What
- Republishing an artifact now accepts an optional
deadlinevalue ofnow,15m,1h,24h,7d, or an ISO UTC timestamp, telling already-open older-version viewers of the artifact when they must stop. Published changes already reach open viewers automatically; this field is only for forcing old versions off. Multiple deadline declarations accumulate, and the earliest one wins. - The file name
preflight.jsat an artifact's root is now reserved: it runs against open pages when the artifact is published, and it must be an ES module of 8 KiB or less with a default-export function, or the publish is refused.
Why
This lets a publisher forcibly retire stale open copies of a republished artifact instead of leaving them running indefinitely, and it reserves a hook point (preflight.js) for publish-time checks.
Names in the bundledeadline
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 Environment variables touched a line naming deadline after this was published.
| `CLAUDE_CODE_WEBFETCH_DEADLINE_MS` | Upper bound in milliseconds on how long [WebFetch](/docs/en/tools-reference#webfetch-tool-behavior) waits for a page to download, including any redirects it follows. A download that hasn't completed b…env-vars see the edit
Confirmed since
Anthropic's documentation has since written up deadline, on Claude Code changelog.
* Fixed WebFetch hanging indefinitely on a server that keeps the response open without finishing; a fetch now fails after 300 seconds. Set `CLAUDE_CODE_WEBFETCH_DEADLINE_MS` to override the deadline (0 turns it off)changelog 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 deadline, on Claude Code changelog.