diff --git a/src/strands/__init__.py b/src/strands/__init__.py
index 2078f16ce..dc3a0c7ff 100644
--- a/src/strands/__init__.py
+++ b/src/strands/__init__.py
@@ -1,6 +1,7 @@
 """A framework for building, deploying, and managing AI agents."""
 
 from . import agent, models, telemetry, types
+from .agent._agent_as_tool import AgentAsTool
 from .agent.agent import Agent
 from .agent.base import AgentBase
 from .event_loop._retry import ModelRetryStrategy
@@ -11,6 +12,7 @@
 
 __all__ = [
     "Agent",
+    "AgentAsTool",
     "AgentBase",
     "AgentSkills",
     "agent",
diff --git a/src/strands/agent/__init__.py b/src/strands/agent/__init__.py
index c901e800f..d0254852d 100644
--- a/src/strands/agent/__init__.py
+++ b/src/strands/agent/__init__.py
@@ -10,6 +10,7 @@
 from typing import Any
 
 from ..event_loop._retry import ModelRetryStrategy
+from ._agent_as_tool import AgentAsTool
 from .agent import Agent
 from .agent_result import AgentResult
 from .base import AgentBase
@@ -24,6 +25,7 @@
     "Agent",
     "AgentBase",
     "AgentResult",
+    "AgentAsTool",
     "ConversationManager",
     "NullConversationManager",
     "SlidingWindowConversationManager",
diff --git a/src/strands/agent/_agent_as_tool.py b/src/strands/agent/_agent_as_tool.py
new file mode 100644
index 000000000..a54b67df9
--- /dev/null
+++ b/src/strands/agent/_agent_as_tool.py
@@ -0,0 +1,237 @@
+"""Agent-as-tool adapter.
+
+This module provides the AgentAsTool class that wraps an Agent (or any AgentBase) as a tool
+so it can be passed to another agent's tool list.
+"""
+
+import copy
+import logging
+from typing import Any
+
+from typing_extensions import override
+
+from ..agent.state import AgentState
+from ..types._events import AgentAsToolStreamEvent, ToolResultEvent
+from ..types.content import Messages
+from ..types.tools import AgentTool, ToolGenerator, ToolSpec, ToolUse
+from .base import AgentBase
+
+logger = logging.getLogger(__name__)
+
+
+class AgentAsTool(AgentTool):
+    """Adapter that exposes an Agent as a tool for use by other agents.
+
+    The tool accepts a single ``input`` string parameter, invokes the wrapped
+    agent, and returns the text response.
+
+    Example:
+        ```python
+        from strands import Agent
+        from strands.agent import AgentAsTool
+
+        researcher = Agent(name="researcher", description="Finds information")
+
+        # Use directly
+        tool = AgentAsTool(researcher, name="researcher", description="Finds information")
+
+        # Or via convenience method
+        tool = researcher.as_tool()
+
+        # Start each invocation with a fresh conversation
+        tool = researcher.as_tool(preserve_context=False)
+
+        writer = Agent(name="writer", tools=[tool])
+        writer("Write about AI agents")
+        ```
+    """
+
+    def __init__(
+        self,
+        agent: AgentBase,
+        *,
+        name: str,
+        description: str,
+        preserve_context: bool = False,
+    ) -> None:
+        r"""Initialize the agent-as-tool adapter.
+
+        Args:
+            agent: The agent to wrap as a tool.
+            name: Tool name. Must match the pattern ``[a-zA-Z0-9_\\-]{1,64}``.
+            description: Tool description.
+            preserve_context: Whether to preserve the agent's conversation history across
+                invocations. When False, the agent's messages and state are reset to the
+                values they had at construction time before each call, ensuring every
+                invocation starts from the same baseline regardless of any external
+                interactions with the agent. Defaults to False. Only effective when the
+                wrapped agent exposes a mutable ``messages`` list and/or an ``AgentState``
+                (e.g. ``strands.agent.Agent``).
