invalid compose project_name '{name}': use lowercase letters

Error message

invalid compose project_name '{name}': use lowercase letters, digits, dashes, and underscores

What it means

mise's compose integration validates the compose project_name from configuration. Project names must start with an ASCII lowercase letter or digit and contain only lowercase letters, digits, dashes, and underscores, matching Docker Compose naming rules. The library throws this error when a configured project name violates those character constraints.

Source

Thrown at src/system/compose.rs:1126

    Ok(std::iter::once(resolved.to_string_lossy().to_string())
        .chain(args.iter().cloned())
        .collect())
}

fn validate_project_name(name: Option<&str>) -> Result<()> {
    let Some(name) = name else {
        return Ok(());
    };
    if name.is_empty()
        || !name
            .chars()
            .next()
            .is_some_and(|character| character.is_ascii_lowercase() || character.is_ascii_digit())
        || !name.chars().all(|character| {
            character.is_ascii_lowercase() || character.is_ascii_digit() || "-_".contains(character)
        })
    {
        bail!(
            "invalid compose project_name '{name}': use lowercase letters, digits, dashes, and underscores"
        );
    }
    Ok(())
}

fn parse_dependency(value: &str) -> Result<ResourceId> {
    let Some((kind, name)) = value.split_once(':') else {
        bail!("invalid compose dependency '{value}': expected '<kind>:<name>'");
    };
    if name.is_empty()
        || !matches!(
            kind,
            "package" | "file" | "directory" | "service" | "user" | "group"
        )
    {
        bail!(
            "invalid compose dependency '{value}': supported kinds are package, file, directory, service, user, and group"

View on GitHub (pinned to afd2eddd3a)

Solutions

Rename the project_name to use only lowercase letters, digits, dashes, and underscores
Ensure the first character is a lowercase letter or digit
Remove uppercase letters, dots, spaces, and other punctuation from the name

Example fix

// before (mise.toml)
[compose]
project_name = "My.Project"
// after
[compose]
project_name = "my-project"

Defensive patterns

Strategy: validation

Validate before calling

fn valid_project_name(name: &str) -> bool {
    name.chars().next().is_some_and(|c| c.is_ascii_lowercase() || c.is_ascii_digit())
        && name.chars().all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '-' || c == '_')
}

Prevention

Keep project names lowercase-kebab-case by convention
Never reuse names containing dots or uppercase from other tools
Check the first character is alphanumeric before saving config

When it happens

Trigger: A compose project_name in mise.toml starts with a dash/underscore, contains uppercase letters, spaces, dots, slashes, or other symbols, or is empty/invalid at the first character.

Common situations: Users copy a Docker Compose project name like 'MyProject' or 'my.project' from docker-compose usage; camelCase names or names with spaces/periods from other tools are pasted into mise.toml.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/f36c6d5f21f8cc51. Report an issue: GitHub.