What's the difference between "you will" and "you shall"?

From Bartleby.com: the traditional rules. The traditional rules state that you use shall to show what happens in the future only when I or we is the subject: I shall (not will) call you tomorrow. We shall (not will) be sure to keep in touch. Will, on the other hand, is used with subjects in the second and third persons: The comet will (not shall) return in 87 years. You will (not shall) probably encounter some heavy seas when you round the point. However, you can use will with a subject in the first person and shall with a subject in the second or third person to express determination, promise, obligation, or permission, depending on the context. Thus I will leave tomorrow indicates that the speaker is determined to leave. You shall leave tomorrow has the ring of a command. The sentence You shall have your money expresses a promise (%u201CI will see that you get your money%u201D), whereas You will have your money makes a simple prediction. 1 the reality. The English and some sticklers about usage are probably the only people who follow these rules, and then not with perfect consistency. In America, people who try to adhere to them run the risk of sounding pretentious or haughty. Americans normally use will to express most of the senses reserved for shall in British usage. Americans use shall chiefly in first person invitations and questions that request an opinion or agreement, such as Shall we go?, and in certain fixed expressions, such as We shall overcome. In formal style, Americans use shall to express an explicit obligation, such as Applicants shall provide a proof of residence, though must or should works just as well here. In speech you can get the distinctions in meaning delineated in the traditional rules by putting stress on the auxiliary verb, as in I will leave tomorrow (%u201CI intend to leave%u201D). You can also choose another auxiliary verb, such as must or have to, that is less open to misinterpretation, or you can make your meaning clear by adding an adverb such as certainly.

Here's Yeats; part of the Lake Isle of Innisfree; note lines 1,3,5

I will arise and go now, and go to Innisfree, And a small cabin build there, of clay and wattles made; Nine bean rows will I have there, a hive for the honeybee, And live alone in the bee-loud glade. And I shall have some peace there, for peace comes dropping slow,

Hmm.... I lost the verse form...

These two words have a variety of usage rules in different style books. I myself only use "shall" in legal documents in usages which imply there is no option, no predicate, the act must occur with nothing further. But a large part of that may be clients like to see their lawyers use more obscure usages because they think they're getting more for their money.

I shall certainly remember that, should I have to see my lawyer ever again. And I will certainly avoid that ever happening.

i tend to think of “will” as anticipatory and “shall” as mandatory….? maybe?