diff --git a/packages/agents-activity/src/activity.ts b/packages/agents-activity/src/activity.ts
index 601b5cb5..a3e2f258 100644
--- a/packages/agents-activity/src/activity.ts
+++ b/packages/agents-activity/src/activity.ts
@@ -26,6 +26,8 @@ import { MessageReaction, messageReactionZodSchema } from './messageReaction'
 import { TextFormatTypes, textFormatTypesZodSchema } from './textFormatTypes'
 import { TextHighlight, textHighlightZodSchema } from './textHighlight'
 import { RoleTypes } from './conversation/roleTypes'
+import { Errors } from './errorHelper'
+import { ExceptionHelper } from './exceptionHelper'
 
 /**
  * Zod schema for validating an Activity object.
@@ -316,13 +318,13 @@ export class Activity {
    */
   constructor (t: ActivityTypes | string) {
     if (t === undefined) {
-      throw new Error('Invalid ActivityType: undefined')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidActivityTypeUndefined)
     }
     if (t === null) {
-      throw new Error('Invalid ActivityType: null')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidActivityTypeNull)
     }
     if ((typeof t === 'string') && (t.length === 0)) {
-      throw new Error('Invalid ActivityType: empty string')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidActivityTypeEmptyString)
     }
 
     this.type = t
@@ -382,7 +384,7 @@ export class Activity {
 
     // if they passed in a value but the channel is blank, this is invalid
     if (value && !channel) {
-      throw new Error(`Invalid channelId ${value}. Found subChannel but no main channel.`)
+      throw ExceptionHelper.generateException(Error, Errors.InvalidChannelIdSubChannelOnly, undefined, { channelId: value })
     }
     this._channelId = channel
     if (subChannel) {
@@ -418,7 +420,7 @@ export class Activity {
    */
   set channelIdSubChannel (value) {
     if (!this._channelId) {
-      throw new Error('Primary channel must be set before setting subChannel')
+      throw ExceptionHelper.generateException(Error, Errors.PrimaryChannelNotSet)
     }
     this.channelId = `${this._channelId}${value ? `:${value}` : ''}`
   }
@@ -467,13 +469,13 @@ export class Activity {
    */
   public getConversationReference (): ConversationReference {
     if (this.recipient === null || this.recipient === undefined) {
-      throw new Error('Activity Recipient undefined')
+      throw ExceptionHelper.generateException(Error, Errors.ActivityRecipientUndefined)
     }
     if (this.conversation === null || this.conversation === undefined) {
-      throw new Error('Activity Conversation undefined')
+      throw ExceptionHelper.generateException(Error, Errors.ActivityConversationUndefined)
     }
     if (this.channelId === null || this.channelId === undefined) {
-      throw new Error('Activity ChannelId undefined')
+      throw ExceptionHelper.generateException(Error, Errors.ActivityChannelIdUndefined)
     }
 
     return {
diff --git a/packages/agents-activity/src/errorHelper.ts b/packages/agents-activity/src/errorHelper.ts
new file mode 100644
index 00000000..9a156eed
--- /dev/null
+++ b/packages/agents-activity/src/errorHelper.ts
@@ -0,0 +1,93 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+import { AgentErrorDefinition } from './exceptionHelper'
+
+/**
+ * Error definitions for the Activity system.
+ * This contains localized error codes for the Activity subsystem of the AgentSDK.
+ *
+ * Each error definition includes an error code (starting from -110000), a description, and a help link
+ * pointing to an AKA link to get help for the given error.
+ *
+ * Usage example:
+ * ```
+ * throw ExceptionHelper.generateException(
+ *   Error,
+ *   Errors.InvalidActivityTypeUndefined
+ * );
+ * ```
+ */
+export const Errors: { [key: string]: AgentErrorDefinition } = {
+  /**
+   * Error thrown when ActivityType is undefined.
+   */
+  InvalidActivityTypeUndefined: {
+    code: -110000,
+    description: 'Invalid ActivityType: undefined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when ActivityType is null.
+   */
+  InvalidActivityTypeNull: {
+    code: -110001,
+    description: 'Invalid ActivityType: null',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when ActivityType is an empty string.
+   */
+  InvalidActivityTypeEmptyString: {
+    code: -110002,
+    description: 'Invalid ActivityType: empty string',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when channelId contains a subChannel but no main channel.
+   */
+  InvalidChannelIdSubChannelOnly: {
+    code: -110003,
+    description: 'Invalid channelId {channelId}. Found subChannel but no main channel.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when attempting to set subChannel before setting primary channel.
+   */
+  PrimaryChannelNotSet: {
+    code: -110004,
+    description: 'Primary channel must be set before setting subChannel',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Activity Recipient is undefined.
+   */
+  ActivityRecipientUndefined: {
+    code: -110005,
+    description: 'Activity Recipient undefined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Activity Conversation is undefined.
+   */
+  ActivityConversationUndefined: {
+    code: -110006,
+    description: 'Activity Conversation undefined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Activity ChannelId is undefined.
+   */
+  ActivityChannelIdUndefined: {
+    code: -110007,
+    description: 'Activity ChannelId undefined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  }
+}
diff --git a/packages/agents-activity/src/index.ts b/packages/agents-activity/src/index.ts
index 0126453f..620696d0 100644
--- a/packages/agents-activity/src/index.ts
+++ b/packages/agents-activity/src/index.ts
@@ -50,3 +50,4 @@ export { ActivityTreatments } from './activityTreatments'
 export { debug, Logger } from './logger'
 
 export { AgentErrorDefinition, AgentError, ExceptionHelper } from './exceptionHelper'
+export { Errors } from './errorHelper'
diff --git a/packages/agents-activity/test/errorHelper.test.ts b/packages/agents-activity/test/errorHelper.test.ts
new file mode 100644
index 00000000..6de67786
--- /dev/null
+++ b/packages/agents-activity/test/errorHelper.test.ts
@@ -0,0 +1,81 @@
+import assert from 'assert'
+import { describe, it } from 'node:test'
+import { AgentErrorDefinition } from '../src/exceptionHelper'
+import { Errors } from '../src/errorHelper'
+
+describe('Activity Errors tests', () => {
+  it('should have InvalidActivityTypeUndefined error definition', () => {
+    const error = Errors.InvalidActivityTypeUndefined
+
+    assert.strictEqual(error.code, -110000)
+    assert.strictEqual(error.description, 'Invalid ActivityType: undefined')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have InvalidActivityTypeNull error definition', () => {
+    const error = Errors.InvalidActivityTypeNull
+
+    assert.strictEqual(error.code, -110001)
+    assert.strictEqual(error.description, 'Invalid ActivityType: null')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have InvalidActivityTypeEmptyString error definition', () => {
+    const error = Errors.InvalidActivityTypeEmptyString
+
+    assert.strictEqual(error.code, -110002)
+    assert.strictEqual(error.description, 'Invalid ActivityType: empty string')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have all error codes in the correct range', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    // All error codes should be negative and in the range -110000 to -110999
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(errorDef.code < 0, `Error code ${errorDef.code} should be negative`)
+      assert.ok(errorDef.code >= -110999, `Error code ${errorDef.code} should be >= -110999`)
+      assert.ok(errorDef.code <= -110000, `Error code ${errorDef.code} should be <= -110000`)
+    })
+  })
+
+  it('should have unique error codes', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    const codes = errorDefinitions.map(e => e.code)
+    const uniqueCodes = new Set(codes)
+
+    assert.strictEqual(codes.length, uniqueCodes.size, 'All error codes should be unique')
+  })
+
+  it('should have help links with tokenized format', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(
+        errorDef.helplink.includes('{errorCode}'),
+        `Help link should contain {errorCode} token: ${errorDef.helplink}`
+      )
+      assert.ok(
+        errorDef.helplink.startsWith('https://aka.ms/M365AgentsErrorCodes/#'),
+        `Help link should start with correct URL: ${errorDef.helplink}`
+      )
+    })
+  })
+
+  it('should have non-empty descriptions', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(errorDef.description.length > 0, 'Description should not be empty')
+    })
+  })
+})
diff --git a/packages/agents-hosting-storage-cosmos/src/cosmosDbPartitionedStorage.ts b/packages/agents-hosting-storage-cosmos/src/cosmosDbPartitionedStorage.ts
index 40641095..79c5943a 100644
--- a/packages/agents-hosting-storage-cosmos/src/cosmosDbPartitionedStorage.ts
+++ b/packages/agents-hosting-storage-cosmos/src/cosmosDbPartitionedStorage.ts
@@ -362,7 +362,7 @@ export class CosmosDbPartitionedStorage implements Storage {
           errorObj,
           {
             maxDepth: maxDepthAllowed.toString(),
-            additionalMessage: additionalMessage
+            additionalMessage
           }
         )
       } else if (obj && typeof obj === 'object') {
diff --git a/packages/agents-hosting/src/activityHandler.ts b/packages/agents-hosting/src/activityHandler.ts
index 4a90fdfc..f55903fb 100644
--- a/packages/agents-hosting/src/activityHandler.ts
+++ b/packages/agents-hosting/src/activityHandler.ts
@@ -4,7 +4,7 @@
  */
 import { debug } from '@microsoft/agents-activity/logger'
 import { TurnContext } from './turnContext'
-import { Activity, ActivityTypes, Channels } from '@microsoft/agents-activity'
+import { Activity, ActivityTypes, Channels, ExceptionHelper } from '@microsoft/agents-activity'
 import { StatusCodes } from './statusCodes'
 import { InvokeResponse } from './invoke/invokeResponse'
 import { InvokeException } from './invoke/invokeException'
@@ -13,6 +13,7 @@ import { SearchInvokeValue } from './invoke/searchInvokeValue'
 import { SearchInvokeResponse } from './invoke/searchInvokeResponse'
 import { AdaptiveCardInvokeResponse } from './invoke/adaptiveCardInvokeResponse'
 import { tokenResponseEventName } from './tokenResponseEventName'
+import { Errors } from './errorHelper'
 
 /** Symbol key for invoke response */
 export const INVOKE_RESPONSE_KEY = Symbol('invokeResponse')
@@ -254,9 +255,9 @@ export class ActivityHandler {
    * @throws Error if context is missing, activity is missing, or activity type is missing
    */
   async run (context: TurnContext): Promise<void> {
-    if (!context) throw new Error('Missing TurnContext parameter')
-    if (!context.activity) throw new Error('TurnContext does not include an activity')
-    if (!context.activity.type) throw new Error('Activity is missing its type')
+    if (!context) throw ExceptionHelper.generateException(Error, Errors.MissingTurnContext)
+    if (!context.activity) throw ExceptionHelper.generateException(Error, Errors.TurnContextMissingActivity)
+    if (!context.activity.type) throw ExceptionHelper.generateException(Error, Errors.ActivityMissingType)
 
     await this.onTurnActivity(context)
   }
diff --git a/packages/agents-hosting/src/agent-client/agentClient.ts b/packages/agents-hosting/src/agent-client/agentClient.ts
index 2678ea52..c7a7ce8e 100644
--- a/packages/agents-hosting/src/agent-client/agentClient.ts
+++ b/packages/agents-hosting/src/agent-client/agentClient.ts
@@ -1,9 +1,10 @@
 import { AuthConfiguration, MsalTokenProvider } from '../auth'
-import { Activity, ConversationReference, RoleTypes } from '@microsoft/agents-activity'
+import { Activity, ConversationReference, RoleTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { v4 } from 'uuid'
 import { debug } from '@microsoft/agents-activity/logger'
 import { ConversationState } from '../state'
 import { TurnContext } from '../turnContext'
+import { Errors } from '../errorHelper'
 
 const logger = debug('agents:agent-client')
 
@@ -115,7 +116,7 @@ export class AgentClient {
     })
     if (!response.ok) {
       await conversationDataAccessor.delete(context, { channelId: activityCopy.channelId!, conversationId: activityCopy.conversation!.id })
-      throw new Error(`Failed to post activity to agent: ${response.statusText}`)
+      throw ExceptionHelper.generateException(Error, Errors.FailedToPostActivityToAgent, undefined, { statusText: response.statusText })
     }
     return response.statusText
   }
@@ -139,10 +140,10 @@ export class AgentClient {
           serviceUrl: process.env[`${agentName}_serviceUrl`]!
         }
       } else {
-        throw new Error(`Missing agent client config for agent ${agentName}`)
+        throw ExceptionHelper.generateException(Error, Errors.MissingAgentClientConfig, undefined, { agentName })
       }
     } else {
-      throw new Error('Agent name is required')
+      throw ExceptionHelper.generateException(Error, Errors.AgentNameRequired)
     }
   }
 }
diff --git a/packages/agents-hosting/src/app/adaptiveCards/activityValueParsers.ts b/packages/agents-hosting/src/app/adaptiveCards/activityValueParsers.ts
index 32153ea2..220c9edc 100644
--- a/packages/agents-hosting/src/app/adaptiveCards/activityValueParsers.ts
+++ b/packages/agents-hosting/src/app/adaptiveCards/activityValueParsers.ts
@@ -3,8 +3,9 @@
  * Licensed under the MIT License.
  */
 
+import { ExceptionHelper, activityZodSchema, AdaptiveCardInvokeAction, adaptiveCardInvokeActionZodSchema } from '@microsoft/agents-activity'
+import { Errors } from '../../errorHelper'
 import { z } from 'zod'
-import { activityZodSchema, AdaptiveCardInvokeAction, adaptiveCardInvokeActionZodSchema } from '@microsoft/agents-activity'
 // import { MessagingExtensionQuery, messagingExtensionQueryZodSchema } from '../messageExtension/messagingExtensionQuery'
 import { adaptiveCardsSearchParamsZodSchema } from './adaptiveCardsSearchParams'
 
