diff --git a/litellm/model_prices_and_context_window_backup.json b/litellm/model_prices_and_context_window_backup.json
index ad19818a5ce..d30cc9f17ab 100644
--- a/litellm/model_prices_and_context_window_backup.json
+++ b/litellm/model_prices_and_context_window_backup.json
@@ -20150,7 +20150,7 @@
     "gemini-3.5-flash-lite": {
         "deprecation_date": "2027-07-21",
         "cache_read_input_token_cost": 3e-08,
-        "cache_read_input_token_cost_flex": 2e-08,
+        "cache_read_input_token_cost_flex": 1.5e-08,
         "cache_read_input_token_cost_priority": 5e-08,
         "input_cost_per_token": 3e-07,
         "input_cost_per_token_batches": 1.5e-07,
@@ -42027,7 +42027,7 @@
     "vertex_ai/gemini-3.5-flash-lite": {
         "deprecation_date": "2027-07-21",
         "cache_read_input_token_cost": 3e-08,
-        "cache_read_input_token_cost_flex": 2e-08,
+        "cache_read_input_token_cost_flex": 1.5e-08,
         "cache_read_input_token_cost_priority": 5e-08,
         "input_cost_per_token": 3e-07,
         "input_cost_per_token_batches": 1.5e-07,
diff --git a/model_prices_and_context_window.json b/model_prices_and_context_window.json
index ad19818a5ce..d30cc9f17ab 100644
--- a/model_prices_and_context_window.json
+++ b/model_prices_and_context_window.json
@@ -20150,7 +20150,7 @@
     "gemini-3.5-flash-lite": {
         "deprecation_date": "2027-07-21",
         "cache_read_input_token_cost": 3e-08,
-        "cache_read_input_token_cost_flex": 2e-08,
+        "cache_read_input_token_cost_flex": 1.5e-08,
         "cache_read_input_token_cost_priority": 5e-08,
         "input_cost_per_token": 3e-07,
         "input_cost_per_token_batches": 1.5e-07,
@@ -42027,7 +42027,7 @@
     "vertex_ai/gemini-3.5-flash-lite": {
         "deprecation_date": "2027-07-21",
         "cache_read_input_token_cost": 3e-08,
-        "cache_read_input_token_cost_flex": 2e-08,
+        "cache_read_input_token_cost_flex": 1.5e-08,
         "cache_read_input_token_cost_priority": 5e-08,
         "input_cost_per_token": 3e-07,
         "input_cost_per_token_batches": 1.5e-07,
diff --git a/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_llm_cost_calc_utils.py b/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_llm_cost_calc_utils.py
index e13643ed6ce..d7f757b5852 100644
--- a/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_llm_cost_calc_utils.py
+++ b/tests/test_litellm/litellm_core_utils/llm_cost_calc/test_llm_cost_calc_utils.py
@@ -3377,6 +3377,53 @@ def test_generic_cost_per_token_gemini_35_flash_lite(_local_model_cost_map):
     assert completion_cost == pytest.approx(0.00125)
 
 
+GEMINI_35_FLASH_LITE_TIER_RATES_BY_SURFACE = [
+    ("gemini", None, 3e-07, 2.5e-06, 3e-08),
+    ("gemini", "flex", 1.5e-07, 1.25e-06, 2e-08),
+    ("gemini", "priority", 5.4e-07, 4.5e-06, 5e-08),
+    ("vertex_ai", None, 3e-07, 2.5e-06, 3e-08),
+    ("vertex_ai", "flex", 1.5e-07, 1.25e-06, 1.5e-08),
+    ("vertex_ai", "priority", 5.4e-07, 4.5e-06, 5e-08),
+]
+
+
+@pytest.mark.parametrize(
+    "custom_llm_provider,service_tier,input_rate,output_rate,cache_read_rate",
+    GEMINI_35_FLASH_LITE_TIER_RATES_BY_SURFACE,
+)
+def test_gemini_35_flash_lite_service_tier_pricing(
+    custom_llm_provider, service_tier, input_rate, output_rate, cache_read_rate, _local_model_cost_map
+):
+    """Regression: Vertex publishes flash-lite flex context caching at $0.015/M while the
+    Gemini API publishes $0.02/M, so vertex_ai flex cache reads must bill 1.5e-08/token
+    instead of the 2e-08 the map used to carry, without disturbing the Gemini API rate."""
+    usage = Usage(
+        prompt_tokens=1_000,
+        completion_tokens=500,
+        total_tokens=1_500,
+        prompt_tokens_details=PromptTokensDetailsWrapper(cached_tokens=200, text_tokens=800),
+    )
+
+    prompt_cost, completion_cost = generic_cost_per_token(
+        model="gemini-3.5-flash-lite",
+        usage=usage,
+        custom_llm_provider=custom_llm_provider,
+        service_tier=service_tier,
+    )
+
+    assert prompt_cost == pytest.approx(800 * input_rate + 200 * cache_read_rate, rel=1e-9)
+    assert completion_cost == pytest.approx(500 * output_rate, rel=1e-9)
+
+
+def test_gemini_35_flash_lite_flex_cache_read_map_entries(_local_model_cost_map):
+    """Each map entry carries its own surface's published flex cache-read rate: the bare
+    and vertex_ai keys are the Vertex surface at $0.015/M, the gemini key is the Gemini
+    API surface at $0.02/M."""
+    assert litellm.model_cost["gemini-3.5-flash-lite"]["cache_read_input_token_cost_flex"] == 1.5e-08
+    assert litellm.model_cost["vertex_ai/gemini-3.5-flash-lite"]["cache_read_input_token_cost_flex"] == 1.5e-08
+    assert litellm.model_cost["gemini/gemini-3.5-flash-lite"]["cache_read_input_token_cost_flex"] == 2e-08
+
+
 @pytest.mark.parametrize(
     "service_tier,input_rate,cache_read_rate,cache_write_rate,output_rate",
     [