CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS is a Claude Code environment variable: Ceiling on subagents running at once, default 20; when full Claude Code tells the model to stop and the user to raise this variable. Gated by tengu_amber_kestrel. First shipped v2.1.217; named in the changelog. Added between v2.1.215 and v2.1.217 and still present in v2.1.294. It is listed in the official reference.

Status	Present in v2.1.294
Added	Added between v2.1.215 and v2.1.217
Category	Agents and subagents
Official docs	Listed

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS": "<value>"
  }
}

Release notes that mention it

Related variables

CLAUDE_CODE_MAX_SUBAGENTS_PER_SESSION: Per-session ceiling on subagent spawns (default 200).
CLAUDE_CODE_WORKFLOW_MAX_CONCURRENT_AGENTS
CLAUDE_CODE_MAX_SUBAGENT_SPAWN_DEPTH: Nesting-depth cap on delegation, default 1 — subagents no longer spawn their own subagents, and the team roster stays flat.
CLAUDE_SUBAGENT_BG_SHELL_MAX_MS: Time cap for shell commands run by background subagents.
CLAUDE_AGENT: Short-form identifier for the current agent, used in inter-agent messaging and log attribution.
CLAUDE_AGENT_SDK_CLIENT_APP: Client application name.
CLAUDE_AGENT_SDK_DISABLE_BUILTIN_AGENTS: Disable built-in agent types.
CLAUDE_AGENT_SDK_MCP_NO_PREFIX: Don't prefix MCP tool names with server name.

Frequently asked questions

What does CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS do?

Ceiling on subagents running at once, default 20; when full Claude Code tells the model to stop and the user to raise this variable. Gated by tengu_amber_kestrel. First shipped v2.1.217; named in the changelog.

Which Claude Code version has CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS?

Added between v2.1.215 and v2.1.217 and still present in v2.1.294.

How do I set CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS?

Export it before starting Claude Code (export CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS=value), or add it to the "env" object in ~/.claude/settings.json to apply it to every session.

All variables, searchable: Claude Code environment variables.