feat: remove core.telemetry as a dependency of llama_stack.apis

Remove circular dependency by moving tracing from API protocol definitions
  to router implementation layer.

  Changes:
  - Create apis/common/tracing.py with marker decorator (zero core dependencies)
  - Add @trace_protocol marker decorator to 11 protocol classes
  - Apply actual tracing in core/routers/__init__.py based on protocol marker
  - Move MetricResponseMixin from core to apis (it's an API response type)
  - APIs package is now self-contained with zero core dependencies

  The tracing functionality remains identical - actual trace_protocol from core
  is applied to router implementations at runtime when both telemetry is enabled
  and the protocol has the __trace_protocol__ marker.

  ## Test Plan

  Manual integration test confirms identical behavior to main branch:

  ```bash
  llama stack list-deps --format uv starter | sh
  export OLLAMA_URL=http://localhost:11434
  llama stack run starter

  curl -X POST http://localhost:8321/v1/chat/completions \
    -H "Content-Type: application/json" \
    -d '{"model": "ollama/gpt-oss:20b",
         "messages": [{"role": "user", "content": "Say hello"}],
         "max_tokens": 10}'

  Verified identical between main and this branch:
  - trace_id present in response
  - metrics array with prompt_tokens, completion_tokens, total_tokens
  - Server logs show trace_protocol applied to all routers

  Existing telemetry integration tests (tests/integration/telemetry/) validate
  trace context propagation and span attributes.

Signed-off-by: Charlie Doern <cdoern@redhat.com>

src/llama_stack/apis/common/responses.py

@@ -34,3 +34,44 @@ class PaginatedResponse(BaseModel):
     data: list[dict[str, Any]]
     has_more: bool
     url: str | None = None
+
+
+# This is a short term solution to allow inference API to return metrics
+# The ideal way to do this is to have a way for all response types to include metrics
+# and all metric events logged to the telemetry API to be included with the response
+# To do this, we will need to augment all response types with a metrics field.
+# We have hit a blocker from stainless SDK that prevents us from doing this.
+# The blocker is that if we were to augment the response types that have a data field
+# in them like so
+# class ListModelsResponse(BaseModel):
+# metrics: Optional[List[MetricEvent]] = None
+# data: List[Models]
+# ...
+# The client SDK will need to access the data by using a .data field, which is not
+# ergonomic. Stainless SDK does support unwrapping the response type, but it
+# requires that the response type to only have a single field.
+
+# We will need a way in the client SDK to signal that the metrics are needed
+# and if they are needed, the client SDK has to return the full response type
+# without unwrapping it.
+
+
+@json_schema_type
+class MetricInResponse(BaseModel):
+    """A metric value included in API responses.
+    :param metric: The name of the metric
+    :param value: The numeric value of the metric
+    :param unit: (Optional) The unit of measurement for the metric value
+    """
+
+    metric: str
+    value: int | float
+    unit: str | None = None
+
+
+class MetricResponseMixin(BaseModel):
+    """Mixin class for API responses that can include metrics.
+    :param metrics: (Optional) List of metrics associated with the API response
+    """
+
+    metrics: list[MetricInResponse] | None = None

src/llama_stack/apis/common/tracing.py

@@ -0,0 +1,22 @@
+# 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.
+
+
+def trace_protocol(cls):
+    """
+    Mark a protocol for automatic tracing when telemetry is enabled.
+
+    This is a metadata-only decorator with no dependencies on core.
+    Actual tracing is applied by core routers at runtime if telemetry is enabled.
+
+    Usage:
+        @runtime_checkable
+        @trace_protocol
+        class MyProtocol(Protocol):
+            ...
+    """
+    cls.__trace_protocol__ = True
+    return cls

src/llama_stack/apis/conversations/conversations.py

@@ -20,8 +20,8 @@ from llama_stack.apis.agents.openai_responses import (
     OpenAIResponseOutputMessageMCPListTools,
     OpenAIResponseOutputMessageWebSearchToolCall,
 )
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, register_schema, webmethod
 
 Metadata = dict[str, str]

src/llama_stack/apis/files/files.py

@@ -11,8 +11,8 @@ from fastapi import File, Form, Response, UploadFile
 from pydantic import BaseModel, Field
 
 from llama_stack.apis.common.responses import Order
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 

src/llama_stack/apis/inference/inference.py

@@ -19,11 +19,10 @@ from pydantic import BaseModel, Field, field_validator
 from typing_extensions import TypedDict
 
 from llama_stack.apis.common.content_types import ContentDelta, InterleavedContent
-from llama_stack.apis.common.responses import Order
+from llama_stack.apis.common.responses import MetricResponseMixin, Order
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.models import Model
 from llama_stack.apis.version import LLAMA_STACK_API_V1, LLAMA_STACK_API_V1ALPHA
