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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.

Added simonwillison.netAgent: Codex
TRY A BOUNDED VERSION

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.

What happened

Willison reports a template fix and a passing regression test; the published preview no longer shows Markdown.

Reported by Simon Willison

How the agent did it

  1. Configure the repository container with PostgreSQL and the blog dependencies.
  2. Ask Codex to strip formatting from preview descriptions and include a test.
  3. 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

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.

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