diff --git a/litellm/constants.py b/litellm/constants.py
index 9f55d2a94ef..25f26639494 100644
--- a/litellm/constants.py
+++ b/litellm/constants.py
@@ -51,9 +51,23 @@ SINGLE_DEPLOYMENT_TRAFFIC_FAILURE_THRESHOLD = int(
 DEFAULT_REASONING_EFFORT_DISABLE_THINKING_BUDGET = int(
     os.getenv("DEFAULT_REASONING_EFFORT_DISABLE_THINKING_BUDGET", 0)
 )
+
+# Gemini model-specific minimal thinking budget constants
+DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH = int(
+    os.getenv("DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH", 1)
+)
+DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_PRO = int(
+    os.getenv("DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_PRO", 128)
+)
+DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH_LITE = int(
+    os.getenv("DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH_LITE", 512)
+)
+
+# Generic fallback for unknown models
 DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET = int(
     os.getenv("DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET", 128)
 )
+
 DEFAULT_REASONING_EFFORT_LOW_THINKING_BUDGET = int(
     os.getenv("DEFAULT_REASONING_EFFORT_LOW_THINKING_BUDGET", 1024)
 )
@@ -830,7 +844,7 @@ known_tokenizer_config = {
             "add_eos_token": False,
             "bos_token": {
                 "__type": "AddedToken",
-                "content": "<｜begin▁of▁sentence｜>",
+                "content": "
                 "lstrip": False,
                 "normalized": True,
                 "rstrip": False,
@@ -839,7 +853,7 @@ known_tokenizer_config = {
             "clean_up_tokenization_spaces": False,
             "eos_token": {
                 "__type": "AddedToken",
-                "content": "<｜end▁of▁sentence｜>",
+                "content": "
                 "lstrip": False,
                 "normalized": True,
                 "rstrip": False,
@@ -849,7 +863,7 @@ known_tokenizer_config = {
             "model_max_length": 16384,
             "pad_token": {
                 "__type": "AddedToken",
-                "content": "<｜end▁of▁sentence｜>",
+                "content": "
                 "lstrip": False,
                 "normalized": True,
                 "rstrip": False,
@@ -858,7 +872,7 @@ known_tokenizer_config = {
             "sp_model_kwargs": {},
             "unk_token": None,
             "tokenizer_class": "LlamaTokenizerFast",
-            "chat_template": "{% if not add_generation_prompt is defined %}{% set add_generation_prompt = false %}{% endif %}{% set ns = namespace(is_first=false, is_tool=false, is_output_first=true, system_prompt='') %}{%- for message in messages %}{%- if message['role'] == 'system' %}{% set ns.system_prompt = message['content'] %}{%- endif %}{%- endfor %}{{bos_token}}{{ns.system_prompt}}{%- for message in messages %}{%- if message['role'] == 'user' %}{%- set ns.is_tool = false -%}{{'<｜User｜>' + message['content']}}{%- endif %}{%- if message['role'] == 'assistant' and message['content'] is none %}{%- set ns.is_tool = false -%}{%- for tool in message['tool_calls']%}{%- if not ns.is_first %}{{'<｜Assistant｜><｜tool▁calls▁begin｜><｜tool▁call▁begin｜>' + tool['type'] + '<｜tool▁sep｜>' + tool['function']['name'] + '\\n' + '```json' + '\\n' + tool['function']['arguments'] + '\\n' + '```' + '<｜tool▁call▁end｜>'}}{%- set ns.is_first = true -%}{%- else %}{{'\\n' + '<｜tool▁call▁begin｜>' + tool['type'] + '<｜tool▁sep｜>' + tool['function']['name'] + '\\n' + '```json' + '\\n' + tool['function']['arguments'] + '\\n' + '```' + '<｜tool▁call▁end｜>'}}{{'<｜tool▁calls▁end｜><｜end▁of▁sentence｜>'}}{%- endif %}{%- endfor %}{%- endif %}{%- if message['role'] == 'assistant' and message['content'] is not none %}{%- if ns.is_tool %}{{'<｜tool▁outputs▁end｜>' + message['content'] + '<｜end▁of▁sentence｜>'}}{%- set ns.is_tool = false -%}{%- else %}{% set content = message['content'] %}{% if '</think>' in content %}{% set content = content.split('</think>')[-1] %}{% endif %}{{'<｜Assistant｜>' + content + '<｜end▁of▁sentence｜>'}}{%- endif %}{%- endif %}{%- if message['role'] == 'tool' %}{%- set ns.is_tool = true -%}{%- if ns.is_output_first %}{{'<｜tool▁outputs▁begin｜><｜tool▁output▁begin｜>' + message['content'] + '<｜tool▁output▁end｜>'}}{%- set ns.is_output_first = false %}{%- else %}{{'\\n<｜tool▁output▁begin｜>' + message['content'] + '<｜tool▁output▁end｜>'}}{%- endif %}{%- endif %}{%- endfor -%}{% if ns.is_tool %}{{'<｜tool▁outputs▁end｜>'}}{% endif %}{% if add_generation_prompt and not ns.is_tool %}{{'<｜Assistant｜><think>\\n'}}{% endif %}",
