Show HN: I made a JSFiddle-style playground to test and share prompts fast https://ift.tt/3rKndSB

Show HN: I made a JSFiddle-style playground to test and share prompts fast I built this out of frustration as I lead the development of AI features at Yola.com. Prompt testing should be simple and straightforward. All I wanted was a simple way to test prompts with variables and jinja2 templates across different models, ideally somthing I could open during a call, run few tests, and share results with my team. But every tool I tried hit me with a clunky UI, required login and API keys, or forced a lengthy setup process. And that's not all. Then came the pricing. The last quote I got for one of the tools on the market was $6,000/year for a team of 16 people in a use-it-or-loose-it way. For a tool we use maybe 2–3 times per sprint. That’s just ridiculous! IMO, it should be something more like JSFiddle. A simple prompt playground that does not require you to signup, does not require API keys, and let's experiment instantly, i.e. you just enter a browser URL and start working. Like JSFiddle has. And mainly, something that costs me nothing if I'm or my team is not using it. Eventually I gave up looking for solution and decided to build it by myself. Here it is: https://langfa.st Help me find what's wrong or missing or does not work from you perspctive. P.S. I did not put any limits or restrictions yet, so test it wisely. Don't make me broke, please. https://langfa.st/ July 12, 2025 at 11:11PM

Show HN: I Built a Stick-On Wireless Lamp That Installs in 30 Seconds https://ift.tt/sQmbnUV

Show HN: I Built a Stick-On Wireless Lamp That Installs in 30 Seconds Hi HN! I recently built a simple, rechargeable wall lamp that doesn't require any tools, wires, or drilling. It sticks to surfaces using adhesive pads, rotates 360°, and charges via USB-C. The goal was to make lighting *super minimal, renter-friendly, and easy to install*. The idea came from personal frustration — I live in a rented apartment where I can’t drill holes, and I wanted a modern-looking light I could reposition easily. I know this isn’t a software product, but I figured some of you might appreciate the problem-solving side of it — designing minimal hardware that’s useful, elegant, and simple. Would love feedback on the product or the landing page: Happy to answer any questions about the design, battery, lighting specs, remote control logic, etc. Thanks! https://ift.tt/VidWoOU July 13, 2025 at 01:56AM

Show HN: I automated code security to help vibe coders from getting busted https://ift.tt/LJ7CrSB

Show HN: I automated code security to help vibe coders from getting busted Hi HN! I’m the developer of Elara, a tool that automatically scans your code for security issues like misconfigurations, secrets, and risky packages, so you can focus on building without stressing about all this stuff. It’s designed to be simple and fast. I see so many people launching products online without even knowing what security risks they might have. If you’re a developer or into tech, you know how hard it is to keep systems safe. Yet shockingly it feels like nobody really cares. I want to help folks catch these issues early, before they get burned. Elara runs multiple security scanners simultaneously, aggregates the results into a single interface, and gives you an actionable to-do list to fix the problems. It’s super simple to try, just log in with GitHub and see for yourself. Would really appreciate your feedback! https://ift.tt/dSAr5yY July 12, 2025 at 09:50PM

Show HN: VibeKin – Gated Discord Tribes via Personality Matching https://ift.tt/Zg9T206

Show HN: VibeKin – Gated Discord Tribes via Personality Matching I built an app that matches users to exclusive Discord communities based on a 25-question personality quiz. Inspired by HEXACO but with a novel fuzzy-clustering twist, it creates a "harmony genome" to gate access, ensuring tight-knit tribes (e.g., wellness or creative niches). Think Reddit but curated via psych. Launched to test the idea—feedback on algo, niches, or scaling? https://tgc.fly.dev July 12, 2025 at 07:32AM

Show HN: Transition – AI Triathlon Coach https://ift.tt/h1Rc0ng

Show HN: Transition – AI Triathlon Coach Hey HN, I’m Alex, a triathlete, dad, and software engineer. I’ve been building Transition — an app for triathletes that creates adaptive training plans based on your goals, schedule, and workout data (Garmin, Strava, etc). Most plans are static, which never really worked for me as a parent and someone with an unpredictable schedule. Transition adjusts every week using your actual workouts and progress, so the plan changes when you miss a session, set a new PR, or need to shift your priorities. I built this because nothing else was flexible enough for my life, and I’m curious if others have the same problem. It’s in beta and free to try. I’d love feedback from the HN crowd — especially around the training logic, onboarding, or any ways to make it more useful for real athletes. Website: https://ift.tt/Rdqzj02 https://ift.tt/Rdqzj02 July 12, 2025 at 08:09AM

Show HN: RULER – Easily apply RL to any agent https://ift.tt/Ch0iNza

Show HN: RULER – Easily apply RL to any agent Hey HN, Kyle here, one of the co-founders of OpenPipe. Reinforcement learning is one of the best techniques for making agents more reliable, and has been widely adopted by frontier labs. However, adoption in the outside community has been slow because it's so hard to implement. One of the biggest challenges when adapting RL to a new task is the need for a task-specific "reward function" (way of measuring success). This is often difficult to define, and requires either high-quality labeled data and/or significant domain expertise to generate. RULER is a drop-in reward function that works across different tasks without any of that complexity. It works by showing N trajectories to an LLM judge and asking it to rank them relative to each other. This sidesteps the calibration issues that plague most LLM-as-judge approaches. Combined with GRPO (which only cares about relative scores within groups), it just works (surprisingly well!). We have a full writeup on the blog, including results on 4 production tasks. On all 4 tasks, small Qwen 2.5 models trained with RULER+GRPO beat the best prompted frontier model, despite being significantly smaller and cheaper to run. Surprisingly, they even beat models trained with hand-crafted reward functions on 3/4 tasks! https://ift.tt/h2KpZOG Repo: https://ift.tt/zP3sB8K https://ift.tt/h2KpZOG July 11, 2025 at 11:17PM

Show HN: An Improvisational Web Server https://ift.tt/9qCtlSj

Show HN: An Improvisational Web Server With Gemini Flash so fast, I wondered what it would be like for an LLM to generate web pages and images on-demand as the URLs are requested. It's been a couple of weeks now since release and there are a ton of cool examples people have created at https://ginprov.com/ . I have about half of my Gemini credits left (it's not too costly) but if it runs out, it's very easy to self-host with your own Gemini key. Some examples: https://ift.tt/rnwKi4P https://ift.tt/PbGxkpl https://ift.tt/nmd8DqO https://ift.tt/qwlW8mF https://ift.tt/vBjtFSW July 11, 2025 at 10:22PM