Beehiiv redirects non-existent newsletters to /?404=... with HTTP 302. With follow_redirects=True, the final 200 was misread as "newsletter exists". Fix: disable redirect following so only a direct HTTP 200 = newsletter real. Also reset state back to last_sent=13 (real). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>