positional `<TARGET>` is a function name, not a file path. F

Error message

positional `<TARGET>` is a function name, not a file path. For a single-file source, use `--file {target}` and pass the function via `-f <NAME>`. For example:

    `baml pack --file {target} -f <NAME>`

What it means

validate_flags checks the positional `<TARGET>` with looks_like_path; if it resembles a file path, the command bails explaining that the positional is a function name, and that single-file sources must use `--file <path>` plus `-f <function-name>`.

Source

Thrown at baml_language/crates/baml_cli/src/pack_command.rs:236

        );
        Ok(crate::ExitCode::Success)
    }

    /// Validate flag combinations the clap-side `Args` derive can't catch.
    fn validate_flags(&self) -> Result<()> {
        if self.expression.is_some() {
            anyhow::bail!(
                "expression mode (`-e` / `--expression`) is not packageable; \
                 pass a positional `<TARGET>` or `-f <NAME>` instead."
            );
        }
        // `--file` and `--project` both name a source location. Reject the
        // combination up front instead of silently preferring one. Same rule
        // as `baml run`.
        validate_file_project_flags(self.file.as_deref(), self.from.as_deref())?;
        if let Some(target) = self.target.as_deref() {
            if looks_like_path(target) {
                anyhow::bail!(
                    "positional `<TARGET>` is a function name, not a file path. \
                     For a single-file source, use `--file {target}` and pass the \
                     function via `-f <NAME>`. For example:\n\
                     \n    `baml pack --file {target} -f <NAME>`\n",
                );
            }
            if !self.functions.is_empty() {
                anyhow::bail!(
                    "positional `<TARGET>` and `-f/--function` are mutually exclusive — \
                     use one or the other (positional packs a single-entry binary; \
                     `-f` produces a subcommand binary)."
                );
            }
        }
        if self.target.is_none() && self.functions.is_empty() {
            anyhow::bail!(
                "no target specified. Pass a positional `<TARGET>` to pack one \
                 function as the binary's only entry point, or one or more \

View on GitHub (pinned to bd85ce9dee)

Solutions

Pass just the function name: `baml pack myFunction`.
For a single-file source, use `baml pack --file path/to_file.baml -f myFunction`.
Keep project-rooted invocation (no path positional) and select targets via `-f`.

Example fix

// before
baml pack ./baml_src/prompt.baml
// after
baml pack --file ./baml_src/prompt.baml -f myFunction

Defensive patterns

Strategy: validation

Validate before calling

# guard: positional must not look like a path
TARGET="$1"
case "$TARGET" in */*|*.baml) echo "use --file $TARGET -f <NAME>"; exit 1;; esac

Prevention

Pass bare function names positionally to pack
Use --file for single-file sources with -f for the function
Avoid tab-completing .baml paths into the target slot

When it happens

Trigger: Run `baml pack some/path/to_file.baml` (or any path-looking positional) instead of a bare function name.

Common situations: Users familiar with `baml run <file.baml>` assuming pack takes a path, or tab-completing a .baml file into the positional slot.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/6ed1d8441c6c45cb. Report an issue: GitHub.