Claude Code Async: Background Agents & Parallel Tasks

Run Claude Code sub-agents in the background while you keep working. True parallel AI development that eliminates blocking and boosts throughput.

Problem: When Claude Code spawns a sub-agent for research or complex analysis, your entire session blocks. You wait while the sub-agent works, unable to continue the conversation.

Quick Win: When Claude spawns a sub-agent, press Ctrl+B to move it to the background:

You: Research authentication best practices for our Next.js app
Claude: I'll spawn a sub-agent to research this...
[Sub-agent starts]
You: [Press Ctrl+B]
You: While that runs, let's work on the database schema...

Your session continues. The sub-agent works independently and surfaces results when done.

Background Agents: True Parallel Execution

Claude Code now supports asynchronous agent execution. When the main agent spawns sub-agents, you can background them and keep working with Claude on other tasks.

The workflow:

Request: Ask Claude to handle a task that benefits from a sub-agent
Claude spawns: The main agent creates a sub-agent for the work
Background it: Press Ctrl+B while the sub-agent runs
Continue working: Keep chatting with the main agent on other tasks
Auto-resume: When the sub-agent completes, it wakes up the main agent with results

Check running agents anytime with /tasks:

/tasks

You'll see each background agent's status, token usage, and progress. Click any agent to inspect details.

When Background Agents Excel

Perfect for background execution:

Research tasks requiring web searches
Code analysis across large codebases
Documentation generation
Security audits and vulnerability scans
Performance profiling reports

Keep in foreground:

Tasks requiring your immediate input
File modifications you need to review
Anything with sequential dependencies on your current work

Background agents become even more powerful when combined with structured orchestration. Instead of manually spawning and backgrounding individual agents, a plan-then-execute pipeline can dispatch multiple specialists in parallel, each working on isolated tasks while you focus on something else entirely. The ClaudeFast Code Kit implements this with its /team-build command, which coordinates 18 specialized agents through dependency chains so background work stays organized without manual tracking.

Background Bash Commands

The same pattern works for long-running shell commands. When Claude runs npm install, docker build, or ffmpeg and it takes a while, background it:

Claude: Running npm install...
[Command starts]
You: [Press Ctrl+B]
You: While that installs, can you review the API routes?

Monitor with /tasks, same as agents.

The `--agent` Flag: Debug Your Sub-Agents

New CLI flag lets you run Claude Code AS any sub-agent:

claude --agent plan

This launches Claude Code with the planning agent's configuration. Ask it questions, test its behavior, verify it works as expected before deploying in workflows.

Use cases:

Debug custom sub-agents before production use
Test agent instructions and tool access
Run specialized agents manually for one-off tasks
Understand built-in agent capabilities

Works with built-in agents (plan, explore, etc.) and your custom agents in .claude/agents/.

Also in This Release

Anthropic shipped several other features alongside background agents:

Instant compaction: The /compact command now executes immediately. Claude maintains a continuous session memory, so compaction just loads the summary into a fresh context. Learn more in our context management guide.

Session memory architecture: Every session now maintains a structured summary including status, completed work, discussion points, and a work log. See memory optimization for details.

Stats dashboard: Run /stats to see your usage patterns, favorite models, token counts, and streaks. Press Ctrl+S to copy for sharing.

Session naming: Use /rename to name sessions, then resume by name with claude --resume session-name. The /resume screen now groups forked sessions and adds keyboard shortcuts (P preview, R rename, B browse forks).

MCP quick toggle: Enable or disable MCP servers without editing config files. See our MCP basics guide for the commands.

Slack integration: Delegate tasks to Claude Code directly from Slack channels. Tag @Claude with bug reports or feature requests for team workflows.

Common Issues

Agent doesn't background: Press Ctrl+B while the agent is actively running, not after it completes.

Lost track of agents: Use /tasks to see all running background processes with their IDs.

Agent completed but no results: The AgentOutputTool automatically surfaces results. If missed, check /tasks for the completed agent's output.

Next Steps

Execution patterns: Master parallel, sequential, and background patterns to choose the right approach
Foundation: Understand agent fundamentals before building complex workflows
Design patterns: Learn sub-agent design for effective task delegation
Distribution: Master task distribution for multi-agent orchestration
Custom agents: Build specialized agents with custom agent patterns

Background agents transform Claude Code from a turn-based assistant into a parallel development environment. Launch research, continue building, get results when ready.