@@ -76,7 +77,7 @@ export function parseValueActionExecuteSelector (value: unknown): ValueAction |
   })
   const safeParsedValue = actionValueExecuteSelector.passthrough().safeParse(value)
   if (!safeParsedValue.success) {
-    throw new Error(`Invalid action value: ${safeParsedValue.error}`)
+    throw ExceptionHelper.generateException(Error, Errors.InvalidActionValue, undefined, { error: JSON.stringify(safeParsedValue.error) })
   }
   const parsedValue = safeParsedValue.data
   return {
diff --git a/packages/agents-hosting/src/app/adaptiveCards/adaptiveCardsActions.ts b/packages/agents-hosting/src/app/adaptiveCards/adaptiveCardsActions.ts
index 0a842020..a932948d 100644
--- a/packages/agents-hosting/src/app/adaptiveCards/adaptiveCardsActions.ts
+++ b/packages/agents-hosting/src/app/adaptiveCards/adaptiveCardsActions.ts
@@ -3,8 +3,9 @@
  * Licensed under the MIT License.
  */
 
-import { Activity, ActivityTypes } from '@microsoft/agents-activity'
+import { Activity, ActivityTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { AdaptiveCardInvokeResponse, AgentApplication, CardFactory, INVOKE_RESPONSE_KEY, InvokeResponse, MessageFactory, RouteSelector, TurnContext, TurnState } from '../../'
+import { Errors } from '../../errorHelper'
 import { AdaptiveCardActionExecuteResponseType } from './adaptiveCardActionExecuteResponseType'
 import { parseAdaptiveCardInvokeAction, parseValueActionExecuteSelector, parseValueDataset, parseValueSearchQuery } from './activityValueParsers'
 import { AdaptiveCardsSearchParams } from './adaptiveCardsSearchParams'
@@ -117,7 +118,7 @@ export class AdaptiveCardsActions<TState extends TurnState> {
                         a?.name !== ACTION_INVOKE_NAME ||
                         (invokeAction?.action.type !== ACTION_EXECUTE_TYPE)
           ) {
-            throw new Error(`Unexpected AdaptiveCards.actionExecute() triggered for activity type: ${invokeAction?.action.type}`
+            throw ExceptionHelper.generateException(Error, Errors.UnexpectedActionExecute, undefined, { activityType: invokeAction?.action.type || 'unknown' }
             )
           }
 
@@ -196,7 +197,7 @@ export class AdaptiveCardsActions<TState extends TurnState> {
       this._app.addRoute(selector, async (context, state) => {
         const a = context?.activity
         if (a?.type !== ActivityTypes.Message || a?.text || typeof a?.value !== 'object') {
-          throw new Error(`Unexpected AdaptiveCards.actionSubmit() triggered for activity type: ${a?.type}`)
+          throw ExceptionHelper.generateException(Error, Errors.UnexpectedActionSubmit, undefined, { activityType: a?.type })
         }
 
         await handler(context, state as TState, (parseAdaptiveCardInvokeAction(a.value)) as TData ?? {} as TData)
@@ -227,7 +228,7 @@ export class AdaptiveCardsActions<TState extends TurnState> {
         async (context, state) => {
           const a = context?.activity
           if (a?.type !== 'invoke' || a?.name !== SEARCH_INVOKE_NAME) {
-            throw new Error(`Unexpected AdaptiveCards.search() triggered for activity type: ${a?.type}`)
+            throw ExceptionHelper.generateException(Error, Errors.UnexpectedSearch, undefined, { activityType: a?.type })
           }
 
           const parsedQuery = parseValueSearchQuery(a.value)
diff --git a/packages/agents-hosting/src/app/agentApplication.ts b/packages/agents-hosting/src/app/agentApplication.ts
index ed823038..1e6a336b 100644
--- a/packages/agents-hosting/src/app/agentApplication.ts
+++ b/packages/agents-hosting/src/app/agentApplication.ts
@@ -3,7 +3,7 @@
  * Licensed under the MIT License.
  */
 
-import { Activity, ActivityTypes, ConversationReference } from '@microsoft/agents-activity'
+import { Activity, ActivityTypes, ConversationReference, ExceptionHelper } from '@microsoft/agents-activity'
 import { ResourceResponse } from '../connector-client'
 import { debug } from '@microsoft/agents-activity/logger'
 import { TurnContext } from '../turnContext'
@@ -11,6 +11,7 @@ import { AdaptiveCardsActions } from './adaptiveCards'
 import { AgentApplicationOptions } from './agentApplicationOptions'
 import { ConversationUpdateEvents } from './conversationUpdateEvents'
 import { AgentExtension } from './extensions'
+import { Errors } from '../errorHelper'
 import { RouteHandler } from './routeHandler'
 import { RouteSelector } from './routeSelector'
 import { TurnEvents } from './turnEvents'
@@ -131,12 +132,12 @@ export class AgentApplication<TState extends TurnState> {
     }
 
     if (this._options.longRunningMessages && !this._adapter && !this._options.agentAppId) {
-      throw new Error('The Application.longRunningMessages property is unavailable because no adapter was configured in the app.')
+      throw ExceptionHelper.generateException(Error, Errors.LongRunningMessagesPropertyUnavailable)
     }
 
     if (this._options.transcriptLogger) {
       if (!this._options.adapter) {
-        throw new Error('The Application.transcriptLogger property is unavailable because no adapter was configured in the app.')
+        throw ExceptionHelper.generateException(Error, Errors.TranscriptLoggerPropertyUnavailable)
       } else {
         this._adapter?.use(new TranscriptLoggerMiddleware(this._options.transcriptLogger))
       }
@@ -152,7 +153,7 @@ export class AgentApplication<TState extends TurnState> {
    */
   public get authorization (): Authorization {
     if (!this._authorization) {
-      throw new Error('The Application.authorization property is unavailable because no authorization options were configured.')
+      throw ExceptionHelper.generateException(Error, Errors.AuthorizationPropertyUnavailable)
     }
     return this._authorization
   }
@@ -436,9 +437,7 @@ export class AgentApplication<TState extends TurnState> {
     if (this.options.authorization) {
       this.authorization.onSignInSuccess(handler)
     } else {
-      throw new Error(
-        'The Application.authorization property is unavailable because no authorization options were configured.'
-      )
+      throw ExceptionHelper.generateException(Error, Errors.AuthorizationPropertyUnavailable)
     }
     return this
   }
@@ -466,9 +465,7 @@ export class AgentApplication<TState extends TurnState> {
     if (this.options.authorization) {
       this.authorization.onSignInFailure(handler)
     } else {
-      throw new Error(
-        'The Application.authorization property is unavailable because no authorization options were configured.'
-      )
+      throw ExceptionHelper.generateException(Error, Errors.AuthorizationPropertyUnavailable)
     }
     return this
   }
@@ -804,7 +801,7 @@ export class AgentApplication<TState extends TurnState> {
    */
   public registerExtension<T extends AgentExtension<TState>> (extension: T, regcb : (ext:T) => void): void {
     if (this._extensions.includes(extension)) {
-      throw new Error('Extension already registered')
+      throw ExceptionHelper.generateException(Error, Errors.ExtensionAlreadyRegistered)
     }
     this._extensions.push(extension)
     regcb(extension)
diff --git a/packages/agents-hosting/src/app/auth/authorization.ts b/packages/agents-hosting/src/app/auth/authorization.ts
index 8d5e3919..7a0d524e 100644
--- a/packages/agents-hosting/src/app/auth/authorization.ts
+++ b/packages/agents-hosting/src/app/auth/authorization.ts
@@ -5,6 +5,8 @@
 
 import { debug } from '@microsoft/agents-activity/logger'
 import { TokenResponse } from '../../oauth'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../../errorHelper'
 import { TurnContext } from '../../turnContext'
 import { TurnState } from '../turnState'
 import { AuthorizationManager } from './authorizationManager'
@@ -148,7 +150,7 @@ export class UserAuthorization implements Authorization {
       return { token }
     }
 
-    throw new Error('Invalid parameters for exchangeToken method.')
+    throw ExceptionHelper.generateException(Error, Errors.InvalidExchangeTokenParameters)
   }
 
   /**
@@ -254,7 +256,7 @@ export class UserAuthorization implements Authorization {
    */
   private getHandler (id: string) {
     if (!Object.prototype.hasOwnProperty.call(this.manager.handlers, id)) {
-      throw new Error(`Cannot find auth handler with ID '${id}'. Ensure it is configured in the agent application options.`)
+      throw ExceptionHelper.generateException(Error, Errors.CannotFindAuthHandler, undefined, { id })
     }
     return this.manager.handlers[id]
   }
diff --git a/packages/agents-hosting/src/app/auth/authorizationManager.ts b/packages/agents-hosting/src/app/auth/authorizationManager.ts
index ff264017..4e863a56 100644
--- a/packages/agents-hosting/src/app/auth/authorizationManager.ts
+++ b/packages/agents-hosting/src/app/auth/authorizationManager.ts
@@ -3,9 +3,10 @@
  * Licensed under the MIT License.
  */
 
-import { Activity, debug } from '@microsoft/agents-activity'
+import { Activity, debug, ExceptionHelper } from '@microsoft/agents-activity'
 import { AgentApplication } from '../agentApplication'
 import { AgenticAuthorization, AzureBotAuthorization } from './handlers'
+import { Errors } from '../../errorHelper'
 import { TurnContext } from '../../turnContext'
 import { HandlerStorage } from './handlerStorage'
 import { ActiveAuthorizationHandler, AuthorizationHandlerStatus, AuthorizationHandler, AuthorizationHandlerSettings, AuthorizationOptions } from './types'
@@ -53,11 +54,11 @@ export class AuthorizationManager {
    */
   constructor (private app: AgentApplication<any>, connections: Connections) {
     if (!app.options.storage) {
-      throw new Error('Storage is required for Authorization. Ensure that a storage provider is configured in the AgentApplication options.')
+      throw ExceptionHelper.generateException(Error, Errors.StorageRequiredForAuthorization)
     }
 
     if (app.options.authorization === undefined || Object.keys(app.options.authorization).length === 0) {
-      throw new Error('The AgentApplication.authorization does not have any auth handlers')
+      throw ExceptionHelper.generateException(Error, Errors.NoAuthHandlersConfigured)
     }
 
     const settings: AuthorizationHandlerSettings = { storage: app.options.storage, connections }
@@ -83,7 +84,7 @@ export class AuthorizationManager {
     // Validate supported types, agentic, and default (Azure Bot - undefined)
     const supportedTypes = ['agentic', undefined]
     if (!supportedTypes.includes(result.type)) {
-      throw new Error(`Unsupported authorization handler type: '${result.type}' for auth handler: '${id}'. Supported types are: '${supportedTypes.filter(Boolean).join('\', \'')}'.`)
+      throw ExceptionHelper.generateException(Error, Errors.UnsupportedAuthorizationHandlerType, undefined, { handlerType: result.type || 'undefined', handlerId: id, supportedTypes: supportedTypes.filter(Boolean).join(', ') })
     }
 
     return result
@@ -134,7 +135,7 @@ export class AuthorizationManager {
       }
 
       if (status !== AuthorizationHandlerStatus.APPROVED) {
-        throw new Error(this.prefix(handler.id, `Unexpected registration status: ${status}`))
+        throw ExceptionHelper.generateException(Error, Errors.UnexpectedRegistrationStatus, undefined, { status })
       }
 
       await storage.delete()
@@ -183,7 +184,7 @@ export class AuthorizationManager {
       return await handler.signin(context, active)
     } catch (cause) {
       await storage.delete()
-      throw new Error(this.prefix(handler.id, 'Failed to sign in'), { cause })
+      throw ExceptionHelper.generateException(Error, Errors.FailedToSignIn, cause instanceof Error ? cause : undefined)
     }
   }
 
@@ -199,7 +200,7 @@ export class AuthorizationManager {
       return this._handlers[id]
     })
     if (unknownHandlers) {
-      throw new Error(`Cannot find auth handlers with ID(s): ${unknownHandlers}`)
+      throw ExceptionHelper.generateException(Error, Errors.CannotFindAuthHandlers, undefined, { unknownHandlers })
     }
     return handlers
   }
diff --git a/packages/agents-hosting/src/app/auth/handlerStorage.ts b/packages/agents-hosting/src/app/auth/handlerStorage.ts
index e0842e63..5fb92247 100644
--- a/packages/agents-hosting/src/app/auth/handlerStorage.ts
+++ b/packages/agents-hosting/src/app/auth/handlerStorage.ts
@@ -3,6 +3,8 @@
  * Licensed under the MIT License.
  */
 
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../../errorHelper'
 import { ActiveAuthorizationHandler } from './types'
 import { TurnContext } from '../../turnContext'
 import { Storage } from '../../storage'
@@ -25,7 +27,7 @@ export class HandlerStorage<TActiveHandler extends ActiveAuthorizationHandler =
     const channelId = this.context.activity.channelId?.trim()
     const userId = this.context.activity.from?.id?.trim()
     if (!channelId || !userId) {
-      throw new Error(`Both 'activity.channelId' and 'activity.from.id' are required to generate the ${HandlerStorage.name} key.`)
+      throw ExceptionHelper.generateException(Error, Errors.ChannelIdAndFromIdRequiredForHandlerStorage)
     }
     return `auth/${channelId}/${userId}`
   }
diff --git a/packages/agents-hosting/src/app/auth/handlers/agenticAuthorization.ts b/packages/agents-hosting/src/app/auth/handlers/agenticAuthorization.ts
index 4f98374a..6be37a73 100644
--- a/packages/agents-hosting/src/app/auth/handlers/agenticAuthorization.ts
+++ b/packages/agents-hosting/src/app/auth/handlers/agenticAuthorization.ts
@@ -3,9 +3,10 @@
  * Licensed under the MIT License.
  */
 
-import { debug } from '@microsoft/agents-activity'
+import { debug, ExceptionHelper } from '@microsoft/agents-activity'
 import { TurnContext } from '../../../turnContext'
 import { AuthorizationHandler, AuthorizationHandlerSettings, AuthorizationHandlerStatus, AuthorizationHandlerTokenOptions } from '../types'
+import { Errors } from '../../../errorHelper'
 import { TokenResponse } from '../../../oauth'
 import { AuthProvider } from '../../../auth'
 
