diff --git a/docs/_static/llama-stack-spec.html b/docs/_static/llama-stack-spec.html
index 0549dda21..213057e81 100644
--- a/docs/_static/llama-stack-spec.html
+++ b/docs/_static/llama-stack-spec.html
@@ -13092,6 +13092,10 @@
                     "unit": {
                         "type": "string",
                         "description": "The unit of measurement for the metric value"
+                    },
+                    "metric_type": {
+                        "$ref": "#/components/schemas/MetricType",
+                        "description": "The type of metric (optional, inferred if not provided for backwards compatibility)"
                     }
                 },
                 "additionalProperties": false,
@@ -13107,6 +13111,17 @@
                 "title": "MetricEvent",
                 "description": "A metric event containing a measured value."
             },
+            "MetricType": {
+                "type": "string",
+                "enum": [
+                    "counter",
+                    "up_down_counter",
+                    "histogram",
+                    "gauge"
+                ],
+                "title": "MetricType",
+                "description": "The type of metric being recorded."
+            },
             "SpanEndPayload": {
                 "type": "object",
                 "properties": {
diff --git a/docs/_static/llama-stack-spec.yaml b/docs/_static/llama-stack-spec.yaml
index aa47cd58d..6dfd1d392 100644
--- a/docs/_static/llama-stack-spec.yaml
+++ b/docs/_static/llama-stack-spec.yaml
@@ -9736,6 +9736,10 @@ components:
           type: string
           description: >-
             The unit of measurement for the metric value
+        metric_type:
+          $ref: '#/components/schemas/MetricType'
+          description: >-
+            The type of metric (optional, inferred if not provided for backwards compatibility)
       additionalProperties: false
       required:
         - trace_id
@@ -9748,6 +9752,15 @@ components:
       title: MetricEvent
       description: >-
         A metric event containing a measured value.
+    MetricType:
+      type: string
+      enum:
+        - counter
+        - up_down_counter
+        - histogram
+        - gauge
+      title: MetricType
+      description: The type of metric being recorded.
     SpanEndPayload:
       type: object
       properties:
diff --git a/llama_stack/apis/telemetry/telemetry.py b/llama_stack/apis/telemetry/telemetry.py
index 92422ac1b..0c7eb2c36 100644
--- a/llama_stack/apis/telemetry/telemetry.py
+++ b/llama_stack/apis/telemetry/telemetry.py
@@ -90,6 +90,21 @@ class EventType(Enum):
     METRIC = "metric"
 
 
+@json_schema_type
+class MetricType(Enum):
+    """The type of metric being recorded.
+    :cvar COUNTER: A counter metric that only increases (e.g., requests_total)
+    :cvar UP_DOWN_COUNTER: A counter that can increase or decrease (e.g., active_connections)
+    :cvar HISTOGRAM: A histogram metric for measuring distributions (e.g., request_duration_seconds)
+    :cvar GAUGE: A gauge metric for point-in-time values (e.g., cpu_usage_percent)
+    """
+
+    COUNTER = "counter"
+    UP_DOWN_COUNTER = "up_down_counter"
+    HISTOGRAM = "histogram"
+    GAUGE = "gauge"
+
+
 @json_schema_type
 class LogSeverity(Enum):
     """The severity level of a log message.
