Simon Willison’s Weblog

Generative AI – The Power and the Glory (via) Michael Liebreich's epic report for BloombergNEF on the current state of play with regards to generative AI, energy usage and data center growth.

I learned so much from reading this. If you're at all interested in the energy impact of the latest wave of AI tools I recommend spending some time with this article.

Just a few of the points that stood out to me:

• This isn't the first time a leap in data center power use has been predicted. In 2007 the EPA predicted data center energy usage would double: it didn't, thanks to efficiency gains from better servers and the shift from in-house to cloud hosting. In 2017 the WEF predicted cryptocurrency could consume al the world's electric power by 2020, which was cut short by the first crypto bubble burst. Is this time different? Maybe.
• Michael re-iterates (Sequoia) David Cahn's $600B question, pointing out that if the anticipated infrastructure spend on AI requires $600bn in annual revenue that means 1 billion people will need to spend $600/year or 100 million intensive users will need to spend $6,000/year.
• Existing data centers often have a power capacity of less than 10MW, but new AI-training focused data centers tend to be in the 75-150MW range, due to the need to colocate vast numbers of GPUs for efficient communication between them - these can at least be located anywhere in the world. Inference is a lot less demanding as the GPUs don't need to collaborate in the same way, but it needs to be close to human population centers to provide low latency responses.
• NVIDIA are claiming huge efficiency gains. "Nvidia claims to have delivered a 45,000 improvement in energy efficiency per token (a unit of data processed by AI models) over the past eight years" - and that "training a 1.8 trillion-parameter model using Blackwell GPUs, which only required 4MW, versus 15MW using the previous Hopper architecture".
• Michael's own global estimate is "45GW of additional demand by 2030", which he points out is "equivalent to one third of the power demand from the world’s aluminum smelters". But much of this demand needs to be local, which makes things a lot more challenging, especially given the need to integrate with the existing grid.
• Google, Microsoft, Meta and Amazon all have net-zero emission targets which they take very seriously, making them "some of the most significant corporate purchasers of renewable energy in the world". This helps explain why they're taking very real interest in nuclear power.

• Elon's 100,000-GPU data center in Memphis currently runs on gas:

  When Elon Musk rushed to get x.AI's Memphis Supercluster up and running in record time, he brought in 14 mobile natural gas-powered generators, each of them generating 2.5MW. It seems they do not require an air quality permit, as long as they do not remain in the same location for more than 364 days.

• Here's a reassuring statistic: "91% of all new power capacity added worldwide in 2023 was wind and solar".

There's so much more in there, I feel like I'm doing the article a disservice by attempting to extract just the points above.

Michael's conclusion is somewhat optimistic:

In the end, the tech titans will find out that the best way to power AI data centers is in the traditional way, by building the same generating technologies as are proving most cost effective for other users, connecting them to a robust and resilient grid, and working with local communities. [...]

When it comes to new technologies – be it SMRs, fusion, novel renewables or superconducting transmission lines – it is a blessing to have some cash-rich, technologically advanced, risk-tolerant players creating demand, which has for decades been missing in low-growth developed world power markets.

(BloombergNEF is an energy research group acquired by Bloomberg in 2009, originally founded by Michael as New Energy Finance in 2004.)

# 1:51 am / ai, ethics, generative-ai, energy

Agents (via) Chip Huyen's 8,000 word practical guide to building useful LLM-driven workflows that take advantage of tools.

Chip starts by providing a definition of "agents" to be used in the piece - in this case it's LLM systems that plan an approach and then run tools in a loop until a goal is achieved. I like how she ties it back to the classic Norvig "thermostat" model - where an agent is "anything that can perceive its environment and act upon that environment" - by classifying tools as read-only actions (sensors) and write actions (actuators).

There's a lot of great advice in this piece. The section on planning is particularly strong, showing a system prompt with embedded examples and offering these tips on improving the planning process:

• Write a better system prompt with more examples.
• Give better descriptions of the tools and their parameters so that the model understands them better.
• Rewrite the functions themselves to make them simpler, such as refactoring a complex function into two simpler functions.
• Use a stronger model. In general, stronger models are better at planning.