@@ -56,7 +57,7 @@ export class AgenticAuthorization implements AuthorizationHandler {
    */
   constructor (public readonly id: string, options: AgenticAuthorizationOptions, private settings: AgenticAuthorizationSettings) {
     if (!this.settings.connections) {
-      throw new Error(this.prefix('The \'connections\' option is not available in the app options. Ensure that the app is properly configured.'))
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionsOptionNotAvailable)
     }
 
     this._options = this.loadOptions(options)
@@ -73,7 +74,7 @@ export class AgenticAuthorization implements AuthorizationHandler {
     }
 
     if (!result.scopes || result.scopes.length === 0) {
-      throw new Error(this.prefix('At least one scope must be specified for the Agentic authorization handler.'))
+      throw ExceptionHelper.generateException(Error, Errors.ScopeRequired)
     }
 
     return result
diff --git a/packages/agents-hosting/src/app/auth/handlers/azureBotAuthorization.ts b/packages/agents-hosting/src/app/auth/handlers/azureBotAuthorization.ts
index ab982139..cc023cb0 100644
--- a/packages/agents-hosting/src/app/auth/handlers/azureBotAuthorization.ts
+++ b/packages/agents-hosting/src/app/auth/handlers/azureBotAuthorization.ts
@@ -4,14 +4,15 @@
  */
 
 import { debug } from '@microsoft/agents-activity/logger'
+import { Activity, ActivityTypes, Channels, ExceptionHelper } from '@microsoft/agents-activity'
 import { AuthorizationHandlerStatus, AuthorizationHandler, ActiveAuthorizationHandler, AuthorizationHandlerSettings, AuthorizationHandlerTokenOptions } from '../types'
 import { MessageFactory } from '../../../messageFactory'
 import { CardFactory } from '../../../cards'
 import { TurnContext } from '../../../turnContext'
 import { TokenExchangeRequest, TokenExchangeInvokeResponse, TokenResponse, UserTokenClient } from '../../../oauth'
 import jwt, { JwtPayload } from 'jsonwebtoken'
+import { Errors } from '../../../errorHelper'
 import { HandlerStorage } from '../handlerStorage'
-import { Activity, ActivityTypes, Channels } from '@microsoft/agents-activity'
 import { InvokeResponse, TokenExchangeInvokeRequest } from '../../../invoke'
 
 const logger = debug('agents:authorization:azurebot')
@@ -169,11 +170,11 @@ export class AzureBotAuthorization implements AuthorizationHandler {
    */
   constructor (public readonly id: string, options: AzureBotAuthorizationOptions, private settings: AzureBotAuthorizationSettings) {
     if (!this.settings.storage) {
-      throw new Error(this.prefix('The \'storage\' option is not available in the app options. Ensure that the app is properly configured.'))
+      throw ExceptionHelper.generateException(Error, Errors.StorageOptionNotAvailable)
     }
 
     if (!this.settings.connections) {
-      throw new Error(this.prefix('The \'connections\' option is not available in the app options. Ensure that the app is properly configured.'))
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionsOptionNotAvailable)
     }
 
     this._options = this.loadOptions(options)
@@ -201,7 +202,7 @@ export class AzureBotAuthorization implements AuthorizationHandler {
     }
 
     if (!result.name) {
-      throw new Error(this.prefix(`The 'name' property or '${this.id}_connectionName' env variable is required to initialize the handler.`))
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionNameRequired, undefined, { handlerId: this.id })
     }
 
     return result
@@ -268,7 +269,7 @@ export class AzureBotAuthorization implements AuthorizationHandler {
     const connection = this._options.name!
 
     if (!channel || !user) {
-      throw new Error(this.prefix('Both \'activity.channelId\' and \'activity.from.id\' are required to perform signout.'))
+      throw ExceptionHelper.generateException(Error, Errors.ChannelIdAndFromIdRequiredForSignout)
     }
 
     logger.debug(this.prefix(`Signing out User '${user}' from => Channel: '${channel}', Connection: '${connection}'`), context.activity)
@@ -356,7 +357,7 @@ export class AzureBotAuthorization implements AuthorizationHandler {
     }
 
     if (!this.isExchangeable(token)) {
-      throw new Error(this.prefix('The current token is not exchangeable for an on-behalf-of flow. Ensure the token audience starts with \'api://\'.'))
+      throw ExceptionHelper.generateException(Error, Errors.TokenNotExchangeable)
     }
 
     try {
@@ -547,7 +548,7 @@ export class AzureBotAuthorization implements AuthorizationHandler {
   private async getUserTokenClient (context: TurnContext): Promise<UserTokenClient> {
     const userTokenClient = context.turnState.get<UserTokenClient>(context.adapter.UserTokenClientKey)
     if (!userTokenClient) {
-      throw new Error(this.prefix('The \'userTokenClient\' is not available in the adapter. Ensure that the adapter supports user token operations.'))
+      throw ExceptionHelper.generateException(Error, Errors.UserTokenClientNotAvailable)
     }
     return userTokenClient
   }
diff --git a/packages/agents-hosting/src/app/streaming/streamingResponse.ts b/packages/agents-hosting/src/app/streaming/streamingResponse.ts
index 71897aad..d17b8d69 100644
--- a/packages/agents-hosting/src/app/streaming/streamingResponse.ts
+++ b/packages/agents-hosting/src/app/streaming/streamingResponse.ts
@@ -3,7 +3,8 @@
  * Licensed under the MIT License.
  */
 
-import { Activity, addAIToActivity, Attachment, Entity, ClientCitation, SensitivityUsageInfo } from '@microsoft/agents-activity'
+import { ExceptionHelper, Activity, addAIToActivity, Attachment, Entity, ClientCitation, SensitivityUsageInfo } from '@microsoft/agents-activity'
+import { Errors } from '../../errorHelper'
 import { TurnContext } from '../../turnContext'
 import { Citation } from './citation'
 import { CitationUtil } from './citationUtil'
@@ -95,7 +96,7 @@ export class StreamingResponse {
      */
   public queueInformativeUpdate (text: string): void {
     if (this._ended) {
-      throw new Error('The stream has already ended.')
+      throw ExceptionHelper.generateException(Error, Errors.StreamAlreadyEnded)
     }
 
     // Queue a typing activity
@@ -123,7 +124,7 @@ export class StreamingResponse {
      */
   public queueTextChunk (text: string, citations?: Citation[]): void {
     if (this._ended) {
-      throw new Error('The stream has already ended.')
+      throw ExceptionHelper.generateException(Error, Errors.StreamAlreadyEnded)
     }
 
     // Update full message text
@@ -143,7 +144,7 @@ export class StreamingResponse {
      */
   public endStream (): Promise<void> {
     if (this._ended) {
-      throw new Error('The stream has already ended.')
+      throw ExceptionHelper.generateException(Error, Errors.StreamAlreadyEnded)
     }
 
     // Queue final message
diff --git a/packages/agents-hosting/src/app/turnState.ts b/packages/agents-hosting/src/app/turnState.ts
index 2c608757..b5fed663 100644
--- a/packages/agents-hosting/src/app/turnState.ts
+++ b/packages/agents-hosting/src/app/turnState.ts
@@ -6,6 +6,8 @@
 import { Storage, StoreItems } from '../storage'
 import { AppMemory } from './appMemory'
 import { TurnStateEntry } from './turnStateEntry'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 import { TurnContext } from '../turnContext'
 import { debug } from '@microsoft/agents-activity/logger'
 
@@ -87,7 +89,7 @@ export class TurnState<
   public get conversation (): TConversationState {
     const scope = this.getScope(CONVERSATION_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     return scope.value as TConversationState
   }
@@ -101,7 +103,7 @@ export class TurnState<
   public set conversation (value: TConversationState) {
     const scope = this.getScope(CONVERSATION_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     scope.replace(value as Record<string, unknown>)
   }
@@ -127,7 +129,7 @@ export class TurnState<
   public get user (): TUserState {
     const scope = this.getScope(USER_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     return scope.value as TUserState
   }
@@ -141,7 +143,7 @@ export class TurnState<
   public set user (value: TUserState) {
     const scope = this.getScope(USER_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     scope.replace(value as Record<string, unknown>)
   }
@@ -157,7 +159,7 @@ export class TurnState<
   public deleteConversationState (): void {
     const scope = this.getScope(CONVERSATION_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     scope.delete()
   }
@@ -173,7 +175,7 @@ export class TurnState<
   public deleteUserState (): void {
     const scope = this.getScope(USER_SCOPE)
     if (!scope) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
     scope.delete()
   }
@@ -316,7 +318,7 @@ export class TurnState<
     }
 
     if (!this._isLoaded) {
-      throw new Error(this._stateNotLoadedString)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateNotLoaded)
     }
 
     let changes: StoreItems | undefined
@@ -378,19 +380,19 @@ export class TurnState<
     const userId = activity?.from?.id
 
     if (!channelId) {
-      throw new Error('missing context.activity.channelId')
+      throw ExceptionHelper.generateException(Error, Errors.MissingContextActivityChannelId)
     }
 
     if (!agentId) {
-      throw new Error('missing context.activity.recipient.id')
+      throw ExceptionHelper.generateException(Error, Errors.MissingContextActivityRecipientId)
     }
 
     if (!conversationId) {
-      throw new Error('missing context.activity.conversation.id')
+      throw ExceptionHelper.generateException(Error, Errors.MissingContextActivityConversationId)
     }
 
     if (!userId) {
-      throw new Error('missing context.activity.from.id')
+      throw ExceptionHelper.generateException(Error, Errors.MissingContextActivityFromId)
     }
 
     const keys: Record<string, string> = {}
@@ -413,14 +415,14 @@ export class TurnState<
   private getScopeAndName (path: string): { scope: TurnStateEntry; name: string } {
     const parts = path.split('.')
     if (parts.length > 2) {
-      throw new Error(`Invalid state path: ${path}`)
+      throw ExceptionHelper.generateException(Error, Errors.InvalidStatePath, undefined, { path })
     } else if (parts.length === 1) {
       parts.unshift(TEMP_SCOPE)
     }
 
     const scope = this.getScope(parts[0])
     if (scope === undefined) {
-      throw new Error(`Invalid state scope: ${parts[0]}`)
+      throw ExceptionHelper.generateException(Error, Errors.InvalidStateScope, undefined, { scope: parts[0] })
     }
     return { scope, name: parts[1] }
   }
diff --git a/packages/agents-hosting/src/app/turnStateProperty.ts b/packages/agents-hosting/src/app/turnStateProperty.ts
index 29aba4d2..143cd3ac 100644
--- a/packages/agents-hosting/src/app/turnStateProperty.ts
+++ b/packages/agents-hosting/src/app/turnStateProperty.ts
@@ -3,6 +3,8 @@
  * Licensed under the MIT License.
  */
 
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 import { TurnContext } from '../turnContext'
 import { StatePropertyAccessor } from '../state'
 import { TurnStateEntry } from './turnStateEntry'
@@ -27,12 +29,12 @@ export class TurnStateProperty<T = any> implements StatePropertyAccessor<T> {
 
     const scope = state.getScope(scopeName)
     if (!scope) {
-      throw new Error(`TurnStateProperty: TurnState missing state scope named "${scope}".`)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateMissingScope, undefined, { scope: scopeName })
     }
 
     this._state = scope
     if (!this._state) {
-      throw new Error(`TurnStateProperty: TurnState missing state scope named "${scope}".`)
+      throw ExceptionHelper.generateException(Error, Errors.TurnStateMissingScope, undefined, { scope: scopeName })
     }
   }
 
diff --git a/packages/agents-hosting/src/auth/authConfiguration.ts b/packages/agents-hosting/src/auth/authConfiguration.ts
index 608659b1..f376df2e 100644
--- a/packages/agents-hosting/src/auth/authConfiguration.ts
+++ b/packages/agents-hosting/src/auth/authConfiguration.ts
@@ -3,6 +3,8 @@
  * Licensed under the MIT License.
  */
 
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 import { debug } from '@microsoft/agents-activity/logger'
 import { ConnectionMapItem } from './msalConnectionManager'
 import objectPath from 'object-path'
@@ -131,13 +133,13 @@ export const loadAuthConfigFromEnv = (cnxName?: string): AuthConfiguration => {
       if (entry) {
         authConfig = entry
       } else {
-        throw new Error(`Connection "${cnxName}" not found in environment.`)
+        throw ExceptionHelper.generateException(Error, Errors.ConnectionNotFoundInEnvironment, undefined, { cnxName })
       }
     } else {
       const defaultItem = envConnections.connectionsMap.find((item) => item.serviceUrl === '*')
       const defaultConn = defaultItem ? envConnections.connections.get(defaultItem.connection) : undefined
       if (!defaultConn) {
-        throw new Error('No default connection found in environment connections.')
+        throw ExceptionHelper.generateException(Error, Errors.NoDefaultConnection)
       }
       authConfig = defaultConn
     }
@@ -173,7 +175,7 @@ export const loadPrevAuthConfigFromEnv: () => AuthConfiguration = () => {
   if (envConnections.connectionsMap.length === 0) {
     // No connections provided, we need to populate the connection map with the old config settings
     if (process.env.MicrosoftAppId === undefined && process.env.NODE_ENV === 'production') {
-      throw new Error('ClientId required in production')
+      throw ExceptionHelper.generateException(Error, Errors.ClientIdRequiredInProduction)
     }
     const authority = process.env.authorityEndpoint ?? 'https://login.microsoftonline.com'
     authConfig = {
@@ -200,7 +202,7 @@ export const loadPrevAuthConfigFromEnv: () => AuthConfiguration = () => {
     const defaultItem = envConnections.connectionsMap.find((item) => item.serviceUrl === '*')
     const defaultConn = defaultItem ? envConnections.connections.get(defaultItem.connection) : undefined
     if (!defaultConn) {
-      throw new Error('No default connection found in environment connections.')
+      throw ExceptionHelper.generateException(Error, Errors.NoDefaultConnection)
     }
     authConfig = defaultConn
   }
@@ -303,7 +305,7 @@ export function getAuthConfigWithDefaults (config?: AuthConfiguration): AuthConf
     const defaultItem = connections.connectionsMap?.find((item) => item.serviceUrl === '*')
     const defaultConn = defaultItem ? connections.connections?.get(defaultItem.connection) : undefined
     if (!defaultConn) {
-      throw new Error('No default connection found in environment connections.')
+      throw ExceptionHelper.generateException(Error, Errors.NoDefaultConnection)
     }
     mergedConfig = buildLegacyAuthConfig(undefined, defaultConn)
   }
@@ -321,10 +323,10 @@ function buildLegacyAuthConfig (envPrefix: string = '', customConfig?: AuthConfi
   const clientId = customConfig?.clientId ?? process.env[`${prefix}clientId`]
 
   if (!clientId && !envPrefix && process.env.NODE_ENV === 'production') {
-    throw new Error('ClientId required in production')
+    throw ExceptionHelper.generateException(Error, Errors.ClientIdRequiredInProduction)
   }
   if (!clientId && envPrefix) {
-    throw new Error(`ClientId not found for connection: ${envPrefix}`)
+    throw ExceptionHelper.generateException(Error, Errors.ClientIdNotFoundForConnection, undefined, { envPrefix })
   }
 
   const tenantId = customConfig?.tenantId ?? process.env[`${prefix}tenantId`]
diff --git a/packages/agents-hosting/src/auth/jwt-middleware.ts b/packages/agents-hosting/src/auth/jwt-middleware.ts
index 4541ff16..9b9f1124 100644
--- a/packages/agents-hosting/src/auth/jwt-middleware.ts
+++ b/packages/agents-hosting/src/auth/jwt-middleware.ts
@@ -9,6 +9,8 @@ import { Request } from './request'
 import jwksRsa, { JwksClient, SigningKey } from 'jwks-rsa'
 import jwt, { JwtHeader, JwtPayload, SignCallback, GetPublicKeyOrSecret } from 'jsonwebtoken'
 import { debug } from '@microsoft/agents-activity/logger'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 
 const logger = debug('agents:jwt-middleware')
 
