, 3 min read
Using Claude Fable 5.2 to build retrofit smart switches
What's new in Claude Fable 5.2, and how I'm using it to build retrofit smart switches that bring my home's traditional lights into Home Assistant.
Hello humans.
Anthropic released Claude Fable 5.2 on 9 November 2026, together with Claude Mythos 5.2. I'm using Fable 5.2 on my current side project: retrofit smart switches for my own house. Here's what changed in the model, and what it's doing for the switches.
What's new in Claude Fable 5.2
Mythos 5.2 is only for organisations Anthropic has verified, so Fable 5.2 is the one most of us will use. It's better at coding and at long agent tasks, and it reads charts, detailed pictures and PDFs much better than before. Here's how it compares with Fable 5.1 on a few of Anthropic's tests:
| Test | Fable 5.1 | Fable 5.2 |
|---|---|---|
| FrontierSWE v2 (coding) | 56.3% | 69.9% |
| FrontierCode 2.0 (coding, Xhigh effort) | 32.4% | 49.1% |
| OSWorld 2.1 (using a computer) | 83.5% | 89.3% |
| Remote Labor Index | 17.9% | 41.3% |
| Chartography (reading charts, no tools) | 44.8% | 73.4% |
These are Anthropic's own numbers, not independent tests.
It's also faster and cheaper. Answers come up to 30% faster than Fable 5.1, and the API price dropped to $8 per million input tokens and $40 per million output tokens, from $10 and $50. A fast mode runs up to 2.5 times faster, at twice the price. It holds 1 million tokens of context and can write up to 128,000 tokens in one answer.
You can use it in the Claude apps on the Pro, Max, Ultra, Team and Enterprise plans, in Claude Code, and on the API as claude-fable-5-2, including through AWS, Google Cloud and Microsoft Foundry. It also has safeguards for cyber security and biology: a question they flag goes to an older model instead. Anthropic says these block about 55% fewer questions than in Fable 5.1.
Why I'm building smart switches
Most of my house still has traditional switches and lights, and every light is switched on by hand. I want the lights to help my parents instead: to come on for them at night, when a camera notices someone, and in harsh weather.
I already run Home Assistant at home, and I've set up smart locks at my dad's homestay. So I'm building my own retrofit smart switches: a small board that fits in the existing switch box and joins the lights to Home Assistant.
Where Fable 5.2 comes in
I got access to Fable 5.2 on the night it came out. Until then I was building the switches in Claude Code with Claude Opus 5.5 at extra high effort. A project like this mixes hardware, firmware and Home Assistant, and that mixed, long work is what Anthropic says 5.2 got better at.
My first night with it was mind-blowing. It was usage-blowing too: it went through my plan's usage limits fast.
The switch, step by step
Plan the boardDone, with Claude
What goes on the board so it fits in the existing switch box.
Write the firmwareDone, with Claude
The code on the switch that turns the light on and off and talks to Home Assistant.
Set up the automationsDone, with Claude
The rules in Home Assistant: at night, when a camera notices someone, and in harsh weather.
Make the boardsNext
Get the boards produced.
Test and fit themAfter that
Test the switches, then fit them in my house.
What's next
The boards aren't made yet. Next is getting them produced, then testing them and fitting them in the house.
One note if you try this yourself: switches run on mains power, which can kill. Have a licensed electrician do the wiring.
Building something like this? Get in touch.
Sources
Introducing Claude Fable 5.2 and Claude Mythos 5.2 and the Claude Fable 5.2 page from Anthropic, and the Claude Fable 5.2 overview in the Claude Platform docs.
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