In partnership with
Claude isn't one thing anymore.
Open the model menu and you'll see a few names. Sonnet. Opus. Haiku. And in the headlines lately, Fable.
Most people pick one at random and never think about it again.
That's usually fine. But knowing the difference takes thirty seconds and saves you time, money, and frustration.
This is the plain-English guide.
Now a word from today's sponsor:
You already have a take on which AI lab ships next.
Claude or Gemini? OpenAI or Anthropic? GPT-7 before year-end or not? If you read tech newsletters, you've already formed opinions on all of it.
Kalshi has real-money markets on which AI model leads benchmarks this week, which lab ships AGI first, when Anthropic releases Mythos, whether OpenAI raises ChatGPT pricing, and which company has the best coding model at year-end. These aren't abstract questions — they're live markets with real money on both sides, moving as labs ship, benchmarks drop, and announcements land.
The edge belongs to whoever actually follows this space. Not the casual observer — the person who reads model cards, tracks evals, and notices when a new release outperforms the field before the mainstream press catches up.
That person has a genuine edge. If that's you, Kalshi lets you act on it.
Okay, the lineup, in the order you'll actually use them.
Sonnet 5. Your default. Use this for almost everything.
Fast, sharp, and it now finishes multi-step jobs on its own. Writing, planning, inbox, research, learning. If you're not sure, it's Sonnet. It's the one you're already on if you're on Free or Pro.
Haiku. The quick one.
Lighter and faster, built for simple, high-volume tasks. Quick rewrites, short answers, anything where speed beats depth. You'll rarely pick it by hand, but it's there.
Opus 4.8. The heavy thinker.
Anthropic's top reasoning model. Reach for it when a problem is genuinely hard and Sonnet's answer feels thin. Deep analysis, tricky strategy, complex writing. Slower and pricier, so save it for the hard stuff.
Fable 5. The frontier.
The most powerful model, back as of this month. Built for heavy, days-long, autonomous work, mostly run by developers and teams through the API. Powerful, premium, and overkill for everyday chat.
So the rule of thumb.
Start on Sonnet 5. Move up to Opus when a hard problem needs more muscle. Ignore Fable unless you're building something big.
Simple as that.
One thing most people get wrong, though.
They blame the model when the answer is weak. Usually the model was fine. The brief was the problem.
A clear, well-fed prompt on Sonnet 5 beats a lazy prompt on the most expensive model every time.
So before you go reaching for something bigger, try giving Claude more context and a sharper instruction. Nine times out of ten, that's the fix.
Not sure which one you're on? Paste this into Claude:
Which Claude model am I talking to right now, and what is it best at? In one short paragraph, tell me whether it's the right choice for [describe the kind of work you do most], or whether I should switch.Which model, and how to drive each one well, is part of the foundation I teach in Claude Mastery.
The full system for getting a team's worth of work out of Claude. Step by step, no tech background needed.
Quick one.
Which model are you on right now? Reply and I'll tell you if it's the right call for what you're doing.
Talk soon,
Zephyr