@@ -23,7 +25,7 @@ const verifyToken = async (raw: string, config: AuthConfiguration): Promise<JwtP
   logger.debug('jwt.decode ', JSON.stringify(payload))
 
   if (!payload) {
-    throw new Error('invalid token')
+    throw ExceptionHelper.generateException(Error, Errors.InvalidToken)
   }
   const audience = payload.aud
 
diff --git a/packages/agents-hosting/src/auth/msalConnectionManager.ts b/packages/agents-hosting/src/auth/msalConnectionManager.ts
index 1878d0f9..b5c71d69 100644
--- a/packages/agents-hosting/src/auth/msalConnectionManager.ts
+++ b/packages/agents-hosting/src/auth/msalConnectionManager.ts
@@ -3,11 +3,12 @@
  * Licensed under the MIT License.
  */
 
-import { Activity, RoleTypes } from '@microsoft/agents-activity'
+import { Activity, RoleTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { AuthConfiguration } from './authConfiguration'
 import { Connections } from './connections'
 import { MsalTokenProvider } from './msalTokenProvider'
 import { JwtPayload } from 'jsonwebtoken'
+import { Errors } from '../errorHelper'
 
 export interface ConnectionMapItem {
   audience?: string
@@ -48,7 +49,7 @@ export class MsalConnectionManager implements Connections {
   getConnection (connectionName: string): MsalTokenProvider {
     const conn = this._connections.get(connectionName)
     if (!conn) {
-      throw new Error(`Connection not found: ${connectionName}`)
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionNotFound, undefined, { connectionName })
     }
     return this.applyConnectionDefaults(conn)
   }
@@ -59,7 +60,7 @@ export class MsalConnectionManager implements Connections {
    */
   getDefaultConnection (): MsalTokenProvider {
     if (this._connections.size === 0) {
-      throw new Error('No connections found for this Agent in the Connections Configuration.')
+      throw ExceptionHelper.generateException(Error, Errors.NoConnectionsFound)
     }
 
     // Return the wildcard map item instance.
@@ -94,7 +95,7 @@ export class MsalConnectionManager implements Connections {
    */
   getTokenProvider (identity: JwtPayload, serviceUrl: string): MsalTokenProvider {
     if (!identity) {
-      throw new Error('Identity is required to get the token provider.')
+      throw ExceptionHelper.generateException(Error, Errors.IdentityRequiredForTokenProvider)
     }
 
     let audience
@@ -129,7 +130,7 @@ export class MsalConnectionManager implements Connections {
         }
       }
     }
-    throw new Error(`No connection found for audience: ${audience} and serviceUrl: ${serviceUrl}`)
+    throw ExceptionHelper.generateException(Error, Errors.NoConnectionForAudienceAndServiceUrl, undefined, { audience, serviceUrl })
   }
 
   /**
diff --git a/packages/agents-hosting/src/auth/msalTokenProvider.ts b/packages/agents-hosting/src/auth/msalTokenProvider.ts
index 430b1a3b..8e67bdec 100644
--- a/packages/agents-hosting/src/auth/msalTokenProvider.ts
+++ b/packages/agents-hosting/src/auth/msalTokenProvider.ts
@@ -6,6 +6,8 @@
 import { ConfidentialClientApplication, LogLevel, ManagedIdentityApplication, NodeSystemOptions } from '@azure/msal-node'
 import axios from 'axios'
 import { AuthConfiguration } from './authConfiguration'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 import { AuthProvider } from './authProvider'
 import { debug } from '@microsoft/agents-activity/logger'
 import { v4 } from 'uuid'
@@ -50,7 +52,7 @@ export class MsalTokenProvider implements AuthProvider {
     if (typeof authConfigOrScope === 'string') {
     // Called as getAccessToken(scope)
       if (!this.connectionSettings) {
-        throw new Error('Connection settings must be provided to constructor when calling getAccessToken(scope)')
+        throw ExceptionHelper.generateException(Error, Errors.ConnectionSettingsRequiredForGetAccessToken)
       }
       authConfig = this.connectionSettings
       actualScope = authConfigOrScope
@@ -78,10 +80,10 @@ export class MsalTokenProvider implements AuthProvider {
       authConfig.certKeyFile === undefined) {
       token = await this.acquireTokenWithUserAssignedIdentity(authConfig, actualScope)
     } else {
-      throw new Error('Invalid authConfig. ')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidAuthConfig)
     }
     if (token === undefined) {
-      throw new Error('Failed to acquire token')
+      throw ExceptionHelper.generateException(Error, Errors.FailedToAcquireToken)
     }
 
     return token
@@ -102,7 +104,7 @@ export class MsalTokenProvider implements AuthProvider {
     if (Array.isArray(authConfigOrScopes)) {
     // Called as acquireTokenOnBehalfOf(scopes, oboAssertion)
       if (!this.connectionSettings) {
-        throw new Error('Connection settings must be provided to constructor when calling acquireTokenOnBehalfOf(scopes, oboAssertion)')
+        throw ExceptionHelper.generateException(Error, Errors.ConnectionSettingsRequiredForAcquireTokenOnBehalfOf)
       }
       authConfig = this.connectionSettings
       actualScopes = authConfigOrScopes
@@ -132,7 +134,7 @@ export class MsalTokenProvider implements AuthProvider {
   public async getAgenticInstanceToken (tenantId: string, agentAppInstanceId: string): Promise<string> {
     logger.debug('Getting agentic instance token')
     if (!this.connectionSettings) {
-      throw new Error('Connection settings must be provided when calling getAgenticInstanceToken')
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionSettingsRequiredForGetAgenticInstanceToken)
     }
     const appToken = await this.getAgenticApplicationToken(tenantId, agentAppInstanceId)
     const cca = new ConfidentialClientApplication({
@@ -150,7 +152,7 @@ export class MsalTokenProvider implements AuthProvider {
     })
 
     if (!token?.accessToken) {
-      throw new Error(`Failed to acquire instance token for agent instance: ${agentAppInstanceId}`)
+      throw ExceptionHelper.generateException(Error, Errors.FailedToAcquireInstanceToken, undefined, { agentAppInstanceId })
     }
 
     return token.accessToken
@@ -187,7 +189,7 @@ export class MsalTokenProvider implements AuthProvider {
    */
   private async acquireTokenByForAgenticScenarios (tenantId: string, clientId: string, clientAssertion: string | undefined, scopes: string[], tokenBodyParameters: { [key: string]: any }): Promise<string | null> {
     if (!this.connectionSettings) {
-      throw new Error('Connection settings must be provided when calling getAgenticInstanceToken')
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionSettingsRequiredForGetAgenticInstanceToken)
     }
 
     // Check cache first
@@ -241,7 +243,7 @@ export class MsalTokenProvider implements AuthProvider {
     })
 
     if (!token) {
-      throw new Error(`Failed to acquire instance token for user token: ${agentAppInstanceId}`)
+      throw ExceptionHelper.generateException(Error, Errors.FailedToAcquireInstanceTokenForUserToken, undefined, { agentAppInstanceId })
     }
 
     return token
@@ -249,7 +251,7 @@ export class MsalTokenProvider implements AuthProvider {
 
   public async getAgenticApplicationToken (tenantId: string, agentAppInstanceId: string): Promise<string> {
     if (!this.connectionSettings?.clientId) {
-      throw new Error('Connection settings must be provided when calling getAgenticApplicationToken')
+      throw ExceptionHelper.generateException(Error, Errors.ConnectionSettingsRequiredForGetAgenticApplicationToken)
     }
     logger.debug('Getting agentic application token')
     const token = await this.acquireTokenByForAgenticScenarios(tenantId, this.connectionSettings.clientId, undefined, ['api://AzureAdTokenExchange/.default'], {
@@ -258,7 +260,7 @@ export class MsalTokenProvider implements AuthProvider {
     })
 
     if (!token) {
-      throw new Error(`Failed to acquire token for agent instance: ${agentAppInstanceId}`)
+      throw ExceptionHelper.generateException(Error, Errors.FailedToAcquireTokenForAgentInstance, undefined, { agentAppInstanceId })
     }
 
     return token
diff --git a/packages/agents-hosting/src/baseAdapter.ts b/packages/agents-hosting/src/baseAdapter.ts
index ea9e3a3b..2a3454f4 100644
--- a/packages/agents-hosting/src/baseAdapter.ts
+++ b/packages/agents-hosting/src/baseAdapter.ts
@@ -6,11 +6,12 @@
 import { Middleware, MiddlewareHandler, MiddlewareSet } from './middlewareSet'
 import { TurnContext } from './turnContext'
 import { debug } from '@microsoft/agents-activity/logger'
-import { Activity, ConversationReference } from '@microsoft/agents-activity'
+import { Activity, ConversationReference, ExceptionHelper } from '@microsoft/agents-activity'
 import { ResourceResponse } from './connector-client/resourceResponse'
 import { AttachmentData } from './connector-client/attachmentData'
 import { AttachmentInfo } from './connector-client/attachmentInfo'
 import { JwtPayload } from 'jsonwebtoken'
+import { Errors } from './errorHelper'
 
 const logger = debug('agents:base-adapter')
 
@@ -202,7 +203,7 @@ export abstract class BaseAdapter {
         if (err instanceof Error) {
           await this.onTurnError(pContext.proxy, err)
         } else {
-          throw new Error('Unknown error type: ' + err.message)
+          throw ExceptionHelper.generateException(Error, Errors.UnknownErrorType, undefined, { message: err.message })
         }
       } else {
         throw err
diff --git a/packages/agents-hosting/src/cloudAdapter.ts b/packages/agents-hosting/src/cloudAdapter.ts
index b54fc599..33140783 100644
--- a/packages/agents-hosting/src/cloudAdapter.ts
+++ b/packages/agents-hosting/src/cloudAdapter.ts
@@ -13,7 +13,7 @@ import { AuthConfiguration, getAuthConfigWithDefaults } from './auth/authConfigu
 import { AuthProvider } from './auth/authProvider'
 import { ApxProductionScope } from './auth/authConstants'
 import { MsalConnectionManager } from './auth/msalConnectionManager'
-import { Activity, ActivityEventNames, ActivityTypes, Channels, ConversationReference, DeliveryModes, ConversationParameters, RoleTypes } from '@microsoft/agents-activity'
+import { Activity, ActivityEventNames, ActivityTypes, Channels, ConversationReference, DeliveryModes, ConversationParameters, RoleTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { ResourceResponse } from './connector-client/resourceResponse'
 import * as uuid from 'uuid'
 import { debug } from '@microsoft/agents-activity/logger'
@@ -23,6 +23,7 @@ import { AttachmentInfo } from './connector-client/attachmentInfo'
 import { AttachmentData } from './connector-client/attachmentData'
 import { normalizeIncomingActivity } from './activityWireCompat'
 import { UserTokenClient } from './oauth'
+import { Errors } from './errorHelper'
 import { HeaderPropagation, HeaderPropagationCollection, HeaderPropagationDefinition } from './headerPropagation'
 import { JwtPayload } from 'jsonwebtoken'
 import { getTokenServiceEndpoint } from './oauth/customUserTokenAPI'
@@ -65,7 +66,7 @@ export class CloudAdapter extends BaseAdapter {
    */
   protected resolveIfConnectorClientIsNeeded (activity: Activity): boolean {
     if (!activity) {
-      throw new TypeError('`activity` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ActivityParameterRequired)
     }
 
     switch (activity.deliveryMode) {
@@ -145,7 +146,7 @@ export class CloudAdapter extends BaseAdapter {
           headers
         )
       } else {
-        throw new Error('Could not create connector client for agentic user')
+        throw ExceptionHelper.generateException(Error, Errors.CouldNotCreateConnectorClient)
       }
     } else {
       // ABS tokens will not have an azp/appid so use the botframework scope.
@@ -249,15 +250,15 @@ export class CloudAdapter extends BaseAdapter {
    */
   async sendActivities (context: TurnContext, activities: Activity[]): Promise<ResourceResponse[]> {
     if (!context) {
-      throw new TypeError('`context` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ContextParameterRequired)
     }
 
     if (!activities) {
-      throw new TypeError('`activities` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ActivitiesParameterRequired)
     }
 
     if (activities.length === 0) {
-      throw new Error('Expecting one or more activities, but the array was empty.')
+      throw ExceptionHelper.generateException(Error, Errors.EmptyActivitiesArray)
     }
 
     const responses: ResourceResponse[] = []
@@ -271,7 +272,7 @@ export class CloudAdapter extends BaseAdapter {
         // no-op
       } else {
         if (!activity.serviceUrl || (activity.conversation == null) || !activity.conversation.id) {
-          throw new Error('Invalid activity object')
+          throw ExceptionHelper.generateException(Error, Errors.InvalidActivityObject)
         }
 
