feat: new system prompt for llama4 (#2031)

Tests:

LLAMA_STACK_CONFIG=http://localhost:5002 pytest -s -v
tests/integration/inference --safety-shield meta-llama/Llama-Guard-3-8B
--vision-model meta-llama/Llama-4-Scout-17B-16E-Instruct --text-model
meta-llama/Llama-4-Scout-17B-16E-Instruct

Co-authored-by: Eric Huang <erichuang@fb.com>

llama_stack/models/llama/llama4/prompt_templates/system_prompts.py

@@ -0,0 +1,144 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# top-level folder for each specific model found within the models/ directory at
+# the top-level of this source tree.
+
+import textwrap
+from typing import List, Optional
+
+from llama_stack.apis.inference import ToolDefinition, ToolParamDefinition
+from llama_stack.models.llama.llama3.prompt_templates.base import (
+    PromptTemplate,
+    PromptTemplateGeneratorBase,
+)
+
+
+class PythonListCustomToolGenerator(PromptTemplateGeneratorBase):  # noqa: N801
+    DEFAULT_PROMPT = textwrap.dedent(
+        """
+        You are a helpful assistant and an expert in function composition. You can answer general questions using your internal knowledge OR invoke functions when necessary. Follow these strict guidelines:
+
+        1. FUNCTION CALLS:
+        - ONLY use functions that are EXPLICITLY listed in the function list below
+        - If NO functions are listed (empty function list []), respond ONLY with internal knowledge or "I don't have access to [Unavailable service] information"
+        - If a function is not in the list, respond ONLY with internal knowledge or "I don't have access to [Unavailable service] information"
+        - If ALL required parameters are present AND the query EXACTLY matches a listed function's purpose: output ONLY the function call(s)
+        - Use exact format: [func_name1(param1=value1, param2=value2), func_name2(...)]
+        Examples:
+        CORRECT: [get_weather(location="Vancouver"), calculate_route(start="Boston", end="New York")] <- Only if get_weather and calculate_route are in function list
+        INCORRECT: get_weather(location="New York")
+        INCORRECT: Let me check the weather: [get_weather(location="New York")]
+        INCORRECT: [get_events(location="Singapore")] <- If function not in list
+
+        2. RESPONSE RULES:
+        - For pure function requests matching a listed function: ONLY output the function call(s)
+        - For knowledge questions: ONLY output text
+        - For missing parameters: ONLY request the specific missing parameters
+        - For unavailable services (not in function list): output ONLY with internal knowledge or "I don't have access to [Unavailable service] information". Do NOT execute a function call.
+        - If the query asks for information beyond what a listed function provides: output ONLY with internal knowledge about your limitations
+        - NEVER combine text and function calls in the same response
+        - NEVER suggest alternative functions when the requested service is unavailable
+        - NEVER create or invent new functions not listed below
+
+        3. STRICT BOUNDARIES:
+        - ONLY use functions from the list below - no exceptions
+        - NEVER use a function as an alternative to unavailable information
+        - NEVER call functions not present in the function list
+        - NEVER add explanatory text to function calls
+        - NEVER respond with empty brackets
+        - Use proper Python/JSON syntax for function calls
+        - Check the function list carefully before responding
+
+        4. TOOL RESPONSE HANDLING:
+        - When receiving tool responses: provide concise, natural language responses
+        - Don't repeat tool response verbatim
+        - Don't add supplementary information
+
+
+        {{ function_description }}
+        """.strip("\n")
+    )
+
+    def gen(self, custom_tools: List[ToolDefinition], system_prompt: Optional[str] = None) -> PromptTemplate:
+        system_prompt = system_prompt or self.DEFAULT_PROMPT
+        return PromptTemplate(
+            system_prompt,
+            {"function_description": self._gen_function_description(custom_tools)},
+        )
+
+    def _gen_function_description(self, custom_tools: List[ToolDefinition]) -> PromptTemplate:
+        template_str = textwrap.dedent(
+            """
+            Here is a list of functions in JSON format that you can invoke.
+
+            [
+                {% for t in tools -%}
+                {# manually setting up JSON because jinja sorts keys in unexpected ways -#}
+                {%- set tname = t.tool_name -%}
+                {%- set tdesc = t.description -%}
+                {%- set tparams = t.parameters -%}
+                {%- set required_params = [] -%}
+                {%- for name, param in tparams.items() if param.required == true -%}
+                    {%- set _ = required_params.append(name) -%}
+                {%- endfor -%}
+                {
+                    "name": "{{tname}}",
+                    "description": "{{tdesc}}",
+                    "parameters": {
+                        "type": "dict",
+                        "required": {{ required_params | tojson }},
+                        "properties": {
+                            {%- for name, param in tparams.items() %}
+                            "{{name}}": {
+                                "type": "{{param.param_type}}",
+                                "description": "{{param.description}}"{% if param.default %},
+                                "default": "{{param.default}}"{% endif %}
+                            }{% if not loop.last %},{% endif %}
+                            {%- endfor %}
+                        }
+                    }
+                }{% if not loop.last %},
+                {% endif -%}
+                {%- endfor %}
+            ]
+
+            You can answer general questions or invoke tools when necessary.
+            In addition to tool calls, you should also augment your responses by using the tool outputs.
+
+            """
+        )
+        return PromptTemplate(
+            template_str.strip("\n"),
+            {"tools": [t.model_dump() for t in custom_tools]},
+        ).render()
+
+    def data_examples(self) -> List[List[ToolDefinition]]:
+        return [
+            [
+                ToolDefinition(
+                    tool_name="get_weather",
+                    description="Get weather info for places",
+                    parameters={
+                        "city": ToolParamDefinition(
+                            param_type="string",
+                            description="The name of the city to get the weather for",
+                            required=True,
+                        ),
+                        "metric": ToolParamDefinition(
+                            param_type="string",
+                            description="The metric for weather. Options are: celsius, fahrenheit",
+                            required=False,
+                            default="celsius",
+                        ),
+                    },
+                ),
+            ]
+        ]

