What it is
Four more environment variables are now recognized and passed through by Claude Code
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.268.
Presence across releases
1Build by build
12One 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_ATTRIBUTION_STATUS_TIMEOUT_MS was v2.1.268, 10 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_attribution, up to twelve of them.
CLAUDE_CODE_ATTRIBUTION_ANNOUNCEMENTNo description from anybody. v2.1.268
CLAUDE_CODE_ATTRIBUTION_HEADERSet to 0 to omit the [attribution block](/docs/en/llm-gateway-protocol#system-prompt-attribution-block), which carries the client version and a prompt fingerprint, from the start of the system prompt. Caching on a direct connection to the Anthropic API is unaffected either way. In some direct-connection setups, Claude Code keeps the block on [auto mode](/docs/en/permission-modes#eliminate-prompts-with-auto-mode) classifier requests even when you set 0. In [System prompt attribution block](/docs/en/llm-gateway-protocol#system-prompt-attribution-block), check which connections and credentials this covers. Before v2.1.181 the block included a per-request token on custom base URLs and Microsoft Foundry connections, so on those versions set it to 0 when your LLM gateway caches on the request body or forwards requests to a third-party provider, or when you connect to Microsoft Foundry directly 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.