[FEATURE]: Non-blocking background task dispatch (like Claude Code's ^+B)

[Dawnfz-Lenfeng]

Summary

When running a long bash command (e.g. npm test, docker build, pytest), the agent is blocked until the command finishes. There is no way to dispatch a terminal task to the background, let the agent continue working, and get notified when the task completes.

Problem

Currently, any bash command issued by the agent blocks the entire session:

• The agent cannot work on other files while waiting for a test run to finish
• The user cannot switch to another sub-agent or task during a long build
• There is no mechanism to "fire and forget" a terminal command and be notified of its result

Claude Code solves this with ^+B — the user presses Ctrl+B while a command is running, which detaches it to the background. The agent continues its conversation, and when the task finishes, the agent is notified inline.

Proposed Solution

Add a background task dispatch mechanism:

1. At the bash tool level: Add a background: bool parameter (default false). When true, the command is dispatched to a background shell process and returns immediately with a task ID.
2. Task polling/completion: The agent (or a system hook) receives a notification when the background task completes, with its stdout/stderr/exit code.
3. TUI keybind (bonus): Allow the user to press a key (e.g. ^+B) to detach a currently running bash command to the background, freeing the agent to continue.

Example UX

Agent runs: !npm test -- --watch
User presses: ^+B
→ Task #42 dispatched to background (webpack watch mode)
Agent continues conversation freely
...later, system message:
→ [Task #42 completed] npm test -- --watch — exit code 0 (12 tests passed)

Difference from existing subagent/background-subagent

This is not about spawning a sub-agent to do AI work. This is specifically about non-blocking bash command execution:

• Existing: task(background=true, ...) spawns a sub-agent for AI research tasks
• Proposed: The bash tool itself supports a background flag, allowing any shell command to run async without blocking the agent

Use Cases

• Run pytest in background while continuing to edit code
• docker build in background, keep working on unrelated files
• Start a dev server in background (npm run dev), then continue editing
• Run a long query against a database while the agent reads related code

Implementation Sketch

1. Add background field to the bash tool schema
2. When background=true, spawn the command in a detached process, return a task handle immediately
3. Register the task in the session runtime so the agent can be notified on completion
4. Optional: expose task_status / task_output tools for the agent to poll results

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Feature Request: Add Background Bash Execution (Like Claude Code’s Ctrl+b) #1970: Feature Request: Add Background Bash Execution (Like Claude Code's Ctrl+b) — nearly identical request for background bash execution with a background: true parameter and Ctrl+B keybind, referencing the same Claude Code feature
• [FEATURE]:AI无法运行背景任务 #18372: AI cannot run background tasks — same request for non-blocking background task execution