Why Franco didnt join the war in Hendaye ?

[Peter89]

And, Franco asked even more : he wanted also French Catalonia,and it was out of the question that France would accept this .

well the source doesn't seem really serious about such point

the only reference to Roussillon in a pair of book and several articles about French-Spanish relations by Catala Séguéla etc I found came from...Germans rather than Spaniards ...and at the great exasperation of these last ones

Yes, that's seem to be the case. I have never seen any reference to any Spanish interest in any part of continental France; even the invasion plans of 1942 were not intended to acquire territory in that country.
But who knows, maybe ljadw has found the philosopher's stone... again?

Neither Spain nor France would ever compromise the natural border of the Pyrenees for any Catalans or Basques who happen to be stuck on the other side of the mountains. Spain did not pose a threat to France in the past 100 years at the time of Hendaye, and Spain could rely on the defense multiplication the Pyrenees could offer.