What it is
Claude Code now recognizes a CLAUDE_CODE_HOST_SESSION_ID environment variable
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.274.
Presence across releases
1Build by build
5One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
First cited
1The earliest release whose published evidence quoted CLAUDE_CODE_HOST_SESSION_ID was v2.1.274, 16 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table above.
Names beside it
Every environment variable in the inventory starting claude_code_host, up to twelve of them.
CLAUDE_CODE_HOST_AUTH_ENV_VARNo description from anybody. v2.1.145
CLAUDE_CODE_HOST_AUTH_REFRESH_TIMEOUT_MSNo description from anybody. v2.1.145
CLAUDE_CODE_HOST_CREDS_FILEA trailing slash in your host credentials file path no longer changes whether the rule matches. v2.1.198
CLAUDE_CODE_HOST_PLATFORMNo description from anybody. v2.1.138
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the environment variable does. All environment variables.