Here’s a randomly generated Vigenere running key cipher. I solved it without a crib using a key search program and a combination interactive solver and hill-climbing program. Both of these programs used local servers to run. The word search server was listening on port 3000, and the hill-climber was listening on port 8080. The search program ran through a list of about 600,000 words and phrases, looking for a corresponding plaintext that included a word or phrase at least 7 letters long. The key search returned four possibilities, one with a 9 letter phrase and three with 7 letters phrases. Three out of the four results actually occurred in the solution. I filled in the rest of the plaintext by switching back and forth between the hill-climber and the interactive solver.
For a crib I’ll include the (caesar-shifted) phrase whose corresponding plaintext included the 9 letter phrase.
Vigenere running key:
UUOHZ LWHJM AATPD XIEZC TVYAO XPJBZ OXFHC VNTLV XZWYD YDYZX JXMLX PMHDZ PXEOS.
caesar-shifted crib: NKSJHJXXFWD
update: I’ll add a caesar-shifted hint:
Hint: YMJ XTQZYNTS XYFWYX BNYM F SFRJ FSI JSIX BNYM F SFRJ