I train a lot, and with AI's help I built a small app that pulls my Garmin and Strava data and helps me structure my training around it.
Made me curious what else people are building. What's something you've put together recently with AI's help, big or small?
I used an AI coding agent to help build the piece that lets other AI agents reliably call our route optimization API. Kind of meta watching my coding agent debug why a different agent kept picking the wrong constraint model. Turns out the hard part wasn't the API call, it was the agent misunderstanding which business rule applied. Ended up spending more time making the docs "agent-readable" than on the API logic itself.
That's a great example of the gap being in shared understanding, not the interface. Makes sense the docs ended up being the real work, an API can be technically correct and still get misread by an agent that doesn't have the business context a human would infer. Which model was doing the debugging, and did it figure out the fix itself or just surface the disagreement?
We did it with Claude Opus, and we intend to generalize the process to other models in order to provide some efficiency scores per model to our users. The process looks like this: we have an agent trying to build a correct integration based on some data, our docs, and a short brief. Then another agents reviews the optimization model against a target model built by our experts for the toy problem, and suggests improvements in the documentation to avoid pitfalls or guide the agent more. Then we start over with the updated doc to assess the improvement. Simple, but cool to watch. Of course we keep humans in the reviewing loop to make sure we do not degrade our docs.
Nice, that's a solid loop. One thing to watch: docs tuned to fix Opus's blind spots might not transfer cleanly to other models. Their pitfalls don't always overlap. Might be worth tracking whether the fixes are model-specific or general doc gaps.
Yeah definitely, that's why we want to expand it to other models asap. Claude was a natural choice since our surveys shows that our users are massively relying on it (more than 75% of them are). Surprisingly enough, the level of non determinism in Claude responses is quite high. At each iteration, we launch 5 to 10 runs in parallel and it's crazy how innovative the same Claude model can be in front of the same initial prompt. So basically, it's not about the documentation, it's about multiplying touchpoints (api reference, sdk docstrings, modeling guides, nudging messages in API responses, etc.) to make sure that whatever the path chosen by the agent, it will end up reading the right piece of documentation to solve the situation.
Makes sense, redundancy beats a single perfect doc if you can't predict which path the agent takes. Curious how you settle on a score when 5-10 runs diverge that much, best-of, median, or something else?
I really enjoyed reading this. I’m still learning and exploring what’s possible with AI, so seeing the different ways people are experimenting with it is genuinely inspiring. I think the best part is that you don’t need to build something huge or perfect to learn something valuable. Even a small idea can teach you a lot when you actually try it. Thanks for sharing this, it definitely gives me a few ideas to explore myself.
Glad you enjoyed reading it :) . Small ideas are honestly the best way to learn, what you figure out along the way matters more than whether the thing itself is impressive.
My fiance wanted a fitness app, so I built 1, decided to add a bit more to it though... So it has a digital pet, AI trainer, mental health section, cycle tracker, smartwatch integration and a few more bells and whistles.
I'm also busy refining my NDA based OS, a SASOS built on a custom language, that runs a ring-0 LLM harness in the kernel, so it can manage it's own hardware
That sounds really cool! I hope she enjoys it!
Mine has AI trainer, I track basically everything when it comes to data, I compare effort, I analyze data, gives health data like fatigue and etc.
Your side project also sounds nice! :)
My idea with the pets was that it's essentially your 'goal', what animal best embodies how you want to be. Eg. if you're a bit shy and want to boost self-confidence, choose a dragon, so through aligning with it, you learn to be more self-confident. If you're anxious and want to learn how to roll with it more, choose the panda, so through alignment, you learn to be calmer and more carefree.
I also made it so event planning, you can pick your dates ahead of time, set your expectations, then it'll adjust your plan leading up to it, so going out for drinks on the weekend isnt a guilty pleasure you need to pay for afterwards, instead you've prepared for it, so it's a reward for putting in the effort ahead of time.
The AI trainer also judges your state and history, so you can ask it questions, eg. if you're feeling meh, ask the trainer if you can skip your workout, or if you really want pizza, whether you're allowed it. It wont always say no and it wont always say yes, it tries to comply with your lifestyle, unless it detects you're slipping and need to be realigned. Alot of thought went into it's systems so it actually acts like a proper trainer, not just a yes-man or bluntly enforces rules.
Also added meal planning and groceries, so it can plan out a grocery list for you and learns from your receipts what's cheap, what's expensive, what's seasonal, etc. So you can get nice meals, without breaking the bank. It tracks per meal what your usage is, so it knows you have 2 tomatoes left. That obviously wont work if you dont eat alone, so I added family tracking too, either full tracking, or as little as just usage based RL from when you notify it you're out of something, it knows your meal was 2 tomatoes, if you ran out of your 5 tomatoes, it means your family ate 3, etc.
