feat: add Crusoe managed inference backend (#20475)

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

python/sglang/__init__.py

@@ -69,6 +69,7 @@ from sglang.utils import LazyImport
 from sglang.version import __version__
 
 Anthropic = LazyImport("sglang.lang.backend.anthropic", "Anthropic")
+Crusoe = LazyImport("sglang.lang.backend.crusoe", "Crusoe")
 LiteLLM = LazyImport("sglang.lang.backend.litellm", "LiteLLM")
 OpenAI = LazyImport("sglang.lang.backend.openai", "OpenAI")
 VertexAI = LazyImport("sglang.lang.backend.vertexai", "VertexAI")
@@ -106,6 +107,7 @@ __all__ = [
     "unconditional_likelihood_normalized",
     "ServerArgs",
     "Anthropic",
+    "Crusoe",
     "LiteLLM",
     "OpenAI",
     "VertexAI",

python/sglang/lang/backend/crusoe.py

@@ -0,0 +1,43 @@
+import os
+from typing import Optional
+
+from sglang.lang.backend.openai import OpenAI
+from sglang.lang.chat_template import ChatTemplate
+
+CRUSOE_BASE_URL = "https://managed-inference-api-proxy.crusoecloud.com/v1/"
+
+
+class Crusoe(OpenAI):
+    """SGLang backend for Crusoe managed inference.
+
+    Crusoe exposes an OpenAI-compatible API, so this is a thin wrapper
+    around the OpenAI backend that handles Crusoe-specific defaults.
+
+    Args:
+        model_name: The model to use, e.g. "meta-llama/Llama-3.1-8B-Instruct".
+        api_key: Crusoe API key. Defaults to CRUSOE_API_KEY env var.
+        base_url: Override the Crusoe endpoint. Defaults to the Crusoe API.
+        chat_template: Optional custom chat template.
+    """
+
+    def __init__(
+        self,
+        model_name: str,
+        api_key: Optional[str] = None,
+        base_url: Optional[str] = None,
+        chat_template: Optional[ChatTemplate] = None,
+        **kwargs,
+    ):
+        resolved_api_key = api_key or os.environ.get("CRUSOE_API_KEY")
+        if not resolved_api_key:
+            raise ValueError(
+                "Crusoe API key required. Pass api_key= or set CRUSOE_API_KEY."
+            )
+
+        super().__init__(
+            model_name=model_name,
+            chat_template=chat_template,
+            api_key=resolved_api_key,
+            base_url=base_url or CRUSOE_BASE_URL,
+            **kwargs,
+        )

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()