Skills with `context: fork` now run in the background by default — set `background: false` if yours was meant to block
Claude Code Changelog·medium signal
v2.1.218 (July 22) changed forked-context skills to run in the background by default, with a per-skill `background: false` opt-out in frontmatter. Any skill authored on the assumption that a fork blocks the main conversation until it returns now behaves differently, and the failure is silent — the main session simply continues. The same release also began accepting `yes`/`no`/`on`/`off`/`1`/`0` (case-insensitive) for skill and plugin frontmatter booleans, and started rejecting agent names containing `:`, which is now reserved for plugin namespacing.