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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.

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Claude Code v2.1.138

1 entries read diff v2.1.137 → v2.1.138 Markdown

Version 2.1.138 is a very small CLI release. The filtered AST diff shows no added or removed declarations and the string-literal diff contains only build metadata, but one existing advanced beta path changed: CLAUDE_CODE_MID_CONVERSATION_SYSTEM can now override the normal Anthropic base URL check for the mid-conversation system beta.

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Changesopen

Advanced Mid-Conversation System Beta Override#

What

Claude Code now allows the CLAUDE_CODE_MID_CONVERSATION_SYSTEM environment override to enable the mid-conversation-system-2026-04-07 beta even when ANTHROPIC_BASE_URL is set to a non-default host.

Usage
ANTHROPIC_BASE_URL=https://your-compatible-endpoint.example \
CLAUDE_CODE_MID_CONVERSATION_SYSTEM=claude-sonnet-4-5 \
claude
Details
  • This is not a new public command or setting; the environment variable already existed in 2.1.137.
  • In 2.1.137, the mid-conversation beta check returned false whenever the base URL was not api.anthropic.com.
  • In 2.1.138, that base URL check is bypassed when CLAUDE_CODE_MID_CONVERSATION_SYSTEM is present.
  • The beta is still constrained by the surrounding provider and model checks, and CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS can still disable experimental betas.
Evidence

Mid-conversation beta gate now checks (!If() && !process.env.CLAUDE_CODE_MID_CONVERSATION_SYSTEM) before adding mid-conversation-system-2026-04-07 (search for "CLAUDE_CODE_MID_CONVERSATION_SYSTEM" and "mid-conversation-system-2026-04-07").

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

1 entry

Notesopen

#

No new slash commands, CLI flags, settings descriptions, tips, permission syntax, hook types, or user-facing messages were detected in the provided CLI diff.

The only added string literals in the AST-extracted string diff are the build timestamp "2026-05-09T04:04:51Z" and git SHA "d6d494651eb469be2ff763ef8d1b882aba8ca635". There is no migration guidance for this release.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

Verbatim
Official · Anthropic

Anthropic’s official release notes

Published verbatim by Anthropic for v2.1.138. Text is unmodified from the upstream changelog. Everything else on this page came out of the bundle instead, which is why the two lists don't match.

  • Internal fixes
Read it on GitHub →
System prompt

No change to the system prompt since v2.1.137.

Claude Code, interactive mode

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