This is corydalis lutea, it's perennial, started blooming in late April and is still flowering at the end of October (barely, but that's OK). Is there really anything else you need to know? It's my favorite perennial plant because it thrives in dry shade, will also take sun and along with cockroaches and Keith Richards, will be the last remaining life on our planet after Armageddon.
The irony of my life is that I'm spending more time writing and talking than actually gardening. I need carefree plants like corydalis lutea to make the garden look respectable all season.
It's about 18 inches tall with gray, greenish foliage and luminescent yellow flowers. It will form a wonderful little colony from seed and the plants will sprout up in the most unlikely spots. It's never invasive as it can easily be potted up and shared with other lucky gardeners.
It's one of my favorite perennials for containers due to the long bloom time.
I recommend this plant to everyone who will listen and gift plants have become the basis of many friendships.
It's hard to find, but worth effort to get into the garden. Go to your local nursery and see if they carry it, if not ask them nicely if they would order it for you. Better yet find someone else who grows it and get some plants.