I noticed Fable 5.1 seems to consume noticeably less of my 5-hour limit now than it did right after launch, so I checked the recent Claude Code fixes. My estimate (NOT an official Anthropic number): For long, tool-heavy or agentic Claude Code sessions, the recent fixes could plausibly mean around 20–50% less unnecessary input usage in cases that were affected by these cache regressions. Measured regression: GitHub issue #91707 analyzed around 5,300 turn boundaries and reported prompt-cache misses increasing from: Claude Code 2.1.224: 7.2% Claude Code 2.1.252: 29.2% The reporter later tested 2.1.259 and found that the main regression was no longer reproducible. Recent official Claude Code fixes: 2.1.259
- Fixed OAuth token refresh invalidating the prompt cache.
- Fixed blocking Stop hooks causing prompt-cache misses on some models. 2.1.260
- Fixed a Fable 5.1-specific issue where context added after tool results was not cached and could be re-sent as uncached input on subsequent tool-call turns.
- Fixed changing Fable 5.1 effort mid-session invalidating the prompt cache.
- Added cache-miss diagnostics to /cost. 2.1.261
- Fixed Agent Team teammates re-sending tool/skill announcements on their second turn, changing the request prefix and causing a prompt-cache miss. There was also another report (#91514) showing how severe a single cache failure could become: roughly 752k cached tokens dropped to around 33k, with roughly 726k tokens being written again. Important: Anthropic has NOT published an official percentage saying Fable 5.1 is now X% cheaper on subscriptions. The 20–50% figure above is only my estimate based on the documented cache bugs, the measured 7.2% → 29.2% miss-rate regression, and the scale of individual cache failures. If Fable 5.1 felt extremely expensive during the first days after launch, it may be worth testing again on Claude Code 2.1.260/2.1.261 or newer. Has anyone else noticed their 5-hour usage lasting longer after these fixes? Sources: Official Claude Code changelog: https://code.claude.com/docs/en/changelog GitHub issue #91707: https://github.com/anthropics/claude-code/issues/91707 GitHub issue #91514: https://github.com/anthropics/claude-code/issues/91514 submitted by /u/AironParsMan
Originally posted by u/AironParsMan on r/ClaudeCode