Cloud sessions now refuse --tools restrictions they cannot apply instead of dropping them

What

--tools is the command-line flag that limits which built-in tools Claude can use. For cloud sessions, which run on Anthropic's servers instead of your computer, Claude Code now checks this flag before the session starts.

• The --tools list is sorted into the default set, refused lists and other lists. Some lists are now accepted.
• Names that are malformed, presets, negations or rules are refused, as are an empty list and a list over a maximum length. The error says a cloud session cannot apply these tool restrictions, so they are refused rather than silently dropped. The same applies to --disallowed-tools.
• A refused list gives a tool_restriction error naming the tools at fault.
• Using --tools when attaching to an existing cloud session gives an attach_restriction error, saying a flag cannot change an existing cloud session.
• On Remote Control, self-hosted or unknown environments, the session is not started, for example: "The cloud session was not started: --tools is not supported in a Remote Control environment."
• A separate error covers --tools when the device is bound without a deferred prompt.
• The old check after creation, builtin_tools_not_echoed, is removed. Session creation now checks the built-in tools itself and stops if they cannot be applied.

Why

If you pass tool restrictions to a cloud session, you now get a clear error when they cannot be honoured, instead of a session that may run without the limits you asked for.