The article is adapted from Chip's brand new O'Reilly book AI Engineering. I think this is an excellent advertisement for the book itself.

# 5:50 pm / ai-agents, llms, ai, generative-ai, llm-tool-use

Phi-4 Bug Fixes by Unsloth (via) This explains why I was seeing weird <|im_end|> suffexes during my experiments with Phi-4 the other day: it turns out the Phi-4 tokenizer definition as released by Microsoft had a bug in it, and there was a small bug in the chat template as well.

Daniel and Michael Han figured this out and have now published GGUF files with their fixes on Hugging Face.

# 1:20 am / llms, ai, phi, generative-ai

Double-keyed Caching: How Browser Cache Partitioning Changed the Web (via) Addy Osmani provides a clear explanation of how browser cache partitioning has changed the landscape of web optimization tricks.

Prior to 2020, linking to resources on a shared CDN could provide a performance boost as the user's browser might have already cached that asset from visiting a previous site.

This opened up privacy attacks, where a malicious site could use the presence of cached assets (based on how long they take to load) to reveal details of sites the user had previously visited.

Browsers now maintain a separate cache-per-origin. This has had less of an impact than I expected: Chrome's numbers show just a 3.6% increase in overall cache miss rate and 4% increase in bytes loaded from the network.

The most interesting implication here relates to domain strategy: hosting different aspects of a service on different subdomains now incurs additional cache-related performance costs compared to keeping everything under the same domain.

# 7 pm / addy-osmani, performance, browsers, caching, web-performance

microsoft/phi-4. Here's the official release of Microsoft's Phi-4 LLM, now officially under an MIT license.

A few weeks ago I covered the earlier unofficial versions, where I talked about how the model used synthetic training data in some really interesting ways.

It benchmarks favorably compared to GPT-4o, suggesting this is yet another example of a GPT-4 class model that can run on a good laptop.

The model already has several available community quantizations. I ran the mlx-community/phi-4-4bit one (a 7.7GB download) using mlx-llm like this:

uv run --with 'numpy<2' --with mlx-lm python -c '
from mlx_lm import load, generate

model, tokenizer = load("mlx-community/phi-4-4bit")

prompt = "Generate an SVG of a pelican riding a bicycle"

if tokenizer.chat_template is not None:
    messages = [{"role": "user", "content": prompt}]
    prompt = tokenizer.apply_chat_template(
        messages, add_generation_prompt=True
    )

response = generate(model, tokenizer, prompt=prompt, verbose=True, max_tokens=2048)
print(response)'

Here's what I got back.

Update: The model is now available via Ollama, so you can fetch a 9.1GB model file using ollama run phi4, after which it becomes available via the llm-ollama plugin.

# 5:57 pm / phi, generative-ai, ai, microsoft, llms, uv, pelican-riding-a-bicycle, llm, ollama

Why are my live regions not working? (via) Useful article to help understand ARIA live regions. Short version: you can add a live region to your page like this:

<div id="notification" aria-live="assertive"></div>

Then any time you use JavaScript to modify the text content in that element it will be announced straight away by any screen readers - that's the "assertive" part. Using "polite" instead will cause the notification to be queued up for when the user is idle instead.

There are quite a few catches. Most notably, the contents of an aria-live region will usually NOT be spoken out loud when the page first loads, or when that element is added to the DOM. You need to ensure the element is available and not hidden before updating it for the effect to work reliably across different screen readers.

I got Claude Artifacts to help me build a demo for this, which is now available at tools.simonwillison.net/aria-live-regions. The demo includes instructions for turning VoiceOver on and off on both iOS and macOS to help try that out.

