Third-party assessments can be conducted on frontier models to confirm evaluations or claims on critical safety capabilities and mitigations. In appropriate contexts, these assessments may help to confirm or build confidence in safety claims, add robust methodological independence, and supplement expertise. This report outlines practices and approaches among Frontier Model Forum (FMF) firms for implementing, where appropriate, rigorous, secure, and fit-for-purpose third-party assessments. Third-party assessments can complement – but do not replace – internal safety processes and corporate governance mechanisms. Internal teams possess deep knowledge of their systems and development processes, and external assessors can offer methodological independence, specialized expertise, and fresh perspectives that may be able to identify issues or validate critical safety claims. These assessments become particularly valuable for models that are approaching, or have reached, enabling capability thresholds, or when implementing novel frontier mitigations. (2025) source Unverified