[Feature] Add Gemini 3.1 Flash Image Preview pricing details

Author: davidvpe

model_prices_and_context_window.json

@@ -16421,6 +16421,39 @@
         "supports_vision": true,
         "supports_web_search": true
     },
+    "gemini/gemini-3.1-flash-image-preview": {
+        "input_cost_per_image": 0.0001375,
+        "input_cost_per_token": 2.5e-07,
+        "litellm_provider": "gemini",
+        "max_input_tokens": 65536,
+        "max_output_tokens": 32768,
+        "max_tokens": 32768,
+        "mode": "image_generation",
+        "output_cost_per_image": 0.045,
+        "output_cost_per_image_token": 6e-05,
+        "output_cost_per_token": 1.5e-06,
+        "rpm": 1000,
+        "tpm": 4000000,
+        "source": "https://ai.google.dev/gemini-api/docs/pricing#gemini-3.1-flash-image-preview",
+        "supported_endpoints": [
+            "/v1/chat/completions",
+            "/v1/completions"
+        ],
+        "supported_modalities": [
+            "text",
+            "image"
+        ],
+        "supported_output_modalities": [
+            "text",
+            "image"
+        ],
+        "supports_function_calling": false,
+        "supports_prompt_caching": true,
+        "supports_response_schema": true,
+        "supports_system_messages": true,
+        "supports_vision": true,
+        "supports_web_search": true
+    },
     "gemini/deep-research-pro-preview-12-2025": {
         "input_cost_per_image": 0.0011,
         "input_cost_per_token": 2e-06,