BoundaryML/baml · error

failed to get as url: %w

Error message

failed to get as url: %w

What it means

Wraps any error from the FFI call to the runtime's `as_url` method, which converts media content into a URL when possible. The underlying cause is preserved via %w. Note this error is distinct from AsUrl returning nil, which simply means the runtime produced no URL for this media.

Source

Thrown at engine/language_client_go/pkg/rawobjects_media.go:122

		return false, fmt.Errorf("failed to get is url: %w", err)
	}

	return result.(bool), nil
}

func (m *mediaHolder) IsBase64() (bool, error) {
	result, err := raw_objects.CallMethod(m, "is_base64", nil)
	if err != nil {
		return false, fmt.Errorf("failed to get is base64: %w", err)
	}

	return result.(bool), nil
}

func (m *mediaHolder) AsUrl() (*string, error) {
	result, err := raw_objects.CallMethod(m, "as_url", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get as url: %w", err)
	}

	if result == nil {
		return nil, nil
	}

	as_url, ok := result.(string)
	if !ok {
		return nil, fmt.Errorf("unexpected type for as_url: %T", result)
	}

	return &as_url, nil
}
func (m *mediaHolder) AsBase64() (*string, error) {
	result, err := raw_objects.CallMethod(m, "as_base64", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get as base64: %w", err)
	}

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check the wrapped cause with errors.Unwrap(err)
2. Verify media.IsUrl() is true (or IsBase64) before expecting a URL conversion; use AsBase64 for base64 media
3. Re-acquire the media object from a fresh BAML response
4. Upgrade Go client and native runtime to matching versions

Example fix

// before
url, err := media.AsUrl() // may fail on base64 media
// after
isUrl, _ := media.IsUrl()
if isUrl {
    url, err := media.AsUrl()
    ...
} else {
    b64, err := media.AsBase64()
    ...
}

isUrl, err := media.IsUrl()
if err != nil || !isUrl { return nil }

url, err := media.AsUrl()
if err != nil {
    log.Printf("as_url failed: %v", err)
    if b64, berr := media.AsBase64(); berr == nil { return useBase64(b64) }
    return nil
}

When it happens

Trigger: Calling AsUrl() on media whose runtime handle is invalid/freed, or when the Rust-side `as_url` method itself errors (e.g. the stored content cannot be represented as a URL).

Common situations: Calling AsUrl on base64 data or raw bytes that have no URL form; stale handles from released responses; client/runtime version skew.

Understand the failure class

Background: "invalid response format", "malformed payload", "missing data field": when an API returns 200 but the response shape is wrong — this error's family across 23 libraries.

Related errors

• failed to get mime type: %w
• failed to get is url: %w
• failed to get is base64: %w
• failed to get as base64: %w
• error decoding type, checked type not found:

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/251663c9ec39d05f. Report an issue: GitHub.