Respect the Thoroughbred startle response
A Thoroughbred is wired for speed, and that wiring does not switch off on a fireworks night. Thin-skinned, quick to notice movement at the edge of vision, and bred to respond instantly, this horse can launch sideways at a flash, gather himself in two strides, and hit a fence or stall door at real pace before a handler has finished turning around. Horses off the track may also carry old associations between loud cracks, crowds, and being asked to run, which layers excitement over fear. Treating the evening as a containment problem first and a calming problem second is the honest approach: the safest Thoroughbred is the one whose every exit has already been thought about in daylight.
Make the stall the safest place he knows that day
Bring him in hours early, exercise him in his normal morning work rather than adding a hard evening session, and let him finish his usual feed before any noise starts. Choose an interior stall away from open doorways where flashes sweep in, bed it generously to cushion scrambling feet, and strip it of hanging equipment, protruding bucket hooks at head height, and anything he could strike while spinning. Check the door hardware under pressure, including hinges and the bottom bolt owners rarely use, and latch every gate between his barn and the road as a second and third line, because a Thoroughbred who gets an aisle often keeps going through a yard gate left ajar.
Place his most settled neighbour where he can see and hear that horse, and keep barn lighting at the level he normally sleeps under rather than flooding the aisle with bright light that makes outside flashes sharper by contrast. Steady hay in front of him matters for this breed too, since a Thoroughbred standing with an empty stomach and nothing to do will listen harder for the next bang.
During the display, protect space and avoid handling
Stay close enough to hear trouble, but do not try to hold, tie, or hand-walk him through volleys to prove he is fine, because a rearing or plunging Thoroughbred on a lead in a confined aisle endangers you both. Observe from a protected spot, noting whether he settles to hay between bursts or escalates: repeated crashing against the partition, frantic calling that does not ease, or a lathered sweat in cool air all say his stress is climbing rather than levelling. Keep the barn closed to visitors, other horses being moved, and vehicles for the night, since each extra movement gives him another reason to fire. If your property layout means he must stay out, choose the smallest interior paddock with the strongest fencing, no corners where he can be trapped by a companion, and no direct line to a road gate.
Check him thoroughly afterwards and plan for a bolt
When quiet returns, approach slowly with normal barn light, let him settle to your voice, then run hands over his legs, chest, and hips for heat, swelling, and cuts from walls or doors before you lead him out to walk off stiffness. Recheck him at morning feed for appetite, droppings, and any lameness that only shows once adrenaline fades, and involve your veterinarian promptly if he has struck himself, is reluctant to bear weight, or remains frantic without any noise. Because even good planning can fail with a horse this fast, prepare his KinsLe Lost Pet Alert System details beforehand, so local people learn he is missing promptly and whoever halts him fields away can return him to the right stable.