@@ -143,12 +158,14 @@ class MetricEvent(EventCommon):
     :param metric: The name of the metric being measured
     :param value: The numeric value of the metric measurement
     :param unit: The unit of measurement for the metric value
+    :param metric_type: The type of metric (optional, inferred if not provided for backwards compatibility)
     """
 
     type: Literal[EventType.METRIC] = EventType.METRIC
     metric: str  # this would be an enum
     value: int | float
     unit: str
+    metric_type: MetricType | None = None
 
 
 @json_schema_type
diff --git a/llama_stack/providers/inline/agents/meta_reference/agent_instance.py b/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
index 5f7c90879..b597473bc 100644
--- a/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
+++ b/llama_stack/providers/inline/agents/meta_reference/agent_instance.py
@@ -4,17 +4,20 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import asyncio
 import copy
 import json
 import re
 import secrets
 import string
+import time
 import uuid
 import warnings
 from collections.abc import AsyncGenerator
 from datetime import UTC, datetime
 
 import httpx
+from opentelemetry.trace import get_current_span
 
 from llama_stack.apis.agents import (
     AgentConfig,
@@ -60,6 +63,7 @@ from llama_stack.apis.inference import (
     UserMessage,
 )
 from llama_stack.apis.safety import Safety
+from llama_stack.apis.telemetry import MetricEvent, Telemetry
 from llama_stack.apis.tools import ToolGroups, ToolInvocationResult, ToolRuntime
 from llama_stack.apis.vector_io import VectorIO
 from llama_stack.core.datatypes import AccessRule
@@ -97,6 +101,7 @@ class ChatAgent(ShieldRunnerMixin):
         tool_runtime_api: ToolRuntime,
         tool_groups_api: ToolGroups,
         vector_io_api: VectorIO,
+        telemetry_api: Telemetry | None,
         persistence_store: KVStore,
         created_at: str,
         policy: list[AccessRule],
@@ -106,6 +111,7 @@ class ChatAgent(ShieldRunnerMixin):
         self.inference_api = inference_api
         self.safety_api = safety_api
         self.vector_io_api = vector_io_api
+        self.telemetry_api = telemetry_api
         self.storage = AgentPersistence(agent_id, persistence_store, policy)
         self.tool_runtime_api = tool_runtime_api
         self.tool_groups_api = tool_groups_api
@@ -167,6 +173,56 @@ class ChatAgent(ShieldRunnerMixin):
     async def create_session(self, name: str) -> str:
         return await self.storage.create_session(name)
 
+    def _emit_metric(
+        self, metric_name: str, value: int | float, unit: str, attributes: dict[str, str] | None = None
+    ) -> None:
+        """Emit a single metric event"""
+        if not self.telemetry_api:
+            return
+
+        span = get_current_span()
+        if not span:
+            return
+
+        context = span.get_span_context()
+        metric = MetricEvent(
+            trace_id=format(context.trace_id, "x"),
+            span_id=format(context.span_id, "x"),
+            metric=metric_name,
+            value=value,
+            timestamp=time.time(),
+            unit=unit,
+            attributes={"agent_id": self.agent_id, **(attributes or {})},
+        )
+
+        # Create task with name for better debugging and capture any async errors
+        task_name = f"metric-{metric_name}-{self.agent_id}"
+        task = asyncio.create_task(self.telemetry_api.log_event(metric), name=task_name)
+
+        def _on_metric_task_done(t: asyncio.Task) -> None:
+            try:
+                exc = t.exception()
+            except asyncio.CancelledError:
+                logger.debug("Metric task %s was cancelled", task_name)
+                return
+            if exc is not None:
+                logger.warning("Metric task %s failed: %s", task_name, exc)
+
+        # Only add callback if task creation succeeded (not None from mocking)
+        if task is not None:
+            task.add_done_callback(_on_metric_task_done)
+
+    def _track_step(self):
+        self._emit_metric("llama_stack_agent_steps_total", 1, "1")
