postMessage("takeover");
c.close();
}}
style={btnStyle}
>
Use here instead
</button>
) : (
<button onClick={() => location.reload()} style={btnStyle}>
Reload & claim this tab
</button>
)}
</div>
);
}
const btnStyle: React.CSSProperties = {
background: "var(--accent2)", color: "#fff", border: "none",
borderRadius: "var(--radius)", padding: "10px 18px", fontSize: 14,
fontWeight: 600, cursor: "pointer",
};
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