LLMs’ performance on machine translation (MT) tasks is often dependent on the data availability in the specific domains and language pairs that they are trained upon. To examine if multiword expressions (MWEs) still present a bottleneck for LLMs regarding language understanding and translation, we report the performance of systems from the WMT 2026 Test Suites shared task, using portions of the publicly available multilingual parallel corpus AlphaMWE as test suites. We received 31 MT systems’ outputs covering English to Chinese (zh), Polish (pl), German (de), and Arabic (ar) including Modern Standard Arabic (MSA) and two dialectal ones (Egyptian and Tunisian Arabic). We carried out automatic evaluations using BLEU, ChrF, and BERT-score to select the top 3 systems per language pair, followed up with human evaluations on the selected systems. Our findings show that figurative and MWE-related phenomena remain challenging for contemporary MT systems, automatic metrics sometimes disagree in system ranking, and human evaluation uncovers language-specific errors that remain hidden by aggregate scores. Inter-annotator analysis further reveals challenges in consistently identifying and calibrating linguistically subtle translation errors, highlighting the need for explicit evaluation guidelines and careful annotator calibration.

This paper presents two-fold contributions: a full revision of the Palestinian morphologically annotated corpus (Curras), and a newly annotated Lebanese corpus (Baladi). Both corpora can be used as a more general Levantine corpus. Baladi consists of around 9.6K morphologically annotated tokens. Each token was manually annotated with several morphological features and using LDC’s SAMA lemmas and tags. The inter-annotator evaluation on most features illustrates 78.5% Kappa and 90.1% F1-Score. Curras was revised by refining all annotations for accuracy, normalization and unification of POS tags, and linking with SAMA lemmas. This revision was also important to ensure that both corpora are compatible and can help to bridge the nuanced linguistic gaps that exist between the two highly mutually intelligible dialects. Both corpora are publicly available through a web portal.