diff --git a/sdk/cosmosdb/cosmos/review/cosmos.api.md b/sdk/cosmosdb/cosmos/review/cosmos.api.md
index 454f36a290fc..66f50c3873ce 100644
--- a/sdk/cosmosdb/cosmos/review/cosmos.api.md
+++ b/sdk/cosmosdb/cosmos/review/cosmos.api.md
@@ -433,6 +433,7 @@ export const Constants: {
         ContentEncoding: string;
         CharacterSet: string;
         UserAgent: string;
+        CustomUserAgent: string;
         IfModifiedSince: string;
         IfMatch: string;
         IfNoneMatch: string;
@@ -706,6 +707,7 @@ export interface CosmosClientOptions {
     aadCredentials?: TokenCredential;
     agent?: Agent;
     connectionPolicy?: ConnectionPolicy;
+    connectionString?: string;
     consistencyLevel?: keyof typeof ConsistencyLevel;
     // Warning: (ae-forgotten-export) The symbol "CosmosHeaders_2" needs to be exported by the entry point index.d.ts
     //
@@ -713,7 +715,7 @@ export interface CosmosClientOptions {
     defaultHeaders?: CosmosHeaders_2;
     // (undocumented)
     diagnosticLevel?: CosmosDbDiagnosticLevel;
-    endpoint: string;
+    endpoint?: string;
     httpClient?: HttpClient;
     key?: string;
     permissionFeed?: PermissionDefinition[];
diff --git a/sdk/cosmosdb/cosmos/src/ClientContext.ts b/sdk/cosmosdb/cosmos/src/ClientContext.ts
index 16a4bcd22ce5..b04fa11f070e 100644
--- a/sdk/cosmosdb/cosmos/src/ClientContext.ts
+++ b/sdk/cosmosdb/cosmos/src/ClientContext.ts
@@ -38,6 +38,7 @@ import type { DiagnosticFormatter } from "./diagnostics/DiagnosticFormatter";
 import { DefaultDiagnosticFormatter } from "./diagnostics/DiagnosticFormatter";
 import { CosmosDbDiagnosticLevel } from "./diagnostics/CosmosDbDiagnosticLevel";
 import { randomUUID } from "@azure/core-util";
+import { getUserAgent } from "./common/platform";
 
 const logger: AzureLogger = createClientLogger("ClientContext");
 
@@ -978,4 +979,14 @@ export class ClientContext {
   public getClientConfig(): ClientConfigDiagnostic {
     return this.clientConfig;
   }
+
+  /**
+   * @internal
+   */
+  public refreshUserAgent(hostFramework: string): void {
+    const updatedUserAgent = getUserAgent(this.cosmosClientOptions.userAgentSuffix, hostFramework);
+    this.cosmosClientOptions.defaultHeaders[Constants.HttpHeaders.UserAgent] = updatedUserAgent;
+    this.cosmosClientOptions.defaultHeaders[Constants.HttpHeaders.CustomUserAgent] =
+      updatedUserAgent;
+  }
 }
diff --git a/sdk/cosmosdb/cosmos/src/CosmosClient.ts b/sdk/cosmosdb/cosmos/src/CosmosClient.ts
index f72c337654e0..313df662b1a9 100644
--- a/sdk/cosmosdb/cosmos/src/CosmosClient.ts
+++ b/sdk/cosmosdb/cosmos/src/CosmosClient.ts
@@ -70,6 +70,10 @@ export class CosmosClient {
   constructor(optionsOrConnectionString: string | CosmosClientOptions) {
     if (typeof optionsOrConnectionString === "string") {
       optionsOrConnectionString = parseConnectionString(optionsOrConnectionString);
+    } else if (optionsOrConnectionString.connectionString) {
+      const { endpoint, key } = parseConnectionString(optionsOrConnectionString.connectionString);
+      optionsOrConnectionString.endpoint = endpoint;
+      optionsOrConnectionString.key = key;
     }
 
     const endpoint = checkURL(optionsOrConnectionString.endpoint);
@@ -95,9 +99,9 @@ export class CosmosClient {
         optionsOrConnectionString.consistencyLevel;
     }
 