+
+    def _track_workflow(self, status: str, duration: float):
+        self._emit_metric("llama_stack_agent_workflows_total", 1, "1", {"status": status})
+        self._emit_metric("llama_stack_agent_workflow_duration_seconds", duration, "s")
+
+    def _track_tool(self, tool_name: str):
+        normalized_name = "rag" if tool_name == "knowledge_search" else tool_name
+        self._emit_metric("llama_stack_agent_tool_calls_total", 1, "1", {"tool": normalized_name})
+
     async def get_messages_from_turns(self, turns: list[Turn]) -> list[Message]:
         messages = []
         if self.agent_config.instructions != "":
@@ -726,6 +782,9 @@ class ChatAgent(ShieldRunnerMixin):
                             )
                         )
 
+                        # Track step execution metric
+                        self._track_step()
+
                         # Add the result message to input_messages for the next iteration
                         input_messages.append(result_message)
 
@@ -900,6 +959,7 @@ class ChatAgent(ShieldRunnerMixin):
             },
         )
         logger.debug(f"tool call {tool_name_str} completed with result: {result}")
+
         return result
 
 
diff --git a/llama_stack/providers/inline/agents/meta_reference/agents.py b/llama_stack/providers/inline/agents/meta_reference/agents.py
index 0f12a0865..bbef57d15 100644
--- a/llama_stack/providers/inline/agents/meta_reference/agents.py
+++ b/llama_stack/providers/inline/agents/meta_reference/agents.py
@@ -39,6 +39,7 @@ from llama_stack.apis.inference import (
     UserMessage,
 )
 from llama_stack.apis.safety import Safety
+from llama_stack.apis.telemetry import Telemetry
 from llama_stack.apis.tools import ToolGroups, ToolRuntime
 from llama_stack.apis.vector_io import VectorIO
 from llama_stack.core.datatypes import AccessRule
@@ -64,6 +65,7 @@ class MetaReferenceAgentsImpl(Agents):
         tool_runtime_api: ToolRuntime,
         tool_groups_api: ToolGroups,
         policy: list[AccessRule],
+        telemetry_api: Telemetry | None = None,
     ):
         self.config = config
         self.inference_api = inference_api
@@ -71,6 +73,7 @@ class MetaReferenceAgentsImpl(Agents):
         self.safety_api = safety_api
         self.tool_runtime_api = tool_runtime_api
         self.tool_groups_api = tool_groups_api
+        self.telemetry_api = telemetry_api
 
         self.in_memory_store = InmemoryKVStoreImpl()
         self.openai_responses_impl: OpenAIResponsesImpl | None = None
@@ -130,6 +133,7 @@ class MetaReferenceAgentsImpl(Agents):
             vector_io_api=self.vector_io_api,
             tool_runtime_api=self.tool_runtime_api,
             tool_groups_api=self.tool_groups_api,
+            telemetry_api=self.telemetry_api,
             persistence_store=(
                 self.persistence_store if agent_info.enable_session_persistence else self.in_memory_store
             ),
diff --git a/llama_stack/providers/inline/telemetry/meta_reference/telemetry.py b/llama_stack/providers/inline/telemetry/meta_reference/telemetry.py
index d99255c79..c5e9959c2 100644
--- a/llama_stack/providers/inline/telemetry/meta_reference/telemetry.py
+++ b/llama_stack/providers/inline/telemetry/meta_reference/telemetry.py
@@ -26,6 +26,7 @@ from llama_stack.apis.telemetry import (
     MetricEvent,
     MetricLabelMatcher,
     MetricQueryType,
+    MetricType,
     QueryCondition,
     QueryMetricsResponse,
     QuerySpanTreeResponse,
@@ -57,6 +58,7 @@ _GLOBAL_STORAGE: dict[str, dict[str | int, Any]] = {
     "counters": {},
     "gauges": {},
     "up_down_counters": {},
+    "histograms": {},
 }
 _global_lock = threading.Lock()
 _TRACER_PROVIDER = None
@@ -227,12 +229,20 @@ class TelemetryAdapter(TelemetryDatasetMixin, Telemetry):
         # Log to OpenTelemetry meter if available
         if self.meter is None:
             return
-        if isinstance(event.value, int):
-            counter = self._get_or_create_counter(event.metric, event.unit)
-            counter.add(event.value, attributes=event.attributes)
