diff --git a/packages/api/src/activities/activity.ts b/packages/api/src/activities/activity.ts
index 6aa799ff6..4fee68a30 100644
--- a/packages/api/src/activities/activity.ts
+++ b/packages/api/src/activities/activity.ts
@@ -69,6 +69,7 @@ export interface IActivity<T extends string = string> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 
@@ -172,6 +173,7 @@ export class Activity<T extends string = string> implements IActivity<T> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 
@@ -277,6 +279,9 @@ export class Activity<T extends string = string> implements IActivity<T> {
     return this;
   }
 
+  /**
+   * @deprecated This will be removed by end of summer 2026.
+   */
   withRelatesTo(value: ConversationReference) {
     this.relatesTo = value;
     return this;
diff --git a/packages/api/src/activities/conversation/end-of-conversation.ts b/packages/api/src/activities/conversation/end-of-conversation.ts
index a3201795e..288dc145b 100644
--- a/packages/api/src/activities/conversation/end-of-conversation.ts
+++ b/packages/api/src/activities/conversation/end-of-conversation.ts
@@ -1,5 +1,8 @@
 import { IActivity } from '../activity';
 
+/**
+ * @deprecated This will be removed by end of summer 2026.
+ */
 export type EndOfConversationCode =
   | 'unknown'
   | 'completedSuccessfully'
@@ -8,6 +11,9 @@ export type EndOfConversationCode =
   | 'botIssuedInvalidMessage'
   | 'channelFailed';
 
+/**
+ * @deprecated This will be removed by end of summer 2026.
+ */
 export interface IEndOfConversationActivity extends IActivity<'endOfConversation'> {
   /**
    * The a code for endOfConversation activities that indicates why the conversation ended.
diff --git a/packages/api/src/activities/handoff.ts b/packages/api/src/activities/handoff.ts
index c7f13f4fd..8f451e4db 100644
--- a/packages/api/src/activities/handoff.ts
+++ b/packages/api/src/activities/handoff.ts
@@ -1,3 +1,6 @@
 import { IActivity } from './activity';
 
