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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.250 Feeds RSS JSON llms.txt

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

Reference / Environment variables

CLAUDE_AGENTS_SELECT

A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.138, including the newest one read.

What it is

Nobody has written a line about this one. It is not in any of Anthropic's reference tables and no changelog entry here carries a description of it. It is in the build, which is the whole of what this page can claim.

Presence across releases

ReleasesReadingDeclared typeDefault
2.1.245 – 2.1.250 5 releases never mined — —
2.1.160 – 2.1.243 75 releases in the build str —
2.1.138 – 2.1.159 20 releases in the build — —

A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.

Changelog entries naming it

No changelog entry here has ever named it. That is a statement about what has been written, not about the name: it has been in the build since v2.1.138 without anybody writing a line about it.

Documentation pages

None of Anthropic's documentation pages this site has a copy of carries this name.

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 2.1.198 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 2.1.198 CLAUDE_AFTER_LAST_COMPACTNo description from anybody. 2.1.138 CLAUDE_AGENT_SDK_CLIENT_APPNo description from anybody. 2.1.138 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) 2.1.138 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 2.1.138 CLAUDE_AGENT_SDK_VERSIONYour entrypoint and SDK version are checked against known values before being reported. 2.1.138 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 background subagents. Default 600000 (10 minutes). The timer resets on each streaming progress event; if no progress arrives within the window, the subagent is aborted and the task is marked failed, surfacing any partial result to the parent 2.1.138 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 2.1.138 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 2.1.138 CLAUDE_AX_PREPARK_MSIn [screen reader mode](/docs/en/accessibility#what-your-screen-reader-hears), how many milliseconds Claude Code waits, with the cursor at the start of the line, before it writes a new or changed line. Default 50. Set 0 to write immediately. Claude Code caps the wait at 5000. Requires Claude Code v2.1.233 or later 2.1.233

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.