-        elif isinstance(event.value, float):
+
+        if event.metric_type == MetricType.HISTOGRAM:
+            histogram = self._get_or_create_histogram(
+                event.metric,
+                event.unit,
+                [0.1, 0.5, 1.0, 2.5, 5.0, 10.0, 25.0, 50.0, 100.0],
+            )
+            histogram.record(event.value, attributes=event.attributes)
+        elif event.metric_type == MetricType.UP_DOWN_COUNTER:
             up_down_counter = self._get_or_create_up_down_counter(event.metric, event.unit)
             up_down_counter.add(event.value, attributes=event.attributes)
+        else:
+            counter = self._get_or_create_counter(event.metric, event.unit)
+            counter.add(event.value, attributes=event.attributes)
 
     def _get_or_create_up_down_counter(self, name: str, unit: str) -> metrics.UpDownCounter:
         assert self.meter is not None
@@ -244,6 +254,16 @@ class TelemetryAdapter(TelemetryDatasetMixin, Telemetry):
             )
         return _GLOBAL_STORAGE["up_down_counters"][name]
 
+    def _get_or_create_histogram(self, name: str, unit: str, buckets: list[float] | None = None) -> metrics.Histogram:
+        assert self.meter is not None
+        if name not in _GLOBAL_STORAGE["histograms"]:
+            _GLOBAL_STORAGE["histograms"][name] = self.meter.create_histogram(
+                name=name,
+                unit=unit,
+                description=f"Histogram for {name}",
+            )
+        return _GLOBAL_STORAGE["histograms"][name]
+
     def _log_structured(self, event: StructuredLogEvent, ttl_seconds: int) -> None:
         with self._lock:
             span_id = int(event.span_id, 16)
diff --git a/llama_stack/providers/registry/agents.py b/llama_stack/providers/registry/agents.py
index 57110d129..9108f0dc5 100644
--- a/llama_stack/providers/registry/agents.py
+++ b/llama_stack/providers/registry/agents.py
@@ -35,6 +35,7 @@ def available_providers() -> list[ProviderSpec]:
                 Api.vector_dbs,
                 Api.tool_runtime,
                 Api.tool_groups,
+                Api.telemetry,
             ],
             description="Meta's reference implementation of an agent system that can use tools, access vector databases, and perform complex reasoning tasks.",
         ),
diff --git a/pyproject.toml b/pyproject.toml
index db0ad1f00..df1744613 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,8 +25,8 @@ classifiers = [
 ]
 dependencies = [
     "aiohttp",
-    "fastapi>=0.115.0,<1.0",                  # server
-    "fire",                                   # for MCP in LLS client
+    "fastapi>=0.115.0,<1.0", # server
+    "fire", # for MCP in LLS client
     "httpx",
     "huggingface-hub>=0.34.0,<1.0",
     "jinja2>=3.1.6",
@@ -44,12 +44,12 @@ dependencies = [
     "tiktoken",
     "pillow",
     "h11>=0.16.0",
-    "python-multipart>=0.0.20",               # For fastapi Form
-    "uvicorn>=0.34.0",                        # server
-    "opentelemetry-sdk>=1.30.0",              # server
+    "python-multipart>=0.0.20", # For fastapi Form
+    "uvicorn>=0.34.0", # server
+    "opentelemetry-sdk>=1.30.0", # server
     "opentelemetry-exporter-otlp-proto-http>=1.30.0", # server
-    "aiosqlite>=0.21.0",                      # server - for metadata store
-    "asyncpg",                                # for metadata store
+    "aiosqlite>=0.21.0", # server - for metadata store
+    "asyncpg", # for metadata store
 ]
 
 [project.optional-dependencies]
diff --git a/tests/unit/providers/agents/__init__.py b/tests/unit/providers/agents/__init__.py
new file mode 100644
index 000000000..756f351d8
--- /dev/null
+++ b/tests/unit/providers/agents/__init__.py
@@ -0,0 +1,5 @@
+# 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.
diff --git a/tests/unit/providers/agents/test_agent_metrics.py b/tests/unit/providers/agents/test_agent_metrics.py
new file mode 100644
index 000000000..acaec837d
--- /dev/null
+++ b/tests/unit/providers/agents/test_agent_metrics.py
@@ -0,0 +1,212 @@
+# 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.
