diff --git a/content-gen/infra/main.bicep b/content-gen/infra/main.bicep
index 092783a12..dc6f99946 100644
--- a/content-gen/infra/main.bicep
+++ b/content-gen/infra/main.bicep
@@ -240,9 +240,9 @@ var useExistingAiFoundryAiProject = !empty(azureExistingAIProjectResourceId)
 var aiFoundryAiServicesResourceGroupName = useExistingAiFoundryAiProject
   ? split(azureExistingAIProjectResourceId, '/')[4]
   : 'rg-${solutionSuffix}'
-// var aiFoundryAiServicesSubscriptionId = useExistingAiFoundryAiProject
-//   ? split(azureExistingAIProjectResourceId, '/')[2]
-//   : subscription().id
+var aiFoundryAiServicesSubscriptionId = useExistingAiFoundryAiProject
+  ? split(azureExistingAIProjectResourceId, '/')[2]
+  : subscription().subscriptionId
 var aiFoundryAiServicesResourceName = useExistingAiFoundryAiProject
   ? split(azureExistingAIProjectResourceId, '/')[8]
   : 'aif-${solutionSuffix}'
@@ -572,6 +572,17 @@ var aiFoundryAiProjectEndpoint = useExistingAiFoundryAiProject
   ? 'https://${aiFoundryAiServicesResourceName}.services.ai.azure.com/api/projects/${aiFoundryAiProjectResourceName}'
   : aiFoundryAiServicesProject!.outputs.apiEndpoint
 
+// ========== Role Assignments for Existing AI Services ========== //
+module existingAiServicesRoleAssignments 'modules/deploy_foundry_role_assignment.bicep' = if (useExistingAiFoundryAiProject) {
+  name: take('module.foundry-role-assignment.${aiFoundryAiServicesResourceName}', 64)
+  scope: resourceGroup(aiFoundryAiServicesSubscriptionId, aiFoundryAiServicesResourceGroupName)
+  params: {
+    aiServicesName: aiFoundryAiServicesResourceName
+    principalId: userAssignedIdentity.outputs.principalId
+    principalType: 'ServicePrincipal'
+  }
+}
+
 // ========== AI Search ========== //
 module aiSearch 'br/public:avm/res/search/search-service:0.11.1' = {
   name: take('avm.res.search.search-service.${aiSearchName}', 64)
diff --git a/content-gen/infra/modules/deploy_foundry_role_assignment.bicep b/content-gen/infra/modules/deploy_foundry_role_assignment.bicep
new file mode 100644
index 000000000..3121ca932
--- /dev/null
+++ b/content-gen/infra/modules/deploy_foundry_role_assignment.bicep
@@ -0,0 +1,84 @@
+// ========== existing-ai-services-roles.bicep ========== //
+// Module to assign RBAC roles to managed identity on an existing AI Services account
+// This is required when reusing an existing AI Foundry project from a different resource group
+
+@description('Required. The principal ID of the managed identity to grant access.')
+param principalId string
+
+@description('Required. The name of the existing AI Services account.')
+param aiServicesName string
+
+@description('Optional. The name of the existing AI Project.')
+param aiProjectName string = ''
+
+@description('Optional. The principal type of the identity.')
+@allowed([
+  'Device'
+  'ForeignGroup'
+  'Group'
+  'ServicePrincipal'
+  'User'
+])
+param principalType string = 'ServicePrincipal'
+
+// ========== Role Definitions ========== //
+
+// Azure AI User role - for AI Foundry project access (used by AIProjectClient for image generation)
+resource azureAiUserRole 'Microsoft.Authorization/roleDefinitions@2022-04-01' existing = {
+  name: '53ca6127-db72-4b80-b1b0-d745d6d5456d'
+}
+
+// Cognitive Services OpenAI User role - for chat completions (used by AzureOpenAIChatClient)
+resource cognitiveServicesOpenAiUserRole 'Microsoft.Authorization/roleDefinitions@2022-04-01' existing = {
+  name: '5e0bd9bd-7b93-4f28-af87-19fc36ad61bd'
+}
+
+// ========== Existing Resources ========== //
+
+// Reference the existing AI Services account
+resource existingAiServices 'Microsoft.CognitiveServices/accounts@2025-04-01-preview' existing = {
+  name: aiServicesName
+}
+
+// Reference the existing AI Project (if provided)
+resource existingAiProject 'Microsoft.CognitiveServices/accounts/projects@2025-04-01-preview' existing = if (!empty(aiProjectName)) {
+  name: aiProjectName
+  parent: existingAiServices
+}
+
+// ========== Role Assignments ========== //
+
+// Azure AI User role assignment - same as reference accelerator
+// Required for AIProjectClient (used for image generation in Foundry mode)
+resource assignAzureAiUserRole 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
+  name: guid(existingAiServices.id, principalId, azureAiUserRole.id)
+  scope: existingAiServices
+  properties: {
+    roleDefinitionId: azureAiUserRole.id
+    principalId: principalId
+    principalType: principalType
+  }
+}
+
+// Cognitive Services OpenAI User role assignment
+// Required for AzureOpenAIChatClient (used for chat completions)
+resource assignCognitiveServicesOpenAiUserRole 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
+  name: guid(existingAiServices.id, principalId, cognitiveServicesOpenAiUserRole.id)
+  scope: existingAiServices
+  properties: {
+    roleDefinitionId: cognitiveServicesOpenAiUserRole.id
+    principalId: principalId
+    principalType: principalType
+  }
+}
+
+// ========== Outputs ========== //
+
+@description('The resource ID of the existing AI Services account.')
+output aiServicesResourceId string = existingAiServices.id
+
+@description('The endpoint of the existing AI Services account.')
+output aiServicesEndpoint string = existingAiServices.properties.endpoint
+
+@description('The principal ID of the existing AI Project (if provided).')
+output aiProjectPrincipalId string = !empty(aiProjectName) ? existingAiProject.identity.principalId : ''