slint-ui/slint · warning

Could not load the slint-dev development binary

Error message

Could not load the slint-dev development binary: ${error}

What it means

This Python UserWarning from `_load_native` means the `slint-dev` package is installed and version-matched, but `importlib.import_module("slint_dev_native")` raised ImportError — its compiled native binary is unavailable on this platform. Slint then falls back to the lean release binary, so functionality continues without system-testing/MCP support.

Solutions

1. Check `pip show slint-dev` and reinstall: `pip install --force-reinstall slint-dev`
2. Verify a native wheel exists for your platform/Python version; if not, accept the fallback or remove slint-dev
3. Check `python -c "import slint_dev_native"` to see the underlying ImportError detail
4. Use an officially supported platform/Python combination

Example fix

// before (terminal)
# slint-dev installed, but import fails on unsupported platform
# after
pip uninstall slint-dev  # rely on the lean release binary

try:
    import slint_dev_native  # noqa
except ImportError as e:
    print(f"slint-dev native unavailable: {e}; release binary will be used")

import warnings
with warnings.catch_warnings(record=True) as caught:
    import slint
native_failed = any("slint-dev development binary" in str(w.message) for w in caught)
if native_failed:
    # proceed with the lean release binary; no system-testing/MCP

When it happens

Trigger: `slint-dev` is installed at the matching version but `import slint_dev_native` fails because no prebuilt native wheel exists for the current platform/Python version, or the wheel is broken/incomplete.

Common situations: Running on an unsupported architecture (e.g. musl, aarch64 variants without wheels), a Python version newer than available dev wheels, corrupted installs, or missing shared-library dependencies on the system.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• Callback ' ' cannot be used with a callback decorator for…
• Callback ' ' cannot be used with a callback decorator for…
• Callback ' ' in global ' ' cannot be used with a callback…
• Callback ' ' in global ' ' cannot be used with a callback…
• Could not compile

AI-assisted analysis of slint-ui/slint@bb937076de (2026-09-16). Data as JSON: /api/errors/51186c2c1cf0db1c. Report an issue: GitHub.

Appendix: source

Thrown at api/python/slint/slint/_native.py:61

        except importlib.metadata.PackageNotFoundError:
            dev_version = None

        if dev_version is not None:
            own_version = importlib.metadata.version("slint")
            if dev_version != own_version:
                warnings.warn(
                    f"Ignoring slint-dev {dev_version}: it does not match slint "
                    f"{own_version}. Install slint-dev=={own_version} to enable the "
                    "development binary with system-testing and MCP support.",
                    stacklevel=2,
                )
            else:
                try:
                    return importlib.import_module("slint_dev_native")
                except ImportError as error:
                    # Installed, but its native binary is unavailable on this
                    # platform. Fall back to the lean release binary.
                    warnings.warn(
                        f"Could not load the slint-dev development binary: {error}",
                        stacklevel=2,
                    )

    from . import slint as native

    return native


if TYPE_CHECKING:
    # Both binary variants expose the same surface, so type-check against the
    # bundled extension's stub (slint.pyi).
    from . import slint as native
else:
    native = _load_native()

View on GitHub (pinned to bb937076de)