feat: add Crusoe managed inference backend (#20475)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

test/manual/test_crusoe_backend.py

@@ -0,0 +1,79 @@
+"""
+Manual tests for the Crusoe managed inference backend.
+
+Requires CRUSOE_API_KEY to be set in the environment.
+
+Run all tests:
+    python3 -m unittest test/manual/test_crusoe_backend.py
+
+Run a single test:
+    python3 -m unittest test_crusoe_backend.TestCrusoeBackend.test_mt_bench
+"""
+
+import unittest
+
+from sglang import Crusoe, set_default_backend
+from sglang.test.test_programs import (
+    test_mt_bench,
+    test_parallel_decoding,
+    test_parallel_encoding,
+    test_stream,
+)
+from sglang.test.test_utils import CustomTestCase
+
+# Default model available on Crusoe managed inference.
+DEFAULT_CRUSOE_MODEL = "nvidia/NVIDIA-Nemotron-3-Nano-30B-A3B"
+
+
+class TestCrusoeBackend(CustomTestCase):
+    backend = None
+
+    @classmethod
+    def setUpClass(cls):
+        cls.backend = Crusoe(DEFAULT_CRUSOE_MODEL)
+
+    def setUp(self):
+        set_default_backend(self.backend)
+
+    def test_mt_bench(self):
+        test_mt_bench()
+
+    def test_stream(self):
+        test_stream()
+
+    def test_parallel_decoding(self):
+        test_parallel_decoding()
+
+    def test_parallel_encoding(self):
+        test_parallel_encoding()
+
+
+class TestCrusoeBackendInit(CustomTestCase):
+    """Unit tests for Crusoe backend initialisation — no network required."""
+
+    def test_raises_without_api_key(self):
+        import os
+
+        key = os.environ.pop("CRUSOE_API_KEY", None)
+        try:
+            with self.assertRaises(ValueError):
+                Crusoe(DEFAULT_CRUSOE_MODEL, api_key=None)
+        finally:
+            if key is not None:
+                os.environ["CRUSOE_API_KEY"] = key
+
+    def test_accepts_explicit_api_key(self):
+        backend = Crusoe(DEFAULT_CRUSOE_MODEL, api_key="test-key")
+        self.assertIsNotNone(backend)
+
+    def test_custom_base_url(self):
+        backend = Crusoe(
+            DEFAULT_CRUSOE_MODEL,
+            api_key="test-key",
+            base_url="https://managed-inference-api-proxy.crusoecloud.com/v1/",
+        )
+        self.assertIsNotNone(backend)
+
+
+if __name__ == "__main__":
+    unittest.main()