A fallback_providers entry naming a `providers.<name>` block (or
`custom:<name>`) without its own api_mode was re-detected from the
resolved host: an Anthropic-Messages proxy on a plain host or a
Responses-only relay behind a generic gateway landed on chat_completions
while resolve_provider_client had already built the declared client
(#33062 bottom thread, #81932 provider-level `transport:`). The hint pass
now reads the named block's api_mode/transport as explicit, and entry-level
`transport:` is accepted as an alias of `api_mode` with the same
canonicalisation the providers block uses (`responses` -> codex_responses).
Fixes#33062Fixes#81932
8f1542422b