This is a Hellcat Firing Pin Safety, #28 on the Hellcat Manual Part List.

Springfield Armory says, “The Hellcat series of 9mm pistols offers CCW enthusiasts a pistol that combines impressive capacity with utterly capable performance. The micro 9mm Hellcat features best in class capacity of 11+1 and 13+1 with included extended magazine, and the RDP (Rapid Defense Package) variant adds in a high-performance Self Indexing Compensator and included HEX Wasp optic. The Hellcat Pro extends the barrel to 3.7” and lengthens the grip to offer an astounding 15+1 capacity. The result? A Hellcat for any need.”