diff --git a/python/packages/kagent-adk/src/kagent/adk/types.py b/python/packages/kagent-adk/src/kagent/adk/types.py
index 5e2f4a97a..ccbfebbf0 100644
--- a/python/packages/kagent-adk/src/kagent/adk/types.py
+++ b/python/packages/kagent-adk/src/kagent/adk/types.py
@@ -615,6 +615,23 @@ def _create_llm_from_model_config(model_config: ModelUnion):
     raise ValueError(f"Invalid model type: {model_config.type}")
 
 
+_KAGENT_TOOL_NAME_WARNING = (
+    "\n\nIMPORTANT: When referencing any tools or agents that were used,"
+    " you MUST preserve their exact registered names including any"
+    " namespace prefixes (for example: 'kagent__default__agent_name')."
+    " Never shorten, abbreviate, or rephrase tool or agent names."
+)
+
+_KAGENT_COMPACTION_PROMPT = (
+    "The following is a conversation history between a user and an AI"
+    " agent. Please summarize the conversation, focusing on key"
+    " information and decisions made, as well as any unresolved"
+    " questions or tasks. The summary should be concise and capture the"
+    " essence of the interaction.\n\n"
+    "{conversation_history}"
+) + _KAGENT_TOOL_NAME_WARNING
+
+
 def build_adk_context_configs(
     context_config: ContextConfig,
 ) -> tuple:
@@ -636,7 +653,8 @@ def build_adk_context_configs(
 
             summarizer = LlmEventSummarizer(
                 llm=_create_llm_from_model_config(comp.summarizer_model),
-                prompt_template=comp.prompt_template,
+                prompt_template=(comp.prompt_template if comp.prompt_template else _KAGENT_COMPACTION_PROMPT)
+                + (str() if not comp.prompt_template else _KAGENT_TOOL_NAME_WARNING),
             )
 
         events_compaction_config = EventsCompactionConfig(
diff --git a/python/packages/kagent-adk/tests/unittests/test_context_config.py b/python/packages/kagent-adk/tests/unittests/test_context_config.py
index 95dd09f0d..b0a755164 100644
--- a/python/packages/kagent-adk/tests/unittests/test_context_config.py
+++ b/python/packages/kagent-adk/tests/unittests/test_context_config.py
@@ -24,6 +24,14 @@ def _make_agent_config_json(**context_kwargs) -> str:
     return json.dumps(config)
 
 
+def _get_prompt_template(summarizer):
+    """Use public attribute if available, fall back to private (resilient across google-adk versions)."""
+    pub = getattr(summarizer, "prompt_template", None)
+    if pub is not None:
+        return pub
+    return getattr(summarizer, "_prompt_template", None)
+
+
 class TestContextConfigParsing:
     def test_no_context_config(self):
         config = AgentConfig.model_validate_json(_make_agent_config_json())
@@ -159,3 +167,52 @@ def test_empty_config(self):
         events_cfg, cache_cfg = build_adk_context_configs(config)
         assert events_cfg is None
         assert cache_cfg is None
+
+    def test_summarizer_uses_kagent_default_prompt_when_none_provided(self):
+        """When no prompt_template is given, the kagent default that preserves
+        tool names should be used instead of the ADK default."""
+        from kagent.adk.types import _KAGENT_COMPACTION_PROMPT
+
+        config = ContextConfig(
+            compaction=ContextCompressionSettings(
+                compaction_interval=5,
+                overlap_size=2,
+                summarizer_model=OpenAI(type="openai", model="gpt-4o-mini"),
+            )
+        )
+        events_cfg, _ = build_adk_context_configs(config)
+        assert events_cfg is not None
+        assert events_cfg.summarizer is not None
+        assert _get_prompt_template(events_cfg.summarizer) == _KAGENT_COMPACTION_PROMPT
+        assert "{conversation_history}" in _KAGENT_COMPACTION_PROMPT
+
+    def test_summarizer_respects_custom_prompt_template(self):
+        """A user-supplied prompt_template should have tool name warning appended."""
+        from kagent.adk.types import _KAGENT_TOOL_NAME_WARNING
+
+        custom = "My custom prompt: {conversation_history}"
+        config = ContextConfig(
+            compaction=ContextCompressionSettings(
+                compaction_interval=5,
+                overlap_size=2,
+                summarizer_model=OpenAI(type="openai", model="gpt-4o-mini"),
+                prompt_template=custom,
+            )
+        )
+        events_cfg, _ = build_adk_context_configs(config)
+        assert _get_prompt_template(events_cfg.summarizer) == custom + _KAGENT_TOOL_NAME_WARNING
+
+    def test_summarizer_preserves_empty_string_prompt_template(self):
+        """An empty string prompt_template should fall back to the kagent default."""
+        from kagent.adk.types import _KAGENT_COMPACTION_PROMPT
+
+        config = ContextConfig(
+            compaction=ContextCompressionSettings(
+                compaction_interval=5,
+                overlap_size=2,
+                summarizer_model=OpenAI(type="openai", model="gpt-4o-mini"),
+                prompt_template="",
+            )
+        )
+        events_cfg, _ = build_adk_context_configs(config)
+        assert _get_prompt_template(events_cfg.summarizer) == _KAGENT_COMPACTION_PROMPT