CLAUDE_CODE_SESSION_ID

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_SESSION_ID is a Claude Code environment variable: Stable identifier for the current session, passed into subprocess environments. Lets subprocess tools — hooks, MCP servers, custom scripts — correlate their work back to the originating session without parsing log files. Backs v2.1.122's PR-URL→session lookup feature. Added between v2.1.118 and v2.1.123 and still present in v2.1.294. It is listed in the official reference.

How to set it

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

export CLAUDE_CODE_SESSION_ID=<value>
claude

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

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

Release notes that mention it

• Claude Code v2.1.123 — Background Daemons, Agent Fleets, and CoWork Memory
• 165 Environment Variables in Claude Code 2.1.69 — What Changed in 50 Versions
• 83 Undocumented Claude Code Environment Variables (v2.1.19)
• claude-code-env-vars-v2-1-215
• claude-code-env-vars-v2-1-210

Related variables

• CLAUDE_BRIDGE_REATTACH_SESSION: Session identity used during bridge reconnection.
• CLAUDE_CODE_BRIDGE_SESSION_ID
• CLAUDE_CODE_CHILD_SESSION
• CLAUDE_CODE_EMIT_SESSION_STATE_EVENTS: Controls whether Claude Code emits session state change events.
• CLAUDE_CODE_FORCE_SESSION_PERSISTENCE
• CLAUDE_CODE_POST_FOR_SESSION_INGRESS_V2: Use POST-based session ingress v2.
• CLAUDE_CODE_REMOTE_SESSION_ID: Remote session identifier.
• CLAUDE_CODE_REMOTE_SESSION_ORIGIN: Provenance tag for cloud/remote sessions, checked against the value "review".

Frequently asked questions

All variables, searchable: Claude Code environment variables.