clockworklabs/SpacetimeDB · error

Unsupported --dotnet-version {version}. Supported values: 8,

Error message

Unsupported --dotnet-version {version}. Supported values: 8, 10.

What it means

The --dotnet-version CLI argument is parsed by parse_dotnet_version (crates/cli/src/common_args.rs:70), which accepts only the literal integers 8 and 10 (the .NET SDK majors supported for generated C# projects). Any other number bails with this message; non-numeric values fail separately with 'Invalid --dotnet-version'.

Source

Thrown at crates/cli/src/common_args.rs:70

        .require_equals(true)
        .default_missing_value("always")
        .help(
            "When publishing to an existing database identity, first DESTROY all data associated with the module. With 'on-conflict': only when breaking schema changes occur."
        )
}

pub fn dotnet_version() -> Arg {
    Arg::new("dotnet_version")
        .long("dotnet-version")
        .value_name("VERSION")
        .value_parser(parse_dotnet_version)
        .help("Target .NET SDK major version for C# projects (e.g. 8 or 10). Auto-detected when omitted.")
}

pub fn parse_dotnet_version(version: &str) -> anyhow::Result<u8> {
    match version.parse::<u8>() {
        Ok(version @ (8 | 10)) => Ok(version),
        Ok(version) => anyhow::bail!("Unsupported --dotnet-version {version}. Supported values: 8, 10."),
        Err(error) => anyhow::bail!("Invalid --dotnet-version: {error}"),
    }
}

pub fn parse_optional_dotnet_version(dotnet_version: Option<&str>) -> anyhow::Result<Option<u8>> {
    dotnet_version.map(parse_dotnet_version).transpose()
}

#[cfg(test)]
mod tests {
    use super::parse_optional_dotnet_version;

    #[test]
    fn dotnet_version_accepts_supported_sdk_majors() {
        assert_eq!(parse_optional_dotnet_version(None).unwrap(), None);
        assert_eq!(parse_optional_dotnet_version(Some("8")).unwrap(), Some(8));
        assert_eq!(parse_optional_dotnet_version(Some("10")).unwrap(), Some(10));
    }

View on GitHub (pinned to 524b4487d9)

Solutions

1. Use exactly 8 or 10: spacetime generate --lang csharp --dotnet-version 10
2. Omit the flag — the CLI auto-detects the installed .NET SDK
3. If you must target another TFM, generate with defaults and adjust the .csproj yourself (unsupported)

Example fix

# before
spacetime generate --lang csharp --dotnet-version 9 --project-dir ./csharp

# after
spacetime generate --lang csharp --dotnet-version 10 --project-dir ./csharp

# Validate before invoking the CLI:
SUPPORTED=(8 10)
if ! printf '%s\n' "${SUPPORTED[@]}" | grep -qx "$DOTNET_VERSION"; then
  echo "--dotnet-version must be one of: ${SUPPORTED[*]}" >&2; exit 2
fi
spacetime generate --lang csharp --dotnet-version "$DOTNET_VERSION" --project-dir ./csharp

const isSupportedDotnetVersion = (v: string): v is '8' | '10' => v === '8' || v === '10';

When it happens

Trigger: Running spacetime generate --lang csharp --dotnet-version 9 (or 6, 7, 11); passing '8.0' also fails, but as the parse error rather than this branch.

Common situations: Teams standardized on .NET 9 assuming it is supported; CI pipelines parameterizing the version and passing an unsupported value; writing 8.0 instead of 8.

Related errors

• --native-aot is only supported for C# projects (--lang cshar
• Unsupported .NET SDK version: {major}. SpacetimeDB requires
• Failed to read directory {}: {}
• uuid counter must be non-negative
• Expected ConnectionId hex string to be 32 characters long, b

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/9d6be28be2aa517f. Report an issue: GitHub.