         if (activity.replyToId) {
@@ -320,7 +321,7 @@ export class CloudAdapter extends BaseAdapter {
       res.end()
     }
     if (!request.body) {
-      throw new TypeError('`request.body` parameter required, make sure express.json() is used as middleware')
+      throw ExceptionHelper.generateException(TypeError, Errors.RequestBodyRequired)
     }
     const incoming = normalizeIncomingActivity(request.body!)
     const activity = Activity.fromObject(incoming)
@@ -387,15 +388,15 @@ export class CloudAdapter extends BaseAdapter {
    */
   async updateActivity (context: TurnContext, activity: Activity): Promise<ResourceResponse | void> {
     if (!context) {
-      throw new TypeError('`context` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ContextParameterRequired)
     }
 
     if (!activity) {
-      throw new TypeError('`activity` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ActivityParameterRequired)
     }
 
     if (!activity.serviceUrl || (activity.conversation == null) || !activity.conversation.id || !activity.id) {
-      throw new Error('Invalid activity object')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidActivityObject)
     }
 
     const response = await context.turnState.get(this.ConnectorClientKey).updateActivity(
@@ -415,11 +416,11 @@ export class CloudAdapter extends BaseAdapter {
    */
   async deleteActivity (context: TurnContext, reference: Partial<ConversationReference>): Promise<void> {
     if (!context) {
-      throw new TypeError('`context` parameter required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ContextParameterRequired)
     }
 
     if (!reference || !reference.serviceUrl || (reference.conversation == null) || !reference.conversation.id || !reference.activityId) {
-      throw new Error('Invalid conversation reference object')
+      throw ExceptionHelper.generateException(Error, Errors.InvalidConversationReference)
     }
 
     await context.turnState.get(this.ConnectorClientKey).deleteActivity(reference.conversation.id, reference.activityId)
@@ -437,11 +438,11 @@ export class CloudAdapter extends BaseAdapter {
     logic: (revocableContext: TurnContext) => Promise<void>,
     isResponse: Boolean = false): Promise<void> {
     if (!reference || !reference.serviceUrl || (reference.conversation == null) || !reference.conversation.id) {
-      throw new Error('continueConversation: Invalid conversation reference object')
+      throw ExceptionHelper.generateException(Error, Errors.ContinueConversationInvalidReference)
     }
 
     if (!botAppIdOrIdentity) {
-      throw new TypeError('continueConversation: botAppIdOrIdentity is required')
+      throw ExceptionHelper.generateException(TypeError, Errors.ContinueConversationBotAppIdRequired)
     }
     const botAppId = typeof botAppIdOrIdentity === 'string' ? botAppIdOrIdentity : botAppIdOrIdentity.aud as string
 
@@ -548,10 +549,14 @@ export class CloudAdapter extends BaseAdapter {
     logic: (context: TurnContext) => Promise<void>
   ): Promise<void> {
     if (typeof serviceUrl !== 'string' || !serviceUrl) {
-      throw new TypeError('`serviceUrl` must be a non-empty string')
+      throw ExceptionHelper.generateException(TypeError, Errors.ServiceUrlRequired)
+    }
+    if (!conversationParameters) {
+      throw ExceptionHelper.generateException(TypeError, Errors.ConversationParametersRequired)
+    }
+    if (!logic) {
+      throw ExceptionHelper.generateException(TypeError, Errors.LogicRequired)
     }
-    if (!conversationParameters) throw new TypeError('`conversationParameters` must be defined')
-    if (!logic) throw new TypeError('`logic` must be defined')
 
     const identity = CloudAdapter.createIdentity(audience)
     const restClient = await this.createConnectorClient(serviceUrl, audience, identity)
@@ -578,15 +583,15 @@ export class CloudAdapter extends BaseAdapter {
    */
   async uploadAttachment (context: TurnContext, conversationId: string, attachmentData: AttachmentData): Promise<ResourceResponse> {
     if (context === undefined) {
-      throw new Error('context is required')
+      throw ExceptionHelper.generateException(Error, Errors.ContextRequired)
     }
 
     if (conversationId === undefined) {
-      throw new Error('conversationId is required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdRequired)
     }
 
     if (attachmentData === undefined) {
-      throw new Error('attachmentData is required')
+      throw ExceptionHelper.generateException(Error, Errors.AttachmentDataRequired)
     }
 
     return await context.turnState.get<ConnectorClient>(this.ConnectorClientKey).uploadAttachment(conversationId, attachmentData)
@@ -600,11 +605,11 @@ export class CloudAdapter extends BaseAdapter {
    */
   async getAttachmentInfo (context: TurnContext, attachmentId: string): Promise<AttachmentInfo> {
     if (context === undefined) {
-      throw new Error('context is required')
+      throw ExceptionHelper.generateException(Error, Errors.ContextRequired)
     }
 
     if (attachmentId === undefined) {
-      throw new Error('attachmentId is required')
+      throw ExceptionHelper.generateException(Error, Errors.AttachmentIdRequired)
     }
 
     return await context.turnState.get<ConnectorClient>(this.ConnectorClientKey).getAttachmentInfo(attachmentId)
@@ -619,15 +624,15 @@ export class CloudAdapter extends BaseAdapter {
    */
   async getAttachment (context: TurnContext, attachmentId: string, viewId: string): Promise<NodeJS.ReadableStream> {
     if (context === undefined) {
-      throw new Error('context is required')
+      throw ExceptionHelper.generateException(Error, Errors.ContextRequired)
     }
 
     if (attachmentId === undefined) {
-      throw new Error('attachmentId is required')
+      throw ExceptionHelper.generateException(Error, Errors.AttachmentIdRequired)
     }
 
     if (viewId === undefined) {
-      throw new Error('viewId is required')
+      throw ExceptionHelper.generateException(Error, Errors.ViewIdRequired)
     }
 
     return await context.turnState.get<ConnectorClient>(this.ConnectorClientKey).getAttachment(attachmentId, viewId)
diff --git a/packages/agents-hosting/src/connector-client/connectorClient.ts b/packages/agents-hosting/src/connector-client/connectorClient.ts
index e84624a0..62374469 100644
--- a/packages/agents-hosting/src/connector-client/connectorClient.ts
+++ b/packages/agents-hosting/src/connector-client/connectorClient.ts
@@ -3,7 +3,7 @@ import axios, { AxiosInstance, AxiosRequestConfig, AxiosResponse } from 'axios'
 import { AuthConfiguration } from '../auth/authConfiguration'
 import { AuthProvider } from '../auth/authProvider'
 import { debug } from '@microsoft/agents-activity/logger'
-import { Activity, ChannelAccount, ConversationParameters, RoleTypes, Channels } from '@microsoft/agents-activity'
+import { Activity, ChannelAccount, ConversationParameters, RoleTypes, Channels, ExceptionHelper } from '@microsoft/agents-activity'
 import { ConversationsResult } from './conversationsResult'
 import { ConversationResourceResponse } from './conversationResourceResponse'
 import { ResourceResponse } from './resourceResponse'
@@ -12,6 +12,7 @@ import { AttachmentData } from './attachmentData'
 import { normalizeOutgoingActivity } from '../activityWireCompat'
 import { getProductInfo } from '../getProductInfo'
 import { HeaderPropagation, HeaderPropagationCollection } from '../headerPropagation'
+import { Errors } from '../errorHelper'
 const logger = debug('agents:connector-client')
 
 export { getProductInfo }
@@ -143,7 +144,7 @@ export class ConnectorClient {
 
   public async getConversationMember (userId: string, conversationId: string): Promise<ChannelAccount> {
     if (!userId || !conversationId) {
-      throw new Error('userId and conversationId are required')
+      throw ExceptionHelper.generateException(Error, Errors.UserIdAndConversationIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'get',
@@ -192,7 +193,7 @@ export class ConnectorClient {
   ): Promise<ResourceResponse> {
     logger.debug(`Replying to activity: ${activityId} in conversation: ${conversationId}`)
     if (!conversationId || !activityId) {
-      throw new Error('conversationId and activityId are required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdAndActivityIdRequired)
     }
 
     const trimmedConversationId: string = this.conditionallyTruncateConversationId(conversationId, body)
@@ -242,7 +243,7 @@ export class ConnectorClient {
   ): Promise<ResourceResponse> {
     logger.debug(`Send to conversation: ${conversationId} activity: ${body.id}`)
     if (!conversationId) {
-      throw new Error('conversationId is required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdRequired)
     }
 
