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 \
claudeDetails
- 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_SYSTEMis present. - The beta is still constrained by the surrounding provider and model checks, and
CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAScan 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.