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Claude prompt caching fails due to timestamp, tool ordering bugs

By PulseAugur Editorial · [2 sources] ·

A developer encountered a significant issue with Claude's prompt caching feature, resulting in a 0% cache hit rate across 1,412 calls. The problem stemmed from three distinct bugs: a dynamic timestamp in the system prompt, randomized tool ordering due to Python's string hashing, and a prompt variant that was too short to be cached. After rectifying these issues by moving the volatile timestamp to a separate, uncached block and ensuring stable ordering for tools, the cache hit rate improved to 94%, reducing input token costs by 58%. AI

IMPACT Highlights the critical need for exact byte-identity in prompt caching and the potential for subtle bugs to negate its benefits.

RANK_REASON Developer reports a bug and its fix in a specific AI product feature.

Read on dev.to — LLM tag →

AI-generated summary · Google Gemini · from 2 sources. How we write summaries →

Claude prompt caching fails due to timestamp, tool ordering bugs

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Developer reports a bug and its fix in a specific AI product feature.
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2 independent sources
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product, infra
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4 days old
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COVERAGE [2]

  1. dev.to — LLM tag TIER_1 English(EN) · jidonglab ·

    Claude Prompt Caching Hit 0 of 1,412 Calls: A Timestamp Killed It

    <p>I turned on Claude prompt caching, shipped it, and moved on to the next thing. A week later I opened the usage logs to admire my savings.</p> <p><code>cache_read_input_tokens: 0</code>. On every call. 1,412 calls in a row.</p> <p>The API never returned an error. My <code>cache…

  2. Mastodon — mastodon.social TIER_1 English(EN) · ngate ·

    🚀 # AI is soooo special it can't possibly be a mere "tool" like those mundane hammers and screwdrivers. 🙄 It's an autonomous entity with a mind of its own, here

    🚀 # AI is soooo special it can't possibly be a mere "tool" like those mundane hammers and screwdrivers. 🙄 It's an autonomous entity with a mind of its own, here to mystify us with its superior cognitive processes while we desperately try to comprehend its godlike essence. 😱🔧 http…

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