     const trimmedConversationId: string = this.conditionallyTruncateConversationId(conversationId, body)
@@ -272,7 +273,7 @@ export class ConnectorClient {
     body: Activity
   ): Promise<ResourceResponse> {
     if (!conversationId || !activityId) {
-      throw new Error('conversationId and activityId are required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdAndActivityIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'put',
@@ -297,7 +298,7 @@ export class ConnectorClient {
     activityId: string
   ): Promise<void> {
     if (!conversationId || !activityId) {
-      throw new Error('conversationId and activityId are required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdAndActivityIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'delete',
@@ -321,7 +322,7 @@ export class ConnectorClient {
     body: AttachmentData
   ): Promise<ResourceResponse> {
     if (conversationId === undefined) {
-      throw new Error('conversationId is required')
+      throw ExceptionHelper.generateException(Error, Errors.ConversationIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'post',
@@ -344,7 +345,7 @@ export class ConnectorClient {
     attachmentId: string
   ): Promise<AttachmentInfo> {
     if (attachmentId === undefined) {
-      throw new Error('attachmentId is required')
+      throw ExceptionHelper.generateException(Error, Errors.AttachmentIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'get',
@@ -368,10 +369,10 @@ export class ConnectorClient {
     viewId: string
   ): Promise<NodeJS.ReadableStream> {
     if (attachmentId === undefined) {
-      throw new Error('attachmentId is required')
+      throw ExceptionHelper.generateException(Error, Errors.AttachmentIdRequired)
     }
     if (viewId === undefined) {
-      throw new Error('viewId is required')
+      throw ExceptionHelper.generateException(Error, Errors.ViewIdRequired)
     }
     const config: AxiosRequestConfig = {
       method: 'get',
diff --git a/packages/agents-hosting/src/errorHelper.ts b/packages/agents-hosting/src/errorHelper.ts
new file mode 100644
index 00000000..52eb5be1
--- /dev/null
+++ b/packages/agents-hosting/src/errorHelper.ts
@@ -0,0 +1,879 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+import { AgentErrorDefinition } from '@microsoft/agents-activity'
+
+/**
+ * Error definitions for the Hosting system.
+ * This contains localized error codes for the Hosting subsystem of the AgentSDK.
+ *
+ * Each error definition includes an error code (starting from -120000), a description, and a help link
+ * pointing to an AKA link to get help for the given error.
+ *
+ * Usage example:
+ * ```
+ * throw ExceptionHelper.generateException(
+ *   Error,
+ *   Errors.MissingTurnContext
+ * );
+ * ```
+ */
+export const Errors: { [key: string]: AgentErrorDefinition } = {
+  // Activity Handler Errors (-120000 to -120019)
+  /**
+   * Error thrown when TurnContext parameter is missing.
+   */
+  MissingTurnContext: {
+    code: -120000,
+    description: 'Missing TurnContext parameter',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when TurnContext does not include an activity.
+   */
+  TurnContextMissingActivity: {
+    code: -120001,
+    description: 'TurnContext does not include an activity',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Activity is missing its type.
+   */
+  ActivityMissingType: {
+    code: -120002,
+    description: 'Activity is missing its type',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when activity object is invalid.
+   */
+  InvalidActivityObject: {
+    code: -120003,
+    description: 'Invalid activity object',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Activity is required.
+   */
+  ActivityRequired: {
+    code: -120004,
+    description: 'Activity is required.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Cloud Adapter Errors (-120020 to -120039)
+  /**
+   * Error thrown when activity parameter is required.
+   */
+  ActivityParameterRequired: {
+    code: -120020,
+    description: '`activity` parameter required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context parameter is required.
+   */
+  ContextParameterRequired: {
+    code: -120021,
+    description: '`context` parameter required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when activities parameter is required.
+   */
+  ActivitiesParameterRequired: {
+    code: -120022,
+    description: '`activities` parameter required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when expecting one or more activities, but the array was empty.
+   */
+  EmptyActivitiesArray: {
+    code: -120023,
+    description: 'Expecting one or more activities, but the array was empty.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when request.body parameter is required.
+   */
+  RequestBodyRequired: {
+    code: -120024,
+    description: '`request.body` parameter required, make sure express.json() is used as middleware',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when conversation reference object is invalid.
+   */
+  InvalidConversationReference: {
+    code: -120025,
+    description: 'Invalid conversation reference object',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when continueConversation has invalid conversation reference object.
+   */
+  ContinueConversationInvalidReference: {
+    code: -120026,
+    description: 'continueConversation: Invalid conversation reference object',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when continueConversation requires botAppIdOrIdentity.
+   */
+  ContinueConversationBotAppIdRequired: {
+    code: -120027,
+    description: 'continueConversation: botAppIdOrIdentity is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when serviceUrl must be a non-empty string.
+   */
+  ServiceUrlRequired: {
+    code: -120028,
+    description: '`serviceUrl` must be a non-empty string',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when conversationParameters must be defined.
+   */
+  ConversationParametersRequired: {
+    code: -120029,
+    description: '`conversationParameters` must be defined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when logic must be defined.
+   */
+  LogicRequired: {
+    code: -120030,
+    description: '`logic` must be defined',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context is required.
+   */
+  ContextRequired: {
+    code: -120031,
+    description: 'context is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when conversationId is required.
+   */
+  ConversationIdRequired: {
+    code: -120032,
+    description: 'conversationId is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when attachmentData is required.
+   */
+  AttachmentDataRequired: {
+    code: -120033,
+    description: 'attachmentData is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when attachmentId is required.
+   */
+  AttachmentIdRequired: {
+    code: -120034,
+    description: 'attachmentId is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when viewId is required.
+   */
+  ViewIdRequired: {
+    code: -120035,
+    description: 'viewId is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when could not create connector client for agentic user.
+   */
+  CouldNotCreateConnectorClient: {
+    code: -120036,
+    description: 'Could not create connector client for agentic user',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Storage Errors (-120040 to -120049)
+  /**
+   * Error thrown when Keys are required when reading.
+   */
+  KeysRequiredForReading: {
+    code: -120040,
+    description: 'Keys are required when reading.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Changes are required when writing.
+   */
+  ChangesRequiredForWriting: {
+    code: -120041,
+    description: 'Changes are required when writing.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when there is an eTag conflict during storage write.
+   */
+  StorageEtagConflict: {
+    code: -120042,
+    description: 'Storage: error writing "{key}" due to eTag conflict.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // State Errors (-120050 to -120059)
+  /**
+   * Error thrown when activity.channelId is missing.
+   */
+  MissingActivityChannelId: {
+    code: -120050,
+    description: 'missing activity.channelId',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when activity.conversation.id is missing.
+   */
+  MissingActivityConversationId: {
+    code: -120051,
+    description: 'missing activity.conversation.id',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when activity.from.id is missing.
+   */
+  MissingActivityFromId: {
+    code: -120052,
+    description: 'missing activity.from.id',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context.activity.channelId is missing.
+   */
+  MissingContextActivityChannelId: {
+    code: -120053,
+    description: 'missing context.activity.channelId',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context.activity.conversation.id is missing.
+   */
+  MissingContextActivityConversationId: {
+    code: -120054,
+    description: 'missing context.activity.conversation.id',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context.activity.from.id is missing.
+   */
+  MissingContextActivityFromId: {
+    code: -120055,
+    description: 'missing context.activity.from.id',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when context.activity.recipient.id is missing.
+   */
+  MissingContextActivityRecipientId: {
+    code: -120056,
+    description: 'missing context.activity.recipient.id',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Turn Context Errors (-120060 to -120069)
+  /**
+   * Error thrown when attempting to set responded to false.
+   */
+  CannotSetRespondedToFalse: {
+    code: -120060,
+    description: "TurnContext: cannot set 'responded' to a value of 'false'.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Header Propagation Errors (-120070 to -120079)
+  /**
+   * Error thrown when Headers must be provided.
+   */
+  HeadersRequired: {
+    code: -120070,
+    description: 'Headers must be provided.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Middleware Errors (-120080 to -120089)
+  /**
+   * Error thrown when invalid plugin type being added to MiddlewareSet.
+   */
+  InvalidMiddlewarePlugin: {
+    code: -120080,
+    description: 'MiddlewareSet.use(): invalid plugin type being added.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Transcript Logger Errors (-120090 to -120099)
+  /**
+   * Error thrown when TranscriptLoggerMiddleware requires a TranscriptLogger instance.
+   */
+  TranscriptLoggerRequired: {
+    code: -120090,
+    description: 'TranscriptLoggerMiddleware requires a TranscriptLogger instance.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when channelId is required for transcript operations.
+   */
+  TranscriptChannelIdRequired: {
+    code: -120091,
+    description: 'channelId is required.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when conversationId is required for transcript operations.
+   */
+  TranscriptConversationIdRequired: {
+    code: -120092,
+    description: 'conversationId is required.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Connector Client Errors (-120100 to -120109)
+  /**
+   * Error thrown when userId and conversationId are required.
+   */
+  UserIdAndConversationIdRequired: {
+    code: -120100,
+    description: 'userId and conversationId are required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when conversationId and activityId are required.
+   */
+  ConversationIdAndActivityIdRequired: {
+    code: -120101,
+    description: 'conversationId and activityId are required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Agent Client Errors (-120110 to -120119)
+  /**
+   * Error thrown when failed to post activity to agent.
+   */
+  FailedToPostActivityToAgent: {
+    code: -120110,
+    description: 'Failed to post activity to agent: {statusText}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when missing agent client config for agent.
+   */
+  MissingAgentClientConfig: {
+    code: -120111,
+    description: 'Missing agent client config for agent {agentName}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Agent name is required.
+   */
+  AgentNameRequired: {
+    code: -120112,
+    description: 'Agent name is required',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // OAuth Errors (-120120 to -120129)
+  /**
+   * Error thrown when failed to sign out.
+   */
+  FailedToSignOut: {
+    code: -120120,
+    description: 'Failed to sign out',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Auth Configuration Errors (-120130 to -120159)
+  /**
+   * Error thrown when Connection not found in environment.
+   */
+  ConnectionNotFoundInEnvironment: {
+    code: -120130,
+    description: 'Connection "{cnxName}" not found in environment.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when No default connection found in environment connections.
+   */
+  NoDefaultConnection: {
+    code: -120131,
+    description: 'No default connection found in environment connections.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when ClientId required in production.
+   */
+  ClientIdRequiredInProduction: {
+    code: -120132,
+    description: 'ClientId required in production',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when ClientId not found for connection.
+   */
+  ClientIdNotFoundForConnection: {
+    code: -120133,
+    description: 'ClientId not found for connection: {envPrefix}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // MSAL Connection Manager Errors (-120160 to -120169)
+  /**
+   * Error thrown when Connection not found.
+   */
+  ConnectionNotFound: {
+    code: -120160,
+    description: 'Connection not found: {connectionName}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when No connections found for this Agent in the Connections Configuration.
+   */
+  NoConnectionsFound: {
+    code: -120161,
+    description: 'No connections found for this Agent in the Connections Configuration.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Identity is required to get the token provider.
+   */
+  IdentityRequiredForTokenProvider: {
+    code: -120162,
+    description: 'Identity is required to get the token provider.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Audience and Service URL are required to get the token provider.
+   */
+  AudienceAndServiceUrlRequired: {
+    code: -120163,
+    description: 'Audience and Service URL are required to get the token provider.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when No connection found for audience and serviceUrl.
+   */
+  NoConnectionForAudienceAndServiceUrl: {
+    code: -120164,
+    description: 'No connection found for audience: {audience} and serviceUrl: {serviceUrl}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // MSAL Token Provider Errors (-120170 to -120189)
+  /**
+   * Error thrown when Connection settings must be provided to constructor when calling getAccessToken.
+   */
+  ConnectionSettingsRequiredForGetAccessToken: {
+    code: -120170,
+    description: 'Connection settings must be provided to constructor when calling getAccessToken(scope)',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Invalid authConfig.
+   */
+  InvalidAuthConfig: {
+    code: -120171,
+    description: 'Invalid authConfig. ',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Failed to acquire token.
+   */
+  FailedToAcquireToken: {
+    code: -120172,
+    description: 'Failed to acquire token',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Connection settings must be provided to constructor when calling acquireTokenOnBehalfOf.
+   */
+  ConnectionSettingsRequiredForAcquireTokenOnBehalfOf: {
+    code: -120173,
+    description: 'Connection settings must be provided to constructor when calling acquireTokenOnBehalfOf(scopes, oboAssertion)',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Connection settings must be provided when calling getAgenticInstanceToken.
+   */
+  ConnectionSettingsRequiredForGetAgenticInstanceToken: {
+    code: -120174,
+    description: 'Connection settings must be provided when calling getAgenticInstanceToken',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Failed to acquire instance token for agent instance.
+   */
+  FailedToAcquireInstanceToken: {
+    code: -120175,
+    description: 'Failed to acquire instance token for agent instance: {agentAppInstanceId}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Failed to acquire instance token for user token.
+   */
+  FailedToAcquireInstanceTokenForUserToken: {
+    code: -120176,
+    description: 'Failed to acquire instance token for user token: {agentAppInstanceId}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Connection settings must be provided when calling getAgenticApplicationToken.
+   */
+  ConnectionSettingsRequiredForGetAgenticApplicationToken: {
+    code: -120177,
+    description: 'Connection settings must be provided when calling getAgenticApplicationToken',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Failed to acquire token for agent instance.
+   */
+  FailedToAcquireTokenForAgentInstance: {
+    code: -120178,
+    description: 'Failed to acquire token for agent instance: {agentAppInstanceId}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // JWT Middleware Errors (-120190 to -120199)
+  /**
+   * Error thrown when token is invalid.
+   */
+  InvalidToken: {
+    code: -120190,
+    description: 'invalid token',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // Base Adapter Errors (-120200 to -120209)
+  /**
+   * Error thrown when unknown error type.
+   */
+  UnknownErrorType: {
+    code: -120200,
+    description: 'Unknown error type: {message}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // App Authorization Errors (-120210 to -120249)
+  /**
+   * Error thrown when The AgentApplication.authorization does not have any auth handlers.
+   */
+  NoAuthHandlersConfigured: {
+    code: -120210,
+    description: 'The AgentApplication.authorization does not have any auth handlers',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Unsupported authorization handler type.
+   */
+  UnsupportedAuthorizationHandlerType: {
+    code: -120211,
+    description: "Unsupported authorization handler type: '{handlerType}' for auth handler: '{handlerId}'. Supported types are: '{supportedTypes}'.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Unexpected registration status.
+   */
+  UnexpectedRegistrationStatus: {
+    code: -120212,
+    description: 'Unexpected registration status: {status}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Failed to sign in.
+   */
+  FailedToSignIn: {
+    code: -120213,
+    description: 'Failed to sign in',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Cannot find auth handlers with IDs.
+   */
+  CannotFindAuthHandlers: {
+    code: -120214,
+    description: 'Cannot find auth handlers with ID(s): {unknownHandlers}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Storage option is not available in the app options.
+   */
+  StorageOptionNotAvailable: {
+    code: -120215,
+    description: "The 'storage' option is not available in the app options. Ensure that the app is properly configured.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Connections option is not available in the app options.
+   */
+  ConnectionsOptionNotAvailable: {
+    code: -120216,
+    description: "The 'connections' option is not available in the app options. Ensure that the app is properly configured.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The name property or connectionName env variable is required.
+   */
+  ConnectionNameRequired: {
+    code: -120217,
+    description: "The 'name' property or '{handlerId}_connectionName' env variable is required to initialize the handler.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Both activity.channelId and activity.from.id are required to perform signout.
+   */
+  ChannelIdAndFromIdRequiredForSignout: {
+    code: -120218,
+    description: "Both 'activity.channelId' and 'activity.from.id' are required to perform signout.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The current token is not exchangeable for an on-behalf-of flow.
+   */
+  TokenNotExchangeable: {
+    code: -120219,
+    description: "The current token is not exchangeable for an on-behalf-of flow. Ensure the token audience starts with 'api://'.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The userTokenClient is not available in the adapter.
+   */
+  UserTokenClientNotAvailable: {
+    code: -120220,
+    description: "The 'userTokenClient' is not available in the adapter. Ensure that the adapter supports user token operations.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when At least one scope must be specified for the Agentic authorization handler.
+   */
+  ScopeRequired: {
+    code: -120221,
+    description: 'At least one scope must be specified for the Agentic authorization handler.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Invalid parameters for exchangeToken method.
+   */
+  InvalidExchangeTokenParameters: {
+    code: -120222,
+    description: 'Invalid parameters for exchangeToken method.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Cannot find auth handler with ID.
+   */
+  CannotFindAuthHandler: {
+    code: -120223,
+    description: "Cannot find auth handler with ID '{id}'. Ensure it is configured in the agent application options.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Both activity.channelId and activity.from.id are required to generate the HandlerStorage key.
+   */
+  ChannelIdAndFromIdRequiredForHandlerStorage: {
+    code: -120224,
+    description: "Both 'activity.channelId' and 'activity.from.id' are required to generate the HandlerStorage key.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // App Application Errors (-120250 to -120269)
+  /**
+   * Error thrown when Storage is required for Authorization.
+   */
+  StorageRequiredForAuthorization: {
+    code: -120250,
+    description: 'Storage is required for Authorization. Ensure that a storage provider is configured in the AgentApplication options.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The Application.authorization property is unavailable.
+   */
+  AuthorizationPropertyUnavailable: {
+    code: -120251,
+    description: 'The Application.authorization property is unavailable because no authorization options were configured.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The Application.longRunningMessages property is unavailable.
+   */
+  LongRunningMessagesPropertyUnavailable: {
+    code: -120252,
+    description: 'The Application.longRunningMessages property is unavailable because no adapter was configured in the app.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when The Application.transcriptLogger property is unavailable.
+   */
+  TranscriptLoggerPropertyUnavailable: {
+    code: -120253,
+    description: 'The Application.transcriptLogger property is unavailable because no adapter was configured in the app.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Extension already registered.
+   */
+  ExtensionAlreadyRegistered: {
+    code: -120254,
+    description: 'Extension already registered',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // App Turn State Errors (-120270 to -120279)
+  /**
+   * Error thrown when TurnState hasn't been loaded.
+   */
+  TurnStateNotLoaded: {
+    code: -120270,
+    description: "TurnState hasn't been loaded. Call load() first.",
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when TurnState missing state scope.
+   */
+  TurnStateMissingScope: {
+    code: -120271,
+    description: 'TurnStateProperty: TurnState missing state scope named "{scope}".',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Invalid state scope.
+   */
+  InvalidStateScope: {
+    code: -120272,
+    description: 'Invalid state scope: {scope}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Invalid state path.
+   */
+  InvalidStatePath: {
+    code: -120273,
+    description: 'Invalid state path: {path}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // App Adaptive Cards Errors (-120280 to -120289)
+  /**
+   * Error thrown when Invalid action value.
+   */
+  InvalidActionValue: {
+    code: -120280,
+    description: 'Invalid action value: {error}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Unexpected AdaptiveCards.actionExecute() triggered for activity type.
+   */
+  UnexpectedActionExecute: {
+    code: -120281,
+    description: 'Unexpected AdaptiveCards.actionExecute() triggered for activity type: {activityType}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Unexpected AdaptiveCards.actionSubmit() triggered for activity type.
+   */
+  UnexpectedActionSubmit: {
+    code: -120282,
+    description: 'Unexpected AdaptiveCards.actionSubmit() triggered for activity type: {activityType}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  /**
+   * Error thrown when Unexpected AdaptiveCards.search() triggered for activity type.
+   */
+  UnexpectedSearch: {
+    code: -120283,
+    description: 'Unexpected AdaptiveCards.search() triggered for activity type: {activityType}',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  },
+
+  // App Streaming Errors (-120290 to -120299)
+  /**
+   * Error thrown when The stream has already ended.
+   */
+  StreamAlreadyEnded: {
+    code: -120290,
+    description: 'The stream has already ended.',
+    helplink: 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}'
+  }
+}
diff --git a/packages/agents-hosting/src/headerPropagation.ts b/packages/agents-hosting/src/headerPropagation.ts
index 4b7b1d5f..fe84d393 100644
--- a/packages/agents-hosting/src/headerPropagation.ts
+++ b/packages/agents-hosting/src/headerPropagation.ts
@@ -3,6 +3,9 @@
  * Licensed under the MIT License.
  */
 
