sgl-project/sglang · error · ValueError

multiple Cargo packages under {workspace} declare python mod

Error message

multiple Cargo packages under {workspace} declare python module {python_module!r}: {sorted(crate.package for crate in matches)}

What it means

Multiple Cargo packages in the workspace declare the same python-module in their sglang metadata, making crate discovery ambiguous; the message lists the conflicting package names.

Source

Thrown at python/sglang/srt/rust_extensions/loader.py:199

        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(),

View on GitHub (pinned to 0132848349)

Solutions

1. Remove or rename the python-module metadata in all but one crate
2. If both crates are legitimate, give them distinct python-module values and import the right one
3. Search the workspace: grep for the module string across Cargo.toml files

import tomllib, pathlib, collections
counts = collections.Counter()
for p in pathlib.Path(ws).rglob("Cargo.toml"):
    d = tomllib.loads(p.read_text())
    m = d.get("package",{}).get("metadata",{}).get("sglang",{}).get("python-module")
    if m: counts[m] += 1
assert counts[python_module] == 1

When it happens

Trigger: Two crates both contain `[package.metadata.sglang] python-module = "<same module>"` (e.g. after copy-pasting a crate or a botched rename leaving the old manifest behind).

Common situations: Duplicating a crate directory without updating metadata; vendored fork coexisting with the original in one workspace.

Related errors

• no Cargo package under {workspace} declares `[package.metada
• Rust workspace for {python_module} was not found at {workspa
• Multiple serve backends matched this request: {names}. Selec
• {name} must have dtype torch.int32
• {name} must be on the same device as block sparse tensors

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/b2d0f28c0afe2687. Report an issue: GitHub.