# 3:54 am / claude-artifacts, aria, ai-assisted-programming, javascript, accessibility, screen-readers

uv python install --reinstall 3.13. I couldn't figure out how to upgrade the version of Python 3.13 I had previous installed using uv - I had Python 3.13.0.rc2. Thanks to Charlie Marsh I learned the command for upgrading to the latest uv-supported release:

uv python install --reinstall 3.13

I can confirm it worked using:

uv run --python 3.13 python -c 'import sys; print(sys.version)'

Caveat from Zanie Blue on my PR to document this:

There are some caveats we'd need to document here, like this will break existing tool installations (and other virtual environments) that depend on the version. You'd be better off doing uv python install 3.13.X to add the new patch version in addition to the existing one.

# 8:43 pm / uv, charlie-marsh, python

The future of htmx. Carson Gross and Alex Petros lay out an ambitious plan for htmx: stay stable, add few features and try to earn the same reputation for longevity that jQuery has (estimated to be used on 75.3% of websites).

In particular, we want to emulate these technical characteristics of jQuery that make it such a low-cost, high-value addition to the toolkits of web developers. Alex has discussed "Building The 100 Year Web Service" and we want htmx to be a useful tool for exactly that use case.

Websites that are built with jQuery stay online for a very long time, and websites built with htmx should be capable of the same (or better).

Going forward, htmx will be developed with its existing users in mind. [...]

People shouldn’t feel pressure to upgrade htmx over time unless there are specific bugs that they want fixed, and they should feel comfortable that the htmx that they write in 2025 will look very similar to htmx they write in 2035 and beyond.

# 11:35 pm / jquery, htmx

Stimulation Clicker (via) Neal Agarwal just created the worst webpage. It's extraordinary. As far as I can tell all of the audio was created specially for this project, so absolutely listen in to the true crime podcast and other delightfully weird little details.

Works best on a laptop - on mobile I ran into some bugs.

# 11:31 pm / art, games

AI’s next leap requires intimate access to your digital life. I'm quoted in this Washington Post story by Gerrit De Vynck about "agents" - which in this case are defined as AI systems that operate a computer system like a human might, for example Anthropic's Computer Use demo.

“The problem is that language models as a technology are inherently gullible,” said Simon Willison, a software developer who has tested many AI tools, including Anthropic’s technology for agents. “How do you unleash that on regular human beings without enormous problems coming up?”

I got the closing quote too, though I'm not sure my skeptical tone of voice here comes across once written down!

“If you ignore the safety and security and privacy side of things, this stuff is so exciting, the potential is amazing,” Willison said. “I just don’t see how we get past these problems.”

# 3:04 am / washington-post, generative-ai, ai-agents, ai, llms, privacy, security, prompt-injection

I Live My Life a Quarter Century at a Time (via) Delightful Steve Jobs era Apple story from James Thomson, who built the first working prototype of the macOS Dock.

# 11 pm / apple, history, steve-jobs

O2 unveils Daisy, the AI granny wasting scammers’ time (via) Bit of a surprising press release here from 14th November 2024: Virgin Media O2 (the UK companies merged in 2021) announced their entrance into the scambaiting game:

Daisy combines various AI models which work together to listen and respond to fraudulent calls instantaneously and is so lifelike it has successfully kept numerous fraudsters on calls for 40 minutes at a time.

Hard to tell from the press release how much this is a sincere ongoing project as opposed to a short-term marketing gimmick.

After several weeks of taking calls in the run up to International Fraud Awareness Week (November 17-23), the AI Scambaiter has told frustrated scammers meandering stories of her family, talked at length about her passion for knitting and provided exasperated callers with false personal information including made-up bank details.

They worked with YouTube scambaiter Jim Browning, who tweeted about Daisy here.

# 9:43 pm / scams, ai, ethics

Using LLMs and Cursor to become a finisher (via) Zohaib Rauf describes a pattern I've seen quite a few examples of now: engineers who moved into management but now find themselves able to ship working code again (at least for their side projects) thanks to the productivity boost they get from leaning on LLMs.

