Build Rust extensions on demand in source checkouts (#34994)

.github/actions/download-rust-ext/action.yml

@@ -49,7 +49,7 @@ runs:
       if: steps.artifact.outcome != 'success'
       uses: actions/cache/restore@v4
       with:
-        path: python/sglang/srt/*/_core*.so
+        path: python/sglang/srt/rust_extensions/_*.so
         key: ${{ inputs.cache_key_prefix }}-${{ hashFiles('rust/**', 'python/setup.py') }}
 
     # Job-wide, but only setup.py reads it, and only while building.

.github/workflows/_pr-test-rust-ext-build.yml

@@ -99,7 +99,7 @@ jobs:
         id: cache
         uses: actions/cache/restore@v4
         with:
-          path: python/sglang/srt/*/_core*.so
+          path: python/sglang/srt/rust_extensions/_*.so
           key: ${{ inputs.cache_key_prefix }}-${{ hashFiles('rust/**', 'python/setup.py') }}
 
       # On a miss: different hash = rust/setup.py moved; no entries = evicted.
@@ -112,7 +112,7 @@ jobs:
         run: |
           if [ -n "${MATCHED_KEY}" ]; then
               echo "hit: ${MATCHED_KEY}"
-              ls -l python/sglang/srt/*/_core*.so
+              ls -l python/sglang/srt/rust_extensions/_*.so
           else
               echo "miss: ${PRIMARY_KEY}"
               echo "entries under ${KEY_PREFIX}- (created / ref / size / key):"
@@ -134,7 +134,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: ${{ inputs.artifact_name }}
-          # Archive holds <pkg>/_core*.so, so it unpacks into python/sglang/srt/.
+          # Archive holds rust_extensions/_*.so, so it unpacks into python/sglang/srt/.
           path: rust-ext-staging/
           if-no-files-found: error
           retention-days: 1
@@ -226,7 +226,7 @@ jobs:
       - name: Save built modules
         uses: actions/cache/save@v4
         with:
-          path: python/sglang/srt/*/_core*.so
+          path: python/sglang/srt/rust_extensions/_*.so
           key: ${{ inputs.cache_key_prefix }}-${{ hashFiles('rust/**', 'python/setup.py') }}
 
       - name: Upload extension modules

.gitignore

@@ -230,6 +230,7 @@ work_dirs/
 
 # Rust lib
 Cargo.lock
+!rust/Cargo.lock
 
 # Generated vision test fixtures (regenerate with: python scripts/generate_vision_golden.py)
 sgl-model-gateway/tests/fixtures/golden/

docker/rocm.Dockerfile

@@ -285,8 +285,8 @@ RUN pip install IPython \
     && pip install pybind11
 
 # Rust toolchain — needed by setuptools-rust to build the sglang-mm extension
-# (sglang.srt.multimodal._core) during the sglang pip install below, and later by
+# (sglang.srt.rust_extensions._multimodal) during the sglang pip install below
-# sgl-model-gateway. Must precede the sglang install.
+# and later by sgl-model-gateway. Must precede the sglang install.
 ENV PATH="/root/.cargo/bin:${PATH}"
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y \
     && rustc --version && cargo --version

python/pyproject.toml

@@ -77,6 +77,7 @@ dependencies = [
   "tilelang==0.1.11",
   "timm==1.0.16",
   "tokenspeed_mla==0.1.8",
+  "tomli ; python_version < '3.11'",
   "torch==2.13.0",
   "torch_memory_saver>=0.0.9.post1",
   "torchaudio==2.11.0",

python/setup.py

@@ -20,8 +20,9 @@ Two filters can narrow the discovered set:
 - SGLANG_BUILD_RUST_EXTS env var, applied at build time on top of the above:
   unset or "all" builds everything, "none" builds nothing, and a
   comma-separated list matches substrings, e.g. "grpc" matches
-  "sglang.srt.grpc._core". It is read directly from os.environ instead of
+  "sglang.srt.rust_extensions._grpc". It is read directly from os.environ
-  sglang.srt.environ, which is not importable until the package is built.
+  instead of sglang.srt.environ, which is not importable until the package is
+  built.
 """
 
 import json

python/sglang/srt/entrypoints/http_server.py

@@ -2687,16 +2687,10 @@ def _start_native_grpc_server_for_runtime(
     template_manager,
     scheduler_info,
 ):
-    try:
+    from sglang.srt.entrypoints.grpc_bridge import RuntimeHandle
-        from sglang.srt.entrypoints.grpc_bridge import RuntimeHandle
+    from sglang.srt.rust_extensions import load_rust_extension
-        from sglang.srt.grpc import _core as grpc_native
+
-    except ImportError as e:
+    grpc_native = load_rust_extension("sglang.srt.rust_extensions._grpc")
-        raise RuntimeError(
-            "Native gRPC extension (sglang.srt.grpc._core) not found in this wheel, "
-            "but --grpc-port was set. The extension is built from "
-            "rust/sglang-grpc/ via setuptools-rust during wheel build. Either "
-            "install a wheel that includes the extension or unset --grpc-port."
-        ) from e
 
     runtime_handle = RuntimeHandle(
         tokenizer_manager=tokenizer_manager,

python/sglang/srt/environ.py

@@ -1523,6 +1523,9 @@ class Envs:
     # Rust server
     # ===================================================================
     SGLANG_RUST_SERVER = EnvBool(False)
+    # Build a missing Rust extension from source (auto), require a bundled or
+    # cached extension (never), or rebuild the local cache entry (force).
+    SGLANG_RUST_BUILD_MODE = EnvStr("auto")
     # Most batched requests one /generate HTTP call may expand into.
     SGLANG_MAX_BATCH_REQS_PER_HTTP_REQ = EnvInt(4096)
 

python/sglang/srt/grpc/__init__.py

@@ -1 +0,0 @@
-# SGLang gRPC module

python/sglang/srt/managers/rust_server.py

@@ -37,7 +37,7 @@ if TYPE_CHECKING:
     from sglang.srt.configs.model_config import ModelConfig
     from sglang.srt.managers.io_struct import BatchTokenIDOutput
     from sglang.srt.managers.scheduler import Scheduler
-    from sglang.srt.server._core import Server
+    from sglang.srt.rust_extensions._server import Server
     from sglang.srt.server_args import ServerArgs
 
 logger = logging.getLogger(__name__)
@@ -367,7 +367,9 @@ class RustServer:
         The caller gates this (``SGLANG_RUST_SERVER`` + rank 0); this always
         creates.
         """
-        from sglang.srt.server._core import Server
+        from sglang.srt.rust_extensions import load_rust_extension
+
+        Server = load_rust_extension("sglang.srt.rust_extensions._server").Server
 
         # Force turn off HF tokenizers rayon's unpinned global thread pool.
         os.environ.setdefault("TOKENIZERS_PARALLELISM", "false")

python/sglang/srt/multimodal/inkling/image_processing_rust.py

@@ -10,8 +10,10 @@ from PIL import Image
 from transformers.image_processing_utils import BaseImageProcessor, BatchFeature
 from transformers.image_utils import ImageInput
 
