Simon Willison’s Weblog

Anthropic status: Model output quality (via) Anthropic previously reported model serving bugs that affected Claude Opus 4 and 4.1 for 56.5 hours. They've now fixed additional bugs affecting "a small percentage" of Sonnet 4 requests for almost a month, plus a less long-lived Haiku 3.5 issue:

Resolved issue 1 - A small percentage of Claude Sonnet 4 requests experienced degraded output quality due to a bug from Aug 5-Sep 4, with the impact increasing from Aug 29-Sep 4. A fix has been rolled out and this incident has been resolved.

Resolved issue 2 - A separate bug affected output quality for some Claude Haiku 3.5 and Claude Sonnet 4 requests from Aug 26-Sep 5. A fix has been rolled out and this incident has been resolved.

They directly address accusations that these stem from deliberate attempts to save money on serving models:

Importantly, we never intentionally degrade model quality as a result of demand or other factors, and the issues mentioned above stem from unrelated bugs.

The timing of these issues is really unfortunate, corresponding with the rollout of GPT-5 which I see as the non-Anthropic model to feel truly competitive with Claude for writing code since their release of Claude 3.5 back in June last year.

# 6:28 am / ai, generative-ai, llms, anthropic, claude, claude-4, gpt-5

I ran Claude in a loop for three months, and it created a genz programming language called cursed (via) Geoffrey Huntley vibe-coded an entirely new programming language using Claude:

The programming language is called "cursed". It's cursed in its lexical structure, it's cursed in how it was built, it's cursed that this is possible, it's cursed in how cheap this was, and it's cursed through how many times I've sworn at Claude.

Geoffrey's initial prompt:

Hey, can you make me a programming language like Golang but all the lexical keywords are swapped so they're Gen Z slang?

Then he pushed it to keep on iterating over a three month period.

Here's Hello World:

vibe main
yeet "vibez"

slay main() {
    vibez.spill("Hello, World!")
}

And here's binary search, part of 17+ LeetCode problems that run as part of the test suite:

slay binary_search(nums normie[], target normie) normie {
    sus left normie = 0
    sus right normie = len(nums) - 1    
    bestie (left <= right) {
        sus mid normie = left + (right - left) / 2
        ready (nums[mid] == target) {
            damn mid
        }
        ready (nums[mid] < target) {
            left = mid + 1
        } otherwise {
            right = mid - 1
        }
    }
    damn -1
}

This is a substantial project. The repository currently has 1,198 commits. It has both an interpreter mode and a compiler mode, and can compile programs to native binaries (via LLVM) for macOS, Linux and Windows.

It looks like it was mostly built using Claude running via Sourcegraph's Amp, which produces detailed commit messages. The commits include links to archived Amp sessions but sadly those don't appear to be publicly visible.

The first version was written in C, then Geoffrey had Claude port it to Rust and then Zig. His cost estimate:

Technically it costs about 5k usd to build your own compiler now because cursed was implemented first in c, then rust, now zig. So yeah, it’s not one compiler it’s three editions of it. For a total of $14k USD.

# 9:31 am / c, programming-languages, ai, rust, zig, generative-ai, llms, ai-assisted-programming, anthropic, claude, vibe-coding, geoffrey-huntley

The 2025 PSF Board Election is Open! The Python Software Foundation's annual board member election is taking place right now, with votes (from previously affirmed voting members) accepted from September 2nd, 2:00 pm UTC through Tuesday, September 16th, 2:00 pm UTC.

I've served on the board since 2022 and I'm running for a second term. Here's the opening section of my nomination statement.

Hi, I'm Simon Willison. I've been a board member of the Python Software Foundation since 2022 and I'm running for re-election in 2025.

Last year I wrote a detailed article about Things I’ve learned serving on the board of the Python Software Foundation. I hope to continue learning and sharing what I've learned for a second three-year term.

One of my goals for a second term is to help deepen the relationship between the AI research world and the Python Software Foundation. There is an enormous amount of value being created in the AI space using Python and I would like to see more of that value flow back into the rest of the Python ecosystem.

I see the Python Package Index (PyPI) as one of the most impactful projects of the Python Software Foundation and plan to continue to advocate for further investment in the PyPI team and infrastructure.

As a California resident I'm excited to see PyCon return to the West Coast, and I'm looking forward to getting involved in helping make PyCon 2026 and 2027 in Long Beach, California as successful as possible.

I'm delighted to have been endorsed this year by Al Sweigart, Loren Crary and Christopher Neugebauer. If you are a voting member I hope I have earned your vote this year.

You can watch video introductions from several of the other nominees in this six minute YouTube video and this playlist.

# 10:13 am / python, psf