Subject verb agreement when the word "in" seperates a subject

The phrase "in context" is a prepositional modifier - it is the equivalent of an adjective and has no effect whatsoever on the noun being singular or plural.

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The words are on page 8

The big words are on page 8

The words in large letters are on page 8

The correct verb here is "are".

The words in context are on page 8

Why? The subject of the verb is "words in context", this is plural and so requires a plural verb form. The question I think you are asking is does the verb refer to "words" or "context", but the verb plainly refers to the words being on page 8, and the fact that they are in context is additional information. You could say "the words are on page 8" but you cannot say "The in context is on page 8." You could of course say "the context is on page 8", but that is not what the original sentence is talking about.

The prepositional phrase is moved forward in this sentence, but prepositional phrases do not impact the verb form.

You could equally say:

In context, the words are on page 8.

or

The words are on page 8 in context.

or

The context for the words is on page 8.

This latter changing the subject of the verb.