+        """
+        super().__init__()
+        self._agent = agent
+        self._tool_name = name
+        self._description = description
+        self._preserve_context = preserve_context
+
+        # When preserve_context=False, we snapshot the agent's initial state so we can
+        # restore it before each invocation. This mirrors GraphNode.reset_executor_state().
+        # We require an Agent instance for this since AgentBase doesn't guarantee
+        # messages/state attributes.
+        self._initial_messages: Messages = []
+        self._initial_state: AgentState = AgentState()
+
+        if not preserve_context:
+            from .agent import Agent
+
+            if not isinstance(agent, Agent):
+                raise TypeError(f"preserve_context=False requires an Agent instance, got {type(agent).__name__}")
+            self._initial_messages = copy.deepcopy(agent.messages)
+            self._initial_state = AgentState(agent.state.get())
+
+    @property
+    def agent(self) -> AgentBase:
+        """The wrapped agent instance."""
+        return self._agent
+
+    @property
+    def tool_name(self) -> str:
+        """Get the tool name."""
+        return self._tool_name
+
+    @property
+    def tool_spec(self) -> ToolSpec:
+        """Get the tool specification."""
+        return {
+            "name": self._tool_name,
+            "description": self._description,
+            "inputSchema": {
+                "json": {
+                    "type": "object",
+                    "properties": {
+                        "input": {
+                            "type": "string",
+                            "description": "The input to send to the agent tool.",
+                        },
+                    },
+                    "required": ["input"],
+                }
+            },
+        }
+
+    @property
+    def tool_type(self) -> str:
+        """Get the tool type."""
+        return "agent"
+
+    @override
+    async def stream(self, tool_use: ToolUse, invocation_state: dict[str, Any], **kwargs: Any) -> ToolGenerator:
+        """Invoke the wrapped agent via streaming and yield events.
+
+        Intermediate agent events are wrapped in AgentAsToolStreamEvent so the caller
+        can distinguish sub-agent progress from regular tool events. The final
+        AgentResult is yielded as a ToolResultEvent.
+
+        Args:
+            tool_use: The tool use request containing the input parameter.
+            invocation_state: Context for the tool invocation.
+            **kwargs: Additional keyword arguments.
+
+        Yields:
+            AgentAsToolStreamEvent for intermediate events, then ToolResultEvent with the final response.
+        """
+        tool_input = tool_use["input"]
+        if isinstance(tool_input, dict):
+            prompt = tool_input.get("input", "")
+        elif isinstance(tool_input, str):
+            prompt = tool_input
+        else:
+            logger.warning("tool_name=<%s> | unexpected input type: %s", self._tool_name, type(tool_input))
+            prompt = str(tool_input)
+
+        tool_use_id = tool_use["toolUseId"]
+
+        if not self._preserve_context:
+            self._reset_agent_state(tool_use_id)
+
+        logger.debug("tool_name=<%s>, tool_use_id=<%s> | invoking agent", self._tool_name, tool_use_id)
+
+        try:
+            result = None
+            async for event in self._agent.stream_async(prompt):
+                if "result" in event:
+                    result = event["result"]
+                else:
+                    yield AgentAsToolStreamEvent(tool_use, event, self)
+
+            if result is None:
+                yield ToolResultEvent(
+                    {
+                        "toolUseId": tool_use_id,
+                        "status": "error",
+                        "content": [{"text": "Agent did not produce a result"}],
+                    }
+                )
+                return
+
+            if result.structured_output:
+                yield ToolResultEvent(
+                    {
+                        "toolUseId": tool_use_id,
+                        "status": "success",
+                        "content": [{"json": result.structured_output.model_dump()}],
+                    }
+                )
+            else:
+                yield ToolResultEvent(
+                    {
+                        "toolUseId": tool_use_id,
+                        "status": "success",
+                        "content": [{"text": str(result)}],
+                    }
+                )
+
+        except Exception as e:
+            logger.warning(
+                "tool_name=<%s>, tool_use_id=<%s> | agent invocation failed: %s",
+                self._tool_name,
+                tool_use_id,
+                e,
+            )
+            yield ToolResultEvent(
+                {
+                    "toolUseId": tool_use_id,
+                    "status": "error",
+                    "content": [{"text": f"Agent error: {e}"}],
+                }
+            )
+
+    def _reset_agent_state(self, tool_use_id: str) -> None:
+        """Reset the wrapped agent to its initial state.
