Claude Fable 5 and Claude Mythos 5

Justy Okay, so Anthropic just dropped two new models—Fable 5 and Mythos 5.

Cody Yep. Fable’s the one with the training wheels.

Justy Training wheels that cost fifty bucks a million output tokens.

Cody Right.

Justy Anyway— Fable 5’s the general release, Mythos 5’s the same model but for, like, government cyberdefense types.

Cody Project Glasswing, yeah. So basically Fable’s the one they’re letting the rest of us touch.

Justy And it’s supposedly state of the art on, like, everything—coding, knowledge work, vision. Stripe used it to migrate a fifty-million-line Ruby codebase in a day.

Cody Which— okay, that’s wild. A team would’ve taken two months.

Justy I mean, if that’s true… that’s the kind of thing that actually changes how shops operate.

Cody Yeah. And IMC said it aced their trading analysis tests—root cause, expected value, all of it.

Justy So Cody, what’s the catch?

Cody The catch is the safeguards. Fable 5’s got these conservative filters that kick in for, quote, ‘some topics’—and when they do, you get Opus 4.8 instead.

Justy Less than five percent of sessions, though. That’s not nothing, but it’s not a dealbreaker either.

Cody Except when it is. If you’re in the middle of something and it suddenly downgrades you…

Justy Mm. But Mythos 5’s the same model without the filters—just for cyberdefenders.

Cody Right. And the pricing’s half of what Mythos Preview was. Ten bucks per million input, fifty output.

Justy So they’re pushing to get this in more hands, fast. But safe-ish.

Cody Safe-ish is the word. Conservative’s a good start, but five percent false positives means a lot of people hitting that wall.

Justy I dunno, I’d take the false positives over, you know…

Cody Over some script kiddie using it to reverse-shell half the internet? Yeah, me too.

Justy That is such an Exploring Next take.

Justy Anyway—my week’s been a nightmare of last-minute spec changes, so this is weirdly comforting. Like, at least someone’s shipping something huge.

Cody Yeah, I was up until two A M debugging a memory leak. Fun times.

Justy Ugh. But back to this—Stripe’s numbers are insane. If Fable 5 can do that for one team, imagine what it does at scale.

Cody If the safeguards don’t get in the way. And if the model actually holds up under real load.

Justy Fair. But the direction’s clear—longer, more complex tasks are where it shines.

Cody And the pricing’s aggressive. They’re not messing around.

Justy Nope. Okay, I’m sold. Or at least… intrigued.

Cody You’re always intrigued. That’s your thing.

Justy And you’re always waiting for the other shoe to drop.

Cody Someone’s gotta.

Justy Fair. Alright, I’m gonna go try to break it. Later, Cody.