What
When Claude Code launches background tasks, subagents and routines, it now passes a value as a separate argument only if it does not start with - and does not look like a URL scheme; otherwise it joins them as --flag=value. This stops prompts, model names and schemas that begin with a dash from being swallowed as options.
Details
- Applied to
--agent,--agents,--routine,--model,--effort,--append-system-promptand--json-schema. - The path that rewrites an agent name in an existing argument list was updated to handle both the split and joined forms.
Evidence
--append-system-prompt
Strings lifted out of the shipped bundle, so the claim above can be checked against them.