sgl-project/sglang · error · RuntimeError

Multiple distributions register serve backend {name!r}: {pro

Error message

Multiple distributions register serve backend {name!r}: {providers}. Uninstall one provider or choose another backend name.

What it means

Raised when more than one installed distribution registers a serve backend under the same name in the 'sglang.serve_backends' entry-point group. SGLang cannot disambiguate which implementation to load, so it refuses with a RuntimeError naming the conflicting provider distributions.

Source

Thrown at python/sglang/cli/serve_backends.py:137

    def get(self, name: str) -> RegisteredServeBackend:
        """Return one backend, importing only the explicitly requested plugin."""

        if name in self._loaded:
            return self._loaded[name]

        candidates = self._entry_points.get(name, [])
        if not candidates:
            available = ", ".join(("auto", *self.available_names))
            raise ValueError(
                f"Unknown serve backend {name!r}. Available values: {available}."
            )
        if len(candidates) > 1:
            providers = ", ".join(
                sorted(
                    self._entry_point_provider(candidate) for candidate in candidates
                )
            )
            raise RuntimeError(
                f"Multiple distributions register serve backend {name!r}: "
                f"{providers}. Uninstall one provider or choose another backend name."
            )

        entry_point = candidates[0]
        try:
            factory = entry_point.load()
            if not callable(factory):
                raise TypeError("the entry point must resolve to a callable factory")
            backend = factory()
        except Exception as exc:
            raise RuntimeError(
                f"Failed to load serve backend {name!r} from "
                f"{self._entry_point_provider(entry_point)}: {exc}"
            ) from exc

        if not isinstance(backend, ServeBackend):
            raise TypeError(

View on GitHub (pinned to 0132848349)

Solutions

pip uninstall one of the conflicting distributions listed in the error message, then retry.
Use a different backend name for the local fork (rename its entry point) so both can coexist.
Verify with `importlib.metadata.entry_points(group='sglang.serve_backends')` that only one candidate remains per name.

Example fix

# before: both sglang-plugin-x and sglang-plugin-x-fork register backend "x"
# after
pip uninstall sglang-plugin-x-fork  # or rename its entry point to "x-dev"

Defensive patterns

Strategy: validation

Validate before calling

from importlib.metadata import entry_points
eps = entry_points(group="sglang.serve_backends")
names = {}
for ep in eps:
    names.setdefault(ep.name, []).append(ep)
amb = {n: ps for n, ps in names.items() if len(ps) > 1}
assert not amb, f"ambiguous backends: {amb}"

Type guard

def is_unambiguous(name: str) -> bool:
    return len(list(entry_points(group="sglang.serve_backends", name=name))) <= 1

Try / catch

try:
    backend = registry.get(name)
except RuntimeError as e:
    if "Multiple distributions" in str(e):
        # print providers, ask user to uninstall one
        ...

Prevention

In CI, assert exactly one entry point per backend name after installing dependencies.
Use a dedicated venv per backend-fork to avoid co-installing duplicate providers.
Name forked backend entry points distinctly (e.g. x-dev) instead of shadowing.

When it happens

Trigger: Two distributions (e.g. an upstream plugin and a local fork, or a renamed package where both old and new are installed) each declare the same backend name in the sglang.serve_backends entry-point group; calling registry.get(name) for that name.

Common situations: Developing a fork of a backend plugin alongside the published one; pip install -e . of a local copy while the PyPI version is still installed; package renames leaving duplicate metadata behind.

Related errors

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/0a10e99254a031e1. Report an issue: GitHub.