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mccoyb

1,561 karma · joined July 20, 2020

5th year MIT PhD student. I work on programming languages and systems.

https://github.com/femtomc

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mccoyb··on Tau² benchmark: How a prompt rewrite boosted GPT-5-mini by 22%
Many of the "look at what I did programming LLMs" blog posts on Hacker News have been developed and put out in academic papers and groups. The posts which gain traction here seem to be perennially behind the state of the art.
mccoyb··on AI coding
Excellent response, completely agree.
mccoyb··on API, Claude.ai, and Console services impacted [resolved]
Share, if you please.
mccoyb··on Incident Report for Anthropic
That I could, except it hangs in the current version of Claude Code when switching from false to true ...
mccoyb··on Incident Report for Anthropic
I read this as changes to quantization and batching techniques. The latter shouldn’t affect logits, the former definitely will …
mccoyb··on Incident Report for Anthropic
Here’s a report: Claude Code (the software) is getting worse by the day.

Removing the shown token comsumption rates (which allowed understanding when tokens were actually being sent / received!) … sometimes hiding the compaction percentage … the incredible lag on ESC interruption on long running sessions, the now broken clearing of the context window content on TASK tool usage

Who the fuck is working on this software and do they actually use it themselves?

Maybe the quality of Claude Code on any given day is indicative of whether their models are degraded …

mccoyb··on The Expression Problem and its solutions (2016)
Does Clojure solve this to a satisfying degree? One gives up static typing to embrace Clojure’s solutions.

On the other hand, Rust / Haskell provide partial solutions with static typing — but run into annoying boilerplate related to the orphan rule.

I’m not sure if there’s a true solution, given the level of thinking which has gone into these two forks in the road.

mccoyb··on Launch HN: VibeFlow (YC S25) – Web app generator with visual, editable workflows
My optimism says the good new stuff is coming slowly because people who care about their craft and taking things slowly aren’t in any rush to get to market.
mccoyb··on RFK Jr demanded a vaccine study be retracted – the journal said no
Share some references, friendo. Claims require evidence.
mccoyb··on A guide to Gen AI / LLM vibecoding for expert programmers
Try and use it for shit and play around with it — you’ll figure out where it sucks, where it is good by yourself.

Play with it — that’s the only way anyone masters anything.

Separate yourself from the results, be prepared to waste time, but try and have some fun and keep your eyes open.

mccoyb··on Sequoia backs Zed
I love the spirit of Zed. From the principles to the low-level implementation details, it all screams "good taste". It's immensely interesting as an object of study (the code is great, from GPUI all the way up).

Having said that, I don't think an editor should be VC backed. It's the obvious pragmatic choice to get a team together to support a thing, but I'm concerned by it.

mccoyb··on Claudia – Desktop companion for Claude code
There's few new ideas in this space, it's pretty boring.

How many ways can you wrap (multiple agents, worktrees, file manager, diff viewer, accept reject loops, preset specifications for agents) -- let's try Electron! Let's try Tauri! Let's try a different TUI!

What if we sat down and really thought about how these agentic IDEs should feel first instead of copy pasting the ideas to get something out to acquire market and mind share? That's significantly harder, and more worthwhile.

That's how these agentic front ends should be advertised: "Claude Code, plus _our special feature_" and then one can immediately see if the software is filled or devoid of interesting ideas.

mccoyb··on Claude Opus 4 and 4.1 can now end a rare subset of conversations
These companies are fundamentally amoral. Any company willing to engage at this scale, in this type of research, cannot be moral.

Why even pretend with this type of work? Laughable.

mccoyb··on Claude Opus 4 and 4.1 can now end a rare subset of conversations
Do you think Claude 4 is conscious?

It has no semblance of a continuous stream of experiences ... it only experiences _a sort of world_ in ~250k tokens.

Perhaps we shouldn't fill up the context window at all? Because we kill that "reality" when we reach the max?

mccoyb··on Claude Opus 4 and 4.1 can now end a rare subset of conversations
A perusal of the source code of, say, Ollama -- or the agentic harnesses of Crush / OpenCode -- will convince you that yes, this should be an extremely a simple feature (management of contexts are part and parcel).

Also, these companies have the most advanced agentic coding systems on the planet. It should be able to fucking implement tree-like chat ...

mccoyb··on Claude Code Output Styles
Love Claude Code. Dislike, to the point of some resentment, that the code (detailing the harness, the system prompt, the agentic patterns) is not open-source and inspectable.
mccoyb··on My AI-driven identity crisis
I think you're accurately describing a "regression to the mean" phenomenon, which LLMs have transmitted to areas involving programmatic control through text.

I recently used an LLM to help scaffold a piece of technical writing. I showed it to several of my peers (sharp and accomplished PhD students), and they immediately identified the paragraphs (even sentences in captions!) written by an LLM. I had spent a good amount of time prompt engineering Opus 4 to try and produce a coherent piece of content aligned with a narrative which I had already developed, but it was still _immediately obvious_ what was not consistent ... it stood out like a sore thumb to experts.

By the the time we finished the content, there was not a sentence of LLM-generated writing in the final product.

Possibly an incorrect extrapolation, but I think my experience here is the current status quo. Code is a bit easier for these systems, because the LLM can align against test suites, type systems, etc. But for writing ... you just can't trust the current capabilities to pass the sniff test by experts.

After all, how does one commmunicate "coherence" as a test which the LLM might align its generations against? That's why you need a shared world model (with your audience) -- and if we could produce a computational representation of such a thing, we might have a chance at better coherent / consistent technical writing generations.

mccoyb··on Why LLMs can't really build software
This is a low information density blog post. I’ve really liked Zed’s blog posts in the past (especially about the editor internals!) so I hope this doesn’t come the wrong way, but this seems to be a loose restatement of what many people are empirically finding out by using LLM agents.

