When the Linux sandbox's socat bridge socket disappears (e.g., because socat died), Claude Code now raises a named SandboxBridgeUnavailableError with a clear message instead of an opaque socket error:
Linux sandbox SOCKS bridge socket is missing (socat may have died). Restart to retry.
Evidence
New SandboxBridgeUnavailableError class — search for "SandboxBridgeUnavailableError" or "bridge socket is missing (socat may have died)"
Strings lifted out of the shipped bundle, so the claim above can be checked against them.