Codex favicon install runbook
Codex runs in a sandbox: the CLI on your machine, or a cloud container that hands back a pull request. Either way it can run a generator, place the files, and wire the head in one pass, but the sandbox's network is usually locked down and the model still can't draw a PNG. Get real image files into the working tree first, then let Codex do the wiring and prove it in the diff.
The sandbox may not reach the internet
Codex's cloud runs default to no network access, so "fetch this logo URL" can silently fail. Commit the source image into the repo, or generate the files where the sandbox can already see them.
It works on a branch, so check the PR
Cloud Codex returns a diff, not a running site. The binary icons have to appear in that PR; if a stray ignore rule drops them, the branch merges with markup pointing at files that were never committed.
URL finder for Codex
Paste your Codex preview link or production domain. We'll grab every favicon, let you choose one, and push it back to the generator.
Paste a domain and tap Scan to see every icon we can harvest.
We will open the generator with your selected favicon pre-loaded as the base image.
Playbook
Follow these beats whenever your builder regenerates UI so favicon coverage stays ahead of AI edits.
1Put the source and the files in the tree
Generate the full kit and add it to the branch, or commit the source logo so a networkless sandbox can still reach it. Don't rely on Codex pulling an image off the open web mid-run.
2Give one wiring instruction
List the exact filenames and sizes you added and tell Codex to reference them following the repo's existing convention (the head or the metadata export, plus manifest.json) and nothing else.
3Read the diff, not just the summary
Confirm every link tag points at a file that is actually in the diff, and that the image binaries are staged. The classic failure is a tidy summary describing icons the commit never contained.
Checklist
Drop this straight into your deployment doc.
Note in AGENTS.md that icons are generated binaries and must not be re-created by the model.
After the run, open the PR's Files changed and confirm the .ico and .png files are there, not just the markup.
If the sandbox has no network, provide the source image in-repo rather than as a URL in the prompt.
Codex favicon FAQ
Can Codex generate the favicon image itself?
No. Codex runs tools and edits files, but the model can't emit binary image data. Generate the PNG and ICO with a real tool (locally, or via a generator it's allowed to run) and let Codex handle placement, markup, and the commit.
Why did Codex fail to fetch my logo from a URL?
Codex's sandbox, especially the cloud agent, usually runs with no network access, so a prompt that says "download this image" hits a wall it won't always report clearly. Commit the source image into the repo so the agent works from a local file instead.
The PR wired the icons but the tab is still blank. Why?
Check that the image files are in the PR, not only the link tags. An ignore rule matching binaries or a build output folder is the usual reason the markup merges while the files it points at never do.
Codex install guide
Add /codex/favicon-install to project README files, onboarding docs, and launch checklists so nobody skips the favicon step.