The mental health section was also quite important to me, it lets your pet pay attention to your biometrics and if you deal with eg. anger issues, or anxiety, it can detect your biometrics and interact over your smartwatch to just help you through the situation.
I'm looking at maybe releasing it on the stores, but I hate subscriptions... And ads... So I wanna make it BYOK, else use my key and pay for the AI usage. That way it's lean and doesnt force anyone into paying a penny more than what they use.
Love the BYOK instinct, no ads no subscriptions is the dream. I went a similar route with mine, my friends get full access for free, and I opened it up publicly too with a free tier that's just limited features rather than a paywall. Keeps it lean like you said, and the people who really get value out of it tend to stick around anyway.
An SVG editor. Basically reads svg and edits OTG. Not export but save back to SVG. Still exploring
That sounds nice, I would guess this was giving you a hard time doing it manually before?
More about exploration. SVG as a CAD app tool not an export.
ah, got it now. I've also created a lot of tool for exploration, most of them tuned out to be absolute surprise to me, wondering what my inital prompt was :D :D
I've been using Claude to build a Russian-syntax programming language
(SkyForge). The interesting part for me wasn't writing the interpreter —
it was building a transpiler that converts my AST into Python AST so
compile() can turn it into native bytecode.
fib(32) went from ~60 seconds (tree-walking interpreter) to ~0.4
seconds (transpiled). That's within 6% of plain CPython.
The AI was genuinely useful for two things: boilerplate (writing 30+
ast.* node types by hand is tedious) and catching weird edge cases
I'd miss — like Python 3.12+ refusing to compile an AST where a child
node's lineno is less than the parent's.
Hardest part: AI tends to invent keywords that don't exist in my
language. Had to write a strict context file of "only these constructs
exist" and it still happens occasionally.
That's a nice trick, going through Python's own AST and compile() instead of writing your own bytecode compiler basically gets you CPython's actual VM for free. 0.4s for fib(32) within 6% of native CPython is a great result for the code you didn't have to write yourself.
The lineno ordering constraint is a fun one to hit blind, that's a genuinely obscure CPython internal to stumble into from a hobby language.
On the invented-keywords problem: have you tried feeding the model a formal grammar file (even a stripped-down EBNF) instead of, or alongside, the prose "only these constructs exist" context? A grammar tends to anchor these things harder than a list of allowed words, since it also constrains structure, not just vocabulary.
Fair point — I haven't tried EBNF yet, which is honestly an oversight
given that I wrote the parser by hand and could have derived the
grammar from it.
What I use instead: a short list of canonical examples, one per
construct. Instead of "these keywords exist", the context file has
a small snippet for
функция,если,для,попробовать, etc.That anchors better than prose because the model copies structure,
not just vocabulary — you can't fake a valid
еслиblock withoutalso writing
иначеin the right place.But you're right that a grammar would be stronger. The thing I keep
hitting is structural drift, not word invention: the model gets the
keywords right but nests a block one level too deep or forgets a
closing brace. A grammar constrains that; examples don't.
Did you have a specific approach for feeding EBNF to a model in
practice, or is it just "paste the grammar in the system prompt"?
Just pasting the grammar into the system prompt is closer to a suggestion than a constraint, the model isn't checking its own output against it token by token, so you get exactly the failure mode you're describing: it "knows" the grammar in the sense of pattern-matching surface structure, but nothing stops it from drifting a level deep on nesting or dropping a closing brace, since there's no verification step.
Two things actually close that gap, and they're different tools for different setups:
If you have access to constrained decoding (llama.cpp's GBNF grammars, or something like the outlines/guidance libraries on top of a local model), you can restrict token sampling so only grammar-valid continuations are ever possible. That's a hard guarantee, not a hope, structural drift becomes literally unsamplable.
If you're on a hosted API without that option, the more practical pattern is generate-then-repair: run the output through your own real parser (the one you already wrote by hand), and when it fails, feed the model the exact error and location rather than asking it to "try again." A real parser catching an unclosed иначе at line 12 is a much sharper signal than the model silently re-guessing.
Given you already have a hand-written parser, the second option is probably the lower-effort win: you already have the ground truth, you're just not closing the loop with it yet.
I just released the beta of Natyv, a desktop development framework that doesn’t rely on a WebView or DOM after about a month of using Claude Code to do the grunt work while I spent my time architecting it all.