-from llama_stack.core.telemetry.telemetry import MetricResponseMixin
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.models.llama.datatypes import (
     BuiltinTool,
     StopReason,

src/llama_stack/apis/models/models.py

@@ -9,9 +9,9 @@ from typing import Any, Literal, Protocol, runtime_checkable
 
 from pydantic import BaseModel, ConfigDict, Field, field_validator
 
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.resource import Resource, ResourceType
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 

src/llama_stack/apis/prompts/prompts.py

@@ -10,8 +10,8 @@ from typing import Protocol, runtime_checkable
 
 from pydantic import BaseModel, Field, field_validator, model_validator
 
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 

src/llama_stack/apis/safety/safety.py

@@ -9,10 +9,10 @@ from typing import Any, Protocol, runtime_checkable
 
 from pydantic import BaseModel, Field
 
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.inference import OpenAIMessageParam
 from llama_stack.apis.shields import Shield
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 

src/llama_stack/apis/shields/shields.py

@@ -8,9 +8,9 @@ from typing import Any, Literal, Protocol, runtime_checkable
 
 from pydantic import BaseModel
 
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.resource import Resource, ResourceType
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 

src/llama_stack/apis/tools/rag_tool.py

@@ -11,8 +11,8 @@ from pydantic import BaseModel, Field, field_validator
 from typing_extensions import runtime_checkable
 
 from llama_stack.apis.common.content_types import URL, InterleavedContent
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, register_schema, webmethod
 
 

src/llama_stack/apis/tools/tools.py

@@ -11,9 +11,9 @@ from pydantic import BaseModel
 from typing_extensions import runtime_checkable
 
 from llama_stack.apis.common.content_types import URL, InterleavedContent
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.resource import Resource, ResourceType
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 from .rag_tool import RAGToolRuntime

src/llama_stack/apis/vector_io/vector_io.py

@@ -13,10 +13,10 @@ from typing import Annotated, Any, Literal, Protocol, runtime_checkable
 from fastapi import Body
 from pydantic import BaseModel, Field
 
+from llama_stack.apis.common.tracing import trace_protocol
 from llama_stack.apis.inference import InterleavedContent
 from llama_stack.apis.vector_stores import VectorStore
 from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.core.telemetry.trace_protocol import trace_protocol
 from llama_stack.schema_utils import json_schema_type, webmethod
 from llama_stack.strong_typing.schema import register_schema
 

src/llama_stack/core/routers/__init__.py

@@ -93,4 +93,11 @@ async def get_auto_router_impl(
 
     impl = api_to_routers[api.value](routing_table, **api_to_dep_impl)
     await impl.initialize()
+
+    # Apply tracing to router implementation if telemetry is enabled and protocol wants tracing
+    if run_config.telemetry.enabled and getattr(impl.__class__, "__trace_protocol__", False):
+        from llama_stack.core.telemetry.trace_protocol import trace_protocol
+
+        trace_protocol(impl.__class__)
+
     return impl

src/llama_stack/core/telemetry/telemetry.py

@@ -163,47 +163,6 @@ class MetricEvent(EventCommon):
     unit: str
 
 
-@json_schema_type
-class MetricInResponse(BaseModel):
-    """A metric value included in API responses.
-    :param metric: The name of the metric
-    :param value: The numeric value of the metric
-    :param unit: (Optional) The unit of measurement for the metric value
-    """
-
-    metric: str
-    value: int | float
-    unit: str | None = None
-
-
-# This is a short term solution to allow inference API to return metrics
-# The ideal way to do this is to have a way for all response types to include metrics
-# and all metric events logged to the telemetry API to be included with the response
-# To do this, we will need to augment all response types with a metrics field.
-# We have hit a blocker from stainless SDK that prevents us from doing this.
-# The blocker is that if we were to augment the response types that have a data field
-# in them like so
-# class ListModelsResponse(BaseModel):
-# metrics: Optional[List[MetricEvent]] = None
-# data: List[Models]
-# ...
-# The client SDK will need to access the data by using a .data field, which is not
-# ergonomic. Stainless SDK does support unwrapping the response type, but it
-# requires that the response type to only have a single field.
-
-# We will need a way in the client SDK to signal that the metrics are needed
-# and if they are needed, the client SDK has to return the full response type
-# without unwrapping it.
-
-
-class MetricResponseMixin(BaseModel):
-    """Mixin class for API responses that can include metrics.
-    :param metrics: (Optional) List of metrics associated with the API response
-    """
-
-    metrics: list[MetricInResponse] | None = None
-
-
 @json_schema_type
 class StructuredLogType(Enum):
     """The type of structured log event payload.