What causes "Enum not found: {}" in BoundaryML/baml?

Define the enum in the .baml schema, or upsert it first with tb.enum_("Color") and add at least one value.

Enum not found: {}

Error message

Enum not found: {}

What it means

Thrown by EnumBuilder::enm(), the resolver used by add_value, set_description, set_alias, alias, description and type_. If the enum is not in the runtime IR, the builder looks in the type-builder graph via maybe_get_enum; when it's absent from both, it bails with 'Enum not found'. You are operating on an enum that exists nowhere.

Source

Thrown at engine/language_client_cffi/src/raw_ptr_wrapper/type_builder/objects.rs:563

            mode: NodeRW::ReadOnly,
        }
    }

    fn mode(self, mode: NodeRW) -> Self {
        Self { mode, ..self }
    }

    fn enm(
        &self,
        rt: &BamlRuntime,
    ) -> anyhow::Result<std::sync::Arc<std::sync::Mutex<type_builder::EnumBuilder>>> {
        // if the IR defines the enum, then its always valid
        if rt.ir.find_enum(self.enum_name.as_str()).is_ok() {
            return Ok(self.type_builder.upsert_enum(self.enum_name.as_str()));
        }

        let Some(enm) = self.type_builder.maybe_get_enum(self.enum_name.as_str()) else {
            anyhow::bail!("Enum not found: {}", self.enum_name);
        };
        Ok(enm)
    }

    fn create_value(&self, name: &str, rt: &BamlRuntime) -> EnumValueBuilder {
        let target_mode = match self.mode {
            NodeRW::ReadOnly => NodeRW::ReadOnly,
            NodeRW::LLMOnly => NodeRW::LLMOnly,
            NodeRW::ReadWrite => {
                if let Ok(enm) = rt.ir.find_enum(self.enum_name.as_str()) {
                    if enm.find_value(name).is_some() {
                        NodeRW::LLMOnly
                    } else {
                        NodeRW::ReadWrite
                    }
                } else {
                    NodeRW::ReadWrite
                }

View on GitHub (pinned to bd85ce9dee)

Solutions

Define the enum in the .baml schema, or upsert it first with tb.enum_("Color") and add at least one value.
Correct the enum name spelling to match the schema.
Verify the enum wasn't renamed/removed in recent .baml changes.
Ensure you're using the same TypeBuilder/BamlRuntime the enum was registered on.

Example fix

// before
tb.enum("Collar").add_value(rt, "red")?; // enum 'Collar' doesn't exist
// after
tb.enum("Color").add_value(rt, "red")?;

Defensive patterns

Strategy: validation

Validate before calling

if rt.ir.find_enum("Color").is_err() {
    // upsert the enum and add values before calling add_value/description/alias
    tb.enum_("Color");
}

Try / catch

match enum_builder.add_value(rt, "red") {
    Err(e) if e.to_string().starts_with("Enum not found") => define_enum_first()?,
    other => other,
}

Prevention

Define enums in .baml or upsert them in the type builder before value operations.
Keep enum names as constants shared between schema and patch code.
Run a startup check that every enum referenced by runtime patches exists in the IR.

When it happens

Trigger: Calling tb.enum_("Color").add_value(...)/description(...)/alias(...) where enum Color is neither defined in any .baml file nor upserted via tb.enum_(...) with add_value in the current type builder.

Common situations: typos in the enum name; referencing an enum removed or renamed in the schema; building an enum dynamically but calling value-level methods before any registration; wrong 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

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/dbda9d7ee5f14d33. Report an issue: GitHub.