What
When Claude Code reads an artifact through its session gateway (the relay that handles shared-artifact traffic) and the read fails with a server error (500 or higher), a rate-limit error (429), or a timeout (408), it now waits and retries the read once before giving up. It honors any Retry-After timing the server provides, within a capped limit. This retryable failure is now reported as a distinct "unavailable" error, separate from a hard error that means the connection was actively blocked.
Why
Many of these failures are brief and transient, so retrying once automatically means a temporary hiccup no longer surfaces as a failure to the user, while still distinguishing genuine outages from a firm network block.