diff --git a/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_context_spec.tf.tmpl b/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_context_spec.tf.tmpl
index 61d15aa4e2fc..01bd61de6652 100644
--- a/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_context_spec.tf.tmpl
+++ b/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_context_spec.tf.tmpl
@@ -11,7 +11,7 @@ resource "google_vertex_ai_reasoning_engine" "{{$.PrimaryResourceId}}" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
         generation_trigger_config {
           generation_rule {
             idle_duration       = "300s"
diff --git a/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_granular_ttl.tf.tmpl b/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_granular_ttl.tf.tmpl
index 694e0db46320..56aa27114671 100644
--- a/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_granular_ttl.tf.tmpl
+++ b/mmv1/templates/terraform/samples/services/vertexai/vertex_ai_reasoning_engine_granular_ttl.tf.tmpl
@@ -6,7 +6,7 @@ resource "google_vertex_ai_reasoning_engine" "{{$.PrimaryResourceId}}" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
       }
       similarity_search_config {
         embedding_model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/text-embedding-005"
diff --git a/mmv1/third_party/terraform/services/vertexai/resource_vertex_ai_reasoning_engine_test.go.tmpl b/mmv1/third_party/terraform/services/vertexai/resource_vertex_ai_reasoning_engine_test.go.tmpl
index efdcd911a2ff..40d435f15b9f 100644
--- a/mmv1/third_party/terraform/services/vertexai/resource_vertex_ai_reasoning_engine_test.go.tmpl
+++ b/mmv1/third_party/terraform/services/vertexai/resource_vertex_ai_reasoning_engine_test.go.tmpl
@@ -857,7 +857,7 @@ resource "google_vertex_ai_reasoning_engine" "primary" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
         generation_trigger_config {
           generation_rule {
             fixed_interval = "600s"
@@ -885,7 +885,7 @@ resource "google_vertex_ai_reasoning_engine" "primary" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
         generation_trigger_config {
           generation_rule {
             event_count         = 10
@@ -946,7 +946,7 @@ resource "google_vertex_ai_reasoning_engine" "primary" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
       }
       similarity_search_config {
         embedding_model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/text-embedding-005"
@@ -1072,7 +1072,7 @@ resource "google_vertex_ai_reasoning_engine" "primary" {
   context_spec {
     memory_bank_config {
       generation_config {
-        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-2.5-flash"
+        model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/gemini-3.5-flash"
       }
       similarity_search_config {
         embedding_model = "projects/${data.google_project.project.project_id}/locations/us-central1/publishers/google/models/text-embedding-005"
@@ -1728,7 +1728,7 @@ resource "google_vertex_ai_reasoning_engine" "reasoning_engine" {
         adk_config {
           json_config = jsonencode({
             name        = "finance_analyst_agent"
-            model       = "gemini-2.5-flash"
+            model       = "gemini-3.5-flash"
             description = "A financial analyst that can look up stock values and return them as tables."
             instruction = "You are a financial analyst. Output data in tables."
           })
@@ -1760,7 +1760,7 @@ resource "google_vertex_ai_reasoning_engine" "reasoning_engine" {
         adk_config {
           json_config = jsonencode({
             name        = "finance_analyst_agent_updated"
-            model       = "gemini-2.5-flash"
+            model       = "gemini-3.5-flash"
             description = "An updated financial analyst agent."
             instruction = "You are an updated financial analyst."
           })