-    optionsOrConnectionString.defaultHeaders[Constants.HttpHeaders.UserAgent] = getUserAgent(
-      optionsOrConnectionString.userAgentSuffix,
-    );
+    const userAgent = getUserAgent(optionsOrConnectionString.userAgentSuffix);
+    optionsOrConnectionString.defaultHeaders[Constants.HttpHeaders.UserAgent] = userAgent;
+    optionsOrConnectionString.defaultHeaders[Constants.HttpHeaders.CustomUserAgent] = userAgent;
 
     const globalEndpointManager = new GlobalEndpointManager(
       optionsOrConnectionString,
@@ -272,4 +276,13 @@ export class CosmosClient {
       this.endpointRefresher.unref();
     }
   }
+
+  /**
+   * Update the host framework. If provided host framework will be used to generate the defualt SDK user agent.
+   * @param hostFramework - A custom string.
+   * @internal
+   */
+  public async updateHostFramework(hostFramework: string): Promise<void> {
+    this.clientContext.refreshUserAgent(hostFramework);
+  }
 }
diff --git a/sdk/cosmosdb/cosmos/src/CosmosClientOptions.ts b/sdk/cosmosdb/cosmos/src/CosmosClientOptions.ts
index 02de08505ea9..3ba5b807dc1d 100644
--- a/sdk/cosmosdb/cosmos/src/CosmosClientOptions.ts
+++ b/sdk/cosmosdb/cosmos/src/CosmosClientOptions.ts
@@ -20,7 +20,7 @@ export interface Agent {
 
 export interface CosmosClientOptions {
   /** The service endpoint to use to create the client. */
-  endpoint: string;
+  endpoint?: string;
   /** The account master or readonly key */
   key?: string;
   /** An object that contains resources tokens.
@@ -60,4 +60,6 @@ export interface CosmosClientOptions {
   diagnosticLevel?: CosmosDbDiagnosticLevel;
   /** @internal */
   plugins?: PluginConfig[];
+  /** An optional parameter that represents the connection string. Your database connection string can be found in the Azure Portal. */
+  connectionString?: string;
 }
diff --git a/sdk/cosmosdb/cosmos/src/common/constants.ts b/sdk/cosmosdb/cosmos/src/common/constants.ts
index 75328fa7909a..75bf0afd76a9 100644
--- a/sdk/cosmosdb/cosmos/src/common/constants.ts
+++ b/sdk/cosmosdb/cosmos/src/common/constants.ts
@@ -22,6 +22,7 @@ export const Constants = {
     ContentEncoding: "Content-Encoding",
     CharacterSet: "CharacterSet",
     UserAgent: "User-Agent",
+    CustomUserAgent: "x-ms-useragent",
     IfModifiedSince: "If-Modified-Since",
     IfMatch: "If-Match",
     IfNoneMatch: "If-None-Match",
diff --git a/sdk/cosmosdb/cosmos/src/common/platform.ts b/sdk/cosmosdb/cosmos/src/common/platform.ts
index d7756ff2afab..28334b9dbfa3 100644
--- a/sdk/cosmosdb/cosmos/src/common/platform.ts
+++ b/sdk/cosmosdb/cosmos/src/common/platform.ts
@@ -6,11 +6,15 @@ import { Constants } from "./constants";
 /**
  * @hidden
  */
-export function getUserAgent(suffix?: string): string {
-  const ua = `${userAgentDetails()} ${Constants.SDKName}/${Constants.SDKVersion}`;
+export function getUserAgent(suffix?: string, hostFramework?: string): string {
+  let ua = `${userAgentDetails()} ${Constants.SDKName}/${Constants.SDKVersion}`;
+  if (hostFramework) {
+    ua = ua + " " + hostFramework;
+  }
   if (suffix) {
-    return ua + " " + suffix;
+    ua = ua + " " + suffix;
   }
+
   return ua;
 }