CLAUDE OPUS 5.5 WILL CHANGE YOUR LIFE But only if you use it right It went live today and I read every guide, watched every video, so you don't have to Here is everything you should know: ➠ 1 Max is the trap. it burns 6x the usage and scores lower than xhigh (around 65% vs 66.4%), so it drains your limit for a worse answer. leave it off ➠ 2 High is the setting you really want. around 64% on Terminal-Bench for around $4 a run, while Fable 5.1 on max only manages 55.8% for around $19 ➠ 3 the price dropped across the board: $4 and $20 per 1M tokens down 20%, cache reads down 60% to $0.20, which is where agents quietly spend most of their money ➠ 4 on the leaderboard it takes #1 on the Artificial Analysis Index at 58 over Fable 5.1 And GPT-6 Astra at 53, with 66.4% on Terminal-Bench 4.0 against 57.9% for Astra ➠ 5 the receipts back it up: a 200k line audit in under 3 hours where Opus 5 needed 20+ hours and 2.5x the tokens, + HAProxy ported from C to Rust in 9.5h against 12h on Fable 5.1 at 51% less ➠ 6 bank the free reset. Every paid sub got one saved reset that expires Oct 22, so fire it the moment you slam into the wall instead of wasting it early ➠ 7 retest your old prompts. 5.5 writes tight and puts the answer first, so the "be concise" hacks you built for Opus 5 can now hurt more than they help ➠ 8 switching models mid-session re-sends your whole context, so have the outgoing agent drop a short handoff note then open a fresh 5.5 chat ➠ 9 the safeguards are aggressive and will route cyber-adjacent work to Opus 4.8 even when it is not security related, so expect it on anything that looks remotely like security ➠ 10 my own take: on long agent runs High often finishes in fewer turns than Medium, so the cheaper tier is not always cheaper once you count the retries. test both on your real workload before you lock one in bookmark this before Max quietly eats your entire week