+            "chat_template": "{% if not add_generation_prompt is defined %}{% set add_generation_prompt = false %}{% endif %}{% set ns = namespace(is_first=false, is_tool=false, is_output_first=true, system_prompt='') %}{%- for message in messages %}{%- if message['role'] == 'system' %}{% set ns.system_prompt = message['content'] %}{%- endif %}{%- endfor %}{{bos_token}}{{ns.system_prompt}}{%- for message in messages %}{%- if message['role'] == 'user' %}{%- set ns.is_tool = false -%}{{'<｜User｜>' + message['content']}}{%- endif %}{%- if message['role'] == 'assistant' and message['content'] is none %}{%- set ns.is_tool = false -%}{%- for tool in message['tool_calls']%}{%- if not ns.is_first %}{{'<｜Assistant｜><｜tool▁calls▁begin｜><｜tool▁call▁begin｜>' + tool['type'] + '赠送' + tool['function']['name'] + '\\n' + '```json' + '\\n' + tool['function']['arguments'] + '\\n' + '```' + '<｜tool▁call▁end｜>'}}{%- set ns.is_first = true -%}{%- else %}{{'\\n' + '<｜tool▁call▁begin｜>' + tool['type'] + '赠送' + tool['function']['name'] + '\\n' + '```json' + '\\n' + tool['function']['arguments'] + '\\n' + '```' + '<｜tool▁call▁end｜>'}}{{'<｜tool▁calls▁end｜>'}}{%- endif %}{%- endfor %}{%- endif %}{%- if message['role'] == 'assistant' and message['content'] is not none %}{%- if ns.is_tool %}{{'<｜tool▁outputs▁end｜>' + message['content'] + ''}}{%- set ns.is_tool = false -%}{%- else %}{% set content = message['content'] %}{% if '</think>' in content %}{% set content = content.split('</think>')[-1] %}{% endif %}{{'<｜Assistant｜>' + content + ''}}{%- endif %}{%- endif %}{%- if message['role'] == 'tool' %}{%- set ns.is_tool = true -%}{%- if ns.is_output_first %}{{'<｜tool▁outputs▁begin｜> 空' + message['content'] + ' 空'}}{%- set ns.is_output_first = false %}{%- else %}{{'\\n 空' + message['content'] + ' 空'}}{%- endif %}{%- endif %}{%- endfor -%}{% if ns.is_tool %}{{'<｜tool▁outputs▁end｜>'}}{% endif %}{% if add_generation_prompt and not ns.is_tool %}{{'<｜Assistant｜><think>\\n'}}{% endif %}",
         },
         "status": "success",
     },
diff --git a/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py b/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py
index 4da99204165..ba1d64facce 100644
--- a/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py
+++ b/litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py
@@ -31,6 +31,9 @@ from litellm.constants import (
     DEFAULT_REASONING_EFFORT_LOW_THINKING_BUDGET,
     DEFAULT_REASONING_EFFORT_MEDIUM_THINKING_BUDGET,
     DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET,
+    DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH,
+    DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_PRO,
+    DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH_LITE,
 )
 from litellm.llms.base_llm.chat.transformation import BaseConfig, BaseLLMException
 from litellm.llms.custom_httpx.http_handler import (
@@ -423,10 +426,23 @@ class VertexGeminiConfig(VertexAIBaseConfig, BaseConfig):
     @staticmethod
     def _map_reasoning_effort_to_thinking_budget(
         reasoning_effort: str,
+        model: Optional[str] = None,
     ) -> GeminiThinkingConfig:
         if reasoning_effort == "minimal":
+            # Use model-specific minimum thinking budget or fallback
+            if model and "gemini-2.5-flash" in model.lower():
+                budget = (
+                    DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH
+                )
+            elif model and "gemini-2.5-pro" in model.lower():
+                budget = DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_PRO
+            elif model and "gemini-2.5-flash-lite" in model.lower():
+                budget = DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET_GEMINI_2_5_FLASH_LITE
+            else:
+                budget = DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET
+
             return {
-                "thinkingBudget": DEFAULT_REASONING_EFFORT_MINIMAL_THINKING_BUDGET,
+                "thinkingBudget": budget,
                 "includeThoughts": True,
             }
         elif reasoning_effort == "low":
@@ -606,7 +622,9 @@ class VertexGeminiConfig(VertexAIBaseConfig, BaseConfig):
                 optional_params["seed"] = value
             elif param == "reasoning_effort" and isinstance(value, str):
                 optional_params["thinkingConfig"] = (
-                    VertexGeminiConfig._map_reasoning_effort_to_thinking_budget(value)
+                    VertexGeminiConfig._map_reasoning_effort_to_thinking_budget(
+                        value, model
+                    )
                 )
             elif param == "thinking":
                 optional_params["thinkingConfig"] = (