Simon WillisonModify

2026-04-25 20:06:55

Since GPT-5.4, we’ve unified Codex and the main model into a single system, so there’s no separate coding line anymore.

GPT-5.5 takes this further, with strong gains in agentic coding, computer use, and any task on a computer.

— Romain Huet, confirming OpenAI won't release a GPT-5.5-Codex model

Tags: generative-ai, gpt, openai, ai, llms

2026-04-25 12:13:36

GPT-5.5 prompting guide

Here's a neat trick they recommend for applications that might spend considerable time thinking before returning a user-visible response:

Before any tool calls for a multi-step task, send a short user-visible update that acknowledges the request and states the first step. Keep it to one or two sentences.

I've already noticed their Codex app doing this, and it does make longer running tasks feel less like the model has crashed.

OpenAI suggest running the following in Codex to upgrade your existing code using advice embedded in their openai-docs skill:

$openai-docs migrate this project to gpt-5.5

The upgrade guide the coding agent will follow is this one, which even includes light instructions on how to rewrite prompts to better fit the model.

Also relevant is the Using GPT-5.5 guide, which opens with this warning:

To get the most out of GPT-5.5, treat it as a new model family to tune for, not a drop-in replacement for gpt-5.2 or gpt-5.4. Begin migration with a fresh baseline instead of carrying over every instruction from an older prompt stack. Start with the smallest prompt that preserves the product contract, then tune reasoning effort, verbosity, tool descriptions, and output format against representative examples.

Interesting to see OpenAI recommend starting from scratch rather than trusting that existing prompts optimized for previous models will continue to work effectively with GPT-5.5.

Tags: ai, openai, prompt-engineering, generative-ai, llms, gpt

2026-04-25 07:35:07

Release: llm 0.31

• New GPT-5.5 OpenAI model: llm -m gpt-5.5. #1418
• New option to set the text verbosity level for GPT-5+ OpenAI models: -o verbosity low. Values are low, medium, high.
• New option for setting the image detail level used for image attachments to OpenAI models: -o image_detail low - values are low, high and auto, and GPT-5.4 and 5.5 also accept original.
• Models listed in extra-openai-models.yaml are now also registered as asynchronous. #1395

Tags: gpt, openai, llm

2026-04-25 06:38:49

The people do not yearn for automation

It’s a superb piece of commentary, and something I expect I’ll be thinking about for a long time to come.

Nilay’s core idea is that people afflicted with “software brain” - who see the world as something to be automated as much as possible, and attempt to model everything in terms of information flows and data - are becoming detached from everyone else.

[…] software brain has ruled the business world for a long time. AI has just made it easier than ever for more people to make more software than ever before — for every kind of business to automate big chunks of itself with software. It’s everywhere: the absolute cutting edge of advertising and marketing is automation with AI. It’s not being a creative.

But: not everything is a business. Not everything is a loop! The entire human experience cannot be captured in a database. That’s the limit of software brain. That’s why people hate AI. It flattens them.

Regular people don’t see the opportunity to write code as an opportunity at all. The people do not yearn for automation. I’m a full-on smart home sicko; the lights and shades and climate controls of my house are automated in dozens of ways. But huge companies like Apple, Google and Amazon have struggled for over a decade now to make regular people care about smart home automation at all. And they just don’t.

Via John Gruber

Tags: ai, generative-ai, llms, nilay-patel, ai-ethics

2026-04-24 14:01:04

Chinese AI lab DeepSeek's last model release was V3.2 (and V3.2 Speciale) last December. They just dropped the first of their hotly anticipated V4 series in the shape of two preview models, DeepSeek-V4-Pro and DeepSeek-V4-Flash.

Both models are 1 million token context Mixture of Experts. Pro is 1.6T total parameters, 49B active. Flash is 284B total, 13B active. They're using the standard MIT license.

I think this makes DeepSeek-V4-Pro the new largest open weights model. It's larger than Kimi K2.6 (1.1T) and GLM-5.1 (754B) and more than twice the size of DeepSeek V3.2 (685B).

Pro is 865GB on Hugging Face, Flash is 160GB. I'm hoping that a lightly quantized Flash will run on my 128GB M5 MacBook Pro. It's possible the Pro model may run on it if I can stream just the necessary active experts from disk.

For the moment I tried the models out via OpenRouter, using llm-openrouter:

llm install llm-openrouter
llm openrouter refresh
llm -m openrouter/deepseek/deepseek-v4-pro 'Generate an SVG of a pelican riding a bicycle'

Here's the pelican for DeepSeek-V4-Flash:

And for DeepSeek-V4-Pro:

For comparison, take a look at the pelicans I got from DeepSeek V3.2 in December, V3.1 in August, and V3-0324 in March 2025.

So the pelicans are pretty good, but what's really notable here is the cost. DeepSeek V4 is a very, very inexpensive model.

This is DeepSeek's pricing page. They're charging $0.14/million tokens input and $0.28/million tokens output for Flash, and $1.74/million input and $3.48/million output for Pro.

Here's a comparison table with the frontier models from Gemini, OpenAI and Anthropic:

DeepSeek-V4-Flash is the cheapest of the small models, beating even OpenAI's GPT-5.4 Nano. DeepSeek-V4-Pro is the cheapest of the larger frontier models.

This note from the DeepSeek paper helps explain why they can price these models so low - they've focused a great deal on efficiency with this release, especially for longer context prompts:

In the scenario of 1M-token context, even DeepSeek-V4-Pro, which has a larger number of activated parameters, attains only 27% of the single-token FLOPs (measured in equivalent FP8 FLOPs) and 10% of the KV cache size relative to DeepSeek-V3.2. Furthermore, DeepSeek-V4-Flash, with its smaller number of activated parameters, pushes efficiency even further: in the 1M-token context setting, it achieves only 10% of the single-token FLOPs and 7% of the KV cache size compared with DeepSeek-V3.2.

DeepSeek's self-reported benchmarks in their paper show their Pro model competitive with those other frontier models, albeit with this note:

Through the expansion of reasoning tokens, DeepSeek-V4-Pro-Max demonstrates superior performance relative to GPT-5.2 and Gemini-3.0-Pro on standard reasoning benchmarks. Nevertheless, its performance falls marginally short of GPT-5.4 and Gemini-3.1-Pro, suggesting a developmental trajectory that trails state-of-the-art frontier models by approximately 3 to 6 months.

I'm keeping an eye on huggingface.co/unsloth/models as I expect the Unsloth team will have a set of quantized versions out pretty soon. It's going to be very interesting to see how well that Flash model runs on my own machine.

Tags: ai, generative-ai, llms, llm, llm-pricing, pelican-riding-a-bicycle, deepseek, llm-release, openrouter, ai-in-china

2026-04-24 12:23:11

Tool: Millisecond Converter

LLM reports prompt durations in milliseconds and I got fed up of having to think about how to convert those to seconds and minutes.

Tags: tools