--- title: Jev's compaction strategy is getting roasted, and the... description: A new compaction strategy called Jev, which prunes agent tool-call history line-by-line instead of summarizing it, is drawing sharp criticism from AI agent... canonical: https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Jev's compaction strategy is getting roasted, and the critique is pretty damning | daily.dev og:description: A new compaction strategy called Jev, which prunes agent tool-call history line-by-line instead of summarizing it, is drawing sharp criticism from AI agent... og:url: https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb og:image: https://api.daily.dev/og/posts/FqoujnFcB.png og:image:alt: Jev's compaction strategy is getting roasted, and the critique is pretty damning og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Jev's compaction strategy is getting roasted, and the critique is pretty damning **[Trends](https://daily.dev/sources/trends)** · 2 min read · 2 upvotes · 0 comments ## Summary A new compaction strategy called Jev, which prunes agent tool-call history line-by-line instead of summarizing it, is drawing sharp criticism from AI agent builders. Theo argues Jev's context-blind deletions cause agents to repeat failed actions, break Anthropic's caching by forcing expensive cache rewrites, and strip encrypted reasoning payloads that frontier models require intact history to regenerate. Armin Ronacher offers a more measured take, saying pruning at compaction time has real cost value even if Jev's implementation is flawed. Others note the underlying gap Jev tries to address — agents still can't use tools or write files during compaction — is real, even if this fix isn't it. ## Content A tool called Jev is making the rounds as a smarter way to handle context compaction in AI agents. The Syntax crew went live to discuss whether the hype is overblown. LangChain is exploring how it fits into agent workflows. The discourse is heating up. Then Theo dropped a six-point takedown, and it's hard to argue with most of it. The core claim: Jev's approach to compaction is "a terrible strategy that fundamentally doesn't understand how compaction and context management work." That's not a vibe, it's a technical indictment. Here's the short version of his case: **It's not actually compaction.** Real compaction is about keeping an agent focused when context gets too long. Jev's implementation goes line-by-line through tool calls, deciding what to keep or drop without knowing the full thread context or even the *result* of the tool call it's evaluating. That's not pruning, that's guessing. **It causes stupid loops.** Delete the record of what the model already tried, and it'll try the same thing again. This is a known failure mode, not an edge case. **It nukes reasoning traces.** Frontier models from Anthropic, OpenAI, and others don't expose reasoning over the API. Anthropic specifically requires you to preserve the full history to get any reasoning data at all. Run Jev on Claude Code and you're actively making the model dumber. **Cache invalidation costs are brutal.** Theo points out that cache writes can eat over 60% of LLM spend in heavy Claude Code or Codex usage. Edit anything early in the history and you're rewriting everything downstream. Jev's constant pruning makes this worse, not better. The one concession: Theo calls it "a cool experiment" and @mitsuhiko pushes back gently, noting that most agent harnesses need some pruning anyway for cost reasons, and Jev might actually help there. @lateinteraction flags a separate but related frustration: agents still can't use tools or write files *during* compaction at all, which is its own weird limitation. The consensus forming here isn't "Jev is useless" but "Jev is being oversold as a compaction solution when it's closer to a probabilistic filter." If you're tempted to swap out Claude Code's default compaction for this, Theo's advice is blunt: don't. ## Questions this post answers ### why does deleting old tool calls from an AI agent's context break Anthropic's prompt caching Deleting an entry mid-history forces every token after that deletion point to be rewritten to cache, since cache writes depend on a stable prefix. For example, removing item 2 from a six-item history requires rewriting items 3 through 6. Cache writes already account for over 60% of total LLM spend in some Claude Code usage, making mid-history deletion far more expensive than leaving unneeded entries in place. _Anyone tuning agent costs around prompt caching can track compaction debates like this on daily.dev._ ### why do frontier models lose reasoning ability when context is compacted mid-conversation Reasoning traces from frontier models like Claude, GPT, Grok, and Gemini are sent as encrypted payloads rather than plain text, and Anthropic specifically requires the full history to be preserved to return any reasoning data at all. Deleting or pruning parts of that history strips these payloads, effectively cutting off the model's ability to reason coherently across a long agent run. _Developers debugging agent reasoning quality can follow discussions like this on daily.dev._ ### what is wrong with Jev's approach to compacting AI coding agent context Jev evaluates and deletes tool calls line-by-line without knowing what came before or what the result was, which can cause agents to lose track of what they already tried and fall into repetitive loops trying the same failed action. Critics also note it breaks prompt caching and discards encrypted reasoning payloads required by frontier models to preserve reasoning quality. _Teams evaluating agent compaction strategies can weigh critiques like this via daily.dev._ --- Tags: [#ai-agents](https://daily.dev/tags/ai-agents), [#claude-code](https://daily.dev/tags/claude-code) [View this post on daily.dev](https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Jev's compaction strategy is getting roasted, and the critique is pretty damning","url":"https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb"},"datePublished":"2026-09-18T06:01:23.332Z","dateModified":"2026-09-21T17:57:06.069Z","description":"A new compaction strategy called Jev, which prunes agent tool-call history line-by-line instead of summarizing it, is drawing sharp criticism from AI agent...","isAccessibleForFree":true,"articleSection":"Trends","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Trends","logo":"https://media.daily.dev/image/upload/s--ZfSp3asX--/f_auto,q_auto/v1780996004/logos/trends?_a=BAMAMiWQ0","url":"https://daily.dev/sources/trends"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":2},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"ai-agents,claude-code","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Trends","item":"https://daily.dev/sources/trends"},{"@type":"ListItem","position":3,"name":"Jev's compaction strategy is getting roasted, and the critique is pretty damning"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/jev-s-compaction-strategy-is-getting-roasted-and-the-critique-is-pretty-damning-fqoujnfcb#faq","mainEntity":[{"@type":"Question","name":"why does deleting old tool calls from an AI agent's context break Anthropic's prompt caching","acceptedAnswer":{"@type":"Answer","text":"Deleting an entry mid-history forces every token after that deletion point to be rewritten to cache, since cache writes depend on a stable prefix. 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