+
+        Restores messages and state to the values captured at construction time.
+        This mirrors the pattern used by ``GraphNode.reset_executor_state()``.
+
+        Args:
+            tool_use_id: Tool use ID for logging context.
+        """
+        from .agent import Agent
+
+        # isinstance narrows the type for mypy; __init__ guarantees this when preserve_context=False
+        if not isinstance(self._agent, Agent):
+            return
+
+        logger.debug(
+            "tool_name=<%s>, tool_use_id=<%s> | resetting agent to initial state",
+            self._tool_name,
+            tool_use_id,
+        )
+        self._agent.messages = copy.deepcopy(self._initial_messages)
+        self._agent.state = AgentState(self._initial_state.get())
+
+    @override
+    def get_display_properties(self) -> dict[str, str]:
+        """Get properties for UI display."""
+        properties = super().get_display_properties()
+        properties["Agent"] = getattr(self._agent, "name", "unknown")
+        return properties
diff --git a/src/strands/agent/agent.py b/src/strands/agent/agent.py
index f378a886a..f09399dbf 100644
--- a/src/strands/agent/agent.py
+++ b/src/strands/agent/agent.py
@@ -62,6 +62,7 @@
 from ..types.content import ContentBlock, Message, Messages, SystemContentBlock
 from ..types.exceptions import ConcurrencyException, ContextWindowOverflowException
 from ..types.traces import AttributeValue
+from ._agent_as_tool import AgentAsTool
 from .agent_result import AgentResult
 from .base import AgentBase
 from .conversation_manager import (
@@ -612,6 +613,40 @@ async def structured_output_async(self, output_model: type[T], prompt: AgentInpu
             finally:
                 await self.hooks.invoke_callbacks_async(AfterInvocationEvent(agent=self, invocation_state={}))
 
+    def as_tool(
+        self,
+        name: str | None = None,
+        description: str | None = None,
+        preserve_context: bool = False,
+    ) -> AgentAsTool:
+        r"""Convert this agent into a tool for use by another agent.
+
+        Args:
+            name: Tool name. Must match the pattern ``[a-zA-Z0-9_\\-]{1,64}``.
+                Defaults to the agent's name.
+            description: Tool description. Defaults to the agent's description.
+            preserve_context: Whether to preserve the agent's conversation history across
+                invocations. When False, the agent's messages and state are reset to the
+                values they had at construction time before each call, ensuring every
+                invocation starts from the same baseline regardless of any external
+                interactions with the agent. Defaults to False.
+
+        Returns:
+            An AgentAsTool wrapping this agent.
+
+        Example:
+            ```python
+            researcher = Agent(name="researcher", description="Finds information")
+            writer = Agent(name="writer", tools=[researcher.as_tool()])
+            writer("Write about AI agents")
+            ```
+        """
+        if not name:
+            name = self.name
+        if not description:
+            description = self.description or f"Use the {name} agent as a tool by providing a natural language input"
+        return AgentAsTool(self, name=name, description=description, preserve_context=preserve_context)
+
     def cleanup(self) -> None:
         """Clean up resources used by the agent.
 
diff --git a/src/strands/types/_events.py b/src/strands/types/_events.py
index 5b0ae78f6..5603aedfb 100644
--- a/src/strands/types/_events.py
+++ b/src/strands/types/_events.py
@@ -21,6 +21,7 @@
 
 if TYPE_CHECKING:
     from ..agent import AgentResult
+    from ..agent._agent_as_tool import AgentAsTool
     from ..multiagent.base import MultiAgentResult, NodeResult
 
 
@@ -323,6 +324,31 @@ def tool_use_id(self) -> str:
         return cast(ToolUse, cast(dict, self.get("tool_stream_event")).get("tool_use"))["toolUseId"]
 
 
+class AgentAsToolStreamEvent(ToolStreamEvent):
+    """Event emitted when an agent-as-tool yields intermediate events during execution.
