user service '{}': environment key {key:?} cannot be set thr

Error message

user service '{}': environment key {key:?} cannot be set through cmd.exe

What it means

On Windows, when a user service request sets environment variables, they are injected by prefixing the command with `set "KEY=VALUE"` executed through cmd.exe. Some characters are illegal or structurally impossible in a cmd.exe environment-variable name, so exec_action rejects them at XML render time rather than emitting a broken service definition.

Source

Thrown at src/system/scheduled_tasks.rs:207

    }
    out.push_str("    </Exec>\n  </Actions>\n");
    out.push_str("</Task>\n");
    Ok(out)
}

/// Split the command line into the executable and its arguments. Task
/// Scheduler has no environment block, so variables are set through
/// `cmd.exe`, which reinterprets some characters; values that it would
/// change are rejected rather than passed through differently.
fn exec_action(request: &ScheduledTaskRequest) -> Result<(String, String)> {
    let (program, args) = split_command(&request.command);
    if request.environment.is_empty() {
        return Ok((program, args));
    }
    let mut sets = vec![];
    for (key, value) in &request.environment {
        if key.is_empty() || key.contains(['=', '"', '%', '\n', '\r']) {
            bail!(
                "user service '{}': environment key {key:?} cannot be set through cmd.exe",
                request.name
            );
        }
        if let Some(c) = value
            .chars()
            .find(|c| matches!(c, '"' | '%' | '&' | '|' | '<' | '>' | '^' | '\n' | '\r'))
        {
            bail!(
                "user service '{}': environment value for {key} contains {c:?}, which cmd.exe would reinterpret; set it inside the program instead",
                request.name
            );
        }
        sets.push(format!("set \"{key}={value}\""));
    }
    // the command line goes through cmd.exe too: what it would split or
    // chain is rejected the same way, rather than run differently
    if let Some(c) = format!("{program} {args}")

View on GitHub (pinned to afd2eddd3a)

Solutions

Remove or fix the offending environment key: it must be a non-empty name without '=', '"', '%', or line breaks.
Strip whitespace/CR-LF from keys when loading environment from files or templates.
Pass such settings to the program another way (config file, arguments) instead of as a cmd.exe environment variable.
Validate the environment map before constructing the service request.

Example fix

// before
request.environment.insert("PATH=C:\\bin".into(), "x".into());
// after
request.environment.insert("BIN_DIR".into(), "C:\\bin".into());

Defensive patterns

Strategy: validation

Validate before calling

fn valid_env_key(key: &str) -> Result<(), String> {
    if key.is_empty() || key.contains(['=', '"', '%', '\n', '\r']) {
        return Err(format!("invalid env key: {key:?}"));
    }
    Ok(())
}

Prevention

Trim and sanitize keys when loading env maps from files (strip BOM, CRLF, whitespace)
Never build keys by string concatenation of config fragments
Reject or log non-conforming keys at config-parse time, not at service-render time
Prefer simple [A-Za-z_][A-Za-z0-9_]* key names

When it happens

Trigger: Calling render_xml (via exec_action) for a scheduled-task/user-service whose request.environment contains a key that is empty or contains '=', a double quote, '%', a newline, or a carriage return.

Common situations: Copy-pasting env entries with stray whitespace or an embedded '=' from a .env file line; programmatic env maps that include empty-string keys; values loaded from files with CRLF endings where keys picked up a trailing '\r'; templating that interpolates '%' into names.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/42dc2e23554ef579. Report an issue: GitHub.