Lessons from building Claude Code: Prompt caching is everything

What to look for

Follow the prompt hierarchy from stable instructions through project and session context to new messages. The sections on tool changes and compaction explain why seemingly small changes can interrupt reuse during a long agent session.

Keep in mind

The implementation details belong to Claude Code and its API behavior. Cache reuse reduces repeated processing; it does not make every token free. Verify actual usage fields and provider-specific cache charges when applying the ideas elsewhere.

Read the original work

Lessons from building Claude Code: Prompt caching is everything ↗

By Thariq Shihipar · Anthropic · claude.dev

Published Apr 30, 2026. Source checked Oct 5, 2026.

Reading note by SaveMyToken · Added Oct 5, 2026. This page is a short editorial introduction; the full article belongs to its original publisher.