Real AI agent use cases, with sources and setup prompts

Build your own Vocaloid music player with Claude Code

He is building a Vocaloid music player with Claude Code, starting from another of his own apps. It worked on day one. The one thing he decided himself was swapping the colors to Miku teal.

$17/mo1 dayBeginnerSource linked

Source

piro0919 on Hacker News · 2026-10-20

Written in our own words. Credit to the original author. Link checked 2026-10-23.

What they did

He is building a Vocaloid music player with Claude Code, starting from another of his own apps. It worked on day one. The one thing he decided himself was swapping the colors to Miku teal.

Result (as claimed)

A personal music player working on day one.

Tools they used

Cost: Claude Code: from $17/mo.

Set it up

  1. Write a one-page brief

    Describe the app in plain words: who it is for, the 3 core screens or actions, and what "done" looks like.

  2. Start the project with your agent

    Open Claude Code and paste the brief. Ask it to propose a stack and a file plan before writing code.

  3. Build one slice at a time

    Ship the smallest working flow first, run it, then add features one by one. Commit after each working step.

  4. Test it like a user

    Click through on desktop and phone. Ask the agent to add basic tests and fix anything that breaks.

  5. Check security and ship

    Keep keys in environment variables, check auth and database rules, then deploy and share the link.

Copy the full setup prompt

Paste into your agent and it will walk you through the setup, asking before anything that sends, posts or spends.

You are helping me set up this AI use case end to end in Claude Code.

Goal: Build your own Vocaloid music player with Claude Code
What the original author did: He is building a Vocaloid music player with Claude Code, starting from another of his own apps. It worked on day one. The one thing he decided himself was swapping the colors to Miku teal.
Reported result (as claimed by the author): A personal music player working on day one.
Source: https://news.ycombinator.com/item?id=50161939
Tools they used: Claude Code
Category: Vibe coding & apps

Please:
1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like).
2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure.
3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data.
4. Finish with a checklist to run it again next time.

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Guides for this use case

How to vibe code an app with Claude Code

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