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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_AGENT_SDK_DISABLE_BUILTIN_AGENTS

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

Set 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)

Anthropic's own wording. Read off Environment variables, captured 2026-08-28.

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 bool —
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

  1. v2.1.232Built-in agent selection is now a single three-way decision

    One resolver now picks no agents, coordinator or default, and the disable env var works as before.

    named in this entry

Documentation pages

A reference table page is one whose own table defines this name, and it is where the description above came from. A page that mentions it carries the name somewhere in its text and may say nothing about it at all. Every page carrying it.

Names beside it

Every environment variable in the inventory starting claude_agent_sdk, up to twelve of them.

CLAUDE_AGENT_SDK_CLIENT_APPNo description from anybody. 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

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.