Zohaib also provides a very useful detailed example of how they use a combination of ChatGPT and Cursor to work on projects, by starting with a spec created through collaboration with o1, then saving that as a SPEC.md Markdown file and adding that to Cursor's context in order to work on the actual implementation.

# 8:56 pm / productivity, o1, ai-assisted-programming, generative-ai, chatgpt, ai, llms

What we learned copying all the best code assistants (via) Steve Krouse describes Val Town's experience so far building features that use LLMs, starting with completions (powered by Codeium and Val Town's own codemirror-codeium extension) and then rolling through several versions of their Townie code assistant, initially powered by GPT 3.5 but later upgraded to Claude 3.5 Sonnet.

This is a really interesting space to explore right now because there is so much activity in it from larger players. Steve classifies Val Town's approach as "fast following" - trying to spot the patterns that are proven to work and bring them into their own product.

It's challenging from a strategic point of view because Val Town's core differentiator isn't meant to be AI coding assistance: they're trying to build the best possible ecosystem for hosting and iterating lightweight server-side JavaScript applications. Isn't this stuff all a distraction from that larger goal?

Steve concludes:

However, it still feels like there’s a lot to be gained with a fully-integrated web AI code editor experience in Val Town – even if we can only get 80% of the features that the big dogs have, and a couple months later. It doesn’t take that much work to copy the best features we see in other tools. The benefits to a fully integrated experience seems well worth that cost. In short, we’ve had a lot of success fast-following so far, and think it’s worth continuing to do so.

It continues to be wild to me how features like this are easy enough to build now that they can be part-time side features at a small startup, and not the entire project.

# 8:49 pm / prompt-engineering, ai-assisted-programming, val-town, generative-ai, steve-krouse, ai, llms

Friday Squid Blogging: Anniversary Post. Bruce Schneier:

I made my first squid post nineteen years ago this week. Between then and now, I posted something about squid every week (with maybe only a few exceptions). There is a lot out there about squid, even more if you count the other meanings of the word.

I think that's 1,004 posts about squid in 19 years. Talk about a legendary streak!

# 4:21 pm / bruce-schneier, streaks

Can LLMs write better code if you keep asking them to “write better code”? (via) Really fun exploration by Max Woolf, who started with a prompt requesting a medium-complexity Python challenge - "Given a list of 1 million random integers between 1 and 100,000, find the difference between the smallest and the largest numbers whose digits sum up to 30" - and then continually replied with "write better code" to see what happened.

It works! Kind of... it's not quite as simple as "each time round you get better code" - the improvements sometimes introduced new bugs and often leaned into more verbose enterprisey patterns - but the model (Claude in this case) did start digging into optimizations like numpy and numba JIT compilation to speed things up.

I used to find the thing where telling an LLM to "do better" worked completely surprising. I've since come to terms with why it works: LLMs are effectively stateless, so each prompt you execute is considered as an entirely new problem. When you say "write better code" your prompt is accompanied with a copy of the previous conversation, so you're effectively saying "here is some code, suggest ways to improve it". The fact that the LLM itself wrote the previous code isn't really important.

I've been having a lot of fun recently using LLMs for cooking inspiration. "Give me a recipe for guacamole", then "make it tastier" repeated a few times results in some bizarre and fun variations on the theme!

# 6 pm / max-woolf, prompt-engineering, ai-assisted-programming, generative-ai, ai, llms, python

Oxide and Friends Predictions 2025—on Monday Jan 6th at 5pm Pacific (via) I'll be participating in the annual Oxide and Friends predictions podcast / live recording next Monday (6th January) at 5pm Pacific, in their Discord.

The event description reads:

Join us in making 1-, 3- and 6-year tech predictions -- and to revisit our 1-year predictions from 2024 and our 3-year predictions from 2022!

I find the idea of predicting six months ahead in terms of LLMs hard to imagine, so six years will be absolute science fiction!

I had a lot of fun talking about open source LLMs on this podcast a year ago.

# 11:09 pm / podcasts, bryan-cantrill, oxide, generative-ai, ai, llms