Abstract
We investigate the problem of role-capability leakage (RCL), in which a role-prompted reasoning model generates convincing in-role text while continuing to exhibit capabilities on benchmarks that exceed those implied by the assigned role. For example, when a model is prompted to assume the role of a kindergarten student, one might expect its performance on a mathematics benchmark to reflect kindergarten-level ability rather than expert-level proficiency in solving calculus problems. We introduce RoleCapBench, a curriculum-grounded benchmark for evaluating RCL across six educational roles and four assessment levels spanning elementary school through A-level, and use it to evaluate three open-weight reasoning models. We find that although the models can generate stylistically convincing in-role responses, they consistently fail to align their underlying capabilities with their assigned roles. Naive role prompting yields strong role-voice scores of 1.218--1.389 while retaining above-role accuracy of 0.811--0.898. RCL persists across a range of prompting conditions, including prompts that explicitly instruct the model to match the role's capability level. To mitigate this problem, we propose Injection, an inference-time intervention that combines explicit, role-specific capability guidelines with a guiding prefilled response prefix. Injection improves role-capability alignment across models, reducing above-role accuracy by up to 0.562 while preserving in-role accuracy with a marginal drop of less than 0.058 across most models. All artifacts, including scripts and evaluation data, will be released upon acceptance.
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Cite this article
APA 7
Sarapat, P., Ruangtanusak, S., Pipatanakul, K., & Taveekitworachai, P. (2026). When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models. https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models
MLA 9
Sarapat, Pakhapoom, et al. "When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models." https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models.
Chicago (author–date)
Sarapat, Pakhapoom, Saksorn Ruangtanusak, Kunat Pipatanakul, and Pittawat Taveekitworachai. 2026. "When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models." https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models.
Harvard
Sarapat, P., Ruangtanusak, S., Pipatanakul, K. and Taveekitworachai, P. (2026) 'When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models', Available at: https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models.
Vancouver
Sarapat P, Ruangtanusak S, Pipatanakul K, Taveekitworachai P. When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models. https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models
IEEE
P. Sarapat, S. Ruangtanusak, K. Pipatanakul, and P. Taveekitworachai, "When a Kindergartener Solves Calculus: Measuring Capability Leakage in Role-Prompted Reasoning Models," https://omanscience.com/en/articles/when-a-kindergartener-solves-calculus-measuring-capability-leakage-in-role-prompted-reasoning-models.