Testing an Identical /Goal app build on Fable 5 vs. GPT 5.6 Sol
I continue to use both Claude Code and Codex to build and update my apps. Both have been great but I still feel the Claude models have had a slight edge for the apps I’ve been working on. I decided to run a test on a new app build using the /goal feature with Anthropic’s latest model Fable 5 against Open AI’s GPT 5.6 Sol to see how they would compare.
I recently used Codex computer use skill to achieve the task of creating a Spotify playlist for a concert setlist on my computer. I gave Codex the setlist url and then it accessed my logged in account to create the playlist. It worked great. I then realized I should build an app for this which was the basis for my test.
I normally would provide a full requirements spec in a markdown file before building an app like this, but I purposely created a very simple prompt for this test using the /goal feature to see how each model would infer functionality by filling in the gaps that weren’t provided.
Here’s the prompt
Create a web app where a user can search for a setlist from setlist.fm using the api https://api.setlist.fm/docs/1.0/index.html and then create a Spotify playlist with the songs from the setlist in their Spotify account using the api https://developer.spotify.com/documentation/web-api/reference/create-playlist
I won’t go into too much detail but wanted to provide some of the interesting things and quick highlights from the test and comparison between what both models created.
| Metric | GPT 5.6 Sol | Fable 5 |
| Build time | 20 minutes 33 seconds (Codex provided) | 10-15 minutes (Claude estimated) |
| Token Usage ($20 plan) | 8% | 21% |
| Web server choice | ChatGPT Hosted Site | Local |
| API Configuration | Worked on first try | Ran into some issues. Was able to resolve them after 3 fixes. |
| Setlist Search | One single text field. Limiting, too many results. | Artist, city, year filters to limit search results. |
| Design / UI | Nice colors & typography. Single page, multi-step interface. | Dull colors, clunkier multi-page steps. Not as clean. |
| Spotify Details | Added ability to make setlists public or private. Put concert location in description. | Better Setlist title, referenced original setlist. Provided app attribution. |
Fable 5 Site
GPT 5.6 Sol Site
I’ve heard about people “one shotting” an app but never really experienced that until using the /goal command. I usually have detailed requirements and then have used either Superpowers or Compound Engineering and spend days iterating an app. This was a fun experiment on a pretty simple app and I can see the value of getting something up and running quick (20 minutes!). I can see that doing this can help you get something running and decide later to iterate a concept without too much work up front.
Some other interesting observations. This is the first time ChatGPT created an app using their new Sites feature instead of setting up a local environment. Not sure how I feel about that yet but it’s probably one of the reasons it completed the app quicker and used less tokens having that functionality it could leverage. ChatGPT also truly one-shotted the app whereas Claude had some API issues I had to work through. Lastly I liked the design/ui of ChatGPT’s app more except for the weaker search functionality. Overall I’d say ChatGPT was the winner in this comparison. However this is just one test and I will continue to use both of them comparing their outputs for the forseeable future.
You can try the Setlist to Playlist app here: https://encore-setlist-playlist.krynsky.chatgpt.site
I’ve updated it to include the better search functionality Fable used. For now I’m using the ChatGPT Sites hosting but If people like it and it becomes popular I will add more features and may migrate it to Vercel as there are some limitations to hosting a ChatGPT site.
Do you have any experiences using the /goal function? Share them in the comments.