Perhaps good for someone just getting their feet wet with these computational objects, but not resolving or explaining things in a clear way, or highlighting trends in research and engineering that might point towards ways forward.

You also have a technical writing no no where you cite a rather precise and specific study with a paraphrase to support your claims … analogous to saying “Godel’s incompleteness theorem means _something something_ about the nature of consciousness”.

A phrase like: “Unfortunately, for now, they cannot (beyond a certain complexity) actually understand what is going on” referencing a precise study … is ambiguous and shoddy technical writing — what exactly does the author mean here? It’s vague.

I think it is even worse here because _the original study_ provides task-specific notions of complexity (a critique of the original study! Won’t different representations lead to different complexity scaling behavior? Of course! That’s what software engineering is all about: I need to think at different levels to control my exposure to complexity)

mccoyb··on My AI-driven identity crisis
I’ve tried to use flagship models to produce long-ish technical writing content and the result has not been satisfactory.

The resulting content lacks consistency and coherency. The generated prose is rather breathless: in carefully articulated content, every sentence should have a place. Flagship models (Opus 4~) don’t seem to understand the value of a sentence.

I’ve tried to prompt engineer this behavior (one should carefully attend to each sentence: how is it contributing to the technical narrative in this section, and overall?), but didn’t have much success.

I suspect this might be solved by research on grounding generation against world models: much of verifying “is this sentence correct here?” has to do with my sharing of a world model of some domain with my audience. I use that world model to debug my own writing.

mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
In regards to the duplication of code — yes I’ve found this to be a tremendous problem.

One technique which appears to combat this is to do “red team / blue team Claude”

Red team Claude is hypercritical, and tries to find weaknesses in the code. Blue team Claude is your partner, who you collaborate with to setup PRs.

While this has definitely been helpful for me finding “issues” that blue team Claude will lie to you about — hallucinations are still a bit of an issue. I mostly put red team Claude into ultrathink + task mode to improve the veracity of its critiques.

mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
I like to be able to tweak things to my liking, and this typically leads me to make my own versions of things.

Probably a bad habit.

mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
This doesn't contribute to the conversation ... without further elaboration on what your point is, I'm assuming that you're pointing out that my question is analogous to previous (good to ask!) questions about market and user model for an "eventually very big" application.

Not very enlightening: just because Dropbox became big in one environment, doesn't mean the same questions aren't important in new spaces.

mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
Makes sense! Thanks for discussing.
mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
The answer here might be: "you're not our market" (which is totally fine! but slightly confusing, because presumably people _using agents like Claude Code_ are ... more advanced than the uninitiated)
mccoyb··on Show HN: Omnara – Run Claude Code from anywhere
One big question I have, in the era of Claude Code (and advancements yet to come) — is why should a hacker submit to using tools behind a SaaS offering … when one can just roll their own tools? I may be mistaken, but I don’t think there is any sort of moat here.

Truly — this is an excellent and accessible idea (bravo!), but if I can whittle away at a free and open source version, why should I ever consider paying for this?

mccoyb··on Claude Code is all you need
I believe these are fundamentally two different types of abuse — the OP is engaging in a significantly less harmful version … the seriously harmful version is the account sharing / massively concurrent one which abuses whatever holes exist in the streaming API to allow Claude to “complete the completion and then stop because of limit” (which I think is there to make the UX better)

Just letting a single instance run all the time … is not that bad, seriously.

mccoyb··on Claude Code is all you need
Just reflecting on my own comment -- what one might want is an automated layout system with a simple "natural language"-like API (perhaps similar to Penrose, although it's been awhile since I looked at that project).

Hardened and long use systems like TikZ of course, do have something like this -- but in complex TikZ graphics, you end up with a mixture of "right of" and "left of" (etc) and low-level manual specification, which I think tends to fall into the zone of issues.

mccoyb··on Claude Code is all you need
Just from personal experience, visual design is the task with the worst outcomes for Claude Code (w/ latest Opus 4.1, etc).

It truly cannot reason well yet about geometry, visual aesthetics, placement, etc. The performance varies: it's quite good at matplotlib but terrible at any non-trivial LaTeX / TikZ layout or graphic. Why? Not a clear idea yet -- would love to think more about it.

I've tried many things now to try and give it eyes (via text), and this is unavoidably a place where things are ... rough ... right now.

I've had bad results with image screenshotting. More often than not, it has no idea what it is looking at -- won't even summarize the image correctly -- or will give me an incorrect take "Yes indeed we fixed the problem as you can tell by <this part of the UI> and <that part of the UI>" which is wrong.

I typically have to come in and make a bunch of fine-grained changes to get something visually appealing. I'm sure at some point we'll have a system which can go all the way, and I'd be excited to find approaches to this problem.

Note -- tasks which involve visual design which I've run into diminishing returns: * proper academic figures (had a good laugh at the GPT 5 announcement issues) * video game UI / assets * UI design for IDEs * Responsive web design for chat-based interfaces

All of these feel like "pelican" tasks -- they enter into a valley which can't be effectively communicated via textual feedback yet ...

mccoyb··on I want everything local – Building my offline AI workspace
That can't be the correct paper...

I think you meant this: https://arxiv.org/abs/2506.08276

mccoyb··on An LLM does not need to understand MCP
Agreed.

Context engineering is "just" prompt engineering for LLMs with tool use: it extends the concerns of prompt engineering with the concern of setting up an environment in which tools can be used, and how the LLM can most effectively interact with the environment.

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