{"version":"2.1.277","anchor":"new-per-tool-backgrounding-policy-field-most-tools-opt-ou","canonical_anchor":"new-per-tool-backgrounding-policy-field-most-tools-opt-ou","heading":"Tools now declare whether their calls can run in the background","tier":"internal","area":"Background Tasks","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.277\/e\/new-per-tool-backgrounding-policy-field-most-tools-opt-ou","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.277","markdown":"### Tools now declare whether their calls can run in the background\n\nEvery built-in tool now has a backgrounding field (never, self, or detach) controlling whether it can move to the background mid-run\n\n**Unclear.** The finding doesn't say what \"self\" backgrounding means in practice or which tool uses it.\n\n**What**\n\nTool definitions now carry a `backgrounding` field that controls whether a call to that tool can be moved to the background while it's still running, rather than blocking the conversation until it finishes. The possible values are `\"never\"`, `\"self\"`, and `\"detach\"`.\n\n- Most built-in tools, including `ExitPlanMode`, `KillShell`, `WebFetch`, `WebSearch`, `PushNotification`, `RunWorkflow`, `FetchInboxMessage`, `ReadMcpResource(Dir)`, scheduled-prompt tools, `Edit`, `NotebookEdit`, `Read`, `Glob`, `TodoRead`\/`TodoWrite`, `SendMessage`, `Bash`, `Task`, `mcp` tools, and self-hosted-runner tools, are explicitly set to `\"never\"`.\n\n- Tools that don't set the field default to `\"never\"` as well.\n\n- At least one tool is set to `\"self\"`.\n\nA helper resolves the effective value, applying the default when a tool doesn't specify one.\n\n**Why**\n\nThis gives Claude Code a consistent, explicit way to know which tool calls are safe to move to the background and which must always block, which matters for features that let long-running tool calls detach without disrupting tools that shouldn't be interrupted or backgrounded.\n\n- Area: Background Tasks\n- Names: `backgrounding`\n- Tier: Under the hood\n- Useful: 3\/5\n- Signal: 3\/5"}