+
+import asyncio
+from unittest.mock import AsyncMock, Mock
+
+import pytest
+from opentelemetry.trace import SpanContext, TraceFlags
+
+from llama_stack.providers.inline.agents.meta_reference.agent_instance import ChatAgent
+
+
+class FakeSpan:
+    def __init__(self, trace_id: int = 123, span_id: int = 456):
+        self._context = SpanContext(
+            trace_id=trace_id,
+            span_id=span_id,
+            is_remote=False,
+            trace_flags=TraceFlags(0x01),
+        )
+
+    def get_span_context(self):
+        return self._context
+
+
+@pytest.fixture
+def agent_with_telemetry():
+    """Create a real ChatAgent with telemetry API"""
+    telemetry_api = AsyncMock()
+
+    agent = ChatAgent(
+        agent_id="test-agent",
+        agent_config=Mock(),
+        inference_api=Mock(),
+        safety_api=Mock(),
+        tool_runtime_api=Mock(),
+        tool_groups_api=Mock(),
+        vector_io_api=Mock(),
+        telemetry_api=telemetry_api,
+        persistence_store=Mock(),
+        created_at="2025-01-01T00:00:00Z",
+        policy=[],
+    )
+    return agent
+
+
+@pytest.fixture
+def agent_without_telemetry():
+    """Create a real ChatAgent without telemetry API"""
+    agent = ChatAgent(
+        agent_id="test-agent",
+        agent_config=Mock(),
+        inference_api=Mock(),
+        safety_api=Mock(),
+        tool_runtime_api=Mock(),
+        tool_groups_api=Mock(),
+        vector_io_api=Mock(),
+        telemetry_api=None,
+        persistence_store=Mock(),
+        created_at="2025-01-01T00:00:00Z",
+        policy=[],
+    )
+    return agent
+
+
+class TestAgentMetrics:
+    def test_step_execution_metrics(self, agent_with_telemetry, monkeypatch):
+        """Test that step execution metrics are emitted correctly"""
+        fake_span = FakeSpan()
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.get_current_span", lambda: fake_span
+        )
+
+        # Capture the metric instead of actually creating async task
+        captured_metrics = []
+
+        async def capture_metric(metric):
+            captured_metrics.append(metric)
+
+        monkeypatch.setattr(agent_with_telemetry.telemetry_api, "log_event", capture_metric)
+
+        def mock_create_task(coro, *, name=None):
+            return asyncio.run(coro)
+
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.asyncio.create_task", mock_create_task
+        )
+
+        agent_with_telemetry._track_step()
+
+        assert len(captured_metrics) == 1
+        metric = captured_metrics[0]
+        assert metric.metric == "llama_stack_agent_steps_total"
+        assert metric.value == 1
+        assert metric.unit == "1"
+        assert metric.attributes["agent_id"] == "test-agent"
+
+    def test_workflow_completion_metrics(self, agent_with_telemetry, monkeypatch):
+        """Test that workflow completion metrics are emitted correctly"""
+        fake_span = FakeSpan()
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.get_current_span", lambda: fake_span
+        )
+
+        captured_metrics = []
+
+        async def capture_metric(metric):
+            captured_metrics.append(metric)
+
+        monkeypatch.setattr(agent_with_telemetry.telemetry_api, "log_event", capture_metric)
+
+        def mock_create_task(coro, *, name=None):
+            return asyncio.run(coro)
+
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.asyncio.create_task", mock_create_task
+        )
+
+        agent_with_telemetry._track_workflow("completed", 2.5)
+
+        assert len(captured_metrics) == 2
+
+        # Check workflow count metric
+        count_metric = captured_metrics[0]
+        assert count_metric.metric == "llama_stack_agent_workflows_total"
+        assert count_metric.value == 1
