BoundaryML/baml · error

LLM Function {} not found

Error message

LLM Function {} not found

What it means

When the REPL evaluates a function-call expression, it looks up the function's parameter names in the runtime's function table; if the name is absent the call is rejected with this error. The runtime has no LLM function registered under that identifier.

Source

Thrown at engine/baml-runtime/src/cli/repl.rs:547

        let run_id = self.current_run_id.unwrap_or(0);
        let handle_llm_function = move |function_name: String,
                                        args: Vec<BamlValue>,
                                        _watch_context: Option<
            baml_compiler::thir::interpret::WatchStreamContext,
        >| {
            let fn_params = fn_params.clone();
            let runtime_clone = runtime_clone.clone();
            let env_vars = env_vars.clone();
            let status_tx = status_tx.clone();
            async move {
                match runtime_clone.as_ref() {
                    Some(runtime) => {
                        if let Some(tx) = &status_tx {
                            let _ = tx.send(LlmStatusEvent::Started(run_id, function_name.clone()));
                        }
                        let param_names = fn_params
                            .get(&function_name)
                            .ok_or_else(|| anyhow!("LLM Function {} not found", function_name))?;
                        let args = args
                            .clone()
                            .into_iter()
                            .zip(param_names.iter())
                            .map(|(arg, name)| (name.clone(), arg.clone()))
                            .collect();
                        let cxt =
                            runtime.create_ctx_manager(BamlValue::String("none".to_string()), None);
                        let status_tx2 = status_tx.clone();
                        let res = runtime
                            .call_function(
                                function_name,
                                &args,
                                &cxt,
                                None,
                                None,
                                None,
                                env_vars,

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check the exact function name spelling against your .baml files
2. Run :load <path-to-baml_src> to (re)load sources containing the function
3. Use :functions (or :help) to list functions the runtime currently knows
4. Verify the loaded directory is the correct baml_src folder

Example fix

// before (REPL input)
:MyFucn(1)
// after
:load ./baml_src
MyFunc(1)

// Before calling, confirm the function exists in loaded sources
// grep the loaded baml_src: grep -r "function MyFunc" baml_src/
// At the REPL, check available functions first (see :help)

match result { Err(e) if e.to_string().contains("not found") => eprintln!("Load sources first: :load ./baml_src ({e})"), other => { let _ = other; } }

When it happens

Trigger: Evaluating FunctionName(args) at the REPL when fn_params has no entry for that name — i.e. the function is not defined in the loaded BAML sources or was not reloaded after defining it.

Common situations: Typos in the function name, calling a function defined in a .baml file that was edited but not :load-reloaded, calling a function from a project whose baml_src was never loaded.

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

• No BAML sources loaded. Use :load <path> to load sources.
• Type error: {}
• Failed to parse function result: {}
• No parsed result available from function call
• No runtime loaded, it should be impossible to call an LLM fu

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/e9cb912f6c1afc4d. Report an issue: GitHub.