diff --git a/openhands-sdk/openhands/sdk/llm/llm.py b/openhands-sdk/openhands/sdk/llm/llm.py
index ecb5649e7d..c4560e8930 100644
--- a/openhands-sdk/openhands/sdk/llm/llm.py
+++ b/openhands-sdk/openhands/sdk/llm/llm.py
@@ -17,6 +17,7 @@
     Field,
     PrivateAttr,
     SecretStr,
+    computed_field,
     field_serializer,
     field_validator,
     model_validator,
@@ -692,6 +693,14 @@ def telemetry(self) -> Telemetry:
             )
         return self._telemetry
 
+    @computed_field(
+        return_type=bool,
+        description=(
+            "Whether this LLM uses subscription-based authentication. "
+            "Serialized so that subscription-specific request handling "
+            "survives transport to a remote agent-server."
+        ),
+    )
     @property
     def is_subscription(self) -> bool:
         """Check if this LLM uses subscription-based authentication.
@@ -705,6 +714,24 @@ def is_subscription(self) -> bool:
         """
         return self._is_subscription
 
+    @model_validator(mode="wrap")
+    @classmethod
+    def _restore_is_subscription(cls, data, handler):
+        """Restore the subscription flag when validating serialized data.
+
+        ``is_subscription`` is a computed field backed by the private
+        ``_is_subscription`` attribute, so plain validation would drop it.
+        Without this, an LLM created via ``LLM.subscription_login()`` loses
+        its subscription-specific request handling (streaming exemption,
+        Codex system prompt transform, reasoning-item stripping) after a
+        dump/validate round trip - e.g. when shipped to a remote
+        agent-server.
+        """
+        llm = handler(data)
+        if isinstance(data, dict) and data.get("is_subscription"):
+            llm._is_subscription = True
+        return llm
+
     def restore_metrics(self, metrics: Metrics) -> None:
         # Only used by ConversationStats to seed metrics
         self._metrics = metrics
diff --git a/tests/sdk/llm/test_subscription_mode.py b/tests/sdk/llm/test_subscription_mode.py
index 2b40419e82..42e3172769 100644
--- a/tests/sdk/llm/test_subscription_mode.py
+++ b/tests/sdk/llm/test_subscription_mode.py
@@ -338,3 +338,22 @@ def test_format_messages_reasoning_item_handling(
 
     serialized = json.dumps(input_items, default=str)
     assert ("rs_should_be_stripped" in serialized) == reasoning_id_present
+
+
+def test_is_subscription_survives_serialization_round_trip():
+    """is_subscription must survive model_dump -> model_validate.
+
+    A RemoteConversation serializes the LLM and the agent-server rebuilds it;
+    if the flag is lost, all subscription-specific request handling (streaming
+    exemption, system prompt transform, reasoning item stripping) silently
+    stops applying on the server side.
+    """
+    llm = _make_subscription_llm()
+    restored = LLM.model_validate(llm.model_dump(context={"expose_secrets": True}))
+    assert restored.is_subscription is True
+
+    plain = LLM(model="gpt-4o")
+    restored_plain = LLM.model_validate(
+        plain.model_dump(context={"expose_secrets": True})
+    )
+    assert restored_plain.is_subscription is False