5 items tagged “val-town”
Val Town provides a web interface for building, running and deploying server-side JavaScript apps.
2024
System prompt for val.town/townie (via) Val Town (previously) provides hosting and a web-based coding environment for Vals - snippets of JavaScript/TypeScript that can run server-side as scripts, on a schedule or hosting a web service.
Townie is Val's new AI bot, providing a conversational chat interface for creating fullstack web apps (with blob or SQLite persistence) as Vals.
In the most recent release of Townie Val added the ability to inspect and edit its system prompt!
I've archived a copy in this Gist, as a snapshot of how Townie works today. It's surprisingly short, relying heavily on the model's existing knowledge of Deno and TypeScript.
I enjoyed the use of "tastefully" in this bit:
Tastefully add a view source link back to the user's val if there's a natural spot for it and it fits in the context of what they're building. You can generate the val source url via import.meta.url.replace("esm.town", "val.town").
The prompt includes a few code samples, like this one demonstrating how to use Val's SQLite package:
import { sqlite } from "https://esm.town/v/stevekrouse/sqlite";
let KEY = new URL(import.meta.url).pathname.split("/").at(-1);
(await sqlite.execute(`select * from ${KEY}_users where id = ?`, [1])).rows[0].idIt also reveals the existence of Val's very own delightfully simple image generation endpoint Val, currently powered by Stable Diffusion XL Lightning on fal.ai.
If you want an AI generated image, use https://maxm-imggenurl.web.val.run/the-description-of-your-image to dynamically generate one.
Here's a fun colorful raccoon with a wildly inappropriate hat.
Val are also running their own gpt-4o-mini proxy, free to users of their platform:
import { OpenAI } from "https://esm.town/v/std/openai";
const openai = new OpenAI();
const completion = await openai.chat.completions.create({
messages: [
{ role: "user", content: "Say hello in a creative way" },
],
model: "gpt-4o-mini",
max_tokens: 30,
});Val developer JP Posma wrote a lot more about Townie in How we built Townie – an app that generates fullstack apps, describing their prototyping process and revealing that the current model it's using is Claude 3.5 Sonnet.
Their current system prompt was refined over many different versions - initially they were including 50 example Vals at quite a high token cost, but they were able to reduce that down to the linked system prompt which includes condensed documentation and just one templated example.
Building search-based RAG using Claude, Datasette and Val Town
Retrieval Augmented Generation (RAG) is a technique for adding extra “knowledge” to systems built on LLMs, allowing them to answer questions against custom information not included in their training data. A common way to implement this is to take a question from a user, translate that into a set of search queries, run those against a search engine and then feed the results back into the LLM to generate an answer.
[... 3,372 words]Val Vibes: Semantic search in Val Town. A neat case-study by JP Posma on how Val Town's developers can use Val Town Vals to build prototypes of new features that later make it into Val Town core.
This one explores building out semantic search against Vals using OpenAI embeddings and the PostgreSQL pgvector extension.
Val Town Newsletter 15 (via) I really like how Val Town founder Steve Krouse now accompanies their “what’s new” newsletter with a video tour of the new features. I’m seriously considering imitating this for my own projects.
The first four Val Town runtimes
(via)
Val Town solves one of my favourite technical problems: how to run untrusted code in a safe sandbox. They're on their fourth iteration of this now, currently using a Node.js application that launches Deno sub-processes using the node-deno-vm npm package and runs code in those, taking advantage of the Deno sandboxing mechanism and terminating processes that take too long in order to protect against while(true) style attacks.