The increased emergence of digital tools in educational contexts have changed the conditions for teaching and learning which, in turn, has meant a need for the development of professional digital competence (PDC) among teachers worldwide. Simultaneously, and aligned with this, programming has become an increasingly important part of schooling in many parts of the world and a step toward developing computational thinking. In this paper we investigate teacher candidates reasoning about programming when involved in problem-solving activities with digital tools. The unit of analysis is programming activities conducted by a group of 17 teacher candidates in a Swedish primary teacher education. The research question posed is: How do digital tools co-determine teacher candidates' reasoning about programming and its pedagogical application during problem-solving activities with digital tools designed for teaching? Drawing from a sociocultural approach, the results of the present study imply that the teacher candidate's appropriation of knowledge is co-determined by the digital tool itself and as such it does not provide any deeper understanding for its pedagogical use.