What it is
MCP tool access can now be restricted by a host-issued grant token via CLAUDE_ARTIFACT_HOST_GRANT
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.271.
Presence across releases
1Build by build
8One 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_ARTIFACT_HOST_GRANT was v2.1.271, 14 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, up to twelve of them.
CLAUDE_AFK_COUNTDOWN_MSHow many milliseconds before auto-continue the on-screen countdown appears on an unanswered [AskUserQuestion](/docs/en/tools-reference) dialog. Default 20000 (20 seconds), capped at the auto-continue timeout. Has no effect unless auto-continue is on; see the [askUserQuestionTimeout](/docs/en/settings-reference#askuserquestiontimeout) setting and CLAUDE_AFK_TIMEOUT_MS. Requires Claude Code v2.1.198 or later v2.1.198
CLAUDE_AFK_TIMEOUT_MSHow many milliseconds of idle time before an unanswered [AskUserQuestion](/docs/en/tools-reference) dialog auto-continues without you. Auto-continue is off by default; opt in with the [askUserQuestionTimeout](/docs/en/settings-reference#askuserquestiontimeout) setting. This variable is an override for demos and automated tests: when set, it takes precedence over that setting and turns auto-continue on even when the setting is unset or never. Setting 0 doesn't turn the timeout off; it closes the dialog immediately. In v2.1.198 and v2.1.199, auto-continue was on by default with a 60000 (60 seconds) timeout. Requires Claude Code v2.1.198 or later v2.1.198
CLAUDE_AFTER_LAST_COMPACTNo description from anybody. v2.1.138
CLAUDE_AGENT_SDK_CLIENT_APPNo description from anybody. v2.1.138
CLAUDE_AGENT_SDK_DISABLE_BUILTIN_AGENTSSet to 1 to disable all built-in [subagent](/docs/en/sub-agents) types such as Explore and Plan. Only applies in non-interactive mode (the -p flag). Useful for SDK users who want a blank slate. This also removes general-purpose, the subagent Claude Code runs when an Agent tool call omits subagent_type. Such a call then fails with [subagent_type is required](/docs/en/errors#subagent-type-is-required) v2.1.138
CLAUDE_AGENT_SDK_MCP_NO_PREFIXSet to 1 to skip the mcp__<server>__ prefix on tool names from SDK-created MCP servers. Tools use their original names. SDK usage only v2.1.138
CLAUDE_AGENT_SDK_VERSIONYour entrypoint and SDK version are checked against known values before being reported. v2.1.138
CLAUDE_AGENTS_SELECTclaude agents resolves its directory filter through storage rather than the raw path. v2.1.138
CLAUDE_AI_ORIGINThe remote trigger tool can create webhook triggers so routines fire on outside events. never mined
CLAUDE_ASYNC_AGENT_STALL_TIMEOUT_MSStall timeout in milliseconds for subagents. Default 600000 (10 minutes); if you raise CLAUDE_STREAM_IDLE_TIMEOUT_MS while the stream watchdog is on, the default rises with it, as [Handle slow or stalled API responses](/docs/en/agent-sdk/typescript#handle-slow-or-stalled-api-responses) describes. The timer resets on each streaming progress event; if no progress arrives within the window, Claude Code aborts the subagent and reports the stall to the parent v2.1.138
CLAUDE_AUTO_BACKGROUND_TASKSSet to 1 to force-enable automatic backgrounding of long-running agent tasks. When enabled, subagents are moved to the background after running for approximately two minutes. Also enables [automatic backgrounding of long MCP tool calls](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) in non-interactive mode on Claude Code v2.1.212 or later v2.1.138
CLAUDE_AUTOCOMPACT_PCT_OVERRIDESet the percentage (1-100) of the auto-compact window at which auto-compaction triggers. Use lower values like 50 to compact earlier; the variable can't raise the threshold, so values above the default percentage are ignored. It applies only in sessions that [compact before the model's context limit](/docs/en/model-config#context-window-and-auto-compaction). Applies to both main conversations and subagents 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.