Codex fixes Markdown leaking into social previews
Simon Willison gave Codex a specific defect in his Django blog: social preview descriptions exposed raw Markdown. Codex changed templates and added a passing test in a configured PostgreSQL environment.
simonwillison.netWhat happened
Willison reports a template fix and a passing regression test; the published preview no longer shows Markdown.
Reported by Simon WillisonHow the agent did it
- Configure the repository container with PostgreSQL and the blog dependencies.
- Ask Codex to strip formatting from preview descriptions and include a test.
- Let it edit the templates and run checks, then inspect the resulting social preview.
Where a person stepped in
Willison configured the environment, disabled agent internet access and inspected the resulting change.
A person approved each step before the agent continued.
More details
About this account
Codex selected the code changes and executed the test loop after receiving the bug and environment details.
Firsthand account links the patch and agent session. Reported result, not an independently reproduced benchmark.
Credit: Simon Willison
Added 14 Oct 2026
Source published 3 Jun 2025
Source checked 14 Oct 2026
Tools and topics
Codex · GitHub · Django · PostgreSQL
Code · Testing
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.
Prompt to try
Editorial adaptation, not the source author’s exact prompt. Replace bracketed inputs and review tool permissions first.
In this repository, fix [specific visible defect]. First reproduce it with the existing test runner. Make the smallest change, add a regression check, and report the diff and test output. Work on a branch; stop before merging or publishing.