Simon Willison’s Weblog

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Tuesday, 9th June 2026

I feel a lot of things changing as working software increasingly comes out on a tap. The Jevon's paradox kicks in and I feel my own demand for software growing substantially. You can ask for anything - explainers, visualizers, dashboards, bespoke single-use apps (e.g. a full wandb that is hyper-specific just for your project), you can 10X your test suite, auto-optimize code, run giant research projects with custom HTML for the results, anything! "Free your mind" (Matrix ref).

Andrej Karpathy, on Claude Fable 5

# 7:03 pm / ai, andrej-karpathy, generative-ai, llms, anthropic, jevons-paradox, claude-mythos

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I've been really enjoying AgentsView by Wes McKinney as a tool for exploring my token usage across different coding agents running on my laptop.

Claude Fable 5 came out today and wasn't yet included in the pricing database AgentsView uses. I used Fable to reverse-engineer AgentsView and figured out this recipe for setting custom prices.

Here's my Claude Fable 5 usage for today so far, plotted by AgentsView as a treemap across my different local projects:

Screenshot of a cost analytics dashboard. Cost Attribution - Click to hide from chart - toggle buttons for Project / Model / Agent and Treemap / List. A treemap shows a large red block: prod_datasette_agent $74.06 89.3%, then blue: cloud $3.98 4.8%, teal: datasette $2.81 3.4%, pink: money $1.92 2.3%, and a thin orange sliver. A legend lists 1 prod_datasette_agent $74.06, 2 cloud $3.98, 3 datasette $2.81, 4 money $1.92, 5 simon $0.15. Below left, Top Sessions by Cost: 1 Claude - Review ./datasette-agent and ./datasette-apps - we are going to a... - prod_datasette_agent · 08a1f374-0e77-420f-be2d-af805d67e8aa - 55.9M $74.06; 2 Claude - issues.db is a copy of the Datasette issues database. There are a... - datasette · 8caa2d2d-b91f-43b3-bf3a-4268995b6011 - 826.8k $2.81; 3 Claude - Consult fly-docs and then look at datasette.cloud (which launche... - cloud · bfcacc70-09d7-4b27-aaec-4bb8accd9fec - 924.7k $2.61; 4 Claude - simonwillisonblog.db is a copy of my blog, plus all my software re... - money · 0c0fb9dc-6347-4e1b-9307-3709a7cdf0c8 - 542.9k $1.92; 5 Claude - Look in datasette.cloud and figure out all remaining steps and dec... - cloud · 45963b5f-608a-4caa-ad6b-6ae81e1dbf0d - 455k $1.37; 6 Claude - simon - simon · deeccb5d-9e90-4b1e-bfe6-c2b271e1b1d4 - 26.4k $0.15. Below right, Cache Efficiency with horizontal bars: Cache Reads 57.6M (nearly full green bar), Cache Writes 769.3K, Uncached Input 64.4K, Output 300.9K (all tiny bars), and a green highlighted note: $516.62 saved vs uncached.

Almost entirely written by the new Claude Fable 5, see my write-up for more details.

Initial impressions of Claude Fable 5

Visit Initial impressions of Claude Fable 5

I didn’t have early access to today’s Claude Fable 5 release, but I’ve spent the past ~5.5 hours putting it through its paces. My initial impressions are that this is something of a beast. It’s slow, expensive and has been quite happily churning through everything I’ve thrown at it so far. As is frequently the case with current frontier models the challenge is finding tasks that it can’t do.

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Monday, 8th June 2026
Wednesday, 10th June 2026

2026 » June

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