-from sglang.srt.multimodal._core import inkling as _rs
 from sglang.srt.multimodal.inkling.image_processing import _load_image_bytes
+from sglang.srt.rust_extensions import load_rust_extension
+
+_rs = load_rust_extension("sglang.srt.rust_extensions._multimodal").inkling
 
 
 def _bits_to_bthwc(

python/sglang/srt/multimodal/processors/inkling.py

@@ -133,7 +133,8 @@ class InklingMultimodalProcessor(SGLangBaseProcessor):
                 logger.info("Using Rust-accelerated Inkling image processor")
             except ImportError:
                 logger.warning(
-                    "SGLANG_INKLING_RS_MM_PREPROCESS=1 but sglang.srt.multimodal._core is not available; "
+                    "SGLANG_INKLING_RS_MM_PREPROCESS=1 but "
+                    "sglang.srt.rust_extensions._multimodal is not available; "
                     "falling back to the default image processor."
                 )
                 image_processor = InklingImageProcessor(patch_size=patch_size)

python/sglang/srt/rust_extensions/__init__.py

@@ -0,0 +1,5 @@
+"""Loading support for SGLang's optional Rust extension modules."""
+
+from sglang.srt.rust_extensions.loader import RustBuildMode, load_rust_extension
+
+__all__ = ["RustBuildMode", "load_rust_extension"]

