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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_CODE_ATTRIBUTION_HEADER

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 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

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 — —
2.1.242 – 2.1.243 2 releases in the build — —
2.1.160 – 2.1.241 73 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

  1. v2.1.229Attribution header can override the environment opt-out

    One first-party request path sends the attribution header even if you opted out via env var.

    named in this entry

  2. v2.1.229Auto-mode side queries always send the billing attribution header

    Auto-mode's side queries send billing attribution metadata even if you set the opt-out variable.

    named in this entry

  3. v2.1.227Billing attribution header carries a prompt id and validates its values

    Usage attribution headers can carry a prompt id, and one env var suppresses the header entirely.

    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_code, up to twelve of them.

CLAUDE_CODE_3P_PROBE_WROTE_OPUS_DEFAULTNo description from anybody. 2.1.207 CLAUDE_CODE_3P_PROBE_WROTE_SONNET_DEFAULTNo description from anybody. 2.1.207 CLAUDE_CODE_ACCESSIBILITYSet to 1 to keep the native terminal cursor visible and disable the inverted-text cursor indicator. Allows screen magnifiers like macOS Zoom to track cursor position 2.1.138 CLAUDE_CODE_ACCOUNT_TAGGED_IDNo description from anybody. 2.1.138 CLAUDE_CODE_ACCOUNT_UUIDThe device bridge is skipped entirely when the host's account UUID doesn't match the stored one. 2.1.138 CLAUDE_CODE_ACT_DONT_REDERIVEThree existing feature gates moved position; their defaults are unchanged. 2.1.162 CLAUDE_CODE_ACTIONNo description from anybody. 2.1.138 CLAUDE_CODE_ADDITIONAL_DIRECTORIES_CLAUDE_MDSet to 1 to load memory files from directories specified with --add-dir. Loads CLAUDE.md, .claude/CLAUDE.md, .claude/rules/*.md, and CLAUDE.local.md. By default, additional directories do not load memory files 2.1.138 CLAUDE_CODE_ADDITIONAL_PROTECTIONNo description from anybody. 2.1.138 CLAUDE_CODE_ADOPT_UNDERIVABLE_PARKED_PERMISSIONA resumed headless session could hand you back a permission prompt left unanswered, but three variables must be set. 2.1.238 CLAUDE_CODE_AGENTNo description from anybody. 2.1.138 CLAUDE_CODE_AGENT_COST_STEERNo description from anybody. 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.