| Many works of science fiction concern the use of mathematics for communication with extraterrestrial being. (See the list of similar works below for some examples.) Madame Defarge in the Charles Dickens classic A Tale of Two Cities famously uses knitting as a code to record names of people to be executed. This short story combines the two ideas with a Polish mathematician using her knitting in an attempt to decode an alien message.
There really is a non-trivial intersection of math and knitting. (For example, see sarah-marie belcastro's Mathematical Knitting website.) The only other work of mathematical fiction I know which talks about knitting is Touch-Me-Not, a mystery novel about a retired math professor who runs a knitting circle.
Thanks to Sam Macdonald of the math department at the University of Nebraska for writing to let me know that this story was published in Clarkesworld Magazine, Issue 224, May 2025. | 
