What
A comprehensive built-in skill for helping users build LLM-powered applications with Claude, including code examples for Python, TypeScript, Java, Go, Ruby, C#, PHP, and cURL.
Status
Added as part of the skills system, contains full documentation for:
- All current Claude models (Opus 4.6, Sonnet 4.6, Haiku 4.5)
- Adaptive thinking, effort parameter, compaction
- Tool use, streaming, batches, files API
- Agent SDK patterns
- Language-specific SDK examples including a new C# SDK section
Evidence
Large string literal beginning with "# Building LLM-Powered Applications with Claude" (search for "Building LLM-Powered Applications with Claude")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.