diff --git a/tests/test_agent/test_loop.py b/tests/test_agent/test_loop.py
new file mode 100644
index 0000000..df218c5
--- /dev/null
+++ b/tests/test_agent/test_loop.py
@@ -0,0 +1,178 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Literal, overload
+
+from plyngent.agent import (
+    AssistantMessageEvent,
+    ChatAgent,
+    MaxRoundsEvent,
+    TextDeltaEvent,
+    ToolCallEvent,
+    ToolRegistry,
+    ToolResultEvent,
+    run_chat_loop,
+    tool,
+)
+from plyngent.config.models import DatabaseConfig
+from plyngent.lmproto.openai_compatible.model import (
+    AnyChatMessage,
+    AssistantChatMessage,
+    AssistantFunctionTool,
+    AssistantFunctionToolCall,
+    ChatCompletionChoice,
+    ChatCompletionChunk,
+    ChatCompletionResponse,
+    ChatCompletionsParam,
+    UserChatMessage,
+)
+from plyngent.memory import MemoryStore
+
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
+
+class ScriptedClient:
+    """Returns scripted non-streaming chat completions in order."""
+
+    _responses: list[ChatCompletionResponse]
+    calls: list[ChatCompletionsParam]
+
+    def __init__(self, responses: list[ChatCompletionResponse]) -> None:
+        self._responses = list(responses)
+        self.calls = []
+
+    @overload
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: Literal[False] = False
+    ) -> ChatCompletionResponse: ...
+
+    @overload
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: Literal[True]
+    ) -> AsyncIterator[ChatCompletionChunk]: ...
+
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: bool = False
+    ) -> ChatCompletionResponse | AsyncIterator[ChatCompletionChunk]:
+        self.calls.append(param)
+        if stream:
+            return self._empty_stream()
+        if not self._responses:
+            msg = "no more scripted responses"
+            raise RuntimeError(msg)
+        return self._responses.pop(0)
+
+    async def _empty_stream(self) -> AsyncIterator[ChatCompletionChunk]:
+        if False:  # pyright: ignore[reportUnreachable]
+            yield  # type: ignore[misc]
+        return
+
+
+def _response(message: AssistantChatMessage) -> ChatCompletionResponse:
+    return ChatCompletionResponse(
+        id="1",
+        object="chat.completion",
+        created=0,
+        model="test",
+        choices=[
+            ChatCompletionChoice(
+                index=0,
+                message=message,
+                logprobs={},
+                finish_reason="stop",
+            )
+        ],
+        system_fingerprint="",
+        usage={},
+    )
+
+
+async def test_run_chat_loop_text_only() -> None:
+    client = ScriptedClient(
+        [
+            _response(AssistantChatMessage(content="hello")),
+        ]
+    )
+    messages: list[AnyChatMessage] = [UserChatMessage(content="hi")]
+    events = [e async for e in run_chat_loop(client, messages, model="m")]
+    assert isinstance(events[0], AssistantMessageEvent)
+    assert isinstance(events[1], TextDeltaEvent)
+    assert events[1].content == "hello"
+    assert len(messages) == 2  # noqa: PLR2004
+    assert len(client.calls) == 1
+
+
+async def test_run_chat_loop_with_tools() -> None:
+    @tool
+    def add(a: int, b: int) -> int:
+        return a + b
+
+    registry = ToolRegistry([add])
+    client = ScriptedClient(
+        [
+            _response(
+                AssistantChatMessage(
+                    content="",
+                    tool_calls=[
+                        AssistantFunctionToolCall(
+                            id="c1",
+                            function=AssistantFunctionTool(name="add", arguments='{"a": 1, "b": 2}'),
+                        )
+                    ],
+                )
+            ),
+            _response(AssistantChatMessage(content="3")),
+        ]
+    )
+    messages: list[AnyChatMessage] = [UserChatMessage(content="1+2")]
+    events = [e async for e in run_chat_loop(client, messages, model="m", tools=registry)]
+    types = [type(e) for e in events]
+    assert ToolCallEvent in types
+    assert ToolResultEvent in types
+    assert any(isinstance(e, TextDeltaEvent) and e.content == "3" for e in events)
+    assert len(client.calls) == 2  # noqa: PLR2004
+    # second call includes tool result message
+    assert any(getattr(m, "tool_call_id", None) == "c1" for m in client.calls[1].messages)
+
+
+async def test_max_rounds() -> None:
