createApi

servicesRecord<string, ServiceConfig>Required

• The services to expose. Each key becomes a property on the returned client.
• Author these with defineService so their literal types survive.

baseUrlstringdefaults to '' (relative requests)

• The origin for every request. Reaches the fetcher through FetcherCallContext.baseUrl rather than being folded into the path.
• Because it is not in the path, it is not in your cache keys — so keys survive a change of environment.

headersHeadersProvider | HeadersProvider[]

• Static records, or functions resolved per request. Functions receive { signal }.
• Applied before service and endpoint headers; the last writer of a name wins.

hooksPartial<PipelineHooks>

• Lifecycle hooks applied to every endpoint in every service.
• These run first, before service and endpoint hooks.

defaultOptionsWithOptionsConfig

• Defaults merged into every endpoint — staleTime, gcTime, timeout, queryKeyPrefix, and any TanStack option.
• Endpoint-level options win over service, which win over these.

fetcherEndpointFetcherdefaults to defaultFetcher

• The transport used by every endpoint. See createFetcher.

ApiClient{ [service]: { queryKey } & { [endpoint]: UnifiedEndpoint } }

• One property per service. Each carries a queryKey of [serviceName], useful as an invalidation prefix, plus every endpoint.