{"version":"2.1.299","anchor":"agent-tool-timing-marks-background-default-cwd-checks","canonical_anchor":"agent-tool-timing-marks-background-default-cwd-checks","heading":"Agent tool changes when subagents run in the background","tier":"notice","area":"Subagents","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.299\/e\/agent-tool-timing-marks-background-default-cwd-checks","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.299","markdown":"### Agent tool changes when subagents run in the background\n\nAgent tool calls can now default to running in the background, a new message can refuse background launches, and the tool checks working folders\n\n**Unclear.** It is not clear what decides whether a subagent now defaults to the background.\n\n**What**\n\nThe Agent tool lets Claude start a subagent, a helper that works on a task on its own. Its `run_in_background` setting decides whether the subagent runs in the background while Claude keeps going.\n\n- Before, a subagent ran in the background only when `run_in_background` was exactly `true`. A new default helper now also takes part, so `run_in_background` can default to background.\n\n- `launchedWithDefaults` is sent only when a helper is on.\n\n- A new fixed message tells Claude that background agents cannot be started in this session right now, and to run the agent with `run_in_background: false`. Where this message is returned was not found.\n\n- The tool checks the `cwd` (the working folder) on each call, and again after a spawn hook rewrites the call. A hook is a user-set command that runs at certain moments.\n\n- The tool takes a timing object and marks time spent waiting on outside work.\n\nThe stock Agent tool description captured under this release is unchanged.\n\n**Why**\n\nSubagents may start running in the background in cases where they did not before, and some background launches may be refused with the new message.\n\n- Area: Subagents\n- Names: `run_in_background`\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 4\/5\n- Scope: individual\n- Heads-up: no"}