Context: Effective feedback is critical for novice programmers, but providing it in a timely and scalable manner poses a significant challenge in higher education [13], [14], [37]. Generative Artificial Intelligence (GenAI), particularly Large Language Models (LLMs) trained on code [9], [36], offers a promising avenue to automate this process [1], [22].

Objectives: This quasi-experimental study aimed to evaluate the usability, student perceptions, and academic impact of two distinct GenAI-assisted feedback tools, both powered by GPT-4o-mini: a conversational assistant (tutorB@t) and a platform-embedded tool integrated with a virtual code evaluator (tutorBot+).

Methods: The study involved 91 undergraduate computer science students, with 37 assigned to the experimental AI-assisted group. We measured student programming performance, passing rates, and user perception using the System Usability Scale (SUS) [6] to assess the perceived utility and ease of use of the developed tools.

Results: Students highly valued the immediacy and accessibility of the AI feedback. Perception scores were positive, with tutorB@t achieving a SUS score of 70.6 and tutorBot+ scoring 65.2, and a high intent to reuse (81% and 79%, respectively). Crucially, despite positive perceptions, the study found no statistically significant difference in objective programming performance or passing rates between the groups. This outcome is attributed primarily to factors such as a lack of group homogeneity, external academic pressures, and occasional student misunderstanding of the GenAI-provided feedback.

Conclusion: Timely, automated feedback from GenAI is highly valued by students for its accessibility. Yet, the current study suggests that design limitations (usability, student misunderstandings, external factors) may mask the direct academic impact, highlighting a need for refined integration and future research incorporating affective measures [15], [38] to fully understand and unlock the pedagogical potential of LLM-based feedback [33].