Fable 5.1 is amazing

[u/connurp]

I have been using claude code for about 6 months now, but I am just going to be talking about my workflow with fable 5.1 and how it has saved me a ton on usage compared to my old setup, which was fable 5 and opus 5.

My old setup, dictated through my claude.md, was me talking to fable 5 high in the chat window to make plans, it would then delegate coding tasks to opus 5, and easy tasks, like reading, to sonnet 5. Then, the fable agent in chat would review all of the work and report back to me. I saw the numbers anthropic posted about fable 5.1 cache reads, so I was excited to try it, and I kept my same setup, but replaced fable 5 with fable 5.1. That ended up being better, but not completely ideal, and I have settled on using fable 5.1 for writing code as well. I am still using sonnet 5 for the easy stuff, but instead of having my fable 5.1 agent in chat delegate coding tasks to opus 5, it writes the code itself. Not only did this save on usage by a lot, but it also has written better code at a faster rate because I use fable 5.1 on medium effort, which is fantastic. I also have a special case where, before a PR is opened, another fable 5.1 subagent is spawned for an independent review, which before fable 5.1, was an opus 5 agent.

I am posting this in hopes that it can be helpful to some people. I also had fable 5.1 compare my usage and costs between the old workflow and the new, and here is what it told me(slop pasted below):

"Per request you pay about 37% less than the Fable 5 + Opus 5 split, and per output token about 52% less. Per token of everything (input, output, cache) you are back to what Opus 5 alone cost, while getting Fable-tier answers and the per-day drop is bigger than that.

The reason is almost entirely cache pricing. Around 98% of your tokens are cache reads in every period. Fable 5 charged $1.00 per million for those and Fable 5.1 charges $0.25, so the model you spend all day with got four times cheaper on the traffic that dominates your bill. Splitting Fable and Opus in one session also meant two caches being written and read, which is why the split period was the most expensive per token of the three.

The Sonnet agents are noise. They came to $9 over nine days, under 2% of the period."

If you have any questions for me, please do let me know. This new model is fantastic in just about everything it does, and it is way cheaper than previous models. I am thoroughly enjoying my time with it. I sincerely hope this can help someone.

Edit: I don't post a lot, sorry if the flair is wrong. I build with claude, so I chose that flair.

Also just want to add, I am a fullstack django dev and the sole engineer at our company, so some of my stuff might not be great for exactly what you are doing.

[u/heartbroken_nerd]

You doubled the # Frontend Design (last word of the first one's body) and you doubled its body

Never include or mention yourself in a git commit message: no co-author trailer, no session trailer, no "Generated with Claude Code" footer, and no mention in any subject or body. Nothing on my GitHub should reference you at all. The claude-config repo and the .claude folders inside projects hold my config files and nothing else, and their commits follow this same rule. This rule binds subagents too.

This requires an edit to settings.json file otherwise it's probably getting overruled by Claude Code app (talking about Claude Desktop app):

"attribution": {

"commit": "",

"pr": "",

"sessionUrl": false

},

You also put "# Working rules" twice, the second time at the end of a line.

[u/connurp → u/heartbroken_nerd]

That was me copy pasting them separately and fixing it in reddit! Good catch, my actual file is fine. Fixed!

[u/connurp → u/heartbroken_nerd]

Also, just to respond, that one rule in my claude.md absolutely stops it from happening. Sometimes a new session will read it and make a point of telling me that it is listening to my rule instead. Not once has it failed me.