Subject is bleeding into edges of picture

Why the hell are we posting in a forum instead of a chat app like Slack, Discord, or other?

Why should people use Slack and/or Discord when there is a perfectly fine Forum? 

Edit: »perfectly fine« may be putting it a bit strongly. 

And are you sure there aren’t any Photoshop-related whatevers on those platforms? 

Using your prompt I can got one version that almost doesn’t »touch« the edge right away. 

Have you tried generating on a non-empty image? 

I'm not sure exactly what you are trying to acheive, but you might be expecting to much of Generative Fill.  It is just one of dozens of tools and functions in Photoshop, and not a be all and end all.  You can get much better results using a reference image.  One professional I know puts a fair bit of work into creating that reference image.

Alternatively, you can use Generative Fill as one step in a process.  It sounds like ytou want the fire to bleed into the hocky puck. So what I did was copy the layer, and use the Remove Tool to remove the puck from the lower layer.

I added a layer mask to the upper layer, and painted around the outline of the puck with a fully hard black brush to mask out the edge of the puck.

You can then use Mask Properties to feather the mask and reduce its density.

I thought the edge looked too smooth, so I used the Smudge tool to drag flame shapes into it.

Tip: this is how to make explosive effects in Photoshop.

Would you be interested in tutorials on advanced use of Photoshop's Firefly related Ai functions?