diff --git a/frontend/sync-client/src/index.ts b/frontend/sync-client/src/index.ts
index e7476470..88a47698 100644
--- a/frontend/sync-client/src/index.ts
+++ b/frontend/sync-client/src/index.ts
@@ -21,12 +21,15 @@ export {
 export { Logger, LogLevel, LogLine } from "./tracing/logger";
 export { type SyncSettings, DEFAULT_SETTINGS } from "./persistence/settings";
 export { rateLimit } from "./utils/rate-limit";
-export type { RelativePath, StoredDatabase } from "./persistence/database";
 export type {
-    FileSystemOperations,
-    FileSnapshot
-} from "./file-operations/filesystem-operations";
-export type { PersistenceProvider } from "./persistence/persistence";
+    DocumentId,
+    RelativePath,
+    StoredDatabase,
+    VaultUpdateId
+} from "./persistence/database";
+export type { FileSystemOperations } from "./file-operations/filesystem-operations";
+export type { FileSnapshot } from "./snapshot";
+export type { MetadataPersistenceProvider as PersistenceProvider } from "./persistence/metadata-persistence-provider";
 export type { CursorSpan } from "./services/types/CursorSpan";
 export type { ClientCursors } from "./services/types/ClientCursors";
 export type { NetworkConnectionStatus } from "./types/network-connection-status";
@@ -36,7 +39,7 @@ export type {
 } from "./errors/errors";
 export type { MaybeOutdatedClientCursors } from "./types/maybe-outdated-client-cursors";
 export { DocumentSyncStatus } from "./types/document-sync-status";
-export { SyncClient } from "./sync-client";
+export { SyncClient, type StoredClient } from "./sync-client";
 export type { TextWithCursors, CursorPosition } from "reconcile-text";
 
 export const debugging = {
diff --git a/frontend/sync-client/src/persistence/settings.ts b/frontend/sync-client/src/persistence/settings.ts
index 1b592d65..c3575548 100644
--- a/frontend/sync-client/src/persistence/settings.ts
+++ b/frontend/sync-client/src/persistence/settings.ts
@@ -1,3 +1,4 @@
+import type { RelativePath } from "./database";
 import type { Logger } from "../tracing/logger";
 import { globsToRegexes } from "../utils/globs-to-regexes";
 import { isInternalPath } from "../utils/portable-path";
@@ -68,7 +69,7 @@ export class Settings {
         );
     }
 
-    public isIgnored(path: string): boolean {
+    public isIgnored(path: RelativePath): boolean {
         return (
             isInternalPath(path) ||
             this.ignorePatterns.some((pattern) => pattern.test(path))
@@ -111,17 +112,20 @@ export class Settings {
             await this.saveData(next);
             this.settings = next;
 
-            if (update.ignorePatterns !== undefined)
+            if (update.ignorePatterns !== undefined) {
                 this.ignorePatterns = globsToRegexes(
                     next.ignorePatterns,
                     this.logger
                 );
+            }
 
             return [this.getSettings(), oldSettings] as const;
         });
 
         // Listeners can themselves update settings. Never await them while
         // holding a lock needed by the operation they invoke.
-        if (notify) await this.onSettingsChanged.triggerAsync(...change);
+        if (notify) {
+            await this.onSettingsChanged.triggerAsync(...change);
+        }
     }
 }
diff --git a/frontend/sync-client/src/services/types/EventBatch.ts b/frontend/sync-client/src/services/types/EventBatch.ts
index a3bfb573..feb7ef59 100644
--- a/frontend/sync-client/src/services/types/EventBatch.ts
+++ b/frontend/sync-client/src/services/types/EventBatch.ts
@@ -5,4 +5,4 @@ export type EventBatch = { headEventId: number,
 /**
  * Last event in this page; `head_event_id` is the vault's current head.
  */
-endEventId?: number, events: Array<EventRecord>, };
+endEventId: number, events: Array<EventRecord>, };
diff --git a/frontend/sync-client/src/services/types/PingResponse.ts b/frontend/sync-client/src/services/types/PingResponse.ts
index c38845d2..1bd35bb5 100644
--- a/frontend/sync-client/src/services/types/PingResponse.ts
+++ b/frontend/sync-client/src/services/types/PingResponse.ts
@@ -18,7 +18,7 @@ isAuthenticated: boolean,
  */
 mergeableFileExtensions: Array<string>, 
 /**
- * API version ensuring backwards & forwards compatibility between the client
+ * API version that must match exactly between the client
  * and server.
  */
 supportedApiVersion: number, };
diff --git a/frontend/sync-client/src/snapshot.ts b/frontend/sync-client/src/snapshot.ts
new file mode 100644
index 00000000..f2802233
--- /dev/null
+++ b/frontend/sync-client/src/snapshot.ts
@@ -0,0 +1,20 @@
+import type { CursorPosition } from "reconcile-text";
+import { hash } from "./utils/hash";
+
+export interface FileSnapshot {
+    content: Uint8Array;
+    cursors?: CursorPosition[];
+}
+
+export interface HashedSnapshot extends FileSnapshot {
+    hash: string;
+}
+
+export async function hashSnapshot(
+    snapshot: FileSnapshot
+): Promise<HashedSnapshot> {
+    // Own the bytes so later adapter mutations cannot invalidate the hash
+    const content = new Uint8Array(snapshot.content);
+
+    return { content, cursors: snapshot.cursors, hash: await hash(content) };
+}
diff --git a/frontend/sync-client/src/tracing/sync-history.ts b/frontend/sync-client/src/tracing/sync-history.ts
index 31f77283..a0e0b348 100644
--- a/frontend/sync-client/src/tracing/sync-history.ts
+++ b/frontend/sync-client/src/tracing/sync-history.ts
@@ -88,11 +88,11 @@ export class SyncHistory {
     }
 
     /**
-    * Insert the entry at the beginning of the history list. If the entry
-    * already in the list, it will get moved to the beginning and updated.
-    *
-    * If the entry list is too long, the oldest entry will be removed.
-    */
+     * Insert the entry at the beginning of the history list. If the entry
+     * already in the list, it will get moved to the beginning and updated.
+     *
+     * If the entry list is too long, the oldest entry will be removed.
+     */
     public addHistoryEntry(entry: CommonHistoryEntry): void {
         const historyEntry = {
             ...entry,
diff --git a/frontend/sync-client/src/types/file-manifest-entries.ts b/frontend/sync-client/src/types/file-manifest-entries.ts
index 1e23dd06..c9acccf9 100644
--- a/frontend/sync-client/src/types/file-manifest-entries.ts
+++ b/frontend/sync-client/src/types/file-manifest-entries.ts
@@ -1,3 +1,3 @@
-import type { FileManifest } from "../services/types/FileManifest";
+import type { DocumentId, RelativePath } from "../persistence/database";
 
-export type FileManifestEntries = FileManifest["entries"];
+export type FileManifestEntries = Record<DocumentId, RelativePath>;