[CI] Pin the Rust TreeCore build to the resolved libtorch instead of interpreter discovery (#37696)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

python/sglang/srt/rust_extensions/torch_build.py

@@ -74,7 +74,11 @@ def torch_build_configuration(
         cxx11_abi = bool(torch_module._C._GLIBCXX_USE_CXX11_ABI)
 
     environment = dict(os.environ if base_environment is None else base_environment)
-    environment["LIBTORCH_USE_PYTORCH"] = "1"
+    environment.pop("LIBTORCH_USE_PYTORCH", None)
+    environment["LIBTORCH"] = os.fspath(torch_root)
+    environment["LIBTORCH_INCLUDE"] = os.fspath(torch_root)
+    environment["LIBTORCH_LIB"] = os.fspath(torch_root)
+    environment["LIBTORCH_CXX11_ABI"] = "1" if cxx11_abi else "0"
     # tch 0.24 targets Torch 2.11. The compatibility header below covers the
     # API removals in the supported 2.12/2.13 builds, after this explicit gate.
     environment["LIBTORCH_BYPASS_VERSION_CHECK"] = "1"

scripts/ci/cuda/ci_install_dependency.sh

@@ -324,20 +324,6 @@ setup_cargo_cache() {
     mark_step_done "${FUNCNAME[0]}"
 }
 
-invalidate_torch_rust_cache() {
-    if [ "${SGLANG_BUILD_RUST_EXTS:-}" = "none" ]; then
-        mark_step_done "${FUNCNAME[0]}"
-        return
-    fi
-
-    # uv's editable build uses a temporary torch path. Rebuild these units
-    # under the lock so Cargo does not reuse that path in a later job.
-    cargo clean --release --manifest-path "${REPO_ROOT}/rust/sglang-radix-tree/Cargo.toml" \
-        -p torch-sys -p sglang-radix-tree
-
-    mark_step_done "${FUNCNAME[0]}"
-}
-
 release_cargo_cache_lock() {
     if [ "${CARGO_TARGET_LOCK_HELD:-0}" = "1" ]; then
         flock --unlock 9
@@ -918,7 +904,6 @@ main() {
     install_pytorch_stack
     install_cuda12_deepep_wheel
     setup_cargo_cache
-    invalidate_torch_rust_cache
     install_sglang
     release_cargo_cache_lock
     # Diffusion B200 CI imports torch inside install_sglang_kernel after removing

test/registered/rust/test_rust_extension.py

@@ -441,10 +441,15 @@ crate-type = ["cdylib"]
                     "PATH": "/usr/bin",
                     "CXXFLAGS": "-O2",
                     "RUSTFLAGS": "-Ctarget-cpu=x86-64",
+                    "LIBTORCH_USE_PYTORCH": "1",
                 },
             )
 
-            self.assertEqual(build.environment["LIBTORCH_USE_PYTORCH"], "1")
+            self.assertNotIn("LIBTORCH_USE_PYTORCH", build.environment)
+            self.assertEqual(build.environment["LIBTORCH"], str(torch_root))
+            self.assertEqual(build.environment["LIBTORCH_INCLUDE"], str(torch_root))
+            self.assertEqual(build.environment["LIBTORCH_LIB"], str(torch_root))
+            self.assertEqual(build.environment["LIBTORCH_CXX11_ABI"], "1")
             self.assertEqual(build.environment["LIBTORCH_BYPASS_VERSION_CHECK"], "1")
             self.assertIn(str(compat_header), build.environment["CXXFLAGS"])
             self.assertIn(

test/registered/unit/tools/test_cuda_ci_install_dependency.py

@@ -1,46 +0,0 @@
-import importlib.util
-import re
-import unittest
-from pathlib import Path
-
-REPO_ROOT = Path(__file__).resolve().parents[4]
-CI_REGISTER_PATH = REPO_ROOT / "python" / "sglang" / "test" / "ci" / "ci_register.py"
-INSTALL_SCRIPT = REPO_ROOT / "scripts" / "ci" / "cuda" / "ci_install_dependency.sh"
-
-
-def _load_module(name, path):
-    spec = importlib.util.spec_from_file_location(name, path)
-    module = importlib.util.module_from_spec(spec)
-    spec.loader.exec_module(module)
-    return module
-
-
-register_cpu_ci = _load_module("ci_register", CI_REGISTER_PATH).register_cpu_ci
-register_cpu_ci(est_time=0, suite="base-a-test-cpu")
-
-
-class TestCudaCiInstallDependencyTorchCache(unittest.TestCase):
-    def test_rebuilds_torch_extensions_before_editable_install(self):
-        script = INSTALL_SCRIPT.read_text()
-
-        self.assertRegex(
-            script,
-            re.compile(
-                r"setup_cargo_cache\s*\n"
-                r"\s*invalidate_torch_rust_cache\s*\n"
-                r"\s*install_sglang"
-            ),
-        )
-        self.assertIn('"${SGLANG_BUILD_RUST_EXTS:-}" = "none"', script)
-        self.assertRegex(
-            script,
-            re.compile(
-                r"cargo clean --release --manifest-path "
-                r"\"\$\{REPO_ROOT\}/rust/sglang-radix-tree/Cargo\.toml\"\s*\\\n"
-                r"\s*-p torch-sys -p sglang-radix-tree"
-            ),
-        )
-
-
-if __name__ == "__main__":
-    unittest.main()