+/**
+ * @deprecated This will be removed by end of summer 2026.
+ */
 export interface IHandoffActivity extends IActivity<'handoff'> {}
diff --git a/packages/api/src/activities/invoke/config/config-fetch.ts b/packages/api/src/activities/invoke/config/config-fetch.ts
index a64c88ada..1ee055506 100644
--- a/packages/api/src/activities/invoke/config/config-fetch.ts
+++ b/packages/api/src/activities/invoke/config/config-fetch.ts
@@ -14,6 +14,7 @@ export interface IConfigFetchInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/config/config-submit.ts b/packages/api/src/activities/invoke/config/config-submit.ts
index 3d3e443a1..9544e6972 100644
--- a/packages/api/src/activities/invoke/config/config-submit.ts
+++ b/packages/api/src/activities/invoke/config/config-submit.ts
@@ -14,6 +14,7 @@ export interface IConfigSubmitInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/execute-action.ts b/packages/api/src/activities/invoke/execute-action.ts
index a9945ecce..d110570ea 100644
--- a/packages/api/src/activities/invoke/execute-action.ts
+++ b/packages/api/src/activities/invoke/execute-action.ts
@@ -14,6 +14,7 @@ export interface IExecuteActionInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/file-consent.ts b/packages/api/src/activities/invoke/file-consent.ts
index 25a394ae1..b09d4b681 100644
--- a/packages/api/src/activities/invoke/file-consent.ts
+++ b/packages/api/src/activities/invoke/file-consent.ts
@@ -14,6 +14,7 @@ export interface IFileConsentInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/handoff-action.ts b/packages/api/src/activities/invoke/handoff-action.ts
index 05c46a10b..a24f45933 100644
--- a/packages/api/src/activities/invoke/handoff-action.ts
+++ b/packages/api/src/activities/invoke/handoff-action.ts
@@ -19,6 +19,7 @@ export interface IHandoffActionInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/anon-query-link.ts b/packages/api/src/activities/invoke/message-extension/anon-query-link.ts
index 593914967..2a233f950 100644
--- a/packages/api/src/activities/invoke/message-extension/anon-query-link.ts
+++ b/packages/api/src/activities/invoke/message-extension/anon-query-link.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionAnonQueryLinkInvokeActivity extends IActivity<
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/card-button-clicked.ts b/packages/api/src/activities/invoke/message-extension/card-button-clicked.ts
index a490d66dd..187233840 100644
--- a/packages/api/src/activities/invoke/message-extension/card-button-clicked.ts
+++ b/packages/api/src/activities/invoke/message-extension/card-button-clicked.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionCardButtonClickedInvokeActivity extends IActiv
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/fetch-task.ts b/packages/api/src/activities/invoke/message-extension/fetch-task.ts
index 1b158b1b7..20b6a34ec 100644
--- a/packages/api/src/activities/invoke/message-extension/fetch-task.ts
+++ b/packages/api/src/activities/invoke/message-extension/fetch-task.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionFetchTaskInvokeActivity extends IActivity<'inv
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/query-link.ts b/packages/api/src/activities/invoke/message-extension/query-link.ts
index c5c205155..0d82fb6f6 100644
--- a/packages/api/src/activities/invoke/message-extension/query-link.ts
+++ b/packages/api/src/activities/invoke/message-extension/query-link.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionQueryLinkInvokeActivity extends IActivity<'inv
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/query-setting-url.ts b/packages/api/src/activities/invoke/message-extension/query-setting-url.ts
index 875229e6d..bf3845ad7 100644
--- a/packages/api/src/activities/invoke/message-extension/query-setting-url.ts
+++ b/packages/api/src/activities/invoke/message-extension/query-setting-url.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionQuerySettingUrlInvokeActivity extends IActivit
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/query.ts b/packages/api/src/activities/invoke/message-extension/query.ts
index ba5d733aa..7da03f1c7 100644
--- a/packages/api/src/activities/invoke/message-extension/query.ts
+++ b/packages/api/src/activities/invoke/message-extension/query.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionQueryInvokeActivity extends IActivity<'invoke'
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/select-item.ts b/packages/api/src/activities/invoke/message-extension/select-item.ts
index a1221f10b..72a1da632 100644
--- a/packages/api/src/activities/invoke/message-extension/select-item.ts
+++ b/packages/api/src/activities/invoke/message-extension/select-item.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionSelectItemInvokeActivity extends IActivity<'in
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/setting.ts b/packages/api/src/activities/invoke/message-extension/setting.ts
index 1bf38bee9..53b567482 100644
--- a/packages/api/src/activities/invoke/message-extension/setting.ts
+++ b/packages/api/src/activities/invoke/message-extension/setting.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionSettingInvokeActivity extends IActivity<'invok
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message-extension/submit-action.ts b/packages/api/src/activities/invoke/message-extension/submit-action.ts
index f11f314cd..6276cb8dc 100644
--- a/packages/api/src/activities/invoke/message-extension/submit-action.ts
+++ b/packages/api/src/activities/invoke/message-extension/submit-action.ts
@@ -14,6 +14,7 @@ export interface IMessageExtensionSubmitActionInvokeActivity extends IActivity<'
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/message/submit-action.ts b/packages/api/src/activities/invoke/message/submit-action.ts
index d1936604e..ada881fef 100644
--- a/packages/api/src/activities/invoke/message/submit-action.ts
+++ b/packages/api/src/activities/invoke/message/submit-action.ts
@@ -34,6 +34,7 @@ export interface IMessageSubmitActionInvokeActivity extends IActivity<'invoke'>
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/tab/tab-fetch.ts b/packages/api/src/activities/invoke/tab/tab-fetch.ts
index 2501e27ea..26c10e9ac 100644
--- a/packages/api/src/activities/invoke/tab/tab-fetch.ts
+++ b/packages/api/src/activities/invoke/tab/tab-fetch.ts
@@ -14,6 +14,7 @@ export interface ITabFetchInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/tab/tab-submit.ts b/packages/api/src/activities/invoke/tab/tab-submit.ts
index 6b0acff2a..053ad5746 100644
--- a/packages/api/src/activities/invoke/tab/tab-submit.ts
+++ b/packages/api/src/activities/invoke/tab/tab-submit.ts
@@ -14,6 +14,7 @@ export interface ITabSubmitInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/task/task-fetch.ts b/packages/api/src/activities/invoke/task/task-fetch.ts
index 3db5e8f34..0f39c19e2 100644
--- a/packages/api/src/activities/invoke/task/task-fetch.ts
+++ b/packages/api/src/activities/invoke/task/task-fetch.ts
@@ -14,6 +14,7 @@ export interface ITaskFetchInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/invoke/task/task-submit.ts b/packages/api/src/activities/invoke/task/task-submit.ts
index ad979f20a..43e123f82 100644
--- a/packages/api/src/activities/invoke/task/task-submit.ts
+++ b/packages/api/src/activities/invoke/task/task-submit.ts
@@ -14,6 +14,7 @@ export interface ITaskSubmitInvokeActivity extends IActivity<'invoke'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/activities/message/message-update.ts b/packages/api/src/activities/message/message-update.ts
index c1b2d27b3..6370aa113 100644
--- a/packages/api/src/activities/message/message-update.ts
+++ b/packages/api/src/activities/message/message-update.ts
@@ -9,6 +9,7 @@ export interface IMessageUpdateActivity extends IActivity<'messageUpdate'> {
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   speak?: string;
 
