diff --git a/.changeset/defer-subduction-connection.md b/.changeset/defer-subduction-connection.md
new file mode 100644
index 00000000..07e49dfb
--- /dev/null
+++ b/.changeset/defer-subduction-connection.md
@@ -0,0 +1,6 @@
+---
+"@inkandswitch/patchwork": patch
+"@inkandswitch/patchwork-bootloader": patch
+---
+
+Patchwork loads persisted Subduction data before opening its sync connection, with a `syncServers.defer` option to opt out.
diff --git a/core/bootloader/src/automerge-worker.ts b/core/bootloader/src/automerge-worker.ts
index 64e2d5d7..027750cd 100644
--- a/core/bootloader/src/automerge-worker.ts
+++ b/core/bootloader/src/automerge-worker.ts
@@ -39,6 +39,7 @@ import {
 
 import { DEFAULT_CLASSIC_SYNC_SERVER } from "./sync-config.js";
 import { keyhiveStorageName, storagePrefix } from "./storage.js";
+import { DeferredWebSocketEndpoint } from "./deferred-websocket-endpoint.js";
 import {
   HANDOFF_CHANNEL,
   SYNCSTATE_CHANNEL,
@@ -56,6 +57,7 @@ import {
 declare const __SYNC_SERVER__: {
   url: string;
   keyhive?: SyncServerSelection;
+  defer?: boolean;
 };
 
 const syncServer =
@@ -194,15 +196,34 @@ function pushSyncState(message: SyncStateDocMessage): void {
 }
 
 const subductionPortProvider = makePortProvider();
+let resolveSubductionStorageLoad: (() => void) | undefined;
+const subductionStorageLoaded = syncServer.defer
+  ? new Promise<void>((resolve) => {
+      resolveSubductionStorageLoad = resolve;
+    })
+  : undefined;
 
 // Memoized so a construction retry reuses the endpoint instead of leaking one
 // per attempt.
-let subductionEndpoints: WorkerWebSocketEndpoint[] | null = null;
-function getSubductionEndpoints(): WorkerWebSocketEndpoint[] {
+type SubductionEndpoint = {
+  readonly url: string;
+  connect(): ReturnType<WorkerWebSocketEndpoint["connect"]>;
+  shutdown?(): void;
+};
+
+let subductionEndpoints: SubductionEndpoint[] | null = null;
+function getSubductionEndpoints(): SubductionEndpoint[] {
   return (subductionEndpoints ??= [
-    new WorkerWebSocketEndpoint(syncServer.url, {
-      worker: subductionPortProvider.source,
-    }),
+    (subductionStorageLoaded
+      ? new DeferredWebSocketEndpoint(
+          new WorkerWebSocketEndpoint(syncServer.url, {
+            worker: subductionPortProvider.source,
+          }),
+          subductionStorageLoaded
+        )
+      : new WorkerWebSocketEndpoint(syncServer.url, {
+          worker: subductionPortProvider.source,
+        })),
   ]);
 }
 
@@ -237,6 +258,20 @@ async function setUpRepoHive(): Promise<RepoHive> {
     ? await buildKeyhiveRepo(syncServer.keyhive)
     : await buildPlainRepo();
 
