What
When you republish an artifact without passing favicon, Claude now reads the existing icon to keep it, and if it cannot read it the publish fails instead of quietly falling back to 📄. This is live in this build with no flag around it.
Details
- Two distinct failures:
favicon required to publishwith reasonmissing_publish_fieldwhen there is no existing page to read from, and a newfavicon_unreadreason when the page exists but its icon could not be read. - The fix in either case is to pass
faviconexplicitly.
Evidence
couldn't read this Artifact's current favicon to keep it, so nothing was published — pass favicon explicitly
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundlefavicon
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Overview touched a line naming favicon after this was published.
Because inference runs in your cloud tenant, Claude Desktop on 3P operates inside whatever compliance boundary your provider and region give you. The desktop application itself contacts Anthropic-operated hosts only to download the VM work…third-party/claude-desktop/overview see the edit
Confirmed since
Anthropic's documentation has since written up favicon, on Agent SDK reference - TypeScript.
Publishes a local `.html` or `.md` file as a hosted artifact page, or lists the user's published artifacts. Omit `action` or pass `"publish"` to publish `file_path`, which is required for the publish action along with `favicon`, one or two…agent-sdk/typescript see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up favicon, on Agent SDK reference - TypeScript.