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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.

← All of v2.1.111 Home All releases ←olderv2.1.110 v2.1.112newer→
Claude Code v2.1.111

SDK: Subagent System Prompt Injection

What

SDK users can now append custom system prompt content to all Task-tool subagents via a new appendSubagentSystemPrompt option.

Usage
// In SDK session options
{
  appendSubagentSystemPrompt: "Your custom instructions here"
}
Details
  • The appendSubagentSystemPrompt field is propagated to nested subagents automatically
  • Gated by the CLAUDE_CODE_ENABLE_APPEND_SUBAGENT_PROMPT environment variable
  • Allows SDK consumers to inject additional instructions into every subagent without modifying the main system prompt
Evidence

SDK subagent prompt support (search for "appendSubagentSystemPrompt") — 0 occurrences in v2.1.110, 13 in v2.1.111

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

Related

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

See this entry in the whole of v2.1.111 →