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from './errorHelper'
+
 /**
  * A class that implements the HeaderPropagationCollection interface.
  * It filters the incoming request headers based on the definition provided and loads them into the outgoing headers collection.
@@ -23,7 +26,7 @@ export class HeaderPropagation implements HeaderPropagationCollection {
 
   constructor (headers: Record<string, string | string[] | undefined>) {
     if (!headers) {
-      throw new Error('Headers must be provided.')
+      throw ExceptionHelper.generateException(Error, Errors.HeadersRequired)
     }
 
     this._incomingRequests = this.normalizeHeaders(headers)
diff --git a/packages/agents-hosting/src/index.ts b/packages/agents-hosting/src/index.ts
index d489aec8..d6f5f707 100644
--- a/packages/agents-hosting/src/index.ts
+++ b/packages/agents-hosting/src/index.ts
@@ -27,3 +27,5 @@ export * from './storage/storage'
 export * from './headerPropagation'
 
 export * from './agent-client'
+
+export { Errors } from './errorHelper'
diff --git a/packages/agents-hosting/src/middlewareSet.ts b/packages/agents-hosting/src/middlewareSet.ts
index 3a192ba2..499e67a8 100644
--- a/packages/agents-hosting/src/middlewareSet.ts
+++ b/packages/agents-hosting/src/middlewareSet.ts
@@ -1,6 +1,8 @@
 /** * Copyright (c) Microsoft Corporation. All rights reserved. * Licensed under the MIT License. */
 import { TurnContext } from './turnContext'
 import { debug } from '@microsoft/agents-activity/logger'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from './errorHelper'
 
 const logger = debug('agents:middleware')
 
@@ -52,7 +54,7 @@ export class MiddlewareSet implements Middleware {
           typeof plugin === 'function' ? plugin : async (context, next) => await plugin.onTurn(context, next)
         )
       } else {
-        throw new Error('MiddlewareSet.use(): invalid plugin type being added.')
+        throw ExceptionHelper.generateException(Error, Errors.InvalidMiddlewarePlugin)
       }
     })
     return this
diff --git a/packages/agents-hosting/src/oauth/userTokenClient.ts b/packages/agents-hosting/src/oauth/userTokenClient.ts
index aec2dabb..a8cf3945 100644
--- a/packages/agents-hosting/src/oauth/userTokenClient.ts
+++ b/packages/agents-hosting/src/oauth/userTokenClient.ts
@@ -2,7 +2,7 @@
 // Licensed under the MIT License.
 
 import axios, { AxiosInstance } from 'axios'
-import { Activity, ConversationReference } from '@microsoft/agents-activity'
+import { Activity, ConversationReference, ExceptionHelper } from '@microsoft/agents-activity'
 import { debug } from '@microsoft/agents-activity/logger'
 import { normalizeTokenExchangeState } from '../activityWireCompat'
 import { AadResourceUrls, SignInResource, TokenExchangeRequest, TokenOrSinginResourceResponse, TokenResponse, TokenStatus } from './userTokenClient.types'
@@ -10,6 +10,7 @@ import { getProductInfo } from '../getProductInfo'
 import { AuthProvider, MsalTokenProvider } from '../auth'
 import { HeaderPropagationCollection } from '../headerPropagation'
 import { getTokenServiceEndpoint } from './customUserTokenAPI'
+import { Errors } from '../errorHelper'
 
 const logger = debug('agents:user-token-client')
 
@@ -157,7 +158,7 @@ export class UserTokenClient {
     const params = { userId, connectionName, channelId }
     const response = await this.client.delete('/api/usertoken/SignOut', { params })
     if (response.status !== 200) {
-      throw new Error('Failed to sign out')
+      throw ExceptionHelper.generateException(Error, Errors.FailedToSignOut)
     }
   }
 
diff --git a/packages/agents-hosting/src/state/conversationState.ts b/packages/agents-hosting/src/state/conversationState.ts
index 8412e271..237a2b2a 100644
--- a/packages/agents-hosting/src/state/conversationState.ts
+++ b/packages/agents-hosting/src/state/conversationState.ts
@@ -6,7 +6,8 @@
 import { AgentState } from './agentState'
 import { Storage } from '../storage/storage'
 import { TurnContext } from '../turnContext'
-import { Activity } from '@microsoft/agents-activity'
+import { Activity, ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 
 /**
  * Manages the state of a conversation.
@@ -30,11 +31,11 @@ export class ConversationState extends AgentState {
     const conversationId = activity && (activity.conversation != null) && activity.conversation.id ? activity.conversation.id : undefined
 
     if (!channelId) {
-      throw new Error('missing activity.channelId')
+      throw ExceptionHelper.generateException(Error, Errors.MissingActivityChannelId)
     }
 
     if (!conversationId) {
-      throw new Error('missing activity.conversation.id')
+      throw ExceptionHelper.generateException(Error, Errors.MissingActivityConversationId)
     }
 
     return `${channelId}/conversations/${conversationId}/${this.namespace}`
diff --git a/packages/agents-hosting/src/state/userState.ts b/packages/agents-hosting/src/state/userState.ts
index b5965891..d5edd17f 100644
--- a/packages/agents-hosting/src/state/userState.ts
+++ b/packages/agents-hosting/src/state/userState.ts
@@ -6,7 +6,8 @@
 import { AgentState } from './agentState'
 import { Storage } from '../storage/storage'
 import { TurnContext } from '../turnContext'
-import { Activity } from '@microsoft/agents-activity'
+import { Activity, ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 
 /**
  * Manages the state of a user.
@@ -31,11 +32,11 @@ export class UserState extends AgentState {
     const userId = activity && (activity.from != null) && activity.from.id ? activity.from.id : undefined
 
     if (!channelId) {
-      throw new Error('missing activity.channelId')
+      throw ExceptionHelper.generateException(Error, Errors.MissingActivityChannelId)
     }
 
     if (!userId) {
-      throw new Error('missing activity.from.id')
+      throw ExceptionHelper.generateException(Error, Errors.MissingActivityFromId)
     }
 
     return `${channelId}/users/${userId}/${this.namespace}`
diff --git a/packages/agents-hosting/src/storage/memoryStorage.ts b/packages/agents-hosting/src/storage/memoryStorage.ts
index 5adc3f19..03901c65 100644
--- a/packages/agents-hosting/src/storage/memoryStorage.ts
+++ b/packages/agents-hosting/src/storage/memoryStorage.ts
@@ -5,6 +5,8 @@
 
 import { Storage, StoreItem } from './storage'
 import { debug } from '@microsoft/agents-activity/logger'
+import { ExceptionHelper } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 
 const logger = debug('agents:memory-storage')
 
@@ -62,7 +64,7 @@ export class MemoryStorage implements Storage {
    */
   async read (keys: string[]): Promise<StoreItem> {
     if (!keys || keys.length === 0) {
-      throw new ReferenceError('Keys are required when reading.')
+      throw ExceptionHelper.generateException(ReferenceError, Errors.KeysRequiredForReading)
     }
 
     const data: StoreItem = {}
@@ -92,7 +94,7 @@ export class MemoryStorage implements Storage {
    */
   async write (changes: StoreItem): Promise<void> {
     if (!changes || changes.length === 0) {
-      throw new ReferenceError('Changes are required when writing.')
+      throw ExceptionHelper.generateException(ReferenceError, Errors.ChangesRequiredForWriting)
     }
 
     for (const [key, newItem] of Object.entries(changes)) {
@@ -105,7 +107,7 @@ export class MemoryStorage implements Storage {
         if (newItem.eTag === oldItem.eTag) {
           this.saveItem(key, newItem)
         } else {
-          throw new Error(`Storage: error writing "${key}" due to eTag conflict.`)
+          throw ExceptionHelper.generateException(Error, Errors.StorageEtagConflict, undefined, { key })
         }
       }
     }
diff --git a/packages/agents-hosting/src/transcript/consoleTranscriptLogger.ts b/packages/agents-hosting/src/transcript/consoleTranscriptLogger.ts
index 0bfd0a40..88598670 100644
--- a/packages/agents-hosting/src/transcript/consoleTranscriptLogger.ts
+++ b/packages/agents-hosting/src/transcript/consoleTranscriptLogger.ts
@@ -1,5 +1,6 @@
-import { Activity } from '@microsoft/agents-activity'
+import { Activity, ExceptionHelper } from '@microsoft/agents-activity'
 import { TranscriptLogger } from './transcriptLogger'
+import { Errors } from '../errorHelper'
 
 /**
  * A transcript logger that logs activities to the console.
@@ -12,7 +13,7 @@ export class ConsoleTranscriptLogger implements TranscriptLogger {
    */
   logActivity (activity: Activity): void | Promise<void> {
     if (!activity) {
-      throw new Error('Activity is required.')
+      throw ExceptionHelper.generateException(Error, Errors.ActivityRequired)
     }
 
     console.log('Activity Log:', activity)
diff --git a/packages/agents-hosting/src/transcript/fileTranscriptLogger.ts b/packages/agents-hosting/src/transcript/fileTranscriptLogger.ts
index cf4164f4..8f0850e6 100644
--- a/packages/agents-hosting/src/transcript/fileTranscriptLogger.ts
+++ b/packages/agents-hosting/src/transcript/fileTranscriptLogger.ts
@@ -4,12 +4,13 @@
  */
 
 import { debug } from '@microsoft/agents-activity/logger'
+import { Activity, ActivityTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { PagedResult, TranscriptInfo } from './transcriptLogger'
 import { TranscriptStore } from './transcriptStore'
 import * as fs from 'fs/promises'
 import * as path from 'path'
 import { EOL } from 'os'
-import { Activity, ActivityTypes } from '@microsoft/agents-activity'
+import { Errors } from '../errorHelper'
 
 const logger = debug('agents:file-transcript-logger')
 
@@ -47,7 +48,7 @@ export class FileTranscriptLogger implements TranscriptStore {
    */
   async logActivity (activity: Activity): Promise<void> {
     if (!activity) {
-      throw new Error('activity is required.')
+      throw ExceptionHelper.generateException(Error, Errors.ActivityRequired)
     }
 
     const transcriptFile = this.getTranscriptFile(activity.channelId!, activity.conversation?.id!)
@@ -328,11 +329,11 @@ export class FileTranscriptLogger implements TranscriptStore {
    */
   private getTranscriptFile (channelId: string, conversationId: string): string {
     if (!channelId?.trim()) {
-      throw new Error('channelId is required.')
+      throw ExceptionHelper.generateException(Error, Errors.TranscriptChannelIdRequired)
     }
 
     if (!conversationId?.trim()) {
-      throw new Error('conversationId is required.')
+      throw ExceptionHelper.generateException(Error, Errors.TranscriptConversationIdRequired)
     }
 
     // Get invalid filename characters (cross-platform)
@@ -353,7 +354,7 @@ export class FileTranscriptLogger implements TranscriptStore {
    */
   private getChannelFolder (channelId: string): string {
     if (!channelId?.trim()) {
-      throw new Error('channelId is required.')
+      throw ExceptionHelper.generateException(Error, Errors.TranscriptChannelIdRequired)
     }
 
     const invalidChars = this.getInvalidPathChars()
diff --git a/packages/agents-hosting/src/transcript/transcriptLoggerMiddleware.ts b/packages/agents-hosting/src/transcript/transcriptLoggerMiddleware.ts
index b7bd0977..a5a957ad 100644
--- a/packages/agents-hosting/src/transcript/transcriptLoggerMiddleware.ts
+++ b/packages/agents-hosting/src/transcript/transcriptLoggerMiddleware.ts
@@ -2,8 +2,9 @@ import { TurnContext } from '../turnContext'
 import { ResourceResponse } from '../connector-client'
 import { Middleware } from '../middlewareSet'
 import { TranscriptLogger } from './transcriptLogger'
-import { Activity, ActivityEventNames, ActivityTypes, ConversationReference, RoleTypes } from '@microsoft/agents-activity'
+import { Activity, ActivityEventNames, ActivityTypes, ConversationReference, RoleTypes, ExceptionHelper } from '@microsoft/agents-activity'
 import { debug } from '@microsoft/agents-activity/logger'
+import { Errors } from '../errorHelper'
 
 const appLogger = debug('agents:rest-client')
 
@@ -20,7 +21,7 @@ export class TranscriptLoggerMiddleware implements Middleware {
    */
   constructor (logger: TranscriptLogger) {
     if (!logger) {
-      throw new Error('TranscriptLoggerMiddleware requires a TranscriptLogger instance.')
+      throw ExceptionHelper.generateException(Error, Errors.TranscriptLoggerRequired)
     }
 
     this.logger = logger
diff --git a/packages/agents-hosting/src/turnContext.ts b/packages/agents-hosting/src/turnContext.ts
index 1f5d3bba..bf79c7b1 100644
--- a/packages/agents-hosting/src/turnContext.ts
+++ b/packages/agents-hosting/src/turnContext.ts
@@ -1,13 +1,14 @@
 /** * Copyright (c) Microsoft Corporation. All rights reserved. * Licensed under the MIT License. */
 import { INVOKE_RESPONSE_KEY } from './activityHandler'
 import { BaseAdapter } from './baseAdapter'
-import { Activity, ActivityTypes, ConversationReference, DeliveryModes, InputHints } from '@microsoft/agents-activity'
+import { Activity, ActivityTypes, ConversationReference, DeliveryModes, InputHints, ExceptionHelper } from '@microsoft/agents-activity'
 import { ResourceResponse } from './connector-client/resourceResponse'
 import { TurnContextStateCollection } from './turnContextStateCollection'
 import { AttachmentInfo } from './connector-client/attachmentInfo'
 import { AttachmentData } from './connector-client/attachmentData'
 import { StreamingResponse } from './app/streaming/streamingResponse'
 import { JwtPayload } from 'jsonwebtoken'
+import { Errors } from './errorHelper'
 