+
+    Extends ToolStreamEvent with a reference to the originating AgentAsTool so callers
+    can distinguish sub-agent stream events from regular tool stream events and access
+    the wrapped agent, tool name, description, etc.
+    """
+
+    def __init__(self, tool_use: ToolUse, tool_stream_data: Any, agent_as_tool: "AgentAsTool") -> None:
+        """Initialize with tool streaming data and agent-tool reference.
+
+        Args:
+            tool_use: The tool invocation producing the stream.
+            tool_stream_data: The yielded event from the sub-agent execution.
+            agent_as_tool: The AgentAsTool instance that produced this event.
+        """
+        super().__init__(tool_use, tool_stream_data)
+        self._agent_as_tool = agent_as_tool
+
+    @property
+    def agent_as_tool(self) -> "AgentAsTool":
+        """The AgentAsTool instance that produced this event."""
+        return self._agent_as_tool
+
+
 class ToolCancelEvent(TypedEvent):
     """Event emitted when a user cancels a tool call from their BeforeToolCallEvent hook."""
 
diff --git a/tests/strands/agent/test_agent.py b/tests/strands/agent/test_agent.py
index 967a0dafb..c089ba808 100644
--- a/tests/strands/agent/test_agent.py
+++ b/tests/strands/agent/test_agent.py
@@ -15,7 +15,7 @@
 
 import strands
 from strands import Agent, Plugin, ToolContext
-from strands.agent import AgentResult
+from strands.agent import AgentAsTool, AgentResult
 from strands.agent.conversation_manager.null_conversation_manager import NullConversationManager
 from strands.agent.conversation_manager.sliding_window_conversation_manager import SlidingWindowConversationManager
 from strands.agent.state import AgentState
@@ -2699,3 +2699,52 @@ def hook_callback(event: BeforeModelCallEvent):
 
     agent("test")
     assert len(hook_called) == 1
+
+
+def test_as_tool_returns_agent_tool():
+    """Test that as_tool returns an AgentAsTool wrapping the agent."""
+    agent = Agent(name="researcher", description="Finds information")
+    tool = agent.as_tool()
+
+    assert isinstance(tool, AgentAsTool)
+    assert tool.agent is agent
+
+
+def test_as_tool_defaults_name_from_agent():
+    """Test that as_tool defaults the tool name to the agent's name."""
+    agent = Agent(name="researcher")
+    tool = agent.as_tool()
+
+    assert tool.tool_name == "researcher"
+
+
+def test_as_tool_defaults_description_from_agent():
+    """Test that as_tool defaults the description to the agent's description."""
+    agent = Agent(name="researcher", description="Finds information")
+    tool = agent.as_tool()
+
+    assert tool.tool_spec["description"] == "Finds information"
+
+
+def test_as_tool_custom_name():
+    """Test that as_tool accepts a custom name."""
+    agent = Agent(name="researcher")
+    tool = agent.as_tool(name="custom_name")
+
+    assert tool.tool_name == "custom_name"
+
+
+def test_as_tool_custom_description():
+    """Test that as_tool accepts a custom description."""
+    agent = Agent(name="researcher", description="Original")
+    tool = agent.as_tool(description="Custom description")
+
+    assert tool.tool_spec["description"] == "Custom description"
+
+
+def test_as_tool_defaults_description_when_agent_has_none():
+    """Test that as_tool generates a default description when agent has none."""
+    agent = Agent(name="researcher")
+    tool = agent.as_tool()
+
+    assert tool.tool_spec["description"] == "Use the researcher agent as a tool by providing a natural language input"
diff --git a/tests/strands/agent/test_agent_as_tool.py b/tests/strands/agent/test_agent_as_tool.py
new file mode 100644
index 000000000..68128e6e5
--- /dev/null
+++ b/tests/strands/agent/test_agent_as_tool.py
@@ -0,0 +1,463 @@
+"""Tests for AgentAsTool - the agent-as-tool adapter."""
