Translate Text (Opus MT)

How it fits

Typical backends

Caveats

• Hard constraintOpus-MT is bilingual — each checkpoint is trained for ONE direction. The translation direction is fixed by the bound model file slot, not by config. A direct-pair checkpoint (such as English-to-German) and a many-to-English checkpoint keep tgt_lang empty; only a multi-target checkpoint needs tgt_lang set to an ISO-639-3 code, prepended internally as a `>>id<<` routing token.
• Parameter interactionChanging device rebuilds the loaded checkpoint in place, so the first call after a change pays the load cost; changing tgt_lang takes effect on the next call with no rebuild.
• Parameter interactionbatch_size bounds memory on a [String] input; num_beams 1 is greedy decoding while higher values trade latency for quality, capped by max_new_tokens.
• I/O contractThe output arm follows the resolved downstream port — a single String joins all segments, a [String] keeps them split, and the Translation arms tag both language fields with the tgt_lang label (the bilingual checkpoint exposes no source code).
• I/O contractEmpty input (or an all-empty list) returns an empty result without running the model, and a fault inside translation is logged and degraded to that same empty result rather than dropping the message.