BoundaryML/baml · error

function `{function_name}` not found

Error message

function `{function_name}` not found

What it means

Runtime lookup failure in `baml run`: the target named on the command line (or via a script's --function) does not match any function declared in the loaded BAML project. The engine's find_user_function returned nothing before execution could start — the name may be misspelled, missing the user. prefix convention, or defined in a file outside the project root.

Source

Thrown at baml_language/crates/baml_cli/src/run_command.rs:570

                    target,
                    &project_root,
                ));
            };

        // Patch `argv[1]` to the engine-canonical display name (strips
        // `user.` prefix) so scripts and the direct path agree.
        if let Some(info) = engine.find_user_function(&function_name) {
            let display = info.display_name.clone();
            let mut patched: Vec<String> = engine.argv().to_vec();
            if patched.len() >= 2 && (was_script || display != *target) {
                patched[1] = display;
                engine.set_argv(patched);
            }
        }

        let func_info = engine
            .find_user_function(&function_name)
            .ok_or_else(|| anyhow!("function `{function_name}` not found"))?;
        baml_exec::validate_help_param(&engine, &function_name)?;

        let target_is_typed = !func_info.param_names.is_empty();
        let parsed = if target_is_typed {
            let display = function_name
                .strip_prefix("user.")
                .unwrap_or(&function_name);
            let bin_name = format!("baml run {display} --");
            match baml_exec::parse_target_argv(
                &bin_name,
                &function_name,
                &func_info,
                &effective_target_args,
            ) {
                Ok(p) => p,
                Err(err) => return surface_clap_error(reporter, err),
            }
        } else {

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check the function name spelling and that it exists in the loaded `.baml` sources
2. List available functions and pick the correct one
3. Ensure the file defining the function is inside the project root so it is compiled

Example fix

// before
baml run --file baml_src/main.baml -f MyFuntion
// after
baml run --file baml_src/main.baml -f MyFunction

const fns = engine.user_functions().map(f => f.qualified_name.replace(/^user\./, '')); if (!fns.includes(name)) throw new Error(`function '${name}' not found; available: ${fns.join(', ')}`);

When it happens

Trigger: `run_single_target` calls `engine.find_user_function(&function_name)` and receives None — the name came from `--function`/`-f` or a script expansion.

Common situations: Typo in the function name; the function exists in a different `.baml` file not included in the project; prefixing mistakes (functions are qualified like `user.<name>`); a script in `baml.toml` referencing a deleted function.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• function `{target_name}` not found
• LLM function not found: {}: {}
• no BAML project found; run `baml init` before adding a gener
• `{}` has no baml.toml; run `baml init` before adding a gener
• compilation failed: {e:?}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/828da57858b66bfb. Report an issue: GitHub.