diff --git a/src/agent/modify.ts b/src/agent/modify.ts
index 22d8103..0a57731 100644
--- a/src/agent/modify.ts
+++ b/src/agent/modify.ts
@@ -27,6 +27,7 @@ function buildModelSettings(
   const isOpenAI = modelHandle.startsWith("openai/");
   const isAnthropic = modelHandle.startsWith("anthropic/");
   const isGoogleAI = modelHandle.startsWith("google_ai/");
+  const isGoogleVertex = modelHandle.startsWith("google_vertex/");
   const isOpenRouter = modelHandle.startsWith("openrouter/");
 
   if (isOpenAI || isOpenRouter) {
@@ -83,7 +84,25 @@ function buildModelSettings(
     return googleSettings;
   }
 
-  // For unknown providers (e.g., openrouter), return generic settings with parallel_tool_calls
+  if (isGoogleVertex) {
+    // Vertex AI uses the same Google provider on the backend; only the handle differs.
+    const googleVertexSettings: Record<string, unknown> = {
+      provider_type: "google_ai",
+      parallel_tool_calls: true,
+    };
+    if (updateArgs?.thinking_budget !== undefined) {
+      (googleVertexSettings as Record<string, unknown>).thinking_config = {
+        thinking_budget: updateArgs.thinking_budget as number,
+      };
+    }
+    if (typeof updateArgs?.temperature === "number") {
+      (googleVertexSettings as Record<string, unknown>).temperature =
+        updateArgs.temperature as number;
+    }
+    return googleVertexSettings;
+  }
+
+  // For unknown providers, return generic settings with parallel_tool_calls
   return { parallel_tool_calls: true };
 }
 
diff --git a/src/models.json b/src/models.json
index 91d6549..6903b4b 100644
--- a/src/models.json
+++ b/src/models.json
@@ -326,5 +326,12 @@
     "label": "o4-mini",
     "description": "OpenAI's latest o-series reasoning model",
     "updateArgs": { "context_window": 180000 }
+  },
+  {
+    "id": "gemini-3-vertex",
+    "handle": "google_vertex/gemini-3-pro-preview",
+    "label": "Gemini 3 Pro (Vertex AI)",
+    "description": "Google's smartest Gemini 3 Pro model on Vertex AI",
+    "updateArgs": { "context_window": 180000, "temperature": 1.0 }
   }
 ]