@@ -20,6 +21,7 @@ export interface IMessageUpdateActivity extends IActivity<'messageUpdate'> {
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   expiration?: Date;
 
@@ -44,6 +46,7 @@ export class MessageUpdateActivity
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   speak?: string;
 
@@ -55,6 +58,7 @@ export class MessageUpdateActivity
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   expiration?: Date;
 
@@ -123,6 +127,7 @@ export class MessageUpdateActivity
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   withSpeak(value: string) {
     this.speak = value;
@@ -140,6 +145,7 @@ export class MessageUpdateActivity
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   withExpiration(value: Date) {
     this.expiration = value;
diff --git a/packages/api/src/activities/message/message.ts b/packages/api/src/activities/message/message.ts
index 3e38beb55..f208b6bfd 100644
--- a/packages/api/src/activities/message/message.ts
+++ b/packages/api/src/activities/message/message.ts
@@ -23,6 +23,7 @@ export interface IMessageActivity extends IActivity<'message'> {
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   speak?: string;
 
@@ -30,6 +31,7 @@ export interface IMessageActivity extends IActivity<'message'> {
    * Indicates whether your bot is accepting,
    * expecting, or ignoring user input after the message is delivered to the client. Possible
    * values include: 'acceptingInput', 'ignoringInput', 'expectingInput'
+   * @deprecated This will be removed by end of summer 2026.
    */
   inputHint?: InputHint;
 
@@ -61,6 +63,7 @@ export interface IMessageActivity extends IActivity<'message'> {
 
   /**
    * The importance of the activity. Possible values include: 'low', 'normal', 'high'
+   * @deprecated This will be removed by end of summer 2026.
    */
   importance?: Importance;
 
@@ -73,6 +76,7 @@ export interface IMessageActivity extends IActivity<'message'> {
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   expiration?: Date;
 
@@ -105,6 +109,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   speak?: string;
 
@@ -112,6 +117,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
    * Indicates whether your bot is accepting,
    * expecting, or ignoring user input after the message is delivered to the client. Possible
    * values include: 'acceptingInput', 'ignoringInput', 'expectingInput'
+   * @deprecated This will be removed by end of summer 2026.
    */
   inputHint?: InputHint;
 
@@ -143,6 +149,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
 
   /**
    * The importance of the activity. Possible values include: 'low', 'normal', 'high'
+   * @deprecated This will be removed by end of summer 2026.
    */
   importance?: Importance;
 
@@ -155,6 +162,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   expiration?: Date;
 
@@ -213,6 +221,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
 
   /**
    * The text to speak.
+   * @deprecated This will be removed by end of summer 2026.
    */
   withSpeak(value: string) {
     this.speak = value;
@@ -223,6 +232,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
    * Indicates whether your bot is accepting,
    * expecting, or ignoring user input after the message is delivered to the client. Possible
    * values include: 'acceptingInput', 'ignoringInput', 'expectingInput'
+   * @deprecated This will be removed by end of summer 2026.
    */
   withInputHint(value: InputHint) {
     this.inputHint = value;
@@ -264,6 +274,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
 
   /**
    * The importance of the activity. Possible values include: 'low', 'normal', 'high'
+   * @deprecated This will be removed by end of summer 2026.
    */
   withImportance(value: Importance) {
     this.importance = value;
@@ -282,6 +293,7 @@ export class MessageActivity extends Activity<'message'> implements IMessageActi
   /**
    * The time at which the activity should be considered to be "expired" and should not be
    * presented to the recipient.
+   * @deprecated This will be removed by end of summer 2026.
    */
   withExpiration(value: Date) {
     this.expiration = value;
diff --git a/packages/api/src/activities/trace.ts b/packages/api/src/activities/trace.ts
index d45a48ae1..d8f663731 100644
--- a/packages/api/src/activities/trace.ts
+++ b/packages/api/src/activities/trace.ts
@@ -2,6 +2,9 @@ import { ConversationReference } from '../models';
 
 import { IActivity } from './activity';
 
+/**
+ * @deprecated This will be removed by end of summer 2026.
+ */
 export interface ITraceActivity extends IActivity<'trace'> {
   /**
    * The name of the operation associated with an invoke or event activity.
@@ -25,6 +28,7 @@ export interface ITraceActivity extends IActivity<'trace'> {
 