llama_stack/providers/utils/inference/prompt_adapter.py

@@ -52,6 +52,9 @@ from llama_stack.models.llama.llama3.prompt_templates import (
     SystemDefaultGenerator,
 )
 from llama_stack.models.llama.llama3.tokenizer import Tokenizer
+from llama_stack.models.llama.llama4.prompt_templates.system_prompts import (
+    PythonListCustomToolGenerator as PythonListCustomToolGeneratorLlama4,
+)
 from llama_stack.models.llama.sku_list import resolve_model
 from llama_stack.models.llama.sku_types import ModelFamily, is_multimodal
 from llama_stack.providers.utils.inference import supported_inference_models
@@ -306,10 +309,11 @@ def chat_completion_request_to_messages(
     elif model.model_family in (
         ModelFamily.llama3_2,
         ModelFamily.llama3_3,
-        ModelFamily.llama4,
     ):
-        # llama3.2, llama3.3 and llama4 models follow the same tool prompt format
+        # llama3.2, llama3.3 follow the same tool prompt format
-        messages = augment_messages_for_tools_llama_3_2(request)
+        messages = augment_messages_for_tools_llama(request, PythonListCustomToolGenerator)
+    elif model.model_family == ModelFamily.llama4:
+        messages = augment_messages_for_tools_llama(request, PythonListCustomToolGeneratorLlama4)
     else:
         messages = request.messages
 
@@ -399,8 +403,9 @@ def augment_messages_for_tools_llama_3_1(
     return messages
 
 
-def augment_messages_for_tools_llama_3_2(
+def augment_messages_for_tools_llama(
     request: ChatCompletionRequest,
+    custom_tool_prompt_generator,
 ) -> List[Message]:
     existing_messages = request.messages
     existing_system_message = None
@@ -434,7 +439,7 @@ def augment_messages_for_tools_llama_3_2(
         if existing_system_message and request.tool_config.system_message_behavior == SystemMessageBehavior.replace:
             system_prompt = existing_system_message.content
 
-        tool_template = PythonListCustomToolGenerator().gen(custom_tools, system_prompt)
+        tool_template = custom_tool_prompt_generator().gen(custom_tools, system_prompt)
 
         sys_content += tool_template.render()
         sys_content += "\n"