 /**
  * Defines a handler for processing and sending activities.
@@ -372,7 +373,7 @@ export class TurnContext {
 
   set responded (value: boolean) {
     if (!value) {
-      throw new Error("TurnContext: cannot set 'responded' to a value of 'false'.")
+      throw ExceptionHelper.generateException(Error, Errors.CannotSetRespondedToFalse)
     }
     this._respondedRef.responded = true
   }
diff --git a/packages/agents-hosting/test/errorHelper.test.ts b/packages/agents-hosting/test/errorHelper.test.ts
new file mode 100644
index 00000000..883e71fc
--- /dev/null
+++ b/packages/agents-hosting/test/errorHelper.test.ts
@@ -0,0 +1,81 @@
+import assert from 'assert'
+import { describe, it } from 'node:test'
+import { AgentErrorDefinition } from '@microsoft/agents-activity'
+import { Errors } from '../src/errorHelper'
+
+describe('Hosting Errors tests', () => {
+  it('should have MissingTurnContext error definition', () => {
+    const error = Errors.MissingTurnContext
+
+    assert.strictEqual(error.code, -120000)
+    assert.strictEqual(error.description, 'Missing TurnContext parameter')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have KeysRequiredForReading error definition', () => {
+    const error = Errors.KeysRequiredForReading
+
+    assert.strictEqual(error.code, -120040)
+    assert.strictEqual(error.description, 'Keys are required when reading.')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have ChangesRequiredForWriting error definition', () => {
+    const error = Errors.ChangesRequiredForWriting
+
+    assert.strictEqual(error.code, -120041)
+    assert.strictEqual(error.description, 'Changes are required when writing.')
+    assert.strictEqual(error.helplink, 'https://aka.ms/M365AgentsErrorCodes/#{errorCode}')
+  })
+
+  it('should have all error codes in the correct range', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    // All error codes should be negative and in the range -120000 to -120299
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(errorDef.code < 0, `Error code ${errorDef.code} should be negative`)
+      assert.ok(errorDef.code >= -120299, `Error code ${errorDef.code} should be >= -120299`)
+      assert.ok(errorDef.code <= -120000, `Error code ${errorDef.code} should be <= -120000`)
+    })
+  })
+
+  it('should have unique error codes', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    const codes = errorDefinitions.map(e => e.code)
+    const uniqueCodes = new Set(codes)
+
+    assert.strictEqual(codes.length, uniqueCodes.size, 'All error codes should be unique')
+  })
+
+  it('should have help links with tokenized format', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(
+        errorDef.helplink.includes('{errorCode}'),
+        `Help link should contain {errorCode} token: ${errorDef.helplink}`
+      )
+      assert.ok(
+        errorDef.helplink.startsWith('https://aka.ms/M365AgentsErrorCodes/#'),
+        `Help link should start with correct URL: ${errorDef.helplink}`
+      )
+    })
+  })
+
+  it('should have non-empty descriptions', () => {
+    const errorDefinitions = Object.values(Errors).filter(
+      val => val && typeof val === 'object' && 'code' in val && 'description' in val && 'helplink' in val
+    ) as AgentErrorDefinition[]
+
+    errorDefinitions.forEach(errorDef => {
+      assert.ok(errorDef.description.length > 0, 'Description should not be empty')
+    })
+  })
+})
diff --git a/packages/agents-hosting/test/hosting/adapter/cloudAdapter.test.ts b/packages/agents-hosting/test/hosting/adapter/cloudAdapter.test.ts
index f1cf6761..e9ba9feb 100644
--- a/packages/agents-hosting/test/hosting/adapter/cloudAdapter.test.ts
+++ b/packages/agents-hosting/test/hosting/adapter/cloudAdapter.test.ts
@@ -172,21 +172,24 @@ describe('CloudAdapter', function () {
   describe('sendActivities', function () {
     it('throws for bad args', async function () {
       // @ts-expect-error
-      await assert.rejects(cloudAdapter.sendActivities(undefined, []), {
-        name: 'TypeError',
-        message: '`context` parameter required'
+      await assert.rejects(cloudAdapter.sendActivities(undefined, []), (err: Error) => {
+        assert.ok(err.name === 'TypeError')
+        assert.ok(err.message.includes('`context` parameter required'))
+        return true
       })
 
       // @ts-expect-error
-      await assert.rejects(cloudAdapter.sendActivities(new TurnContext(cloudAdapter), undefined), {
-        name: 'TypeError',
-        message: '`activities` parameter required'
+      await assert.rejects(cloudAdapter.sendActivities(new TurnContext(cloudAdapter), undefined), (err: Error) => {
+        assert.ok(err.name === 'TypeError')
+        assert.ok(err.message.includes('`activities` parameter required'))
+        return true
       })
 
       // @ts-expect-error
-      await assert.rejects(cloudAdapter.sendActivities(new TurnContext(cloudAdapter), []), {
-        name: 'Error',
-        message: 'Expecting one or more activities, but the array was empty.'
+      await assert.rejects(cloudAdapter.sendActivities(new TurnContext(cloudAdapter), []), (err: Error) => {
+        assert.ok(err.name === 'Error')
+        assert.ok(err.message.includes('Expecting one or more activities, but the array was empty.'))
+        return true
       })
     })
 
@@ -291,15 +294,14 @@ describe('CloudAdapter', function () {
 
       const { logic } = bootstrap()
 
-      const error = new Error('continueConversation: Invalid conversation reference object')
-
       await assert.rejects(
         cloudAdapter.continueConversation(authentication.clientId as string, conversationReference, (context) => {
           logic(context)
-
-          throw error
         }),
-        error
+        (err: Error) => {
+          assert.ok(err.message.includes('continueConversation: Invalid conversation reference object'))
+          return true
+        }
       )
     })
   })
diff --git a/packages/agents-hosting/test/hosting/adapter/turnContext.test.ts b/packages/agents-hosting/test/hosting/adapter/turnContext.test.ts
index 271504cb..00e4811a 100644
--- a/packages/agents-hosting/test/hosting/adapter/turnContext.test.ts
+++ b/packages/agents-hosting/test/hosting/adapter/turnContext.test.ts
@@ -116,8 +116,9 @@ describe('TurnContext', { timeout: 5000 }, function () {
   it('should throw if you set responded to false.', function () {
     const context = new TurnContext(new SimpleAdapter(), testMessage)
     context.responded = true
-    assert.throws(() => (context.responded = false), {
-      message: "TurnContext: cannot set 'responded' to a value of 'false'."
+    assert.throws(() => (context.responded = false), (err: Error) => {
+      assert.ok(err.message.includes("TurnContext: cannot set 'responded' to a value of 'false'."))
+      return true
     })
   })
 
diff --git a/packages/agents-hosting/test/hosting/app/authorization.test.ts b/packages/agents-hosting/test/hosting/app/authorization.test.ts
index dbad865b..3fd8f24a 100644
--- a/packages/agents-hosting/test/hosting/app/authorization.test.ts
+++ b/packages/agents-hosting/test/hosting/app/authorization.test.ts
@@ -17,7 +17,10 @@ describe('AgentApplication', () => {
         authorization: {}
       })
       assert.equal(app.options.authorization, undefined)
-    }, { message: 'Storage is required for Authorization. Ensure that a storage provider is configured in the AgentApplication options.' })
+    }, (err: Error) => {
+      assert.ok(err.message.includes('Storage is required for Authorization. Ensure that a storage provider is configured in the AgentApplication options.'))
+      return true
+    })
   })
 
   it('should not allow empty handlers', () => {
@@ -27,7 +30,10 @@ describe('AgentApplication', () => {
         authorization: {}
       })
       assert.equal(app.options.authorization, undefined)
-    }, { message: 'The AgentApplication.authorization does not have any auth handlers' })
+    }, (err: Error) => {
+      assert.ok(err.message.includes('The AgentApplication.authorization does not have any auth handlers'))
+      return true
+    })
   })
 
   it('should initialize successfully with valid auth configuration', () => {
@@ -46,14 +52,20 @@ describe('AgentApplication', () => {
     assert.throws(() => {
       const auth = app.authorization
       assert.equal(auth, undefined)
-    }, { message: 'The Application.authorization property is unavailable because no authorization options were configured.' })
+    }, (err: Error) => {
+      assert.ok(err.message.includes('The Application.authorization property is unavailable because no authorization options were configured.'))
+      return true
+    })
   })
 
   it('should throw when registering onSignInSuccess without authorization', () => {
     const app = new AgentApplication()
     assert.throws(() => {
       app.onSignInSuccess(async () => {})
-    }, { message: 'The Application.authorization property is unavailable because no authorization options were configured.' })
+    }, (err: Error) => {
+      assert.ok(err.message.includes('The Application.authorization property is unavailable because no authorization options were configured.'))
+      return true
+    })
   })
 
   it('should support multiple auth handlers', () => {
@@ -104,15 +116,18 @@ describe('AgentApplication', () => {
     }
   })
 
-  it('should throw when using a non-existent auth handler id', () => {
+  it('should throw when using a non-existent auth handler id', async () => {
     const app = new AgentApplication({
       storage: new MemoryStorage(),
       authorization: {
         testAuth: { name: 'test' }
       }
     })
-    assert.rejects(async () => {
+    await assert.rejects(async () => {
       await app.authorization.getToken({} as any, 'nonExistinghandler')
-    }, { message: "Cannot find auth handler with ID 'nonExistinghandler'. Ensure it is configured in the agent application options." })
+    }, (err: Error) => {
+      assert.ok(err.message.includes("Cannot find auth handler with ID 'nonExistinghandler'. Ensure it is configured in the agent application options."))
+      return true
+    })
   })
 })
diff --git a/packages/agents-hosting/test/hosting/fileTranscriptLogger.test.ts b/packages/agents-hosting/test/hosting/fileTranscriptLogger.test.ts
index 09711c1a..47709990 100644
--- a/packages/agents-hosting/test/hosting/fileTranscriptLogger.test.ts
+++ b/packages/agents-hosting/test/hosting/fileTranscriptLogger.test.ts
@@ -28,7 +28,10 @@ describe('FileTranscriptLogger', () => {
     it('should throw error when logging null activity', async () => {
       await assert.rejects(
         async () => await store.logActivity(null as any),
-        /activity is required/
+        (err: Error) => {
+          assert.ok(err.message.toLowerCase().includes('activity is required'))
+          return true
+        }
       )
     })
 
diff --git a/packages/agents-hosting/test/hosting/jwt-middleware.test.ts b/packages/agents-hosting/test/hosting/jwt-middleware.test.ts
index fb66893e..ec050ca4 100644
--- a/packages/agents-hosting/test/hosting/jwt-middleware.test.ts
+++ b/packages/agents-hosting/test/hosting/jwt-middleware.test.ts
@@ -84,7 +84,11 @@ describe('authorizeJWT', () => {
     await authorizeJWT(config)(req as Request, res as Response, next)
 
     assert((res.status as sinon.SinonStub).calledOnceWith(401))
-    assert((res.send as sinon.SinonStub).calledOnceWith({ 'jwt-auth-error': 'invalid token' }))
+    const sendCall = (res.send as sinon.SinonStub).getCall(0)
+    assert(sendCall, 'send should be called')
+    const sentData = sendCall.args[0]
+    assert(sentData['jwt-auth-error'], 'jwt-auth-error should be present')
+    assert(sentData['jwt-auth-error'].includes('invalid token'), `jwt-auth-error should contain 'invalid token', got: ${sentData['jwt-auth-error']}`)
     assert((next as sinon.SinonStub).notCalled)
 
     verifyStub.restore()
diff --git a/packages/agents-hosting/test/hosting/storage/memoryStorage.test.ts b/packages/agents-hosting/test/hosting/storage/memoryStorage.test.ts
index 74485fcf..2a71df97 100644
--- a/packages/agents-hosting/test/hosting/storage/memoryStorage.test.ts
+++ b/packages/agents-hosting/test/hosting/storage/memoryStorage.test.ts
@@ -13,9 +13,8 @@ describe('MemoryStorage', () => {
     it('should throw an error if keys are empty', async () => {
       await assert.rejects(
         async () => await memoryStorage.read([]),
-        {
-          name: 'ReferenceError',
-          message: 'Keys are required when reading.'
+        (err: Error) => {
+          return err.name === 'ReferenceError' && err.message.includes('Keys are required when reading.')
         }
       )
     })
@@ -24,9 +23,8 @@ describe('MemoryStorage', () => {
       await assert.rejects(
         // @ts-expect-error
         async () => await memoryStorage.read(null),
-        {
-          name: 'ReferenceError',
-          message: 'Keys are required when reading.'
+        (err: Error) => {
+          return err.name === 'ReferenceError' && err.message.includes('Keys are required when reading.')
         }
       )
     })
@@ -47,9 +45,8 @@ describe('MemoryStorage', () => {
     it('should throw an error if changes are not empty array', async () => {
       await assert.rejects(
         async () => await memoryStorage.write([]),
-        {
-          name: 'ReferenceError',
-          message: 'Changes are required when writing.'
+        (err: Error) => {
+          return err.name === 'ReferenceError' && err.message.includes('Changes are required when writing.')
         }
       )
     })
@@ -58,9 +55,8 @@ describe('MemoryStorage', () => {
       await assert.rejects(
         // @ts-expect-error
         async () => await memoryStorage.write(null),
-        {
-          name: 'ReferenceError',
-          message: 'Changes are required when writing.'
+        (err: Error) => {
+          return err.name === 'ReferenceError' && err.message.includes('Changes are required when writing.')
         }
       )
     })
@@ -84,9 +80,8 @@ describe('MemoryStorage', () => {
       await assert.rejects(
         async () =>
           await memoryStorage.write({ key1: { value: 'conflict', eTag: 'invalid' } }),
-        {
-          name: 'Error',
-          message: 'Storage: error writing "key1" due to eTag conflict.'
+        (err: Error) => {
+          return err.name === 'Error' && err.message.includes('Storage: error writing "key1" due to eTag conflict.')
         }
       )
     })