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from strands.agent import AgentAsTool
+from strands.agent.agent_result import AgentResult
+from strands.telemetry.metrics import EventLoopMetrics
+from strands.types._events import AgentAsToolStreamEvent, ToolResultEvent, ToolStreamEvent
+
+
+async def _mock_stream_async(result, intermediate_events=None):
+    """Helper that yields intermediate events then the final result event."""
+    for event in intermediate_events or []:
+        yield event
+    yield {"result": result}
+
+
+@pytest.fixture
+def mock_agent():
+    agent = MagicMock()
+    agent.name = "test_agent"
+    agent.description = "A test agent"
+    return agent
+
+
+@pytest.fixture
+def fake_agent():
+    """A real Agent instance for tests that need Agent-specific features."""
+    from strands.agent.agent import Agent
+
+    return Agent(name="fake_agent", callback_handler=None)
+
+
+@pytest.fixture
+def tool(mock_agent):
+    return AgentAsTool(mock_agent, name="test_agent", description="A test agent", preserve_context=True)
+
+
+@pytest.fixture
+def tool_use():
+    return {
+        "toolUseId": "tool-123",
+        "name": "test_agent",
+        "input": {"input": "hello"},
+    }
+
+
+@pytest.fixture
+def agent_result():
+    return AgentResult(
+        stop_reason="end_turn",
+        message={"role": "assistant", "content": [{"text": "response text"}]},
+        metrics=EventLoopMetrics(),
+        state={},
+    )
+
+
+# --- init ---
+
+
+def test_init(mock_agent):
+    tool = AgentAsTool(mock_agent, name="my_tool", description="custom desc", preserve_context=True)
+    assert tool.tool_name == "my_tool"
+    assert tool._description == "custom desc"
+    assert tool.agent is mock_agent
+
+
+def test_init_preserve_context_defaults_false(fake_agent):
+    tool = AgentAsTool(fake_agent, name="t", description="d")
+    assert tool._preserve_context is False
+
+
+def test_init_preserve_context_true(mock_agent):
+    tool = AgentAsTool(mock_agent, name="t", description="d", preserve_context=True)
+    assert tool._preserve_context is True
+
+
+# --- properties ---
+
+
+def test_tool_properties(tool):
+    assert tool.tool_name == "test_agent"
+    assert tool.tool_type == "agent"
+
+    spec = tool.tool_spec
+    assert spec["name"] == "test_agent"
+    assert spec["description"] == "A test agent"
+
+    schema = spec["inputSchema"]["json"]
+    assert schema["type"] == "object"
+    assert "input" in schema["properties"]
+    assert schema["properties"]["input"]["type"] == "string"
+    assert schema["required"] == ["input"]
+
+    props = tool.get_display_properties()
+    assert props["Agent"] == "test_agent"
+    assert props["Type"] == "agent"
+
+
+# --- stream ---
+
+
+@pytest.mark.asyncio
+async def test_stream_success(tool, mock_agent, tool_use, agent_result):
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result)
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    result_events = [e for e in events if isinstance(e, ToolResultEvent)]
+    assert len(result_events) == 1
+    assert result_events[0]["tool_result"]["status"] == "success"
+    assert result_events[0]["tool_result"]["content"][0]["text"] == "response text\n"
+
+
+@pytest.mark.asyncio
+async def test_stream_passes_input_to_agent(tool, mock_agent, tool_use, agent_result):
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result)
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    mock_agent.stream_async.assert_called_once_with("hello")
+
+
+@pytest.mark.asyncio
+async def test_stream_empty_input(tool, mock_agent, agent_result):
+    empty_tool_use = {
+        "toolUseId": "tool-123",
+        "name": "test_agent",
+        "input": {},
+    }
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result)
+
+    async for _ in tool.stream(empty_tool_use, {}):
+        pass
+
+    mock_agent.stream_async.assert_called_once_with("")
+
+
+@pytest.mark.asyncio
+async def test_stream_string_input(tool, mock_agent, agent_result):
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "test_agent",
+        "input": "direct string",
+    }
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result)
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    mock_agent.stream_async.assert_called_once_with("direct string")
+
+
+@pytest.mark.asyncio
+async def test_stream_error(tool, mock_agent, tool_use):
+    mock_agent.stream_async.side_effect = RuntimeError("boom")
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    assert len(events) == 1