python/sglang/srt/rust_extensions/loader.py

@@ -0,0 +1,412 @@
+"""Load bundled Rust extensions or build them from an SGLang source tree."""
+
+from __future__ import annotations
+
+import fcntl
+import hashlib
+import importlib
+import importlib.util
+import json
+import logging
+import os
+import shutil
+import struct
+import subprocess
+import sys
+import sysconfig
+import tempfile
+from contextlib import contextmanager
+from dataclasses import dataclass
+from pathlib import Path
+from types import ModuleType
+from typing import Iterator, Literal
+
+try:
+    import tomllib
+except ModuleNotFoundError:
+    import tomli as tomllib  # type: ignore[no-redef]
+
+from sglang.srt.environ import envs
+
+logger = logging.getLogger(__name__)
+
+RustBuildMode = Literal["auto", "never", "force"]
+
+_FINGERPRINT_VERSION = 1
+_IGNORED_SOURCE_DIRECTORIES = frozenset(
+    {".git", ".mypy_cache", ".pytest_cache", "__pycache__", "target"}
+)
+_BUILD_ENVIRONMENT_VARIABLES = (
+    "CARGO_BUILD_TARGET",
+    "CARGO_ENCODED_RUSTFLAGS",
+    "RUSTFLAGS",
+)
+
+_RUST_WORKSPACE = Path(__file__).resolve().parents[4] / "rust"
+
+
+@dataclass(frozen=True)
+class _CrateSpec:
+    """One extension crate, discovered from its Cargo manifest."""
+
+    package: str
+    library: str
+    python_module: str
+    workspace: Path
+    features: tuple[str, ...]
+
+
+@dataclass(frozen=True)
+class _BuildContext:
+    source_digest: str
+    fingerprint: str
+    target_fingerprint: str
+
+
+def load_rust_extension(
+    python_module: str,
+    *,
+    mode: RustBuildMode | None = None,
+    cache_dir: Path | None = None,
+    workspace: Path | None = None,
+) -> ModuleType:
+    """Import a PyO3 extension, compiling it locally when permitted and needed.
+
+    The crate is discovered from the workspace under ``rust/``: the one whose
+    Cargo manifest declares ``[package.metadata.sglang] python-module`` equal
+    to ``python_module`` (the same metadata setup.py uses for wheel builds), so
+    new crates need no registration here.
+
+    ``auto`` prefers a module bundled in the installed wheel, then a cached
+    local build, and finally Cargo. ``never`` permits the first two but never
+    invokes Cargo. ``force`` rebuilds from source and replaces the cache entry.
+    ``mode`` defaults to ``SGLANG_RUST_BUILD_MODE``.
+    """
+    if mode is None:
+        mode = envs.SGLANG_RUST_BUILD_MODE.get()
+    if mode not in ("auto", "never", "force"):
+        raise ValueError(
+            f"invalid Rust extension build mode {mode!r}; expected auto, never, or force"
+        )
+
+    if mode != "force":
+        module = _import_bundled_extension(python_module)
+        if module is not None:
+            return module
+    elif python_module in sys.modules:
+        raise RuntimeError(
+            f"cannot force-build {python_module} after it has been imported; "
+            "start a new Python process"
+        )
+
+    if workspace is None:
+        workspace = _RUST_WORKSPACE
+    crate = _discover_crate(workspace, python_module)
+    context = _build_context(crate)
+    cache_root = _cache_root(cache_dir)
+    extension_path = _cached_extension_path(cache_root, crate, context.fingerprint)
+    lock_path = (
+        cache_root / "locks" / f"{crate.package}-{context.target_fingerprint}.lock"
+    )
+
+    with _filesystem_lock(lock_path):
+        if mode != "force" and extension_path.is_file():
+            return _load_extension_from_path(crate.python_module, extension_path)
+
+        if mode == "never":
+            raise ModuleNotFoundError(
+                f"{crate.python_module} is not bundled or cached, and Rust extension "
+                "build mode is 'never'",
+                name=crate.python_module,
+            )
+
+        target_dir = cache_root / "targets" / context.target_fingerprint
+        artifact = _cargo_build(crate, target_dir)
+        if _source_digest(crate.workspace) != context.source_digest:
+            raise RuntimeError(
+                f"Rust sources under {crate.workspace} changed during the build; "
+                "the result was not cached"
+            )
+        _stage_atomically(artifact, extension_path)
+        return _load_extension_from_path(crate.python_module, extension_path)
+
+
+def _import_bundled_extension(module_name: str) -> ModuleType | None:
+    try:
+        return importlib.import_module(module_name)
+    except ModuleNotFoundError as exc:
+        if exc.name == module_name:
+            return None
+        raise
+
+
+def _discover_crate(workspace: Path, python_module: str) -> _CrateSpec:
+    workspace = Path(workspace).resolve()
+    workspace_manifest = workspace / "Cargo.toml"
+    lockfile = workspace / "Cargo.lock"
+    if not workspace_manifest.is_file():
+        raise FileNotFoundError(
+            f"Rust workspace for {python_module} was not found at {workspace}"
+        )
+    if not lockfile.is_file():
+        raise FileNotFoundError(
+            f"{lockfile} is required for reproducible `cargo build --locked` builds"
+        )
+
+    matches: list[_CrateSpec] = []
+    declared_modules: list[str] = []
+    for manifest in _source_files(workspace):
+        if manifest.name != "Cargo.toml":
+            continue
+        with manifest.open("rb") as file:
+            document = tomllib.load(file)
+        package = document.get("package")
+        if not isinstance(package, dict):
+            continue
+        sglang_metadata = package.get("metadata", {}).get("sglang", {})
+        declared_module = sglang_metadata.get("python-module")
+        if declared_module is None:
+            continue
+        declared_modules.append(declared_module)
+        if declared_module != python_module:
+            continue
+
+        package_name = package.get("name")
+        library = document.get("lib", {}).get("name")
+        if not package_name or not library:
+            raise ValueError(
+                f"{manifest} declares python-module {python_module!r} but must "
+                "also set `package.name` and `lib.name`"
+            )
+        matches.append(
+            _CrateSpec(
+                package=package_name,
+                library=library,
+                python_module=python_module,
+                workspace=workspace,
+                features=tuple(sglang_metadata.get("features", ())),
+            )
+        )
+
+    if not matches:
+        raise ModuleNotFoundError(
+            f"no Cargo package under {workspace} declares "
+            f'`[package.metadata.sglang] python-module = "{python_module}"`; '
+            f"declared modules: {sorted(declared_modules)}",
+            name=python_module,
+        )
+    if len(matches) > 1:
+        raise ValueError(
+            f"multiple Cargo packages under {workspace} declare python module "
+            f"{python_module!r}: {sorted(crate.package for crate in matches)}"
+        )
+    return matches[0]
+
+
+def _build_context(crate: _CrateSpec) -> _BuildContext:
+    source_digest = _source_digest(crate.workspace)
+    toolchain = {
+        "cargo": _command_version(
+            "cargo", "--version", "--verbose", cwd=crate.workspace
+        ),
+        "rustc": _command_version("rustc", "-vV", cwd=crate.workspace),
+    }
+    python_abi = {
+        "cache_tag": sys.implementation.cache_tag,
+        "ext_suffix": sysconfig.get_config_var("EXT_SUFFIX"),
+        "platform": sysconfig.get_platform(),
+        "pointer_bits": struct.calcsize("P") * 8,
+        "soabi": sysconfig.get_config_var("SOABI"),
+        "version": list(sys.version_info[:3]),
+    }
+    build_environment = {
+        name: os.environ.get(name) for name in _BUILD_ENVIRONMENT_VARIABLES
+    }
+    target_inputs = {
+        "build_environment": build_environment,
+        "python_abi": python_abi,
+        "toolchain": toolchain,
+    }
+    target_fingerprint = _json_digest(target_inputs)[:24]
+    fingerprint = _json_digest(
+        {
+            "fingerprint_version": _FINGERPRINT_VERSION,
+            "package": crate.package,
+            "library": crate.library,
+            "python_module": crate.python_module,
+            "source_digest": source_digest,
+            **target_inputs,
+        }
+    )
+    return _BuildContext(
+        source_digest=source_digest,
+        fingerprint=fingerprint,
+        target_fingerprint=target_fingerprint,
+    )
+
+
+def _source_digest(workspace: Path) -> str:
+    digest = hashlib.sha256()
+    for path in _source_files(workspace):
+        relative_path = path.relative_to(workspace).as_posix().encode()
+        digest.update(len(relative_path).to_bytes(8, "big"))
+        digest.update(relative_path)
+        if path.is_symlink():
+            contents = os.readlink(path).encode()
+        else:
+            contents = path.read_bytes()
+        digest.update(len(contents).to_bytes(8, "big"))
+        digest.update(contents)
+    return digest.hexdigest()
+
+
+def _source_files(workspace: Path) -> Iterator[Path]:
+    for root, directories, filenames in os.walk(workspace):
+        directories[:] = sorted(
+            name for name in directories if name not in _IGNORED_SOURCE_DIRECTORIES
+        )
+        root_path = Path(root)
+        for filename in sorted(filenames):
+            yield root_path / filename
+
+
+def _command_version(command: str, *arguments: str, cwd: Path) -> str:
+    try:
+        result = subprocess.run(
+            [command, *arguments],
+            check=True,
+            capture_output=True,
+            text=True,
+            cwd=cwd,
+        )
+    except (OSError, subprocess.CalledProcessError) as exc:
+        raise RuntimeError(
+            f"failed to query the Rust toolchain with `{command} {' '.join(arguments)}`"
+        ) from exc
+    return result.stdout.strip()
+
+
+def _json_digest(value: object) -> str:
+    serialized = json.dumps(
+        value, sort_keys=True, separators=(",", ":"), ensure_ascii=True
+    ).encode()
+    return hashlib.sha256(serialized).hexdigest()
+
+
+def _cache_root(cache_dir: Path | None) -> Path:
+    if cache_dir is not None:
+        return Path(cache_dir).expanduser().resolve()
+    sglang_cache = envs.SGLANG_CACHE_DIR.get()
+    return Path(sglang_cache).expanduser().resolve() / "rust_extensions"
+
+
+def _cached_extension_path(
+    cache_root: Path, crate: _CrateSpec, fingerprint: str
+) -> Path:
+    extension_suffix = sysconfig.get_config_var("EXT_SUFFIX")
+    if not extension_suffix:
+        raise RuntimeError("Python did not report an EXT_SUFFIX for native extensions")
+    module_leaf = crate.python_module.rsplit(".", 1)[-1]
+    return (
+        cache_root
+        / "artifacts"
+        / crate.package
+        / fingerprint
+        / (module_leaf + extension_suffix)
+    )
+
+
+@contextmanager
+def _filesystem_lock(path: Path) -> Iterator[None]:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("a+b") as lock_file:
+        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
+        try:
+            yield
+        finally:
+            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
+
+
+def _cargo_build(crate: _CrateSpec, target_dir: Path) -> Path:
+    target_dir.mkdir(parents=True, exist_ok=True)
+    command = [
+        "cargo",
+        "build",
+        "--release",
+        "--locked",
+        "--package",
+        crate.package,
+    ]
+    if crate.features:
+        command.extend(("--features", ",".join(crate.features)))
+
+    environment = os.environ.copy()
+    environment["CARGO_TARGET_DIR"] = os.fspath(target_dir)
+    environment["PYO3_PYTHON"] = sys.executable
+    logger.info("Building %s with `%s`", crate.python_module, " ".join(command))
+    try:
+        subprocess.run(command, cwd=crate.workspace, env=environment, check=True)
+    except (OSError, subprocess.CalledProcessError) as exc:
+        raise RuntimeError(f"failed to build {crate.python_module} with Cargo") from exc
+
+    release_dir = target_dir / "release"
+    if target := environment.get("CARGO_BUILD_TARGET"):
+        release_dir = target_dir / target / "release"
+    artifact = release_dir / _cargo_library_filename(crate.library)
+    if not artifact.is_file():
+        raise FileNotFoundError(
+            f"Cargo completed but did not produce the expected artifact {artifact}"
+        )
+    return artifact
+
+
+def _cargo_library_filename(library: str) -> str:
+    if sys.platform == "win32":
+        return f"{library}.dll"
+    if sys.platform == "darwin":
+        return f"lib{library}.dylib"
+    return f"lib{library}.so"
+
+
+def _stage_atomically(source: Path, destination: Path) -> None:
+    destination.parent.mkdir(parents=True, exist_ok=True)
+    descriptor, temporary_name = tempfile.mkstemp(
+        prefix=f".{destination.name}.", dir=destination.parent
+    )
+    temporary_path = Path(temporary_name)
+    try:
+        with (
+            os.fdopen(descriptor, "wb") as destination_file,
+            source.open("rb") as source_file,
+        ):
+            shutil.copyfileobj(source_file, destination_file)
+            destination_file.flush()
+            os.fsync(destination_file.fileno())
+        temporary_path.chmod(0o755)
+        os.replace(temporary_path, destination)
+        directory_descriptor = os.open(destination.parent, os.O_RDONLY)
+        try:
+            os.fsync(directory_descriptor)
+        finally:
+            os.close(directory_descriptor)
+    finally:
+        temporary_path.unlink(missing_ok=True)
+
+
+def _load_extension_from_path(module_name: str, path: Path) -> ModuleType:
+    loaded = sys.modules.get(module_name)
+    if loaded is not None:
+        return loaded
+    module_spec = importlib.util.spec_from_file_location(module_name, path)
+    if module_spec is None or module_spec.loader is None:
+        raise ImportError(
+            f"could not create an import spec for {module_name} at {path}"
+        )
+    module = importlib.util.module_from_spec(module_spec)
+    sys.modules[module_name] = module
+    try:
+        module_spec.loader.exec_module(module)
+    except BaseException:
+        sys.modules.pop(module_name, None)
+        raise
+    return module

python/sglang/test/test_utils.py

@@ -219,17 +219,10 @@ def is_rust_server_built():
     """Return whether the embedded Rust server extension (``SGLANG_RUST_SERVER``)
     is importable.
 
