feat: #3001 add Modal sandbox idle timeout option

src/agents/extensions/sandbox/modal/sandbox.py

@@ -158,6 +158,7 @@ class ModalSandboxClientOptions(BaseSandboxClientOptions):
     timeout: int = 300  # Lifetime of a sandbox from creation in seconds, defaults to 5 minutes
     use_sleep_cmd: bool = True
     image_builder_version: str | None = _DEFAULT_IMAGE_BUILDER_VERSION
+    idle_timeout: int | None = None
 
     def __init__(
         self,
@@ -171,6 +172,7 @@ def __init__(
         timeout: int = 300,  # 5 minutes
         use_sleep_cmd: bool = True,
         image_builder_version: str | None = _DEFAULT_IMAGE_BUILDER_VERSION,
+        idle_timeout: int | None = None,
         *,
         type: Literal["modal"] = "modal",
     ) -> None:
@@ -186,6 +188,7 @@ def __init__(
             timeout=timeout,
             use_sleep_cmd=use_sleep_cmd,
             image_builder_version=image_builder_version,
+            idle_timeout=idle_timeout,
         )
 
 
@@ -319,6 +322,7 @@ class ModalSandboxSessionState(SandboxSessionState):
     timeout: int = 300  # 5 minutes
     use_sleep_cmd: bool = True
     image_builder_version: str | None = _DEFAULT_IMAGE_BUILDER_VERSION
+    idle_timeout: int | None = None
 
 
 @dataclass
@@ -571,6 +575,7 @@ async def _ensure_sandbox(self) -> bool:
             volumes=volumes,
             gpu=self.state.gpu,
             timeout=self.state.timeout,
+            idle_timeout=self.state.idle_timeout,
         )
         async with _override_modal_image_builder_version(self.state.image_builder_version):
             if self.state.sandbox_create_timeout_s is None:
@@ -1625,6 +1630,7 @@ async def _run_restore() -> None:
                 volumes=self._modal_cloud_bucket_mounts_for_manifest(),
                 gpu=self.state.gpu,
                 timeout=self.state.timeout,
+                idle_timeout=self.state.idle_timeout,
             )
             try:
                 mkdir_proc = await sb.exec.aio("mkdir", "-p", "--", root.as_posix(), text=False)
@@ -1839,6 +1845,7 @@ async def create(
         - snapshot_filesystem_restore_timeout_s: float | None
           (async timeout for snapshot restore call)
         - timeout: int (maximum sandbox lifetime in seconds, default 300)
+        - idle_timeout: int | None (maximum sandbox inactivity in seconds, default None)
         - image_builder_version: str | None (Modal image builder version, default "2025.06")
         """
 
@@ -1960,6 +1967,7 @@ async def create(
             timeout=options.timeout,
             use_sleep_cmd=options.use_sleep_cmd,
             image_builder_version=image_builder_version,
+            idle_timeout=options.idle_timeout,
         )
         if sandbox_create_timeout_s is not None:
             state.sandbox_create_timeout_s = float(sandbox_create_timeout_s)

tests/extensions/test_sandbox_modal.py

@@ -377,6 +377,25 @@ async def test_modal_sandbox_create_passes_manifest_environment(
     assert os.environ.get("MODAL_IMAGE_BUILDER_VERSION") is None
 
 
+@pytest.mark.asyncio
+async def test_modal_sandbox_create_passes_idle_timeout(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    modal_module, create_calls, _registry_tags = _load_modal_module(monkeypatch)
+
+    client = modal_module.ModalSandboxClient()
+    session = await client.create(
+        options=modal_module.ModalSandboxClientOptions(
+            app_name="sandbox-tests",
+            idle_timeout=60,
+        ),
+    )
+
+    assert create_calls
+    assert create_calls[0]["idle_timeout"] == 60
+    assert session.state.idle_timeout == 60
+
+
 @pytest.mark.asyncio
 async def test_modal_sandbox_create_sets_default_cmd_for_custom_registry_image(
     monkeypatch: pytest.MonkeyPatch,
@@ -478,6 +497,27 @@ def test_modal_deserialize_session_state_defaults_missing_image_builder_version(
     assert restored.image_builder_version == "2025.06"
 
 
+def test_modal_deserialize_session_state_defaults_missing_idle_timeout(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    modal_module, _create_calls, _registry_tags = _load_modal_module(monkeypatch)
+
+    state = modal_module.ModalSandboxSessionState(
+        manifest=Manifest(root="/workspace"),
+        snapshot=modal_module.resolve_snapshot(None, "snapshot"),
+        app_name="sandbox-tests",
+        idle_timeout=60,
+    )
+    payload = state.model_dump(mode="json")
+    payload.pop("idle_timeout")
+
+    restored = modal_module.ModalSandboxClient().deserialize_session_state(
+        cast(dict[str, object], payload)
+    )
+
+    assert restored.idle_timeout is None
+
+
 @pytest.mark.asyncio
 async def test_modal_sandbox_create_passes_modal_cloud_bucket_mounts(
     monkeypatch: pytest.MonkeyPatch,
@@ -2764,6 +2804,7 @@ async def test_modal_snapshot_filesystem_restore_preserves_exposed_ports(
         app_name="sandbox-tests",
         workspace_persistence="snapshot_filesystem",
         exposed_ports=(8765,),
+        idle_timeout=60,
     )
     session = modal_module.ModalSandboxSession.from_state(state)
     call_names: list[str] = []
@@ -2789,6 +2830,7 @@ async def _fake_call_modal(
 
     assert create_calls
     assert create_calls[0]["encrypted_ports"] == (8765,)
+    assert create_calls[0]["idle_timeout"] == 60
     assert sys.modules["modal"].Image.from_id_calls == ["snap-123"]
     assert call_names == []
     assert call_timeouts == []

tests/sandbox/test_client_options.py

@@ -57,6 +57,7 @@ def test_sandbox_client_options_exclude_unset_preserves_type_discriminator() ->
         "timeout": 300,
         "use_sleep_cmd": True,
         "image_builder_version": "2025.06",
+        "idle_timeout": None,
     }
 
 

tests/sandbox/test_compatibility_guards.py

@@ -439,6 +439,7 @@ def test_optional_sandbox_dataclass_constructor_field_order_is_stable(
                 "timeout",
                 "use_sleep_cmd",
                 "image_builder_version",
+                "idle_timeout",
             ),
         ),
         (
@@ -612,6 +613,7 @@ def test_optional_sandbox_client_options_positional_field_order_is_stable(
                 "timeout",
                 "use_sleep_cmd",
                 "image_builder_version",
+                "idle_timeout",
             ),
         ),
         (