optional pre-release identifier in app version must be…

Error message

optional pre-release identifier in app version must be numeric-only and cannot be greater than 65535 for msi target

What it means

convert_version in the WiX MSI bundler can represent a semver pre-release only if the pre-release identifier parses as a single number ≤ 65535, which it then appends as the 4th MSI field. Any other pre-release (e.g. "beta", "rc.1", or a number above 65535) fails this check and bails, because MSI versions must be purely numeric.

Solutions

Use a purely numeric pre-release ≤ 65535 (e.g. "2.0.0-3") if you need MSI pre-release versions
Drop the pre-release tag for msi builds ("2.0.0") and track the channel elsewhere
Normalize the version in CI: map textual pre-releases (beta, rc) to numeric equivalents before tauri build

Example fix

// before (tauri.conf.json)
"version": "2.0.0-beta.3"
// after
"version": "2.0.0-3"

Defensive patterns

Strategy: validation

Validate before calling

fn msi_prerelease_ok(v: &str) -> bool {
  match v.split_once('-') {
    None => true,
    Some((_, pre)) => {
      let pre = pre.split('+').next().unwrap_or("");
      pre.parse::<u64>().map(|n| n <= 65535).unwrap_or(false)
    }
  }
}

Try / catch

match bundle_msi(cfg) {
  Err(e) if e.to_string().contains("pre-release") => eprintln!("use numeric pre-release or drop it for msi"),
  Err(e) => eprintln!("bundling failed: {e}"),
  Ok(_) => {},
}

Prevention

For MSI pre-releases use numeric-only tags like "1.2.3-1"
Drop textual tags (beta/rc) for msi targets and encode the channel in the product name
Normalize versions in CI with a mapping step before bundling

When it happens

Trigger: Bundling an msi with a version like "1.2.3-beta", "1.2.3-rc.1", or "1.2.3-70000" — a pre-release identifier that is non-numeric or exceeds 65535 — via build_wix_app_installer.

Common situations: Publishing beta/RC builds to Windows testers ("2.0.0-beta.3"); release channels using textual pre-release tags; semver pre-releases with multiple dot-separated identifiers.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of tauri-apps/tauri@460ec35447 (2026-09-18). Data as JSON: /api/errors/a8b022841735ed87. Report an issue: GitHub.

Appendix: source

Thrown at crates/tauri-bundler/src/bundle/windows/msi/mod.rs:368

        "{}.{}.{}.{}",
        version.major, version.minor, version.patch, version.build
      ));
    } else {
      crate::error::bail!(
        "optional build metadata in app version must be numeric-only and cannot be greater than 65535 for msi target"
      );
    }
  }

  if !version.pre.is_empty() {
    let pre = version.pre.parse::<u64>();
    if pre.is_ok() && pre.unwrap() <= 65535 {
      return Ok(format!(
        "{}.{}.{}.{}",
        version.major, version.minor, version.patch, version.pre
      ));
    } else {
      crate::error::bail!(
        "optional pre-release identifier in app version must be numeric-only and cannot be greater than 65535 for msi target"
      );
    }
  }

  Ok(version_str.to_string())
}

/// Runs the Candle.exe executable for Wix. Candle parses the wxs file and generates the code for building the installer.
fn run_candle(
  settings: &Settings,
  wix_toolset_path: &Path,
  cwd: &Path,
  wxs_file_path: PathBuf,
  extensions: Vec<PathBuf>,
) -> crate::Result<()> {
  let arch = match settings.binary_arch() {
    Arch::X86_64 => "x64",

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