-    ``sglang/srt/server/`` is not in the source tree — it is produced by
+    The ``sglang.srt.rust_extensions`` Python package is always present; the
-    ``setup.py build_rust --inplace``, so on a build without it ``find_spec``
+    private ``_server`` module exists only when the PyO3 extension was built.
-    raises ``ModuleNotFoundError`` for the missing *parent* package rather than
-    returning ``None`` for the missing leaf. Suites gate a rust-server subclass on
-    this at class-definition time, so letting that escape would fail the whole
-    module import instead of skipping the one class.
     """
-    try:
+    return importlib.util.find_spec("sglang.srt.rust_extensions._server") is not None
-        return importlib.util.find_spec("sglang.srt.server._core") is not None
-    except ModuleNotFoundError:
-        return False
 
 
 def _use_cached_default_models(model_repo: str):

rust/Cargo.lock

@@ -982,9 +982,9 @@ checksum = "d0881ea181b1df73ff77ffaaf9c7544ecc11e82fba9b5f27b262a3c73a332555"
 
 [[package]]
 name = "dynamo-parsers"
-version = "7.0.1"
+version = "7.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "97cce1ec70f4c4896ff9a4e0bb29cd603f465e599c94bf2085b71872a3a58c70"
+checksum = "7a7f84812e7ce1d3dace1b8d69853cc6c49759cbd07dfbb59452aa928645b031"
 dependencies = [
  "aho-corasick",
  "anyhow",
@@ -1005,9 +1005,9 @@ dependencies = [
 
 [[package]]
 name = "dynamo-protocols"
-version = "5.1.0"
+version = "5.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "696b6df4c817c16dc0a619d43f6af5ecc4f045a6b6be7ef516bfe502f977764b"
+checksum = "97fd951c32c033f4f220b6087db91d7f7d475f1bf1f886c8e60798ac1cf4cc9a"
 dependencies = [
  "async-openai",
  "derive_builder",
@@ -1022,9 +1022,9 @@ dependencies = [
 
 [[package]]
 name = "dynamo-renderer"
-version = "5.0.0"
+version = "5.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0423da7bec83734e7567b1c8895fd2e7a1a98256253a29fe128032ac01cefac1"
+checksum = "dfe04753d666e3462e3eed4abcf2a4d05997cf2dea45858733f2bdea5b61f733"
 dependencies = [
  "anyhow",
  "chrono",
@@ -1040,9 +1040,9 @@ dependencies = [
 
 [[package]]
 name = "dynamo-tokenizers"
-version = "1.7.0"
+version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a81f7b7693282f4693a3b4c60174e14260cf011ab493a7ca9b4deb2fa98ecee"
+checksum = "821c767e896f1f225b6411a5ce41dba7f114c2c97db862a13fd962195665075e"
 dependencies = [
  "aho-corasick",
  "anyhow",
@@ -1162,21 +1162,24 @@ dependencies = [
 
 [[package]]
 name = "fastokens"
-version = "0.2.1"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8728655e193e0d08d7a95d63cf1fdb9b768d282cab0a112ecb006615bae9f067"
+checksum = "35ff8cf975d8f772e7d4c3be439659b0b23b1ae1086ebee7204573807053ff7f"
 dependencies = [
  "daachorse",
  "fancy-regex 0.17.0",
  "hf-hub",
  "icu_normalizer",
+ "libc",
  "memchr",
  "pcre2",
  "rayon",
+ "regex-syntax",
  "serde",
  "serde_json",
  "strum",
  "thiserror",
+ "ureq",
 ]
 
 [[package]]
@@ -1633,7 +1636,7 @@ dependencies = [
  "libc",
  "percent-encoding",
  "pin-project-lite",
- "socket2 0.6.5",
+ "socket2 0.5.10",
  "tokio",
  "tower-service",
  "tracing",
@@ -2123,9 +2126,9 @@ dependencies = [
 
 [[package]]
 name = "minijinja"
-version = "2.21.0"
+version = "2.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb3d648e68cea56d9858d535ee28f9538404e2dd8cb08ed0bd05dca379477f39"
+checksum = "86886cf6dbf4e614b19c9a1eec9775f021869d7eadde0fc73921a81b90c9b4c9"
 dependencies = [
  "indexmap 2.14.0",
  "memo-map",
@@ -2135,9 +2138,9 @@ dependencies = [
 
 [[package]]
 name = "minijinja-contrib"
-version = "2.21.0"
+version = "2.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85342f6fac0be8ccd5bd00d9066be538f34f393f577b75d81b17c8398a6b43bb"
+checksum = "bd3e5f077bc2379f0f7d911e7cfdd921114ed99fc884533dca502944cb355b11"
 dependencies = [
  "minijinja",
  "serde",
@@ -2940,7 +2943,7 @@ dependencies = [
  "quinn-udp",
  "rustc-hash 2.1.3",
  "rustls",
- "socket2 0.6.5",
+ "socket2 0.5.10",
  "thiserror",
  "tokio",
  "tracing",
@@ -2978,7 +2981,7 @@ dependencies = [
  "cfg_aliases",
  "libc",
  "once_cell",
- "socket2 0.6.5",
+ "socket2 0.5.10",
  "tracing",
  "windows-sys 0.61.2",
 ]

rust/sglang-grpc/Cargo.toml

@@ -8,7 +8,7 @@ license.workspace = true
 # Consumed by python/setup.py: registers this crate as a PyO3 extension module
 # of the main sglang wheel at the given import path.
 [package.metadata.sglang]
-python-module = "sglang.srt.grpc._core"
+python-module = "sglang.srt.rust_extensions._grpc"
 # Always build optimized, even for an editable install.
 debug = false
 

rust/sglang-grpc/pyproject.toml

@@ -1,7 +1,7 @@
 # Standalone dev builds only (`maturin build` / `maturin develop`); the
 # extension ships to users inside the main sglang wheel via setuptools-rust
-# (python/pyproject.toml, target sglang.srt.grpc._core). Requires a repo
+# (python/pyproject.toml, target sglang.srt.rust_extensions._grpc). Requires a
-# checkout (build.rs reads ../../proto), so this is not publishable as an
+# repo checkout (build.rs reads ../../proto), so this is not publishable as an
 # sdist. protoc is not required: build.rs falls back to a vendored binary.
 [build-system]
 requires = ["maturin>=1.5,<2"]
@@ -14,4 +14,4 @@ description = "In-process Rust gRPC server for SGLang"
 requires-python = ">=3.10"
 
