BoundaryML/baml · error

Class with name {name} does not exist

Error message

Class with name {name} does not exist

What it means

TypeBuilder::class looks up an existing class builder by name. If the class exists in the runtime IR but was not added to this TypeBuilder (maybe_get_class returns None), or does not exist at all, the lookup fails with this error.

Source

Thrown at engine/language_client_cffi/src/raw_ptr_wrapper/type_builder/objects.rs:101

    pub fn class(&self, rt: &BamlRuntime, name: &str) -> anyhow::Result<ClassBuilder> {
        match rt.ir.find_class(name) {
            Ok(cls) => {
                let _ = self.type_builder.upsert_class(name);
                let builder = ClassBuilder::new(self.type_builder.clone(), name.to_string());
                if !cls.item.attributes.dynamic() {
                    Ok(builder.mode(NodeRW::ReadOnly))
                } else {
                    Ok(builder.mode(NodeRW::ReadWrite))
                }
            }
            Err(_) => match self.type_builder.maybe_get_class(name) {
                Some(_) => Ok(ClassBuilder::new(
                    self.type_builder.clone(),
                    name.to_string(),
                )),
                None => {
                    anyhow::bail!("Class with name {name} does not exist");
                }
            },
        }
    }

    pub fn r#enum(&self, rt: &BamlRuntime, name: &str) -> anyhow::Result<EnumBuilder> {
        match rt.ir.find_enum(name) {
            Ok(enm) => {
                let _ = self.type_builder.upsert_enum(name);
                let builder = EnumBuilder::new(self.type_builder.clone(), name.to_string());
                if !enm.item.attributes.dynamic() {
                    return Ok(builder.mode(NodeRW::ReadOnly));
                }
                Ok(builder.mode(NodeRW::ReadWrite))
            }
            Err(_) => match self.type_builder.maybe_get_enum(name) {
                Some(_) => Ok(EnumBuilder::new(
                    self.type_builder.clone(),

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Add the class first with tb.add_class(rt, name) before looking it up
2. Verify the exact class name against the BAML source (case-sensitive)
3. Ensure you are using the same TypeBuilder instance the class was registered on

Example fix

// before
let cb = tb.class(rt, "Resum")?; // typo -> does not exist
// after
let cb = match tb.class(rt, "Resume") {
    Ok(cb) => cb,
    Err(_) => tb.add_class(rt, "Resume")?,
};

# verify name against known classes
assert "Resume" in known_class_names, f"class 'Resume' not defined"

try:
    cb = tb.class(name)
except Exception as e:
    if "does not exist" in str(e):
        cb = tb.add_class(rt, name)
    else:
        raise

When it happens

Trigger: Calling tb.class(rt, "Name") for a class name that is neither in the runtime IR nor in this TypeBuilder (typo, or the class was never added via add_class).

Common situations: Typo in the class name; calling .class() before add_class(); trying to modify a class registered on a different TypeBuilder instance.

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

• Class {} not found
• Class with name {name} already exists
• Enum with name {name} does not exist
• Class not found: {}
• Property not found: {} in class {}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/f2d991eb882de87d. Report an issue: GitHub.