diff --git a/litellm/proxy/_experimental/mcp_server/discoverable_endpoints.py b/litellm/proxy/_experimental/mcp_server/discoverable_endpoints.py
index ed374635fe..3beddd2c43 100644
--- a/litellm/proxy/_experimental/mcp_server/discoverable_endpoints.py
+++ b/litellm/proxy/_experimental/mcp_server/discoverable_endpoints.py
@@ -512,12 +512,13 @@ async def exchange_token_with_server(
     result = {
         "access_token": access_token,
         "token_type": token_response.get("token_type", "Bearer"),
-        "expires_in": token_response.get("expires_in", 3600),
     }
 
-    if "refresh_token" in token_response and token_response["refresh_token"]:
+    if token_response.get("expires_in") is not None:
+        result["expires_in"] = token_response["expires_in"]
+    if token_response.get("refresh_token"):
         result["refresh_token"] = token_response["refresh_token"]
-    if "scope" in token_response and token_response["scope"]:
+    if token_response.get("scope"):
         result["scope"] = token_response["scope"]
 
     # RFC 6749 §5.1: token responses must not be cached.
diff --git a/tests/test_litellm/proxy/_experimental/mcp_server/test_discoverable_endpoints.py b/tests/test_litellm/proxy/_experimental/mcp_server/test_discoverable_endpoints.py
index da66d60aed..6fd935e336 100644
--- a/tests/test_litellm/proxy/_experimental/mcp_server/test_discoverable_endpoints.py
+++ b/tests/test_litellm/proxy/_experimental/mcp_server/test_discoverable_endpoints.py
@@ -1,5 +1,6 @@
 """Tests for MCP OAuth discoverable endpoints"""
 
+import json
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -2661,3 +2662,74 @@ async def test_token_endpoint_sets_no_store_cache_control():
 
     assert response.headers["cache-control"] == "no-store"
     assert response.headers["pragma"] == "no-cache"
+
+
+async def _exchange_with_upstream_token_response(upstream_body):
+    from fastapi import Request
+
+    from litellm.proxy._experimental.mcp_server.discoverable_endpoints import (
+        exchange_token_with_server,
+    )
+    from litellm.proxy._types import MCPTransport
+    from litellm.types.mcp import MCPAuth
+    from litellm.types.mcp_server.mcp_server_manager import MCPServer
+
+    server = MCPServer(
+        server_id="t",
+        name="t",
+        server_name="t",
+        alias="t",
+        transport=MCPTransport.http,
+        auth_type=MCPAuth.oauth2,
+        client_id="cid",
+        client_secret="cs",
+        authorization_url="https://provider.com/oauth/authorize",
+        token_url="https://provider.com/oauth/token",
+    )
+    mock_request = MagicMock(spec=Request)
+    mock_request.base_url = "https://litellm.example.com/"
+    mock_request.headers = {}
+
+    fake_http_response = MagicMock()
+    fake_http_response.json.return_value = upstream_body
+    fake_http_response.raise_for_status = MagicMock()
+    fake_http_client = MagicMock()
+    fake_http_client.post = AsyncMock(return_value=fake_http_response)
+
+    with patch(
+        "litellm.proxy._experimental.mcp_server.discoverable_endpoints.get_async_httpx_client",
+        return_value=fake_http_client,
+    ):
+        response = await exchange_token_with_server(
+            request=mock_request,
+            mcp_server=server,
+            grant_type="authorization_code",
+            code="c",
+            redirect_uri="http://127.0.0.1:3000/cb",
+            client_id="cid",
+            client_secret=None,
+            code_verifier=None,
+        )
+    return json.loads(response.body)
+
+
+@pytest.mark.asyncio
+async def test_token_exchange_omits_expires_in_when_upstream_omits_it():
+    """A provider that issues a non-expiring token (e.g. Slack without token
+    rotation) returns no ``expires_in``. The exchange must mirror that and omit
+    ``expires_in`` rather than fabricate a 1-hour TTL, so the stored credential
+    is treated as non-expiring instead of dying after an hour."""
+    body = await _exchange_with_upstream_token_response(
+        {"access_token": "tok", "token_type": "Bearer"}
+    )
+    assert "expires_in" not in body
+
+
+@pytest.mark.asyncio
+async def test_token_exchange_passes_through_upstream_expires_in():
+    """When the provider does send ``expires_in`` (e.g. Slack with token
+    rotation), the exchange forwards the real value unchanged."""
+    body = await _exchange_with_upstream_token_response(
+        {"access_token": "tok", "token_type": "Bearer", "expires_in": 43200}
+    )
+    assert body["expires_in"] == 43200