 [tool.maturin]
-module-name = "_core"
+module-name = "_grpc"

rust/sglang-grpc/src/lib.rs

@@ -257,7 +257,7 @@ fn start_server(
 }
 
 #[pymodule]
-fn _core(m: &Bound<'_, PyModule>) -> PyResult<()> {
+fn _grpc(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(start_server, m)?)?;
     m.add_class::<GrpcServerHandle>()?;
     m.add_class::<ChunkSendStatus>()?;

rust/sglang-mm/Cargo.toml

@@ -11,17 +11,17 @@ license.workspace = true
 # features: the wheel build needs the PyO3 bindings, which are NOT default (see
 # [features] below).
 [package.metadata.sglang]
-python-module = "sglang.srt.multimodal._core"
+python-module = "sglang.srt.rust_extensions._multimodal"
 debug = false
 features = ["python", "parallel"]
 
 [lib]
 # Unique per-crate artifact name (the shared workspace target/ dir cannot hold
-# two `lib_core` cdylibs). The importable Python module is still `_core`: the
+# multiple `lib_core` cdylibs). The importable Python module is `_multimodal`: the
-# name comes from the `#[pymodule]` entry point and the setuptools-rust
+# name comes from the `#[pymodule]` entry point and the setuptools-rust target,
-# `target` in python/pyproject.toml, which renames the built artifact.
+# which renames the built artifact.
 name = "sglang_mm_core"
-# cdylib: the PyO3 module (`sglang.srt.multimodal._core`).
+# cdylib: the PyO3 module (`sglang.srt.rust_extensions._multimodal`).
 # rlib:   pure-Rust core linked by sglang-server's native MM path.
 crate-type = ["cdylib", "rlib"]
 

rust/sglang-mm/README.md

@@ -6,9 +6,9 @@ GIL-released.
 
 Built two ways:
 
-- **PyO3 extension** `sglang.srt.multimodal._core` (features `python,parallel`,
+- **PyO3 extension** `sglang.srt.rust_extensions._multimodal` (features
-  requested by the wheel build) via setuptools-rust when installing sglang —
+  `python,parallel`, requested by the wheel build) via setuptools-rust when
-  used by Python processors and parity tests.
+  installing sglang — used by Python processors and parity tests.
 - **Pure-Rust `rlib`** (default features, i.e. neither) linked by
   `sglang-server`'s MM worker path — that copy needs no pyo3, no libpython, and
   no rayon: it spawns no threads and runs inline on the calling thread, because
@@ -19,7 +19,7 @@ Built two ways:
 
 ```
 src/
-├── lib.rs                    # module root; PyO3 module (_core) feature-gated
+├── lib.rs                    # module root; PyO3 module (_multimodal) feature-gated
 ├── pipeline.rs               # the server-pipeline contract: MmFamilyProcessor
 │                             #   trait + the carriers (Tensor, TokenLayout, ...)
 ├── driver.rs                 # model-independent request driver (fetch →
@@ -115,7 +115,7 @@ un-stripped URL to `open()`).
 ## Python API
 
 ```python
-from sglang.srt.multimodal._core import common, inkling
+from sglang.srt.rust_extensions._multimodal import common, inkling
 
 # Common (model-agnostic)
 common.resize_rgb(arr, out_w, out_h)
@@ -174,7 +174,8 @@ impl ImageProcessorSpec for MyModelProcessor {
 
 4. Wire up in `src/lib.rs`: `mod my_model;` and `my_model::register(m)?;`.
 
-5. Add Python processor class that calls `from sglang.srt.multimodal._core import my_model`.
+5. Add Python processor class that calls
+   `from sglang.srt.rust_extensions._multimodal import my_model`.
 
 ## Available transform primitives (`common::transforms`)
 

rust/sglang-mm/bench/bench_parity.py

@@ -5,7 +5,6 @@ import numpy as np
 import torch
 from PIL import Image
 
-from sglang.srt.multimodal._core import inkling as _rs_inkling
 from sglang.srt.multimodal.inkling.image_processing import (
     IMAGE_MEAN,
     IMAGE_STD,
@@ -13,6 +12,7 @@ from sglang.srt.multimodal.inkling.image_processing import (
     _encode_image_bytes,
     _fill_patches_numba,
 )
+from sglang.srt.rust_extensions._multimodal import inkling as _rs_inkling
 
 PS = 40
 

rust/sglang-mm/pyproject.toml

@@ -9,4 +9,4 @@ description = "Rust-accelerated multimodal preprocessing for SGLang"
 requires-python = ">=3.10"
 
 [tool.maturin]
-module-name = "_core"
+module-name = "_multimodal"

rust/sglang-mm/src/lib.rs

@@ -1,7 +1,7 @@
 //! sglang-mm: Rust-accelerated multimodal preprocessing for SGLang.
 //!
 //! Built two ways:
-//! * PyO3 extension `sglang.srt.multimodal._core` (feature `python`, default),
+//! * PyO3 extension `sglang.srt.rust_extensions._multimodal` (feature `python`),
 //!   used by Python processors (e.g. Inkling) and by parity tests.
 //! * Pure-Rust `rlib` (`default-features = false`), linked by `sglang-server`'s
 //!   MM worker path — no pyo3 in that dependency graph.
@@ -18,7 +18,7 @@ use pyo3::prelude::*;
 
 #[cfg(feature = "python")]
 #[pymodule]
-fn _core(m: &Bound<'_, PyModule>) -> PyResult<()> {
+fn _multimodal(m: &Bound<'_, PyModule>) -> PyResult<()> {
     common::register(m)?;
     inkling::register(m)?;
     qwen_vl::register(m)?;

rust/sglang-mm/tests/test_golden.py

@@ -4,7 +4,7 @@ import os
 import numpy as np
 import pytest
 
-from sglang.srt.multimodal._core import inkling as _rs_inkling
+from sglang.srt.rust_extensions._multimodal import inkling as _rs_inkling
 
 GOLDEN_DIR = os.environ.get(
     "INKLING_MM_GOLDEN_DIR",

rust/sglang-mm/tests/test_hash_fetch.py

@@ -15,12 +15,12 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "bench"))
 from bench_parity import make_photo_like
 
 from sglang.srt.managers.mm_utils import data_hash, hash_feature
-from sglang.srt.multimodal._core import common as _rs_common
 from sglang.srt.multimodal.inkling import InklingProcessor
 from sglang.srt.multimodal.inkling.image_processing_rust import (
     InklingRustImageProcessor,
 )
 from sglang.srt.multimodal.processors import inkling as prc
+from sglang.srt.rust_extensions._multimodal import common as _rs_common
 
 
 def png_bytes(arr):

rust/sglang-mm/tests/test_resize_parity.py

@@ -6,8 +6,8 @@ import numpy as np
 import pytest
 from PIL import Image
 
-from sglang.srt.multimodal._core import common as _rs_common
+from sglang.srt.rust_extensions._multimodal import common as _rs_common
-from sglang.srt.multimodal._core import inkling as _rs_inkling
+from sglang.srt.rust_extensions._multimodal import inkling as _rs_inkling
 
 
 def py_scaled_dims(

rust/sglang-server/Cargo.toml

@@ -7,7 +7,7 @@ license.workspace = true
 
 # Consumed by python/setup.py: registers this crate as a PyO3 extension module.
 [package.metadata.sglang]
-python-module = "sglang.srt.server._core"
+python-module = "sglang.srt.rust_extensions._server"
 # Always build optimized, even for an editable install.
 debug = false
 

rust/sglang-server/pyproject.toml

@@ -13,4 +13,4 @@ classifiers = [
 dynamic = ["version"]
 
