BoundaryML/baml · critical

error decoding value, checked type not found:

Error message

error decoding value, checked type not found: 

What it means

After decoding a checked value's payload and checks, the decoder looks up the checked type's Go type by name in the supplied TypeMap. If the name is absent, it panics, because it cannot construct the target struct holding Value and Checks fields. This means the TypeMap generated from the BAML schema does not know this checked type.

Solutions

1. Run `baml-cli generate` (or your build step) to regenerate baml_client after schema changes
2. Ensure the Go binary is rebuilt after regeneration so the new TypeMap is compiled in
3. Verify check/assert names in the .baml schema match those the client was generated with
4. Align baml_go bindings and BAML runtime versions

Example fix

// before (stale generated client after adding a check)
// after
// terminal: baml-cli generate && go build ./...

if _, ok := typeMap.GetType(checkedName); !ok { return fmt.Errorf("type %v missing; regenerate client", checkedName) }

defer func() { if r := recover(); r != nil { return fmt.Errorf("checked type not in typemap: %v", r) } }()

When it happens

Trigger: Decode() on a CFFIValueChecked whose Name is not registered in typeMap — typically when generated client types are stale relative to the BAML schema (a check/assert type was added or renamed).

Common situations: Editing a BAML file to add a new check without regenerating baml_client; switching branches where the schema changed; running an older compiled client against a newer .baml schema.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• decodeCheckedValue: valueChecked is nil
• decodeUnionValue: valueUnion is nil
• error decoding value
• internal error: attempted to register unknown function
• invalid media type

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/4ff6b6edc3de76c2. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_go/baml_go/serde/decode.go:307

func decodeCheckedValue(valueChecked *cffi.CFFIValueChecked, typeMap TypeMap) (reflect.Value, reflect.Type) {
	if valueChecked == nil {
		panic("decodeCheckedValue: valueChecked is nil")
	}

	value := valueChecked.Value
	decodedValue, _ := Decode(value, typeMap)
	checks := make(map[string]shared.Check, len(valueChecked.Checks))
	for _, check := range valueChecked.Checks {
		checks[string(check.Name)] = shared.Check{
			Name:       string(check.Name),
			Expression: string(check.Expression),
			Status:     string(check.Status),
		}
	}
	goType, ok := typeMap.GetType(valueChecked.Name)
	if !ok {
		panic("error decoding value, checked type not found: " + valueChecked.Name.String())
	}
	checkedValue := reflect.New(goType)
	checkedValue.Elem().FieldByName("Value").Set(decodedValue)
	checkedValue.Elem().FieldByName("Checks").Set(reflect.ValueOf(checks))
	return checkedValue.Elem(), goType
}

func decodeStreamStateType(state cffi.CFFIStreamState) shared.StreamStateType {
	switch state {
	case cffi.CFFIStreamState_PENDING:
		return shared.StreamStatePending
	case cffi.CFFIStreamState_STARTED:
		return shared.StreamStateIncomplete
	case cffi.CFFIStreamState_DONE:
		return shared.StreamStateComplete
	default:
		panic("unexpected stream state")
	}

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