<p>Undergraduate thesis advising in English education programs in Indonesia predominantly serves as a site of perpetuating colonial ideologies of native-speakerism and neoliberalism instead of a sphere for democratic knowledge generation. Addressing this issue, in this ethnographic participatory action research, as an advisor I employed posthuman cultural-historical activity theory (CHAT) to advise two pre-service teachers engaging in their undergraduate thesis work to promote the two participants’ language teacher-researcher identity construction (LTRI) by means of facilitating different ways of assemblages or entanglements of human and non-human agents to resist colonial ideologies of native-speakerism, neoliberalism and positivism as a form of decolonial agenda. Findings indicated that situating the framework involved six main operations oriented toward the primacy of human and non-human entanglements in praxis in which they constructed their LTRI in entanglements of social, material, and affective activity of advising praxes. By maneuvering tensions or contradictions resulting from colonial ideologies, they unpacked the ideology work, networked activity systems, creatively engaged with non-human agents, and performed different operations in advising praxes to pursue their pre-service service teacher-researcher agenda of decolonizing their own undergraduate thesis work. The study further offers implications for undergraduate thesis advisors to pursue decolonial agenda in advising activity system both discursively and performatively by supporting the advisees’ LTRI construction in social, material and affective activity, creating transformative and democratic spaces for knowledge production.</p>