 [tool.maturin]
-module-name = "_core"
+module-name = "_server"

rust/sglang-server/src/api_server/openai/chat.rs

@@ -836,6 +836,7 @@ pub(super) fn chat_logprobs(extras: Option<&ChunkExtras>) -> ChatChoiceLogprobs
             bytes: Some(token.as_bytes().to_vec()),
             token,
             logprob,
+            token_id: u32::try_from(token_id).ok(),
             top_logprobs,
         });
     }
@@ -1020,6 +1021,7 @@ mod tests {
         let logprobs = chat_logprobs(Some(&extras));
         let token = &logprobs.content.unwrap()[0];
         assert_eq!(token.token, "x");
+        assert_eq!(token.token_id, Some(7));
         assert_eq!(token.top_logprobs.len(), 2);
         assert_eq!(token.top_logprobs[1].token, "y");
     }

rust/sglang-server/src/lib.rs

@@ -292,7 +292,7 @@ static LOG_GUARD: std::sync::OnceLock<tracing_appender::non_blocking::WorkerGuar
     std::sync::OnceLock::new();
 
 #[pymodule]
-fn _core(m: &Bound<'_, PyModule>) -> PyResult<()> {
+fn _server(m: &Bound<'_, PyModule>) -> PyResult<()> {
     // Initialize tracing once; ignore if already set by the host process.
     // Non-blocking writer: emitting threads (axum workers, egress, detok) only
     // enqueue; a dedicated thread does the stdout formatting-flush + syscall.

scripts/ci/cuda/ci_install_dependency.sh

@@ -460,7 +460,7 @@ require_prebuilt_rust_exts() {
         return
     fi
 
-    # Exact EXT_SUFFIX rather than a _core*.so glob: no crate sets abi3, so a module
+    # Exact EXT_SUFFIX rather than an _*.so glob: no crate sets abi3, so a module
     # built for another minor version satisfies the glob while the import system
     # ignores it, leaving is_rust_server_built() false and the Rust-server tests
     # silently skipped. Stages have no setup-python, so the interpreter is whatever
@@ -469,13 +469,13 @@ require_prebuilt_rust_exts() {
     local suffix
     suffix=$(python3 -c 'import sysconfig; print(sysconfig.get_config_var("EXT_SUFFIX"))')
     local missing=()
-    local pkg
+    local module
-    for pkg in server grpc multimodal; do
+    for module in server grpc multimodal; do
-        [ -f "python/sglang/srt/${pkg}/_core${suffix}" ] || missing+=("${pkg}")
+        [ -f "python/sglang/srt/rust_extensions/_${module}${suffix}" ] || missing+=("${module}")
     done
     if [ ${#missing[@]} -gt 0 ]; then
-        echo "::warning::no prebuilt _core${suffix} for: ${missing[*]}; building from source"
+        echo "::warning::no prebuilt Rust extension ${suffix} for: ${missing[*]}; building from source"
-        ls -l python/sglang/srt/*/_core*.so 2>/dev/null || echo "(no extension modules at all)"
+        ls -l python/sglang/srt/rust_extensions/_*.so 2>/dev/null || echo "(no extension modules at all)"
         export SGLANG_BUILD_RUST_EXTS=
         mark_step_done "${FUNCNAME[0]}"
         return
@@ -812,7 +812,7 @@ print(f"sglang resolves to {spec.origin}")
 # so a .so that cannot load passes find_spec and only fails inside some suite.
 import importlib
 for mod in ("server", "grpc", "multimodal"):
-    name = f"sglang.srt.{mod}._core"
+    name = f"sglang.srt.rust_extensions._{mod}"
     try:
         importlib.import_module(name)
     except Exception as exc:

scripts/ci/musa/musa_install_dependency.sh

@@ -74,7 +74,8 @@ else
 
     rm -f "${REPO_ROOT}/python/pyproject.toml" && mv "${REPO_ROOT}/python/pyproject_other.toml" "${REPO_ROOT}/python/pyproject.toml"
 
-    # setuptools-rust builds the sglang-mm extension (sglang.srt.multimodal._core)
+    # setuptools-rust builds the sglang-mm extension
+    # (sglang.srt.rust_extensions._multimodal)
     # declared in pyproject_other.toml, so a Rust toolchain must be present like
     # on the CUDA/AMD CI paths. Idempotent; installs per-user under $HOME/.cargo.
     # Export PATH here because the pip install below runs in this same shell

scripts/ci/utils/stage_rust_ext_modules.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# Copy the built PyO3 extension modules into rust-ext-staging/<pkg>/ for
+# Copy the built PyO3 extension modules into rust-ext-staging/rust_extensions/ for
 # upload-artifact. Shared by both jobs of _pr-test-rust-ext-build.yml, so the
 # archive layout and the module-count check cannot drift between them.
 #
@@ -12,24 +12,24 @@ shopt -s nullglob
 # module would silently shift the archive layout.
 rm -rf rust-ext-staging
 built=()
-# Same suffix set across pkgs, or one ABI's Rust-server tests silently skip.
+# Same suffix set across modules, or one ABI's Rust-server tests silently skip.
 expected_suffixes=""
-for pkg in server grpc multimodal; do
+mkdir -p rust-ext-staging/rust_extensions
-    found=(python/sglang/srt/"${pkg}"/_core*.so)
+for module in server grpc multimodal; do
+    found=(python/sglang/srt/rust_extensions/_"${module}"*.so)
     if [ ${#found[@]} -eq 0 ]; then
-        echo "::error::no extension module found for ${pkg}"
+        echo "::error::no extension module found for ${module}"
         exit 1
     fi
-    suffixes=$(printf '%s\n' "${found[@]##*/_core}" | sort)
+    suffixes=$(printf '%s\n' "${found[@]##*/_${module}}" | sort)
     if [ -z "${expected_suffixes}" ]; then
         expected_suffixes="${suffixes}"
     elif [ "${suffixes}" != "${expected_suffixes}" ]; then
-        echo "::error::extension modules for ${pkg} do not match server's interpreter set"
+        echo "::error::extension modules for ${module} do not match server's interpreter set"
         printf 'have:\n%s\nwant:\n%s\n' "${suffixes}" "${expected_suffixes}"
         exit 1
     fi
-    mkdir -p "rust-ext-staging/${pkg}"
+    cp "${found[@]}" rust-ext-staging/rust_extensions/
-    cp "${found[@]}" "rust-ext-staging/${pkg}/"
     built+=("${found[@]}")
 done
 max_allowed="${MAX_GLIBC:-}"

