diff --git a/litellm/model_prices_and_context_window_backup.json b/litellm/model_prices_and_context_window_backup.json
index 63ca003a26d..6288a7c6184 100644
--- a/litellm/model_prices_and_context_window_backup.json
+++ b/litellm/model_prices_and_context_window_backup.json
@@ -25164,6 +25164,58 @@
         "supports_web_search": true,
         "tpm": 800000
     },
+    "openrouter/google/gemini-3.1-flash-lite-preview": {
+        "cache_read_input_token_cost": 2.5e-08,
+        "cache_read_input_token_cost_per_audio_token": 5e-08,
+        "input_cost_per_audio_token": 5e-07,
+        "input_cost_per_token": 2.5e-07,
+        "litellm_provider": "openrouter",
+        "max_audio_length_hours": 8.4,
+        "max_audio_per_prompt": 1,
+        "max_images_per_prompt": 3000,
+        "max_input_tokens": 1048576,
+        "max_output_tokens": 65536,
+        "max_pdf_size_mb": 30,
+        "max_tokens": 65536,
+        "max_video_length": 1,
+        "max_videos_per_prompt": 10,
+        "mode": "chat",
+        "output_cost_per_reasoning_token": 1.5e-06,
+        "output_cost_per_token": 1.5e-06,
+        "rpm": 2000,
+        "source": "https://ai.google.dev/pricing/gemini-3",
+        "supported_endpoints": [
+            "/v1/chat/completions",
+            "/v1/completions",
+            "/v1/batch"
+        ],
+        "supported_modalities": [
+            "text",
+            "image",
+            "audio",
+            "video"
+        ],
+        "supported_output_modalities": [
+            "text"
+        ],
+        "supports_audio_input": true,
+        "supports_audio_output": false,
+        "supports_code_execution": true,
+        "supports_file_search": true,
+        "supports_function_calling": true,
+        "supports_parallel_function_calling": true,
+        "supports_pdf_input": true,
+        "supports_prompt_caching": true,
+        "supports_reasoning": true,
+        "supports_response_schema": true,
+        "supports_system_messages": true,
+        "supports_tool_choice": true,
+        "supports_url_context": true,
+        "supports_video_input": true,
+        "supports_vision": true,
+        "supports_web_search": true,
+        "tpm": 800000
+    },
     "openrouter/google/gemini-3.1-pro-preview": {
         "cache_read_input_token_cost": 2e-07,
         "cache_read_input_token_cost_above_200k_tokens": 4e-07,
diff --git a/model_prices_and_context_window.json b/model_prices_and_context_window.json
index 90ff7d1103c..a7cdb7904dd 100644
--- a/model_prices_and_context_window.json
+++ b/model_prices_and_context_window.json
@@ -25149,6 +25149,58 @@
         "supports_web_search": true,
         "tpm": 800000
     },
+    "openrouter/google/gemini-3.1-flash-lite-preview": {
+        "cache_read_input_token_cost": 2.5e-08,
+        "cache_read_input_token_cost_per_audio_token": 5e-08,
+        "input_cost_per_audio_token": 5e-07,
+        "input_cost_per_token": 2.5e-07,
+        "litellm_provider": "openrouter",
+        "max_audio_length_hours": 8.4,
+        "max_audio_per_prompt": 1,
+        "max_images_per_prompt": 3000,
+        "max_input_tokens": 1048576,
+        "max_output_tokens": 65536,
+        "max_pdf_size_mb": 30,
+        "max_tokens": 65536,
+        "max_video_length": 1,
+        "max_videos_per_prompt": 10,
+        "mode": "chat",
+        "output_cost_per_reasoning_token": 1.5e-06,
+        "output_cost_per_token": 1.5e-06,
+        "rpm": 2000,
+        "source": "https://ai.google.dev/pricing/gemini-3",
+        "supported_endpoints": [
+            "/v1/chat/completions",
+            "/v1/completions",
+            "/v1/batch"
+        ],
+        "supported_modalities": [
+            "text",
+            "image",
+            "audio",
+            "video"
+        ],
+        "supported_output_modalities": [
+            "text"
+        ],
+        "supports_audio_input": true,
+        "supports_audio_output": false,
+        "supports_code_execution": true,
+        "supports_file_search": true,
+        "supports_function_calling": true,
+        "supports_parallel_function_calling": true,
+        "supports_pdf_input": true,
+        "supports_prompt_caching": true,
+        "supports_reasoning": true,
+        "supports_response_schema": true,
+        "supports_system_messages": true,
+        "supports_tool_choice": true,
+        "supports_url_context": true,
+        "supports_video_input": true,
+        "supports_vision": true,
+        "supports_web_search": true,
+        "tpm": 800000
+    },
     "openrouter/google/gemini-3.1-pro-preview": {
         "cache_read_input_token_cost": 2e-07,
         "cache_read_input_token_cost_above_200k_tokens": 4e-07,
diff --git a/tests/test_litellm/test_cost_calculator.py b/tests/test_litellm/test_cost_calculator.py
index 0258eaabe33..87f44909ec2 100644
--- a/tests/test_litellm/test_cost_calculator.py
+++ b/tests/test_litellm/test_cost_calculator.py
@@ -1859,7 +1859,7 @@ def test_gemini_without_cache_tokens_details():
             "promptTokensDetails": [
                 {"modality": "TEXT", "tokenCount": 6},
                 {"modality": "IMAGE", "tokenCount": 258},
-            ]
+            ],
             # No cacheTokensDetails
         }
     }
@@ -1997,3 +1997,27 @@ def test_additional_costs_only_for_azure_ai():
         completion_tokens=50,
     )
     assert result is None, "Vertex AI should have no additional costs"
+
+
+def test_openrouter_gemini_3_1_flash_lite_preview_pricing():
+    """
+    Test that openrouter/google/gemini-3.1-flash-lite-preview has a pricing entry.
+
+    Regression test for https://github.com/BerriAI/litellm/issues/25604
+
+    The model exists and is callable via OpenRouter, but was missing from
+    model_prices_and_context_window.json when other Gemini 3.x variants were present.
+    This caused ValueError: This model isn't mapped yet during router pre-call checks.
+    """
+    os.environ["LITELLM_LOCAL_MODEL_COST_MAP"] = "True"
+    litellm.model_cost = litellm.get_model_cost_map(url="")
+
+    model_name = "openrouter/google/gemini-3.1-flash-lite-preview"
+    model_info = litellm.model_cost.get(model_name)
+
+    assert model_info is not None, f"Missing model pricing entry: {model_name}"
+    assert model_info["litellm_provider"] == "openrouter"
+    assert model_info["input_cost_per_token"] == 2.5e-07
+    assert model_info["output_cost_per_token"] == 1.5e-06
+    assert model_info["max_input_tokens"] == 1048576
+    assert model_info["max_output_tokens"] == 65536