OpenRouterAuthError

Creates a typed error from an HTTP Response.

Attempts to parse the body as JSON (OpenRouter's standard { error: { message, code, metadata } } shape). Falls back to the raw HTTP status text when the body is missing or unparseable.

Status-code mapping:

• 401 / 403 -> OpenRouterAuthError
• 429 -> OpenRouterRateLimitError
• anything else -> OpenRouterError