+    assert events[0]["tool_result"]["status"] == "error"
+    assert "boom" in events[0]["tool_result"]["content"][0]["text"]
+
+
+@pytest.mark.asyncio
+async def test_stream_propagates_tool_use_id(tool, mock_agent, tool_use, agent_result):
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result)
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    result_events = [e for e in events if isinstance(e, ToolResultEvent)]
+    assert result_events[0]["tool_result"]["toolUseId"] == "tool-123"
+
+
+@pytest.mark.asyncio
+async def test_stream_forwards_intermediate_events(tool, mock_agent, tool_use, agent_result):
+    intermediate = [{"data": "partial"}, {"data": "more"}]
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result, intermediate)
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    stream_events = [e for e in events if isinstance(e, AgentAsToolStreamEvent)]
+    assert len(stream_events) == 2
+    assert stream_events[0]["tool_stream_event"]["data"]["data"] == "partial"
+    assert stream_events[1]["tool_stream_event"]["data"]["data"] == "more"
+    assert stream_events[0].agent_as_tool is tool
+    assert stream_events[0].tool_use_id == "tool-123"
+
+
+@pytest.mark.asyncio
+async def test_stream_events_not_double_wrapped_by_executor(tool, mock_agent, tool_use, agent_result):
+    """AgentAsToolStreamEvent is a ToolStreamEvent subclass, so the executor should pass it through directly."""
+    intermediate = [{"data": "chunk"}]
+    mock_agent.stream_async.return_value = _mock_stream_async(agent_result, intermediate)
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    stream_events = [e for e in events if isinstance(e, AgentAsToolStreamEvent)]
+    assert len(stream_events) == 1
+
+    event = stream_events[0]
+    # It's a ToolStreamEvent (so the executor yields it directly)
+    assert isinstance(event, ToolStreamEvent)
+    # But it's specifically an AgentAsToolStreamEvent (not re-wrapped)
+    assert type(event) is AgentAsToolStreamEvent
+    # And it references the originating AgentAsTool
+    assert event.agent_as_tool is tool
+
+
+@pytest.mark.asyncio
+async def test_stream_no_result_yields_error(tool, mock_agent, tool_use):
+    async def _empty_stream():
+        return
+        yield  # noqa: RET504 - make it an async generator
+
+    mock_agent.stream_async.return_value = _empty_stream()
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    assert len(events) == 1
+    assert events[0]["tool_result"]["status"] == "error"
+    assert "did not produce a result" in events[0]["tool_result"]["content"][0]["text"]
+
+
+@pytest.mark.asyncio
+async def test_stream_structured_output(tool, mock_agent, tool_use):
+    from pydantic import BaseModel
+
+    class MyOutput(BaseModel):
+        answer: str
+
+    structured = MyOutput(answer="42")
+    result = AgentResult(
+        stop_reason="end_turn",
+        message={"role": "assistant", "content": [{"text": "ignored"}]},
+        metrics=EventLoopMetrics(),
+        state={},
+        structured_output=structured,
+    )
+    mock_agent.stream_async.return_value = _mock_stream_async(result)
+
+    events = [event async for event in tool.stream(tool_use, {})]
+
+    result_events = [e for e in events if isinstance(e, ToolResultEvent)]
+    assert result_events[0]["tool_result"]["status"] == "success"
+    assert result_events[0]["tool_result"]["content"][0]["json"] == {"answer": "42"}
+
+
+# --- preserve_context ---
+
+
+@pytest.mark.asyncio
+async def test_stream_resets_to_initial_state_when_preserve_context_false(fake_agent):
+    fake_agent.messages = [{"role": "user", "content": [{"text": "initial"}]}]
+    fake_agent.state.set("counter", 0)
+
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc", preserve_context=False)
+
+    # Mutate agent state as if a previous invocation happened
+    fake_agent.messages.append({"role": "assistant", "content": [{"text": "reply"}]})
+    fake_agent.state.set("counter", 5)
+
+    # Mock stream_async so we don't need a real model
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "fake_agent",
+        "input": {"input": "hello"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    assert fake_agent.messages == [{"role": "user", "content": [{"text": "initial"}]}]
+    assert fake_agent.state.get("counter") == 0
+
+
+@pytest.mark.asyncio
+async def test_stream_resets_on_every_invocation(fake_agent):
+    """Each call should reset to the same initial snapshot, not to the previous call's state."""