test/registered/rust/test_rust_extension.py

@@ -0,0 +1,350 @@
+import importlib.abc
+import importlib.machinery
+import multiprocessing
+import os
+import subprocess
+import sys
+import threading
+import time
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from types import ModuleType
+from unittest import mock
+
+from sglang.srt.rust_extensions import load_rust_extension
+from sglang.srt.rust_extensions import loader as rust_extension
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+def _hold_filesystem_lock(path: str, ready, release) -> None:
+    with rust_extension._filesystem_lock(Path(path)):
+        ready.set()
+        release.wait(timeout=10)
+
+
+class _FailingExtensionLoader(importlib.abc.Loader):
+    def create_module(self, spec):
+        return None
+
+    def exec_module(self, module):
+        raise RuntimeError("broken extension")
+
+
+class TestRustExtension(CustomTestCase):
+    def _workspace(self, root: Path) -> Path:
+        workspace = root / "rust"
+        crate = workspace / "demo"
+        crate.mkdir(parents=True)
+        (workspace / "Cargo.toml").write_text(
+            '[workspace]\nmembers = ["demo"]\n', encoding="utf-8"
+        )
+        (workspace / "Cargo.lock").write_text(
+            "# generated lockfile\n", encoding="utf-8"
+        )
+        (crate / "Cargo.toml").write_text(
+            """
+[package]
+name = "demo-extension"
+version = "0.1.0"
+
+[package.metadata.sglang]
+python-module = "demo._core"
+features = ["python"]
+
+[lib]
+name = "demo_extension"
+crate-type = ["cdylib"]
+""".strip() + "\n",
+            encoding="utf-8",
+        )
+        (crate / "lib.rs").write_text("fn input() {}\n", encoding="utf-8")
+        return workspace
+
+    def test_bundled_wheel_extension_never_touches_source_or_cargo(self):
+        bundled = ModuleType("demo._core")
+        with (
+            mock.patch.object(
+                rust_extension.importlib, "import_module", return_value=bundled
+            ),
+            mock.patch.object(rust_extension, "_discover_crate") as discover,
+            mock.patch.object(rust_extension, "_build_context") as fingerprint,
+            mock.patch.object(rust_extension, "_cargo_build") as cargo_build,
+        ):
+            self.assertIs(
+                load_rust_extension(
+                    "demo._core", mode="auto", workspace=Path("/workspace/not-present")
+                ),
+                bundled,
+            )
+        discover.assert_not_called()
+        fingerprint.assert_not_called()
+        cargo_build.assert_not_called()
+
+    def test_discovery_reads_crate_manifest_metadata(self):
+        with TemporaryDirectory() as directory:
+            workspace = self._workspace(Path(directory))
+            crate = rust_extension._discover_crate(workspace, "demo._core")
+            self.assertEqual(crate.package, "demo-extension")
+            self.assertEqual(crate.library, "demo_extension")
+            self.assertEqual(crate.python_module, "demo._core")
+            self.assertEqual(crate.features, ("python",))
+
+            with self.assertRaisesRegex(
+                ModuleNotFoundError, r"declared modules: \['demo\._core'\]"
+            ):
+                rust_extension._discover_crate(workspace, "demo._missing")
+
+    def test_fingerprint_is_content_based_and_covers_build_inputs(self):
+        with TemporaryDirectory() as directory:
+            workspace = self._workspace(Path(directory))
+            crate = rust_extension._discover_crate(workspace, "demo._core")
+            with mock.patch.object(
+                rust_extension,
+                "_command_version",
+                side_effect=lambda command, *args, **kwargs: f"{command} 1.0",
+            ):
+                first = rust_extension._build_context(crate)
+                source = workspace / "demo" / "lib.rs"
+                os.utime(source, (1, 1))
+                self.assertEqual(first, rust_extension._build_context(crate))
+
+                source.write_text("fn changed() {}\n", encoding="utf-8")
+                changed_source = rust_extension._build_context(crate)
+                self.assertNotEqual(first.fingerprint, changed_source.fingerprint)
+
+                with mock.patch.dict(os.environ, {"RUSTFLAGS": "-Ctarget-cpu=native"}):
+                    changed_flags = rust_extension._build_context(crate)
+                self.assertNotEqual(
+                    changed_source.fingerprint, changed_flags.fingerprint
+                )
+                self.assertNotEqual(
+                    changed_source.target_fingerprint,
+                    changed_flags.target_fingerprint,
+                )
+
+    def test_auto_builds_once_then_uses_cache(self):
+        with TemporaryDirectory() as directory:
+            root = Path(directory)
+            workspace = self._workspace(root)
+            artifact = root / "libdemo_extension.so"
+            artifact.write_bytes(b"extension")
+            context = rust_extension._BuildContext("source", "fingerprint", "target")
+            loaded = ModuleType("demo._core")
+            with (
+                mock.patch.object(
+                    rust_extension, "_import_bundled_extension", return_value=None
+                ),
+                mock.patch.object(
+                    rust_extension, "_build_context", return_value=context
+                ),
+                mock.patch.object(
+                    rust_extension, "_source_digest", return_value="source"
+                ),
+                mock.patch.object(
+                    rust_extension, "_cargo_build", return_value=artifact
+                ) as cargo_build,
+                mock.patch.object(
+                    rust_extension,
+                    "_load_extension_from_path",
+                    return_value=loaded,
+                ),
+            ):
+                self.assertIs(
+                    rust_extension.load_rust_extension(
+                        "demo._core", workspace=workspace, cache_dir=root / "cache"
+                    ),
+                    loaded,
+                )
+                self.assertIs(
+                    rust_extension.load_rust_extension(
+                        "demo._core", workspace=workspace, cache_dir=root / "cache"
+                    ),
+                    loaded,
+                )
+            cargo_build.assert_called_once()
+
+    def test_never_rejects_missing_cache_without_building(self):
+        with TemporaryDirectory() as directory:
+            root = Path(directory)
+            workspace = self._workspace(root)
+            context = rust_extension._BuildContext("source", "fingerprint", "target")
+            with (
+                mock.patch.object(
+                    rust_extension, "_import_bundled_extension", return_value=None
+                ),
+                mock.patch.object(
+                    rust_extension, "_build_context", return_value=context
+                ),
+                mock.patch.object(rust_extension, "_cargo_build") as cargo_build,
+            ):
+                with self.assertRaisesRegex(
+                    ModuleNotFoundError, "build mode is 'never'"
+                ):
+                    rust_extension.load_rust_extension(
+                        "demo._core",
+                        mode="never",
+                        workspace=workspace,
+                        cache_dir=root / "cache",
+                    )
+            cargo_build.assert_not_called()
+
+    def test_force_skips_bundled_import_and_rebuilds_cached_artifact(self):
+        with TemporaryDirectory() as directory:
+            root = Path(directory)
+            workspace = self._workspace(root)
+            crate = rust_extension._discover_crate(workspace, "demo._core")
+            artifact = root / "libdemo_extension.so"
+            artifact.write_bytes(b"new extension")
+            context = rust_extension._BuildContext("source", "fingerprint", "target")
+            cached = rust_extension._cached_extension_path(
+                root / "cache", crate, context.fingerprint
+            )
+            cached.parent.mkdir(parents=True)
+            cached.write_bytes(b"old extension")
+            with (
+                mock.patch.object(
+                    rust_extension, "_import_bundled_extension"
+                ) as bundled_import,
+                mock.patch.object(
+                    rust_extension, "_build_context", return_value=context
+                ),
+                mock.patch.object(
+                    rust_extension, "_source_digest", return_value="source"
+                ),
+                mock.patch.object(
+                    rust_extension, "_cargo_build", return_value=artifact
+                ) as cargo_build,
+                mock.patch.object(
+                    rust_extension,
+                    "_load_extension_from_path",
+                    return_value=ModuleType("demo._core"),
+                ),
+            ):
+                rust_extension.load_rust_extension(
+                    "demo._core",
+                    mode="force",
+                    workspace=workspace,
+                    cache_dir=root / "cache",
+                )
+            bundled_import.assert_not_called()
+            cargo_build.assert_called_once()
+            self.assertEqual(cached.read_bytes(), b"new extension")
+
+    def test_cargo_build_uses_locked_release_and_declared_features(self):
+        with TemporaryDirectory() as directory:
+            root = Path(directory)
+            workspace = self._workspace(root)
+            crate = rust_extension._discover_crate(workspace, "demo._core")
+            target_dir = root / "target"
+
+            def run(command, *, cwd, env, check):
+                self.assertTrue(check)
+                self.assertEqual(cwd, crate.workspace)
+                self.assertEqual(env["PYO3_PYTHON"], sys.executable)
+                artifact = Path(env["CARGO_TARGET_DIR"]) / "release"
+                artifact.mkdir(parents=True)
+                (artifact / "libdemo_extension.so").write_bytes(b"extension")
+                return subprocess.CompletedProcess(command, 0)
+
+            with mock.patch.object(
+                rust_extension.subprocess, "run", side_effect=run
+            ) as cargo:
+                artifact = rust_extension._cargo_build(crate, target_dir)
+
+            self.assertEqual(artifact, target_dir / "release/libdemo_extension.so")
+            self.assertEqual(
+                cargo.call_args.args[0],
+                [
+                    "cargo",
+                    "build",
+                    "--release",
+                    "--locked",
+                    "--package",
+                    "demo-extension",
+                    "--features",
+                    "python",
+                ],
+            )
+
+    def test_filesystem_lock_serializes_processes(self):
+        with TemporaryDirectory() as directory:
+            lock_path = Path(directory) / "build.lock"
+            context = multiprocessing.get_context("fork")
+            ready = context.Event()
+            release = context.Event()
+            process = context.Process(
+                target=_hold_filesystem_lock,
+                args=(os.fspath(lock_path), ready, release),
+            )
+            process.start()
+            self.assertTrue(ready.wait(timeout=5))
+
+            acquired = threading.Event()
+
+            def acquire_in_parent():
+                with rust_extension._filesystem_lock(lock_path):
+                    acquired.set()
+
+            thread = threading.Thread(target=acquire_in_parent)
+            thread.start()
+            try:
+                time.sleep(0.1)
+                self.assertFalse(acquired.is_set())
+            finally:
+                release.set()
+                process.join(timeout=5)
+                thread.join(timeout=5)
+            self.assertEqual(process.exitcode, 0)
+            self.assertTrue(acquired.is_set())
+
+    def test_failed_import_does_not_poison_sys_modules(self):
+        module_name = "demo._broken_core"
+        module_spec = importlib.machinery.ModuleSpec(
+            module_name, _FailingExtensionLoader()
+        )
+        with mock.patch.object(
+            rust_extension.importlib.util,
+            "spec_from_file_location",
+            return_value=module_spec,
+        ):
+            with self.assertRaisesRegex(RuntimeError, "broken extension"):
+                rust_extension._load_extension_from_path(
+                    module_name, Path("/cache/_broken_core.so")
+                )
+        self.assertNotIn(module_name, sys.modules)
+
+    def test_checked_in_crates_are_discovered_from_wheel_metadata(self):
+        for python_module, package, library, features in (
+            (
+                "sglang.srt.rust_extensions._server",
+                "sglang-server",
+                "sglang_server",
+                (),
+            ),
+            (
+                "sglang.srt.rust_extensions._grpc",
+                "sglang-grpc",
+                "sglang_grpc_core",
+                (),
+            ),
+            (
+                "sglang.srt.rust_extensions._multimodal",
+                "sglang-mm",
+                "sglang_mm_core",
+                ("python", "parallel"),
+            ),
+        ):
+            crate = rust_extension._discover_crate(
+                rust_extension._RUST_WORKSPACE, python_module
+            )
+            self.assertEqual(crate.package, package)
+            self.assertEqual(crate.library, library)
+            self.assertEqual(crate.features, features)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/multimodal/rust/_mm_rust_utils.py

