A refreshed BMW 4 Series is in development, as we've seen in a plethora of spy photos. But the purple ragtop featured here is actually the first time we caught a high-performance M4 test vehicle in public.

As you can see, it wears the same amount of camouflage at the front and rear as other 4 Series prototypes snapped by our spy photographers. That doesn't mean the M4 will carry the same updates, however. Details of the lower fascia look very much like the current model with all the vents and contrasting angles, but it might adopt a more aggressive appearance similar to the M4 CSL. Higher up we see slightly smaller headlights, a feature shared with the refreshed 4 Series. The grille appears the same, for better or worse.

Gallery: BMW M4 Convertible Facelift Spy Photos

If the front fascia wasn't enough to convince you this is an M4, the rear should erase all doubts. There's no missing the quad exhaust outlets tucked between the diffuser. The bottom portion of the fascia doesn't look any different from the current M4, and vertical reflectors are in the same spot as well. The upper portion looks a bit flatter, however, and it's not hard to see new the taillights. The size and shape of the lenses look the same, but internal structures are different.

Moving inside, we aren't treated to a clear look of the interior but we suspect changes will be relegated to minor differences in trim. We do spot some coverings piled on top of the dash that could be used to hide digital panels. The steering wheel looks like it has a thick cover as well.

As for under-the-bonnet changes, don't expect some fantastic new powertrain. Not that the current twin-turbocharged I6 isn't already amazing with 543 bhp offered in CSL trim. That's obviously a rare animal, but lower-spec M4s with xDrive could sneak upward to 525 bhp. We know the engine is certainly capable of it, and it could mean small power increases for other M4 trims as well.

This lightly camouflaged test vehicle looks production ready, but don't be fooled. 2024 M4 models are already up on BMW's configurator, which means this is at least a 2025 model-year vehicle. That means an official debut could happen late this year, or more likely, early in 2024.