+    fake_agent.messages = [{"role": "user", "content": [{"text": "seed"}]}]
+    fake_agent.state.set("count", 1)
+
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc", preserve_context=False)
+
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-1",
+        "name": "fake_agent",
+        "input": {"input": "first"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+    fake_agent.messages.append({"role": "assistant", "content": [{"text": "added"}]})
+    fake_agent.state.set("count", 99)
+
+    tool_use["toolUseId"] = "tool-2"
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    assert fake_agent.messages == [{"role": "user", "content": [{"text": "seed"}]}]
+    assert fake_agent.state.get("count") == 1
+
+
+@pytest.mark.asyncio
+async def test_stream_initial_snapshot_is_deep_copy(fake_agent):
+    """Mutating the agent's messages after construction should not affect the snapshot."""
+    fake_agent.messages = [{"role": "user", "content": [{"text": "original"}]}]
+
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc", preserve_context=False)
+
+    fake_agent.messages[0]["content"][0]["text"] = "mutated"
+    fake_agent.messages.append({"role": "assistant", "content": [{"text": "extra"}]})
+
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "fake_agent",
+        "input": {"input": "hello"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    assert fake_agent.messages == [{"role": "user", "content": [{"text": "original"}]}]
+
+
+@pytest.mark.asyncio
+async def test_stream_resets_empty_initial_state_when_preserve_context_false(fake_agent):
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc", preserve_context=False)
+
+    fake_agent.messages = [{"role": "user", "content": [{"text": "old"}]}]
+    fake_agent.state.set("key", "value")
+
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "fake_agent",
+        "input": {"input": "hello"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    assert fake_agent.messages == []
+    assert fake_agent.state.get() == {}
+
+
+@pytest.mark.asyncio
+async def test_stream_resets_context_by_default(fake_agent):
+    """Default preserve_context=False means each invocation starts fresh."""
+    fake_agent.messages = [{"role": "user", "content": [{"text": "old"}]}]
+    fake_agent.state.set("key", "value")
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc")
+
+    # Mutate after construction
+    fake_agent.messages.append({"role": "assistant", "content": [{"text": "extra"}]})
+    fake_agent.state.set("key", "changed")
+
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "fake_agent",
+        "input": {"input": "hello"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    # Should reset to construction-time snapshot
+    assert fake_agent.messages == [{"role": "user", "content": [{"text": "old"}]}]
+    assert fake_agent.state.get("key") == "value"
+
+
+@pytest.mark.asyncio
+async def test_stream_preserves_context_when_explicitly_true(fake_agent):
+    fake_agent.messages = [{"role": "user", "content": [{"text": "old"}]}]
+    fake_agent.state.set("key", "value")
+    tool = AgentAsTool(fake_agent, name="fake_agent", description="desc", preserve_context=True)
+
+    fake_agent.stream_async = lambda prompt, **kw: _mock_stream_async(
+        AgentResult(
+            stop_reason="end_turn",
+            message={"role": "assistant", "content": [{"text": "ok"}]},
+            metrics=EventLoopMetrics(),
+            state={},
+        )
+    )
+
+    tool_use = {
+        "toolUseId": "tool-123",
+        "name": "fake_agent",
+        "input": {"input": "hello"},
+    }
+
+    async for _ in tool.stream(tool_use, {}):
+        pass
+
+    assert len(fake_agent.messages) >= 1
+    assert fake_agent.state.get("key") == "value"
+
+
+def test_preserve_context_false_requires_agent_instance():
+    """Default preserve_context=False should raise TypeError for non-Agent instances."""
