BoundaryML/baml · error

Enum {} does not exist

Error message

Enum {} does not exist

What it means

Thrown by find_enum_value in the BAML runtime's output-format renderer when an enum referenced in a prompt/output schema neither exists in the IR nor has a runtime override. The renderer walks the intermediate representation (IR) to render enums for the LLM output contract; if the enum walker errored (enum not in the schema) and no RuntimeEnumOverride was supplied, it bails immediately.

Source

Thrown at engine/baml-runtime/src/internal/prompt_renderer/render_output_format.rs:180

    }

    let name = Name::new_with_alias(field_name.to_string(), alias.value());
    let desc = desc.value();
    let r#type = field_walker.r#type();
    let needed = needed.value().unwrap_or(false);

    Ok(Some((name, r#type.clone(), desc, needed)))
}

fn find_enum_value(
    enum_name: &str,
    value_name: &str,
    enum_walker: &Result<EnumWalker<'_>>,
    overrides: &Option<&RuntimeEnumOverride>,
    ctx: &RuntimeContext,
) -> Result<Option<(Name, Option<String>)>> {
    if enum_walker.is_err() && overrides.is_none() {
        anyhow::bail!("Enum {} does not exist", enum_name);
    }

    let value_walker = match enum_walker {
        Ok(e) => e.find_value(value_name),
        Err(_) => None,
    };

    let value_overrides = overrides.map(|o| o.values.get(value_name)).flatten();

    if value_overrides.is_none() && value_walker.is_none() {
        anyhow::bail!("Enum {} does not have a value: {}", enum_name, value_name);
    }

    let mut skip = OverridableValue::Unset;
    let mut alias = OverridableValue::Unset;
    let mut desc = OverridableValue::Unset;
    if let Some(attrs) = value_overrides {
        match attrs.skip {

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check the enum name referenced by the response model for typos and confirm it is defined in a .baml file included in the project.
2. If the enum is intentionally dynamic (test/eval overrides), pass a RuntimeEnumOverride containing that enum in the RuntimeContext.
3. Re-run baml-cli generate / refresh the runtime so the IR includes newly added enums.
4. If the enum was renamed, update all classes/enums referencing the old name.

Example fix

// before (baml)
class Output {
  category Category // Category not defined
}
// after
enum Category { A B }
class Output {
  category Category
}

// before rendering, confirm every enum type used in output schema exists
// (pseudo: iterate schema fields, check runtime.ir().find_enum(name).is_ok())
if runtime.ir().find_enum("Category").is_err() && override_for("Category").is_none() {
    panic!("Enum Category missing from schema and overrides");
}

fn enum_exists(runtime: &BamlRuntime, name: &str) -> bool {
    runtime.ir().find_enum(name).is_ok()
}

When it happens

Trigger: Rendering output format for a response model whose field type references an enum name not present in any BAML schema file, and no RuntimeEnumOverride was passed via RuntimeContext (e.g. test-case or client overrides).

Common situations: Typo in the enum name in a class field; enum defined in a file not included in the BAML source set; renaming/deleting an enum while tests or clients still reference it; relying on dynamic overrides but forgetting to provide them.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Enum {} does not have a value: {}
• Enum {} not found
• Schema inconsistency: {message}
• Unknown enum: {0}
• Enum '{0}' not found

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/90e5cb908136b93c. Report an issue: GitHub.