BoundaryML/baml · error

failed to get headers: %w

Error message

failed to get headers: %w

What it means

httpRequest.Headers() invokes the runtime 'headers' method via the raw-objects bridge. 'failed to get headers: %w' means the bridge call failed before any headers were produced — the underlying object could not execute 'headers'.

Source

Thrown at engine/language_client_go/pkg/rawobjects_http_request.go:72

func (h *httpRequest) Method() (string, error) {
	result, err := raw_objects.CallMethod(h, "method", nil)
	if err != nil {
		return "", fmt.Errorf("failed to get method: %w", err)
	}

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

	return method, nil
}

func (h *httpRequest) Headers() (map[string]string, error) {
	result, err := raw_objects.CallMethod(h, "headers", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get headers: %w", err)
	}

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

	return headers, nil
}

func (h *httpRequest) Body() (HTTPBody, error) {
	result, err := raw_objects.CallMethod(h, "body", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get body: %w", err)
	}

	body, ok := result.(HTTPBody)
	if !ok {

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Inspect the wrapped cause (%w)
2. Keep request access within the dispatch lifecycle
3. Ensure the runtime defines a working 'headers' method
4. Re-dispatch the request if stale

if req == nil { return errors.New("request unavailable") }

func (h *httpRequest) hasHeaders() bool { return h != nil && h.RawObject != nil }

hs, err := req.Headers()
if err != nil {
    return fmt.Errorf("cannot read headers: %w", err)
}

When it happens

Trigger: Calling Headers() on an invalid or detached request object, or when the runtime 'headers' implementation throws (e.g. header parsing failed in the runtime).

Common situations: Reading headers after runtime disposal; handlers erroring while normalizing header names; version mismatches.

Related errors

• failed to get JSON: %w
• failed to get ID: %w
• failed to get URL: %w
• failed to get method: %w
• unexpected type for headers: %T

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/8fc5d4a748141730. Report an issue: GitHub.