Context.In Software Engineering, Model-Driven Engineering (MDE) is a methodology that considers Metamodels as a cornerstone. As an abstract artifact, a metamodel plays a significant role in the specification of a software language, particularly, in generating other artifacts of lower abstraction level, such as code. Developers then enrich the generated code to build their language services and tooling, e.g., editors, and checkers.Problem.When a metamodel evolves, the generated code is automatically updated. As a consequence, the developers’ additional code is impacted and needs to be co-evolved accordingly.Contribution.This paper proposes a new fully automatic code co-evolution approach with the evolution of the Ecore metamodel. The approach relies on pattern matching of the additional code errors. This process aims to analyze the abstraction gap between the evolved metamodel elements and the code errors to co-evolve them.Evaluation and Results.We evaluated our approach on nine Eclipse projects from OCL, Modisco, and Papyrus over several evolved versions of three metamodels. Results show that we automatically co-evolved 771 errors due to metamodel evolution with 631 matched and applied resolutions. Our approach reached an average of 82% of precision and 81% of recall, varying from 48% to 100% for precision and recall respectively. To check the effect of the co-evolution and its behavioral correctness, we rely on generated test cases before and after co-evolution. We observed that the percentage of passing, failing, and erroneous tests remained the same with insignificant variations in some projects. Thus, suggesting the behavioral correctness of the co-evolution Moreover, we conducted a comparison with the use of quick fixes that represent a usual tool for correcting code errors in an IDE. We found that our automatic co-evolution approach outperforms the use of quick fixes that lacked the context of metamodel evolution. Finally, we also compared our approach with the state-of-the-art semi-automatic co-evolution approach. As expected, precision and recall are slightly better with semi-automation, but with the burden of manual intervention, which is alleviated with our automatic co-evolution.