+    @tool
+    def ping() -> str:
+        return "pong"
+
+    registry = ToolRegistry([ping])
+    forever = _response(
+        AssistantChatMessage(
+            content="",
+            tool_calls=[
+                AssistantFunctionToolCall(
+                    id="c",
+                    function=AssistantFunctionTool(name="ping", arguments="{}"),
+                )
+            ],
+        )
+    )
+    client = ScriptedClient([forever, forever, forever])
+    messages: list[AnyChatMessage] = [UserChatMessage(content="x")]
+    events = [e async for e in run_chat_loop(client, messages, model="m", tools=registry, max_rounds=2)]
+    assert any(isinstance(e, MaxRoundsEvent) and e.rounds == 2 for e in events)  # noqa: PLR2004
+    assert len(client.calls) == 2  # noqa: PLR2004
+
+
+async def test_chat_agent_memory_roundtrip() -> None:
+    store = await MemoryStore.open(DatabaseConfig())
+    session = await store.create_session(name="t")
+    client = ScriptedClient([_response(AssistantChatMessage(content="yo"))])
+    agent = ChatAgent(client, model="m", memory=store, session_id=session.sid)
+    events = [e async for e in agent.run("hi")]
+    assert any(isinstance(e, TextDeltaEvent) and e.content == "yo" for e in events)
+
+    loaded = await store.list_messages(session.sid)
+    assert len(loaded) == 2  # noqa: PLR2004
+    assert isinstance(loaded[0], UserChatMessage)
+    assert loaded[0].content == "hi"
+
+    agent2 = ChatAgent(client, model="m", memory=store, session_id=session.sid)
+    await agent2.load_history()
+    assert len(agent2.messages) == 2  # noqa: PLR2004
+    await store.close()
diff --git a/tests/test_agent/test_tools.py b/tests/test_agent/test_tools.py
new file mode 100644
index 0000000..0adf409
--- /dev/null
+++ b/tests/test_agent/test_tools.py
@@ -0,0 +1,90 @@
+from __future__ import annotations
+
+from plyngent.agent import ToolRegistry, schema_from_callable, tool
+
+
+def test_tool_decorator_infers_schema() -> None:
+    @tool
+    def add(a: int, b: int = 0) -> int:
+        """Add two numbers."""
+        return a + b
+
+    assert add.name == "add"
+    assert add.description == "Add two numbers."
+    assert add.parameters["type"] == "object"
+    assert add.parameters["properties"]["a"] == {"type": "integer"}
+    assert add.parameters["properties"]["b"] == {"type": "integer"}
+    assert add.parameters["required"] == ["a"]
+
+
+def test_tool_decorator_overrides() -> None:
+    @tool(name="ping", description="health")
+    def health() -> str:
+        return "ok"
+
+    assert health.name == "ping"
+    assert health.description == "health"
+
+
+def test_schema_from_callable_optional() -> None:
+    def f(x: str | None = None) -> str:
+        return x or ""
+
+    schema = schema_from_callable(f)
+    assert schema["properties"]["x"] == {"type": "string"}
+    assert "required" not in schema
+
+
+async def test_registry_execute_sync_and_async() -> None:
+    @tool
+    def echo(text: str) -> str:
+        return text
+
+    @tool
+    async def upper(text: str) -> str:
+        return text.upper()
+
+    registry = ToolRegistry([echo, upper])
+    assert await registry.execute("echo", '{"text": "hi"}') == "hi"
+    assert await registry.execute("upper", '{"text": "hi"}') == "HI"
+
+
+async def test_registry_unknown_and_bad_json() -> None:
+    @tool
+    def noop() -> str:
+        return "ok"
+
+    registry = ToolRegistry([noop])
+    assert "unknown" in await registry.execute("missing", "{}")
+    assert "invalid" in await registry.execute("noop", "not-json")
+
+
+async def test_registry_handler_error() -> None:
+    @tool
+    def boom() -> str:
+        msg = "nope"
+        raise RuntimeError(msg)
+
+    registry = ToolRegistry([boom])
+    result = await registry.execute("boom", "{}")
+    assert "failed" in result
+
+
+def test_tool_items() -> None:
+    @tool
+    def f(x: int) -> int:
+        return x
+
+    items = ToolRegistry([f]).tool_items()
+    assert len(items) == 1
+    assert items[0].function.name == "f"
+
+
+def test_schema_list_and_bool() -> None:
+    def g(flags: list[bool], *, ok: bool) -> None:
+        del flags, ok
+
+    schema = schema_from_callable(g)
+    assert schema["properties"]["flags"]["type"] == "array"
+    assert schema["properties"]["flags"]["items"] == {"type": "boolean"}
+    assert schema["properties"]["ok"] == {"type": "boolean"}