BoundaryML/baml · error

`-e` is not compatible with `--file`. Expression mode…

Error message

`-e` is not compatible with `--file`. Expression mode evaluates inline source; remove one of the two.

What it means

`baml run -e` evaluates inline source, while `--file` changes which source files are loaded. The CLI rejects this combination up front because expression mode short-circuits project/file loading, so `--file` would silently do nothing.

Solutions

1. Remove the `--file <path>` argument and keep `-e <expr>`
2. Remove the `-e <expr>` argument and rely on `--file` plus a function target

Example fix

// before
baml run --file baml_src/main.baml -e 'test()'
// after
baml run -e 'test()'

if (args.includes('-e') && (args.includes('--file') || args.some(a => a.startsWith('--file=')))) { throw new Error('Remove either -e or --file'); }

When it happens

Trigger: Invoking `baml run` with both an expression passed via `-e <expr>` and a file passed via `--file <path>`.

Common situations: A developer combining an example expression snippet with an existing `--file` invocation, or scripting a command that templated both flags.

Understand the failure class

Background: "mutually exclusive" flag errors: what "can't supply both nx and xx", "--raw is not compatible with -i" and "cannot be used with" mean, and how to fix them — this error's family across 29 libraries.

Related errors

• `-e` is not compatible with `--list`. Expression mode…
• are mutually exclusive dispatch modes — pick one.
• {bail_context}
• Cannot generate HIR/bytecode due to validation errors
• compilation failed

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/285958c1414b0379. Report an issue: GitHub.

Appendix: source

Thrown at baml_language/crates/baml_cli/src/run_command.rs:419

        if used.len() > 1 {
            anyhow::bail!(
                "{} are mutually exclusive dispatch modes — pick one.",
                used.join(" and ")
            );
        }

        // `--file` is the standalone-source alternative to `--project`. Both
        // pointing at sources would be ambiguous (which one wins?), so
        // reject an explicit combination up front.
        validate_file_project_flags(self.file.as_deref(), self.from.as_deref())?;

        // Expression mode short-circuits before reaching project / file
        // loading, so combining `-e` with surfaces that change *what* is
        // loaded silently does nothing. Reject up front to avoid the
        // footgun.
        if self.expression.is_some() {
            if self.file.is_some() {
                anyhow::bail!(
                    "`-e` is not compatible with `--file`. Expression mode \
                     evaluates inline source; remove one of the two."
                );
            }
            if self.list {
                anyhow::bail!(
                    "`-e` is not compatible with `--list`. Expression mode \
                     evaluates an expression; `--list` enumerates targets — \
                     pick one."
                );
            }
        }

        if let Some(expr_source) = &self.expression {
            // `-e -` reads stdin / `-e @file` reads file. Load once so
            // the engine compile and `argv[1]` see the same text.
            let expr_body = load_expression_source(expr_source)?;
            return self.run_expression(&expr_body, reporter);

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