Developer Yuki Yoshioka (@yoppy0123) notes that from Claude Code v2.1.260, Fable 5.1 keeps the prompt cache valid when effort is changed mid-conversation, cutting repeated prefill cost from effort switches. The post warns Opus 5 is not listed in the notes and likely lacks the same fix yet, so treat models differently after upgrading.

Key Takeaways

  • ✓Claude Code v2.1.260: Fable 5.1 mid-chat effort changes no longer invalidate the prompt cache.
  • ✓Helps adjust reasoning effort without re-paying large context prefill.
  • ✓Opus 5 not confirmed in notes — do not assume all models behave the same.
⚡

Key Decision Metrics at a Glance

TL;DR Verdict
🏆 Benchmark RankRank
See how it ranks on the leaderboard
Full Leaderboard→
💰 Cost & PlansCompare
Claude Fable 5.1 · in: $10 / out: $50
Compare Plans↗
🛠️ Ecosystem & IDERules
Claude Code (Anthropic)
Setup IDE Rules↗
🧭

Heavy Claude Code use: compare subscription limits and API bills

Compare 40 dev plans & simulate token costs vs $20/mo subscriptions

⚔️ Compare Model→💰 Compare plans & limits↗
Action HubReady to adopt this in production?

Benchmark side-by-side against alternatives, or calculate monthly token cost vs subscription break-even.

⚔️ Launch VS Compare→💳 View Plans↗
Up NextAnthropic brings in-country Claude inference to India: Opus 5, Sonnet 5 and Haiku 4.5 via Amazon Bedrock with data kept in India
Read Now→