diff --git a/frontend/sync-client/src/consts.ts b/frontend/sync-client/src/consts.ts
index dbab3de0..8fa50f47 100644
--- a/frontend/sync-client/src/consts.ts
+++ b/frontend/sync-client/src/consts.ts
@@ -2,3 +2,4 @@ export const TIMEOUT_FOR_MERGING_HISTORY_ENTRIES_IN_SECONDS = 60;
 export const DIFF_CACHE_SIZE_MB = 2;
 export const MAX_LOG_MESSAGE_COUNT = 100000;
 export const MAX_HISTORY_ENTRY_COUNT = 5000;
+export const SUPPORTED_API_VERSION = 1;
diff --git a/frontend/sync-client/src/index.ts b/frontend/sync-client/src/index.ts
index 81b7f7ff..f09d339c 100644
--- a/frontend/sync-client/src/index.ts
+++ b/frontend/sync-client/src/index.ts
@@ -25,6 +25,8 @@ export type { PersistenceProvider } from "./persistence/persistence";
 export type { CursorSpan } from "./services/types/CursorSpan";
 export type { ClientCursors } from "./services/types/ClientCursors";
 export type { NetworkConnectionStatus } from "./types/network-connection-status";
+export type { ServerVersionMismatchError } from "./services/server-version-mismatch-error";
+export type { AuthenticationError } from "./services/authentication-error";
 export type { MaybeOutdatedClientCursors } from "./types/maybe-outdated-client-cursors";
 export { DocumentSyncStatus } from "./types/document-sync-status";
 export { SyncClient } from "./sync-client";
diff --git a/frontend/sync-client/src/services/authentication-error.ts b/frontend/sync-client/src/services/authentication-error.ts
new file mode 100644
index 00000000..9daa1937
--- /dev/null
+++ b/frontend/sync-client/src/services/authentication-error.ts
@@ -0,0 +1,6 @@
+export class AuthenticationError extends Error {
+	public constructor(message: string) {
+		super(message);
+		this.name = "AuthenticationError";
+	}
+}
diff --git a/frontend/sync-client/src/services/server-config.ts b/frontend/sync-client/src/services/server-config.ts
index b5ba5b15..b3107d10 100644
--- a/frontend/sync-client/src/services/server-config.ts
+++ b/frontend/sync-client/src/services/server-config.ts
@@ -1,9 +1,13 @@
-import { createPromise } from "../utils/create-promise";
+import { SUPPORTED_API_VERSION } from "../consts";
+import { AuthenticationError } from "./authentication-error";
+import { ServerVersionMismatchError } from "./server-version-mismatch-error";
 import type { SyncService } from "./sync-service";
 import type { PingResponse } from "./types/PingResponse";
 
 export interface ServerConfigData {
 	mergeableFileExtensions: string[];
+	supportedApiVersion: number;
+	isAuthenticated: boolean;
 }
 
 export class ServerConfig {
@@ -15,6 +19,22 @@ export class ServerConfig {
 	public async initialize(): Promise<void> {
 		this.response = this.syncService.ping();
 		this.config = await this.response;
+
+		if (this.config.supportedApiVersion !== SUPPORTED_API_VERSION) {
+			const shouldUpgradeClient =
+				this.config.supportedApiVersion > SUPPORTED_API_VERSION;
+			throw new ServerVersionMismatchError(
+				`Unsupported API version: ${this.config.supportedApiVersion}. Consider upgrading the ${
+					shouldUpgradeClient ? "client" : "sync-server"
+				} to ensure compatibility.`
+			);
+		}
+
+		if (!this.config.isAuthenticated) {
+			throw new AuthenticationError(
+				"Failed to authenticate with the sync-server."
+			);
+		}
 	}
 
