Feature Request: Global auto-background mode for long-running tool calls / subagents

Feature Request

Summary

Add a global setting or configuration option to automatically run long-running tool calls and subagents in the background, without requiring the user to manually press Ctrl+B each time.

Current Behavior

• Long-running tool calls (Bash, Agent, etc.) block the conversation until complete
• Users must manually press Ctrl+B to move a running tool to the background
• The background: true frontmatter option exists for individual subagent definitions, but there is no global "prefer background" mode

Desired Behavior

A setting in Claude Code (e.g. in settings.json or as an environment variable) that automatically backgrounds long-running tool calls so the user can continue chatting while they run. Something like:

\\\json
{
"autoBackground": true
}
\\\

Or an environment variable:
\\\
CLAUDE_CODE_AUTO_BACKGROUND=1
\\\

Use Case

When working on complex, long-running tasks (e.g. exploration agents, research agents, build pipelines), it's common to launch multiple agents and want to continue the conversation while they run. Currently this requires manually hitting Ctrl+B every time, which is easy to forget and breaks flow.

A global auto-background mode would make parallel agent workflows seamless without requiring manual intervention for each tool call.

Workaround

Currently the closest option is defining subagents in .claude/agents/ with background: true in their frontmatter, but this only applies to specific pre-defined subagents and not to ad-hoc tool calls or Bash commands.

Additional Context

The /tasks command and background task infrastructure already exist — this request is just for a way to opt into background-by-default behavior globally rather than per-agent.