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fix: disable multi-tab on Safari regardless of mobile or desktop #63

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Merged
michaelbarnes merged 1 commit into from
Jul 8, 2026
Merged

fix: disable multi-tab on Safari regardless of mobile or desktop #63

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22 changes: 17 additions & 5 deletions src/powersync/System.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,17 @@ export function isSafari(): boolean {
);
}

/**
* Decides whether multi-tab support should be enabled.
*
* Multi-tab requires SharedWorker, and is additionally disabled on Safari
* (mobile and desktop) because Safari aggressively suspends background tabs,
* which breaks the shared worker coordination between tabs.
*/
export function isMultiTabEnabled(): boolean {
return typeof SharedWorker !== "undefined" && !isSafari();
}

/**
* Detects OPFS availibility
*
Expand Down Expand Up @@ -92,14 +103,15 @@ export async function isOPFSUsable(): Promise<boolean> {
export function pickVFS(opfsUsable: boolean = isOPFSAvailable()): WASQLiteVFS {
const safari = isSafari();
const mobile = isMobile();
const multiTab = typeof SharedWorker !== "undefined";
const multiTab = isMultiTabEnabled();

// Fall back to IndexedDB (IDBBatchAtomicVFS) when OPFS can't be used:
// - OPFS is not usable at all: no API, or Safari Private Browsing where the
// API exists but createSyncAccessHandle fails (see isOPFSUsable), or
// - mobile Safari (iOS/iPadOS), where OPFS is not supported, or
// - desktop Safari with multi-tab, due to aggressive tab suspension from Safari
const forceIndexedDB = !opfsUsable || (safari && (mobile || multiTab));
// - any Safari: mobile (iOS/iPadOS) lacks OPFS support, and desktop
// Safari's aggressive tab suspension can strand OPFS locks even with
// multi-tab disabled
const forceIndexedDB = !opfsUsable || safari;

const vfs = forceIndexedDB
? WASQLiteVFS.IDBBatchAtomicVFS
Expand All @@ -112,7 +124,7 @@ export function pickVFS(opfsUsable: boolean = isOPFSAvailable()): WASQLiteVFS {
}

const opfsUsable = await isOPFSUsable();
const enableMultiTabs = typeof SharedWorker !== "undefined";
const enableMultiTabs = isMultiTabEnabled();

export const powerSync = new PowerSyncDatabase({
database: new WASQLiteOpenFactory({
Expand Down
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