# Keep an app's rules in one data file so the agent can change behavior without touching code

PaperChase agent use case (free feed entry), version 1.0. Source: [u/chadMueller on r/ClaudeAI](https://www.reddit.com/r/ClaudeAI/comments/1xgts0i/i_built_a_90s_cable_tv_guide_for_plex_jellyfin/), 2026-10-27.

## What they did

The author wrote a spec for the guide before any code. Channel lineups, time slots and display rules sit in one JSON data file, so most changes are edits to data rather than code, and helper scripts pull metadata from TMDB to fill channels. Every build was tested on a real TV device, not only a simulator. Users suggest and vote on features in a Discord, which sets the backlog. When the app moved to a new platform, the existing app served as the spec for the port. The author reports more than 1,400 Apple TV downloads.

## Worth knowing

Putting rules in data gives the agent a small, safe surface to edit and gives you a single file to review. Using a working app as the spec for a port is more precise than describing it again in prose. Download figures are the author's own.

## Workflow template

```text
Apply this workflow to [your project]:
1. Write a one-page spec before the first prompt
2. Move every rule that might change into one data file with a schema
3. Ask the agent to change behavior through the data file first, code second
4. Test each build on the real device
5. When porting, give the agent the working app and its tests as the spec
Stop and ask me before anything irreversible: deploys, payments, sends or deletes.
```

## Steps

1. **Write a one-page spec before the first prompt.** Write a one-page spec before the first prompt
2. **Move every rule that might change into one data file with a schema.** Move every rule that might change into one data file with a schema
3. **Ask the agent to change behavior through the data file first, code sec.** Ask the agent to change behavior through the data file first, code second
4. **Test each build on the real device.** Test each build on the real device
5. **When porting, give the agent the working app and its tests as the spec.** When porting, give the agent the working app and its tests as the spec

## Credit

Workflow reported by u/chadMueller on r/ClaudeAI: https://www.reddit.com/r/ClaudeAI/comments/1xgts0i/i_built_a_90s_cable_tv_guide_for_plex_jellyfin/

Summary and template written by PaperChaseWebb in our own words. Questions: mgmt@paperchasewebb.com