   /**
    * A reference to another conversation or activity.
+   * @deprecated This will be removed by end of summer 2026.
    */
   relatesTo?: ConversationReference;
 }
diff --git a/packages/api/src/clients/conversation/index.ts b/packages/api/src/clients/conversation/index.ts
index 3a2f8578a..a7a3df5bd 100644
--- a/packages/api/src/clients/conversation/index.ts
+++ b/packages/api/src/clients/conversation/index.ts
@@ -10,7 +10,7 @@ import { ActivityParams, ConversationActivityClient } from './activity';
 import { ConversationMemberClient } from './member';
 
 /**
- * @deprecated The GET /v3/conversations endpoint is not supported. This type will be removed in a future version.
+ * @deprecated This will be removed by end of summer 2026.
  */
 export type GetConversationsParams = {
   readonly continuationToken?: string;
@@ -18,16 +18,16 @@ export type GetConversationsParams = {
 
 export type CreateConversationParams = {
   /**
-   * @deprecated Ignored by the backend. This field will be removed in a future version.
+   * @deprecated This will be removed by end of summer 2026.
    */
   readonly isGroup?: boolean;
   /**
-   * @deprecated Ignored by the backend. This field will be removed in a future version.
+   * @deprecated This will be removed by end of summer 2026.
    */
   readonly bot?: Partial<Account>;
   readonly members?: Account[];
   /**
-   * @deprecated Ignored by the backend. This field will be removed in a future version.
+   * @deprecated This will be removed by end of summer 2026.
    */
   readonly topicName?: string;
   readonly tenantId?: string;
@@ -36,7 +36,7 @@ export type CreateConversationParams = {
 };
 
 /**
- * @deprecated The GET /v3/conversations endpoint is not supported. This type will be removed in a future version.
+ * @deprecated This will be removed by end of summer 2026.
  */
 export type GetConversationsResponse = {
   /**
@@ -103,14 +103,14 @@ export class ConversationClient {
       getPaged: (pageSize?: number, continuationToken?: string) =>
         this._members.getPaged(conversationId, pageSize, continuationToken),
       /**
-       * @deprecated The DELETE member endpoint is not supported by the backend. This method will be removed in a future version.
+       * @deprecated This will be removed by end of summer 2026.
        */
       delete: (id: string) => this._members.delete(conversationId, id),
     };
   }
 
   /**
-   * @deprecated The GET /v3/conversations endpoint is not supported. This method will be removed in a future version.
+   * @deprecated This will be removed by end of summer 2026.
    */
   async get(params: GetConversationsParams) {
     const q = qs.stringify(params, { addQueryPrefix: true });
diff --git a/packages/api/src/clients/conversation/member.ts b/packages/api/src/clients/conversation/member.ts
index 910849099..9ebb92c65 100644
--- a/packages/api/src/clients/conversation/member.ts
+++ b/packages/api/src/clients/conversation/member.ts
@@ -62,7 +62,7 @@ export class ConversationMemberClient {
   }
 
   /**
-   * @deprecated The DELETE member endpoint is not supported by the backend. This method will be removed in a future version.
+   * @deprecated This will be removed by end of summer 2026.
    */
   async delete(conversationId: string, id: string) {
     const res = await this.http.delete<void>(
diff --git a/packages/api/src/models/account.ts b/packages/api/src/models/account.ts
index 38b9cb6a9..0a81f4517 100644
--- a/packages/api/src/models/account.ts
+++ b/packages/api/src/models/account.ts
@@ -4,7 +4,15 @@ import { Role } from './role';
 export type Account<P = any> = {
   readonly id: string;
   readonly aadObjectId?: string;
+  /**
+   * @deprecated This will be removed by end of summer 2026.
+   */
   readonly role: Role;
+  /**
+   * The type of the account. Possible values: 'person', 'bot', 'channel', 'team', 'tag'.
+   * Primarily present on mention entities for non-person accounts. Absent for regular person accounts.
+   */
+  readonly type?: string;
   readonly name: string;
   readonly properties?: P;
   readonly membershipSources?: MembershipSource[];
diff --git a/packages/api/src/models/attachment/attachment.ts b/packages/api/src/models/attachment/attachment.ts
index 1e4fe7d3b..8f9445509 100644
--- a/packages/api/src/models/attachment/attachment.ts
+++ b/packages/api/src/models/attachment/attachment.ts
@@ -1,6 +1,7 @@
 export type Attachment = {
   /**
    * @member {string} [id] The id of the attachment.
+   * @deprecated This will be removed by end of summer 2026.
    */
   id?: string;