CLAUDE_CODE_PLAIN_DELTA_TAKE_AT_SOURCE

Updated November 2, 2026 by Alex Sorokoletov

CLAUDE_CODE_PLAIN_DELTA_TAKE_AT_SOURCE is a Claude Code environment variable: When set to true, wraps the model call so plain-text deltas are captured at the source instead of through the normal path. Added between v2.1.315 and v2.1.317 and still present in v2.1.317. It is not in the official reference.

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_PLAIN_DELTA_TAKE_AT_SOURCE=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_PLAIN_DELTA_TAKE_AT_SOURCE": "<value>"
  }
}

Related variables

• CLAUDE_CODE_PLAIN_DELTA_FAST_PATH: When set, enables a fast path for emitting plain text streaming deltas directly; the fast path is disabled when it is unset.
• ANTHROPIC_BETAS: Comma-separated beta feature headers.
• ANTHROPIC_CUSTOM_HEADERS: Custom HTTP headers (newline-separated Key: Value).
• ANTHROPIC_FEDERATION_RULE_ID
• ANTHROPIC_ORGANIZATION_ID
• ANTHROPIC_WORKSPACE_ID
• BETA_TRACING_ENDPOINT: Custom endpoint for beta tracing.
• CLAUDE_AFK_COUNTDOWN_MS: Milliseconds before the away-from-keyboard timeout at which the warning countdown begins; defaults to 20000 and is capped at the timeout length.

Frequently asked questions

All variables, searchable: Claude Code environment variables.