Abstract <p>Firefighting suits are essential protective equipment to protect firefighters from heat damage and flame burns. However, damage to firefighting suits can pose a great threat to the lives of firefighters, so how to make firefighting suits serve as a timely warning of fire damage while providing flame-retardant protection remains a challenge. Here, an aramid coaxial composite aerogel fiber modified by MXene was constructed for temperature sensing before burning and warning once burning. The achieved fiber with a multicore–shell structure, the innermost layer is silica aerogel, together with aramid aerogel for enhancing thermal insulation performance; MXene layer is applied as the outer layer to perform the function of combustion response and encapsulated with intrinsically flame-retardant sodium alginate (SA). The obtained AAF/MXene/SA fiber sensor has high-temperature sensitivity (TCR: − 1.589%/°C) and intelligent thermal response function. It can respond quickly when exposed to a flame (&lt; 2&#xa0;s) and extinguish rapidly (~ 2&#xa0;s) after being removed from the flame. This work introduces a new type of dual-mode intelligent thermal response strategy for firefighting suits, providing dual responses before and after burning, which offering new ideas for the further development of intelligent firefighting suits.</p> Graphical abstract <p></p>