HTTP-level error emitted by the IMF transport. Carries retryable so the retry policy in transport/retry.ts can distinguish transient (429 / 5xx) from permanent (4xx) failures, and retryAfterHeader so a server-supplied Retry-After can override the exponential back-off schedule.
The constructor disambiguates a class of confusing IMF Azure APIM responses: when the Ocp-Apim-Subscription-Key header is absent the gateway masks SDMX /data/... endpoints as HTTP 404 "Resource not found" (verified via curl 2026-05-10); with an invalid key it returns 401 / 403. Both modes produce a single "subscription key missing or invalid" diagnostic so operators don't waste time chasing a generic 404.
HTTP-level error emitted by the IMF transport. Carries
retryableso the retry policy intransport/retry.tscan distinguish transient (429 / 5xx) from permanent (4xx) failures, andretryAfterHeaderso a server-suppliedRetry-Aftercan override the exponential back-off schedule.The constructor disambiguates a class of confusing IMF Azure APIM responses: when the
Ocp-Apim-Subscription-Keyheader is absent the gateway masks SDMX/data/...endpoints as HTTP 404 "Resource not found" (verified via curl 2026-05-10); with an invalid key it returns 401 / 403. Both modes produce a single "subscription key missing or invalid" diagnostic so operators don't waste time chasing a generic 404.