@@ -21,13 +21,13 @@ register_cpu_ci(
 
 
 def load_core():
-    """The Rust ``_core`` extension, or ``None`` (→ skip) when not built
+    """The Rust ``_multimodal`` extension, or ``None`` (→ skip) when not built
     locally. In CI a missing extension is a hard failure, never a silent
     skip — the CPU suite builds it from source."""
     try:
-        from sglang.srt.multimodal import _core
+        from sglang.srt.rust_extensions import _multimodal
 
-        return _core
+        return _multimodal
     except ImportError:
         if is_in_ci():
             raise

test/registered/unit/server_args/test_server_args.py

@@ -2119,8 +2119,6 @@ class TestGrpcServerArgs(CustomTestCase):
         arg-parsing tests above never call start_server, so a stray kwarg (e.g.
         the removed max_prefill_tokens) would only surface as a TypeError at
         launch. This mocks the native extension and locks the kwarg set."""
-        import sys
-
         from sglang.srt.entrypoints import http_server
 
         fake_core = SimpleNamespace(start_server=MagicMock(return_value="handle"))
@@ -2128,13 +2126,14 @@ class TestGrpcServerArgs(CustomTestCase):
         server_args = SimpleNamespace(
             host="127.0.0.1", grpc_port=50051, grpc_worker_threads=4
         )
-        with patch.dict(
+        with (
-            sys.modules,
+            patch(
-            {
+                "sglang.srt.rust_extensions.load_rust_extension",
-                "sglang.srt.grpc": SimpleNamespace(_core=fake_core),
+                return_value=fake_core,
-                "sglang.srt.grpc._core": fake_core,
+            ) as load_rust_extension,
-                "sglang.srt.entrypoints.grpc_bridge": fake_bridge,
+            patch.dict(
-            },
+                "sys.modules", {"sglang.srt.entrypoints.grpc_bridge": fake_bridge}
+            ),
         ):
             handle = http_server._start_native_grpc_server_for_runtime(
                 server_args=server_args,
@@ -2144,6 +2143,7 @@ class TestGrpcServerArgs(CustomTestCase):
             )
 
         self.assertEqual(handle, "handle")
+        load_rust_extension.assert_called_once_with("sglang.srt.rust_extensions._grpc")
         _, kwargs = fake_core.start_server.call_args
         self.assertEqual(
             set(kwargs), {"host", "port", "runtime_handle", "worker_threads"}

test/registered/vlm/test_rust_native_mm_e2e.py

@@ -48,7 +48,7 @@ def solid_image_data_url(fmt):
 
 
 @unittest.skipIf(
-    importlib.util.find_spec("sglang.srt.server._core") is None,
+    importlib.util.find_spec("sglang.srt.rust_extensions._server") is None,
     "sglang-server rust extension not installed (e.g. AMD suite)",
 )
 class TestRustServerNativeMm(CustomTestCase):

test/registered/vlm/test_rust_native_mm_mmmu.py

@@ -98,7 +98,7 @@ class QwenGenerateVisionSampler(SamplerBase):
 
 
 @unittest.skipIf(
-    importlib.util.find_spec("sglang.srt.server._core") is None,
+    importlib.util.find_spec("sglang.srt.rust_extensions._server") is None,
     "sglang-server rust extension not installed (e.g. AMD suite)",
 )
 class TestRustNativeMmMMMU(CustomTestCase):