+        assert count_metric.attributes["status"] == "completed"
+
+        # Check duration metric
+        duration_metric = captured_metrics[1]
+        assert duration_metric.metric == "llama_stack_agent_workflow_duration_seconds"
+        assert duration_metric.value == 2.5
+        assert duration_metric.unit == "s"
+
+    def test_tool_usage_metrics(self, agent_with_telemetry, monkeypatch):
+        """Test that tool usage metrics are emitted correctly"""
+        fake_span = FakeSpan()
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.get_current_span", lambda: fake_span
+        )
+
+        captured_metrics = []
+
+        async def capture_metric(metric):
+            captured_metrics.append(metric)
+
+        monkeypatch.setattr(agent_with_telemetry.telemetry_api, "log_event", capture_metric)
+
+        def mock_create_task(coro, *, name=None):
+            return asyncio.run(coro)
+
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.asyncio.create_task", mock_create_task
+        )
+
+        agent_with_telemetry._track_tool("web_search")
+
+        assert len(captured_metrics) == 1
+        metric = captured_metrics[0]
+        assert metric.metric == "llama_stack_agent_tool_calls_total"
+        assert metric.attributes["tool"] == "web_search"
+
+    def test_knowledge_search_tool_mapping(self, agent_with_telemetry, monkeypatch):
+        """Test that knowledge_search tool is mapped to rag"""
+        fake_span = FakeSpan()
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.get_current_span", lambda: fake_span
+        )
+
+        captured_metrics = []
+
+        async def capture_metric(metric):
+            captured_metrics.append(metric)
+
+        monkeypatch.setattr(agent_with_telemetry.telemetry_api, "log_event", capture_metric)
+
+        def mock_create_task(coro, *, name=None):
+            return asyncio.run(coro)
+
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.asyncio.create_task", mock_create_task
+        )
+
+        agent_with_telemetry._track_tool("knowledge_search")
+
+        assert len(captured_metrics) == 1
+        metric = captured_metrics[0]
+        assert metric.attributes["tool"] == "rag"
+
+    def test_no_telemetry_api(self, agent_without_telemetry):
+        """Test that methods work gracefully when telemetry_api is None"""
+        # These should not crash
+        agent_without_telemetry._track_step()
+        agent_without_telemetry._track_workflow("failed", 1.0)
+        agent_without_telemetry._track_tool("web_search")
+
+    def test_no_active_span(self, agent_with_telemetry, monkeypatch):
+        """Test that methods work gracefully when no span is active"""
+        monkeypatch.setattr(
+            "llama_stack.providers.inline.agents.meta_reference.agent_instance.get_current_span", lambda: None
+        )
+
+        # These should not crash and should not call telemetry
+        agent_with_telemetry._track_step()
+        agent_with_telemetry._track_workflow("failed", 1.0)
+        agent_with_telemetry._track_tool("web_search")
+
+        # Telemetry should not have been called
+        agent_with_telemetry.telemetry_api.log_event.assert_not_called()
diff --git a/tests/unit/providers/telemetry/__init__.py b/tests/unit/providers/telemetry/__init__.py
new file mode 100644
index 000000000..756f351d8
--- /dev/null
+++ b/tests/unit/providers/telemetry/__init__.py
@@ -0,0 +1,5 @@
+# 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.
diff --git a/tests/unit/providers/telemetry/test_agent_metrics_histogram.py b/tests/unit/providers/telemetry/test_agent_metrics_histogram.py
new file mode 100644
index 000000000..1ab7d5835
--- /dev/null
+++ b/tests/unit/providers/telemetry/test_agent_metrics_histogram.py
@@ -0,0 +1,292 @@
+# 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.
