This study developed and optimized oat‑based noodles using agar extracted from Chondracanthus chamissoi (yuyo) via ultrasound-assisted extraction (UAE). Two extraction methods—one with and one without acetic acid—were tested. Three formulations were evaluated following a simplex-centroid mixture design. Physicochemical properties such as gel strength, pH, water activity, rheological behavior, composition, and energy were assessed. UAE without acid yielded the highest dry agar (97.1 %), while acid pretreatment enhanced process speed but reduced yield (80.5 %). The optimal formulation (43.2 % agar, 55.0 % oat flour, 1.9 % olive oil) delivered 14.1 % protein, 2.7 % fat, and 392 kcal 100 g⁻¹. The noodles showed stable rheological performance (G′ > G″). This is the first report to demonstrate the feasibility of using Peruvian yuyo agar in cereal-based foods, contributing to both product innovation and sustainable resource valorization. Results indicate potential for industrial application in functional foods using local marine biomass and low‑impact processing techniques