diff --git a/src/agents/sandbox/manifest.py b/src/agents/sandbox/manifest.py
index 97a3677442..4ea0d4652f 100644
--- a/src/agents/sandbox/manifest.py
+++ b/src/agents/sandbox/manifest.py
@@ -1,5 +1,6 @@
 import abc
 import inspect
+import os
 from collections.abc import Iterator, Mapping
 from dataclasses import dataclass
 from pathlib import Path, PurePath, PurePosixPath
@@ -147,6 +148,19 @@ async def resolve(self) -> str:
         return self.value
 
 
+class OsEnvValue(EnvValue):
+    """Reads the value from the environment of the process creating the sandbox.
+
+    An unset variable resolves to the empty string.
+    """
+
+    type: Literal["os_env"] = "os_env"
+    name: str
+
+    async def resolve(self) -> str:
+        return os.environ.get(self.name, "")
+
+
 def _serialize_env_value_with_type(value: EnvValue, serialized: object) -> dict[str, Any]:
     if EnvValue._subclass_registry.get(value.type) is not type(value):
         raise PydanticSerializationError(
diff --git a/tests/sandbox/test_compatibility_guards.py b/tests/sandbox/test_compatibility_guards.py
index 0e3a2bcea4..3c4ca3b2e8 100644
--- a/tests/sandbox/test_compatibility_guards.py
+++ b/tests/sandbox/test_compatibility_guards.py
@@ -40,7 +40,7 @@
     RcloneMountPattern,
     S3FilesMountPattern,
 )
-from agents.sandbox.manifest import EnvValue, StrEnvValue
+from agents.sandbox.manifest import EnvValue, OsEnvValue, StrEnvValue
 from agents.sandbox.session.sandbox_client import BaseSandboxClientOptions
 from agents.sandbox.session.sandbox_session_state import SandboxSessionState
 from agents.sandbox.snapshot import LocalSnapshot, NoopSnapshot, RemoteSnapshot, SnapshotBase
@@ -894,6 +894,7 @@ def test_core_discriminator_type_strings_are_stable() -> None:
         InContainerMountStrategy: "in_container",
         DockerVolumeMountStrategy: "docker_volume",
         StrEnvValue: "str",
+        OsEnvValue: "os_env",
     }
 
     for cls, expected_type in expected_types.items():
diff --git a/tests/sandbox/test_manifest.py b/tests/sandbox/test_manifest.py
index 0f5eef6bc1..f8fb0ddb31 100644
--- a/tests/sandbox/test_manifest.py
+++ b/tests/sandbox/test_manifest.py
@@ -16,7 +16,14 @@
     MountpointMountPattern,
 )
 from agents.sandbox.errors import InvalidManifestPathError
-from agents.sandbox.manifest import EnvEntry, Environment, EnvValue, Manifest, StrEnvValue
+from agents.sandbox.manifest import (
+    EnvEntry,
+    Environment,
+    EnvValue,
+    Manifest,
+    OsEnvValue,
+    StrEnvValue,
+)
 from agents.sandbox.manifest_render import _truncate_manifest_description
 
 
@@ -340,6 +347,62 @@ def test_manifest_round_trips_str_env_value() -> None:
     }
 
 
+@pytest.mark.asyncio
+async def test_os_env_value_resolves_from_the_process_environment(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setenv("SANDBOX_TEST_OS_ENV_VALUE", "from-host")
+
+    assert await OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE").resolve() == "from-host"
+
+
+@pytest.mark.asyncio
+async def test_os_env_value_resolves_unset_and_empty_variables_to_an_empty_string(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.delenv("SANDBOX_TEST_OS_ENV_VALUE", raising=False)
+
+    assert await OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE").resolve() == ""
+
+    monkeypatch.setenv("SANDBOX_TEST_OS_ENV_VALUE", "")
+
+    assert await OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE").resolve() == ""
+
+
+def test_manifest_round_trips_os_env_value() -> None:
+    manifest = Manifest(
+        environment=Environment(value={"TOKEN": OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE")})
+    )
+
+    payload = manifest.model_dump(mode="json")
+    restored = Manifest.model_validate(payload)
+
+    assert payload["environment"] == {
+        "value": {"TOKEN": {"type": "os_env", "name": "SANDBOX_TEST_OS_ENV_VALUE"}}
+    }
+    assert type(restored.environment.value["TOKEN"]) is OsEnvValue
+
+
+@pytest.mark.asyncio
+async def test_environment_resolves_os_env_values_alongside_literals(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setenv("SANDBOX_TEST_OS_ENV_VALUE", "from-host")
+    environment = Environment(
+        value={
+            "PLAIN": "literal",
+            "DIRECT": OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE"),
+            "ENTRY": EnvEntry(value=OsEnvValue(name="SANDBOX_TEST_OS_ENV_VALUE")),
+        }
+    )
+
+    assert await environment.resolve() == {
+        "PLAIN": "literal",
+        "DIRECT": "from-host",
+        "ENTRY": "from-host",
+    }
+
+
 def test_manifest_reads_legacy_discriminator_free_str_env_values() -> None:
     payload = {
         "environment": {