+
+from unittest.mock import Mock
+
+import pytest
+
+from llama_stack.apis.telemetry import MetricEvent, MetricType
+from llama_stack.providers.inline.telemetry.meta_reference.config import TelemetryConfig
+from llama_stack.providers.inline.telemetry.meta_reference.telemetry import TelemetryAdapter
+
+
+class TestAgentMetricsHistogram:
+    """Unit tests for histogram support in telemetry adapter for agent metrics"""
+
+    @pytest.fixture
+    def telemetry_config(self):
+        """Basic telemetry config for testing"""
+        return TelemetryConfig(
+            service_name="test-service",
+            sinks=[],
+        )
+
+    @pytest.fixture
+    def telemetry_adapter(self, telemetry_config):
+        """TelemetryAdapter with mocked meter"""
+        adapter = TelemetryAdapter(telemetry_config, {})
+        # Mock the meter to avoid OpenTelemetry setup
+        adapter.meter = Mock()
+        return adapter
+
+    def test_get_or_create_histogram_new(self, telemetry_adapter):
+        """Test creating a new histogram"""
+        mock_histogram = Mock()
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+
+        # Clear global storage to ensure clean state
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+
+        result = telemetry_adapter._get_or_create_histogram("test_histogram", "s", [0.1, 0.5, 1.0, 5.0, 10.0])
+
+        assert result == mock_histogram
+        telemetry_adapter.meter.create_histogram.assert_called_once_with(
+            name="test_histogram",
+            unit="s",
+            description="Histogram for test_histogram",
+        )
+        assert _GLOBAL_STORAGE["histograms"]["test_histogram"] == mock_histogram
+
+    def test_get_or_create_histogram_existing(self, telemetry_adapter):
+        """Test retrieving an existing histogram"""
+        mock_histogram = Mock()
+
+        # Pre-populate global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {"existing_histogram": mock_histogram}
+
+        result = telemetry_adapter._get_or_create_histogram("existing_histogram", "ms")
+
+        assert result == mock_histogram
+        # Should not create a new histogram
+        telemetry_adapter.meter.create_histogram.assert_not_called()
+
+    def test_log_metric_duration_histogram(self, telemetry_adapter):
+        """Test logging duration metrics creates histogram"""
+        mock_histogram = Mock()
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+
+        metric_event = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="llama_stack_agent_workflow_duration_seconds",
+            value=15.7,
+            timestamp=1234567890.0,
+            unit="s",
+            attributes={"agent_id": "test-agent"},
+            metric_type=MetricType.HISTOGRAM,
+        )
+
+        telemetry_adapter._log_metric(metric_event)
+
+        # Verify histogram was created and recorded
+        telemetry_adapter.meter.create_histogram.assert_called_once_with(
+            name="llama_stack_agent_workflow_duration_seconds",
+            unit="s",
+            description="Histogram for llama_stack_agent_workflow_duration_seconds",
+        )
+        mock_histogram.record.assert_called_once_with(15.7, attributes={"agent_id": "test-agent"})
+
+    def test_log_metric_duration_histogram_default_buckets(self, telemetry_adapter):
+        """Test that duration metrics use default buckets"""
+        mock_histogram = Mock()
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+
+        metric_event = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="custom_duration_seconds",
+            value=5.2,
+            timestamp=1234567890.0,
+            unit="s",
+            attributes={},
+            metric_type=MetricType.HISTOGRAM,
+        )
+
+        telemetry_adapter._log_metric(metric_event)
+
+        # Verify histogram was created (buckets are not passed to create_histogram in OpenTelemetry)
+        mock_histogram.record.assert_called_once_with(5.2, attributes={})
+
+    def test_log_metric_non_duration_counter(self, telemetry_adapter):
+        """Test that non-duration metrics still use counters"""
+        mock_counter = Mock()
+        telemetry_adapter.meter.create_counter.return_value = mock_counter
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["counters"] = {}
+
+        metric_event = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="llama_stack_agent_workflows_total",
+            value=1,
+            timestamp=1234567890.0,
+            unit="1",
+            attributes={"agent_id": "test-agent", "status": "completed"},
+        )
+
+        telemetry_adapter._log_metric(metric_event)
+
+        # Verify counter was used, not histogram
+        telemetry_adapter.meter.create_counter.assert_called_once()
+        telemetry_adapter.meter.create_histogram.assert_not_called()
