Credit instruments such as callable bonds, options on (sovereign) bond futures, and bond options are sensitive to changes in the implied volatilities of the underlying's issuer credit spread rates. These instruments can be affected by two types of vega risk factors: general interest rate risk (GIRR) vega and credit spread risk (CSR) vega. The GIRR vega captures the sensitivity of the instrument's value to changes in the volatility of the general interest rate, while the CSR vega captures the sensitivity to changes in the volatility of the issuer's credit spread. 

The sensitivity-based method (SBM) outlined in Article 325m(2) of the CRR requires institutions to calculate risk sensitivities for market risk own funds requirements. However, it is not explicitly clear how to treat instruments that are sensitive to both GIRR and CSR when only a single volatility surface is used for pricing purposes. This single volatility surface may encapsulate both general market and issuer-specific volatility effects, leading to a question of whether separate vega sensitivities for GIRR and CSR should be calculated or whether a single vega sensitivity can be used for both. 

In this context, FAQ5 related to MAR 21.8 of the Basel framework clarifies that for callable bonds, options on sovereign bond futures and bond options, delta, vega and curvature capital requirements must be computed for both GIRR and CSR.