+  if (resolveSubductionStorageLoad) {
+    const release = resolveSubductionStorageLoad;
+    resolveSubductionStorageLoad = undefined;
+    void (async () => {
+      const subduction = await built.repo.subduction;
+      await Promise.all(
+        (await subduction.sedimentreeIds()).map((id) => subduction.getBlobs(id))
+      );
+      log("subduction storage loaded");
+    })()
+      .catch((error) => log("subduction storage load failed", error))
+      .finally(release);
+  }
+
   (self as any).repo = built.repo;
   if (built.hive) (self as any).hive = built.hive;
   if (built.identity) (self as any).syncIdentity = built.identity;
diff --git a/core/bootloader/src/deferred-websocket-endpoint.ts b/core/bootloader/src/deferred-websocket-endpoint.ts
new file mode 100644
index 00000000..cc71941b
--- /dev/null
+++ b/core/bootloader/src/deferred-websocket-endpoint.ts
@@ -0,0 +1,30 @@
+type WebSocketEndpoint<Transport> = {
+  readonly url: string;
+  connect(): Promise<Transport>;
+  shutdown?(): void;
+};
+
+/**
+ * Defers opening a WebSocket until the supplied startup work has completed.
+ */
+export class DeferredWebSocketEndpoint<Transport>
+  implements WebSocketEndpoint<Transport>
+{
+  constructor(
+    private endpoint: WebSocketEndpoint<Transport>,
+    private ready: Promise<void>
+  ) {}
+
+  get url(): string {
+    return this.endpoint.url;
+  }
+
+  async connect(): Promise<Transport> {
+    await this.ready;
+    return this.endpoint.connect();
+  }
+
+  shutdown(): void {
+    this.endpoint.shutdown?.();
+  }
+}
diff --git a/core/patchwork/src/repo.ts b/core/patchwork/src/repo.ts
index bc1231fb..fe02022e 100644
--- a/core/patchwork/src/repo.ts
+++ b/core/patchwork/src/repo.ts
@@ -29,6 +29,7 @@ const log = debug("patchwork:setup:repo");
 declare const __SYNC_SERVER__: {
   url: string;
   keyhive?: SyncServerSelection;
+  defer?: boolean;
 };
 const syncServer =
   typeof __SYNC_SERVER__ !== "undefined"
diff --git a/core/patchwork/src/site-kit/options.ts b/core/patchwork/src/site-kit/options.ts
index f8cfbe03..f4c81ff3 100644
--- a/core/patchwork/src/site-kit/options.ts
+++ b/core/patchwork/src/site-kit/options.ts
@@ -48,6 +48,8 @@ export type PatchworkKeyhiveSyncServer =
 export type PatchworkSyncServersOptions = {
   /** wss:// URL for the legacy automerge-repo sync-server channel (connected on demand via connectClassicSync). Default: wss://sync3.automerge.org. Pass false to skip its preconnect hint. */
   classic?: string | false;
+  /** Wait for persisted Subduction data before opening the primary sync connection. Defaults to true. */
+  defer?: boolean;
 } & PatchworkPrimarySyncServerOptions;
 
 export const DEFAULT_TITLE = "Patchwork";
diff --git a/core/patchwork/src/site-kit/sync-servers.ts b/core/patchwork/src/site-kit/sync-servers.ts
index 98fb5d93..02de8f81 100644
--- a/core/patchwork/src/site-kit/sync-servers.ts
+++ b/core/patchwork/src/site-kit/sync-servers.ts
@@ -14,6 +14,7 @@ export const DEFAULT_SYNC_SERVERS = {
 export function resolvePrimarySyncServer(options: PatchworkSiteOptions): {
   url: string;
   keyhive?: SyncServerSelection;
+  defer?: boolean;
 } {
   const servers = options.syncServers || undefined;
   if (servers?.keyhive) {
@@ -21,16 +22,19 @@ export function resolvePrimarySyncServer(options: PatchworkSiteOptions): {
       return {
         keyhive: servers.keyhive,
         url: DEFAULT_SYNC_SERVERS[servers.keyhive],
+        defer: servers.defer ?? true,
       };
     }
     const { url, ...identity } = servers.keyhive;
     return {
       keyhive: identity,
       url,
+      defer: servers.defer ?? true,
     };
   }
   return {
     url: servers?.subduction ?? DEFAULT_SYNC_SERVERS.subduction,
+    defer: servers?.defer ?? true,
   };
 }
 
@@ -47,7 +51,7 @@ export function resolveSyncServers(options: PatchworkSiteOptions): string[] {
   if (options.syncServers === false) return [];
   const primary = resolvePrimarySyncServer(options);
   const classic = options.syncServers?.classic ?? DEFAULT_SYNC_SERVERS.classic;
-  const origins = [primary.url];
+  const origins = primary.defer ? [] : [primary.url];
   if (classic) origins.push(classic);
   return origins.map(wsToHttpOrigin);
 }