+        mock_counter.add.assert_called_once_with(1, attributes={"agent_id": "test-agent", "status": "completed"})
+
+    def test_log_metric_no_meter(self, telemetry_adapter):
+        """Test metric logging when meter is None"""
+        telemetry_adapter.meter = None
+
+        metric_event = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="test_duration_seconds",
+            value=1.0,
+            timestamp=1234567890.0,
+            unit="s",
+            attributes={},
+        )
+
+        # Should not raise exception
+        telemetry_adapter._log_metric(metric_event)
+
+    def test_histogram_name_detection_patterns(self, telemetry_adapter):
+        """Test various duration metric name patterns"""
+        mock_histogram = Mock()
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+
+        duration_metrics = [
+            "workflow_duration_seconds",
+            "request_duration_seconds",
+            "processing_duration_seconds",
+            "llama_stack_agent_workflow_duration_seconds",
+        ]
+
+        for metric_name in duration_metrics:
+            _GLOBAL_STORAGE["histograms"] = {}  # Reset for each test
+
+            metric_event = MetricEvent(
+                trace_id="123",
+                span_id="456",
+                metric=metric_name,
+                value=1.0,
+                timestamp=1234567890.0,
+                unit="s",
+                attributes={},
+                metric_type=MetricType.HISTOGRAM,
+            )
+
+            telemetry_adapter._log_metric(metric_event)
+            mock_histogram.record.assert_called()
+
+        # Reset call count for negative test
+        mock_histogram.record.reset_mock()
+        telemetry_adapter.meter.create_histogram.reset_mock()
+
+        # Test non-duration metric
+        non_duration_metric = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="workflow_total",  # No "_duration_seconds" suffix
+            value=1,
+            timestamp=1234567890.0,
+            unit="1",
+            attributes={},
+        )
+
+        telemetry_adapter._log_metric(non_duration_metric)
+
+        # Should not create histogram for non-duration metric
+        telemetry_adapter.meter.create_histogram.assert_not_called()
+        mock_histogram.record.assert_not_called()
+
+    def test_histogram_global_storage_isolation(self, telemetry_adapter):
+        """Test that histogram storage doesn't interfere with counters"""
+        mock_histogram = Mock()
+        mock_counter = Mock()
+
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+        telemetry_adapter.meter.create_counter.return_value = mock_counter
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+        _GLOBAL_STORAGE["counters"] = {}
+
+        # Create histogram
+        duration_metric = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="test_duration_seconds",
+            value=1.0,
+            timestamp=1234567890.0,
+            unit="s",
+            attributes={},
+            metric_type=MetricType.HISTOGRAM,
+        )
+        telemetry_adapter._log_metric(duration_metric)
+
+        # Create counter
+        counter_metric = MetricEvent(
+            trace_id="123",
+            span_id="456",
+            metric="test_counter",
+            value=1,
+            timestamp=1234567890.0,
+            unit="1",
+            attributes={},
+        )
+        telemetry_adapter._log_metric(counter_metric)
+
+        # Verify both were created and stored separately
+        assert "test_duration_seconds" in _GLOBAL_STORAGE["histograms"]
+        assert "test_counter" in _GLOBAL_STORAGE["counters"]
+        assert "test_duration_seconds" not in _GLOBAL_STORAGE["counters"]
+        assert "test_counter" not in _GLOBAL_STORAGE["histograms"]
+
+    def test_histogram_buckets_parameter_ignored(self, telemetry_adapter):
+        """Test that buckets parameter doesn't affect histogram creation (OpenTelemetry handles buckets internally)"""
+        mock_histogram = Mock()
+        telemetry_adapter.meter.create_histogram.return_value = mock_histogram
+
+        # Clear global storage
+        from llama_stack.providers.inline.telemetry.meta_reference.telemetry import _GLOBAL_STORAGE
+
+        _GLOBAL_STORAGE["histograms"] = {}
+
+        # Call with buckets parameter
+        result = telemetry_adapter._get_or_create_histogram(
+            "test_histogram", "s", buckets=[0.1, 0.5, 1.0, 5.0, 10.0, 25.0, 50.0, 100.0]
+        )
+
+        # Buckets are not passed to OpenTelemetry create_histogram
+        telemetry_adapter.meter.create_histogram.assert_called_once_with(
+            name="test_histogram",
+            unit="s",
+            description="Histogram for test_histogram",
+        )
+        assert result == mock_histogram