I wasted $43 rebuilding a Vectorize index the wrong way — here's the $5.50 fix

Last month's Anthropic bill hit $312. Sixty percent of it traced back to a single 6-hour window when I was doing an in-place Vectorize index rebuild. Here's the part I didn't expect: the rebuild didn't throw errors. Queries returned results, scores just quietly dropped from 0.78 to 0.61. My agent interpreted that as "no relevant docs found" and fell back to Claude directly — 2,880 times over six hours. At ~5K input tokens per query on Sonnet, that's $43 in LLM fallback costs from what I thought...