BoundaryML/baml · error

`--file` and `--project` are mutually exclusive; `--file` al

Error message

`--file` and `--project` are mutually exclusive; `--file` already names the single source to load.

What it means

validate_file_project_flags enforces that `--file` and `--project` are mutually exclusive: both select a source location, and `--file` already means 'load exactly this one file'. Passing both is ambiguous, so the CLI refuses the invocation up front.

Source

Thrown at baml_language/crates/baml_cli/src/project_load.rs:26

use crate::reporter::Reporter;

/// The source location shape shared by `run`, `pack`, and `playground`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) enum SourceLocation {
    /// A resolved BAML project root discovered by walking up from `from` or cwd.
    Project { root: PathBuf, files: Vec<PathBuf> },
    /// A hermetic single-file source selected through `--file`.
    StandaloneFile { file: PathBuf, root: PathBuf },
}

/// `--file` and `--project` both name a source location.
pub(crate) fn validate_file_project_flags(
    file: Option<&Path>,
    project: Option<&Path>,
) -> Result<()> {
    if file.is_some() && project.is_some() {
        anyhow::bail!(
            "`--file` and `--project` are mutually exclusive; `--file` already names \
             the single source to load."
        );
    }
    Ok(())
}

/// Resolve the CLI source location exactly like `baml run` project/file mode.
pub(crate) fn resolve_source_location(
    from: Option<&Path>,
    file: Option<&Path>,
    reporter: Option<&Reporter>,
) -> Result<SourceLocation> {
    validate_file_project_flags(file, from)?;

    if let Some(file) = file {
        let canonical = resolve_standalone_file(file)?;
        let root = canonical

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Remove --project and keep only --file to compile/test a single standalone file.
2. Remove --file and keep only --project to load the whole project.
3. If a wrapper script adds --project conditionally, gate it so it's omitted whenever --file is supplied.

Example fix

// before
baml dev --project ./baml_src --file ./baml_src/main.baml

// after
baml dev --file ./baml_src/main.baml

#!/usr/bin/env bash
EXTRA=()
[ -n "$FILE" ] && EXTRA+=(--file "$FILE")
[ -z "$FILE" ] && [ -n "$PROJECT" ] && EXTRA+=(--project "$PROJECT")
baml dev "${EXTRA[@]}"

When it happens

Trigger: Any CLI command (baml dev/test/validate via validate_flags, resolve_source_location, run_with_reporter, or test_run_allows_file_with_omitted_from) invoked with both a --file path and a --project path set at the same time.

Common situations: Shell scripts accumulating flags where --project is always passed and --file is appended conditionally; copying an example command line and adding --file; an alias wrapping the command with --project baked in.

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

• `--sdk-import-path` is only valid for the Go generator
• compilation failed: {e:?}
• expression mode (`-e` / `--expression`) is not packageable;
• positional `<TARGET>` is a function name, not a file path. F
• no `.baml` files found in {}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/e4598317bc2d5406. Report an issue: GitHub.