+
+    class _NotAnAgent:
+        name = "not_agent"
+
+        async def invoke_async(self, prompt=None, **kwargs):
+            pass
+
+        def __call__(self, prompt=None, **kwargs):
+            pass
+
+        def stream_async(self, prompt=None, **kwargs):
+            pass
+
+    with pytest.raises(TypeError, match="requires an Agent instance"):
+        AgentAsTool(_NotAnAgent(), name="bad", description="desc")
diff --git a/tests/strands/types/test__events.py b/tests/strands/types/test__events.py
index 6163faeb6..48465e1f6 100644
--- a/tests/strands/types/test__events.py
+++ b/tests/strands/types/test__events.py
@@ -6,6 +6,7 @@
 
 from strands.telemetry import EventLoopMetrics
 from strands.types._events import (
+    AgentAsToolStreamEvent,
     AgentResultEvent,
     CitationStreamEvent,
     EventLoopStopEvent,
@@ -465,3 +466,39 @@ def test_event_inheritance(self):
             assert hasattr(event, "is_callback_event")
             assert hasattr(event, "as_dict")
             assert hasattr(event, "prepare")
+
+
+class TestAgentAsToolStreamEvent:
+    """Tests for AgentAsToolStreamEvent."""
+
+    def test_initialization(self):
+        """Test AgentAsToolStreamEvent initialization with agent-tool reference."""
+        tool_use: ToolUse = {
+            "toolUseId": "agent_tool_123",
+            "name": "researcher",
+            "input": {"input": "hello"},
+        }
+        agent_event = {"data": "partial response"}
+        mock_agent_as_tool = MagicMock()
+        mock_agent_as_tool.tool_name = "researcher"
+
+        event = AgentAsToolStreamEvent(tool_use, agent_event, mock_agent_as_tool)
+
+        assert event["tool_stream_event"]["tool_use"] == tool_use
+        assert event["tool_stream_event"]["data"] == agent_event
+        assert event.agent_as_tool is mock_agent_as_tool
+        assert event.tool_use_id == "agent_tool_123"
+
+    def test_is_tool_stream_event_subclass(self):
+        """Test that AgentAsToolStreamEvent is a ToolStreamEvent subclass."""
+        tool_use: ToolUse = {
+            "toolUseId": "id_123",
+            "name": "tool",
+            "input": {},
+        }
+        mock_agent_as_tool = MagicMock()
+        event = AgentAsToolStreamEvent(tool_use, {}, mock_agent_as_tool)
+
+        assert isinstance(event, ToolStreamEvent)
+        assert isinstance(event, TypedEvent)
+        assert type(event) is AgentAsToolStreamEvent
diff --git a/tests_integ/test_agent_as_tool.py b/tests_integ/test_agent_as_tool.py
new file mode 100644
index 000000000..a808fcd23
--- /dev/null
+++ b/tests_integ/test_agent_as_tool.py
@@ -0,0 +1,36 @@
+import pytest
+
+from strands import Agent, tool
+
+
+@tool
+def get_tiger_height() -> int:
+    """Returns the height of a tiger in centimeters."""
+    return 100
+
+
+@pytest.mark.asyncio
+async def test_stream_async_with_agent_tool():
+    inner_agent = Agent(
+        name="myAgentTool",
+        description="An agent tool knowledgeable about tigers",
+        tools=[get_tiger_height],
+    )
+    agent_tool = inner_agent.as_tool()
+    agent = Agent(
+        name="myOtherAgent",
+        tools=[agent_tool],
+    )
+
+    result = await agent.invoke_async(
+        prompt="Invoke the myAgentTool and ask about the height of tigers.",
+    )
+
+    # Outer agent completed and called the agent tool
+    assert result.stop_reason == "end_turn"
+    assert "myAgentTool" in result.metrics.tool_metrics
+    assert result.metrics.tool_metrics["myAgentTool"].success_count >= 1
+
+    # Inner agent called get_tiger_height
+    assert "get_tiger_height" in inner_agent.event_loop_metrics.tool_metrics
+    assert inner_agent.event_loop_metrics.tool_metrics["get_tiger_height"].success_count >= 1