 	public async checkConnection(forceUpdate = false): Promise<{
diff --git a/frontend/sync-client/src/services/server-version-mismatch-error.ts b/frontend/sync-client/src/services/server-version-mismatch-error.ts
new file mode 100644
index 00000000..0f37fc6f
--- /dev/null
+++ b/frontend/sync-client/src/services/server-version-mismatch-error.ts
@@ -0,0 +1,6 @@
+export class ServerVersionMismatchError extends Error {
+	public constructor(message: string) {
+		super(message);
+		this.name = "ServerVersionMismatchError";
+	}
+}
diff --git a/frontend/sync-client/src/services/types/PingResponse.ts b/frontend/sync-client/src/services/types/PingResponse.ts
index ea691a93..cc7370e7 100644
--- a/frontend/sync-client/src/services/types/PingResponse.ts
+++ b/frontend/sync-client/src/services/types/PingResponse.ts
@@ -17,4 +17,9 @@ export interface PingResponse {
 	 * List of file extensions that are allowed to be merged.
 	 */
 	mergeableFileExtensions: string[];
+	/**
+	 * API version ensuring backwards & forwards compatibility between the client
+	 * and server.
+	 */
+	supportedApiVersion: number;
 }
diff --git a/frontend/sync-client/src/sync-client.ts b/frontend/sync-client/src/sync-client.ts
index d0af6bfe..06c839c9 100644
--- a/frontend/sync-client/src/sync-client.ts
+++ b/frontend/sync-client/src/sync-client.ts
@@ -220,8 +220,6 @@ export class SyncClient {
 		}
 		this.hasStarted = true;
 
-		await this.serverConfig.initialize();
-
 		if (
 			!this.unloadTelemetry &&
 			this.settings.getSettings().enableTelemetry
@@ -311,6 +309,7 @@ export class SyncClient {
 		this.resetInMemoryState();
 		this.hasStartedOfflineSync = false;
 		this.hasFinishedOfflineSync = false;
+		this.serverConfig.reset();
 
 		// restart syncing
 		this.fetchController.finishReset();
@@ -457,6 +456,8 @@ export class SyncClient {
 	private async startSyncing(): Promise<void> {
 		this.checkIfDestroyed();
 
+		await this.serverConfig.initialize();
+
 		if (!this.hasStartedOfflineSync) {
 			this.hasStartedOfflineSync = true;
 			await this.syncer.scheduleSyncForOfflineChanges();
diff --git a/sync-server/src/consts.rs b/sync-server/src/consts.rs
index 881bd727..3c672520 100644
--- a/sync-server/src/consts.rs
+++ b/sync-server/src/consts.rs
@@ -16,3 +16,5 @@ pub const DEFAULT_LOG_DIRECTORY: &str = "logs";
 pub const DEFAULT_LOG_ROTATION_INTERVAL: Duration = Duration::from_secs(60 * 60 * 24); // 1 day
 
 pub const DEFAULT_MERGEABLE_FILE_EXTENSIONS: &[&str] = &["md", "txt"];
+
+pub const SUPPORTED_API_VERSION: u32 = 1;
diff --git a/sync-server/src/server/ping.rs b/sync-server/src/server/ping.rs
index ec019a1d..82eefff7 100644
--- a/sync-server/src/server/ping.rs
+++ b/sync-server/src/server/ping.rs
@@ -11,6 +11,7 @@ use serde::Deserialize;
 use super::{auth::auth, responses::PingResponse};
 use crate::{
     app_state::{AppState, database::models::VaultId},
+    consts::SUPPORTED_API_VERSION,
     errors::SyncServerError,
     utils::normalize::normalize,
 };
@@ -34,5 +35,6 @@ pub async fn ping(
         server_version: env!("CARGO_PKG_VERSION").to_owned(),
         is_authenticated,
         mergeable_file_extensions: state.config.server.mergeable_file_extensions.clone(),
+        supported_api_version: SUPPORTED_API_VERSION,
     }))
 }
diff --git a/sync-server/src/server/responses.rs b/sync-server/src/server/responses.rs
index 22918106..a8b3fcd7 100644
--- a/sync-server/src/server/responses.rs
+++ b/sync-server/src/server/responses.rs
@@ -19,6 +19,10 @@ pub struct PingResponse {
 
     /// List of file extensions that are allowed to be merged.
     pub mergeable_file_extensions: Vec<String>,
+
+    /// API version ensuring backwards & forwards compatibility between the client
+    /// and server.
+    pub supported_api_version: u32,
 }
 
 /// Response to a fetch latest documents request.