What causes "--native-aot is only supported for C# projects (--lang csharp)" in clockworklabs/SpacetimeDB?

Remove --native-aot when the module is not C#

clockworklabs/SpacetimeDB · error · anyhow::Error

--native-aot is only supported for C# projects (--lang…

Error message

--native-aot is only supported for C# projects (--lang csharp)

What it means

--native-aot enables experimental NativeAOT-LLVM wasm compilation, which is implemented only for the C# module toolchain. If --lang selects rust or typescript as the server language, init refuses to continue. Note the check only inspects --lang; combined with --template it is skipped, so this fires on the --lang path.

Solutions

Remove --native-aot when the module is not C#
Or switch to `--lang csharp` (or `--lang c#`) and keep --native-aot
Remember AOT builds are currently Windows-only build hosts; plan CI accordingly

Example fix

# before
spacetime init myapp --lang rust --native-aot
# after
spacetime init myapp --lang rust

Defensive patterns

Strategy: validation

Prevention

Gate --native-aot on server language being csharp in your scaffolding scripts
Track that NativeAOT-LLVM building is Windows-only when planning CI

When it happens

Trigger: `spacetime init myapp --lang rust --native-aot` or `--lang typescript --native-aot`; automation that enables AOT for all projects regardless of language.

Common situations: Enabling a promising flag globally in scripts; copy-pasting a C#-oriented command and swapping the language; misreading AOT as a generic optimization.

Related errors

AI-assisted analysis of clockworklabs/SpacetimeDB@fdd647dfac (2026-08-20). Data as JSON: /api/errors/d915a1bc0e6b1b19. Report an issue: GitHub.

Appendix: source

Thrown at crates/cli/src/subcommands/init.rs:1784

    }

    let is_interactive = !options.non_interactive;
    let template = options.template.as_ref();
    let server_lang = options.lang.as_ref();
    let project_name_arg = options.project_name.as_ref();

    // Validate that template and lang options are not used together
    if template.is_some() && server_lang.is_some() {
        anyhow::bail!("Cannot specify both --template and --lang. Language is determined by the template.");
    }

    // Validate that --native-aot is only used with C# projects
    if options.native_aot {
        if let Some(lang) = server_lang
            && lang.to_lowercase() != "csharp"
            && lang.to_lowercase() != "c#"
        {
            anyhow::bail!("--native-aot is only supported for C# projects (--lang csharp)");
        }
        // Print warning about Windows-only support
        println!(
            "{}",
            "Note: NativeAOT-LLVM is experimental and building for this platform is currently only supported on Windows.".yellow()
        );
    }

    // Validate that --dotnet-version is only used with C# projects
    if options.dotnet_version.is_some()
        && let Some(lang) = server_lang
        && lang.to_lowercase() != "csharp"
        && lang.to_lowercase() != "c#"
    {
        anyhow::bail!("--dotnet-version is only supported for C# projects (--lang csharp)");
    }

    if !is_interactive {

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