[Feature Request] Support custom pre-compact, compact, and post-compact commands to run instead of default after context window is 95% full #3349

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1. github-actions

   added

   enhancementNew feature or requestNew feature or request

   area:core

   memory

   on Jul 11, 2025
2. brianbowden

   changed the title [-][Feature Request] Set custom commands to run instead of /compact after context window is 95% full[/-] [+][Feature Request] Set custom pre-compact, compact, and post-compact commands to run instead of default after context window is 95% full[/+] on Jul 11, 2025
3. brianbowden

   changed the title [-][Feature Request] Set custom pre-compact, compact, and post-compact commands to run instead of default after context window is 95% full[/-] [+][Feature Request] Support custom pre-compact, compact, and post-compact commands to run instead of default after context window is 95% full[/+] on Jul 11, 2025
4. coygeek commented on Aug 24, 2025

   

   coygeek

   on Aug 24, 2025

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   Hey, this is a really interesting and well-thought-out feature request. I've definitely had similar frustrations where /compact loses the specific context I've carefully built up for a task.

   The good news is that the dev team seems to have anticipated this need, and there's a feature that gets you about 90% of the way there already: Hooks. Specifically, the PreCompact hook.

   Based on the Hooks Guide and the Hooks Reference, you can set up a script to run automatically right before a compaction event happens.

   Here’s how you could build the workflow you're describing:

   1. Create a PreCompact Hook:
      You'd register a custom script to run on the PreCompact event. The hook even receives a trigger field in its JSON input, so your script will know if it was triggered by "auto" (the 95% threshold) or "manual" (a user running /compact). This directly addresses your need to handle the auto-compact event specifically.

   2. Build Your Custom "Compaction" Logic:
      Your script would receive the path to the current conversation transcript. It could then:

      • Parse the transcript to identify the key context (like the GitHub issue IDs you mentioned).
      • Use the gh CLI or a GitHub MCP server to fetch the latest, most relevant details for those issues.
      • Generate a new, condensed summary prompt that preserves the exact context you need for your work.

   3. Preventing the Default /compact:
      This is the key part. While the docs aren't super explicit about this for PreCompact, the "Advanced JSON Output" section for hooks mentions a common field: {"continue": false}. My interpretation is that you could have your script output this JSON to stdout. This should, in theory, stop Claude Code from proceeding with the default, built-in compaction after your hook runs.

   4. Injecting the New Context (Post-Compact):
      While there isn't a PostCompact hook, you can build this into your PreCompact script. After generating the new context, your script could print a message to the user like:

      Context window full. Default compaction stopped.
      Run '/clear' and then paste the following to continue with a fresh context:
      
      "Based on GitHub issue #1234, which is about [...], and the current state of files X and Y, let's continue working on the solution."
      

   It's not fully automated, but it turns a manual, multi-step research process into a single-step "copy-paste" action prompted by your own custom logic.

   Here's how you might configure it in your .claude/settings.json:

   {
     "hooks": {
       "PreCompact": [
         {
           "matcher": "auto", // Only run for automatic compaction
           "hooks": [
             {
               "type": "command",
               "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/rebuild-context.sh"
             }
           ]
         }
       ]
     }
   }

   While you can't replace the /compact command itself or add a post-compact hook directly, the PreCompact hook seems powerful enough to achieve your goal of taking control over context management when the window gets full.

   Hope this helps! Let us know if you get a script working, I'd be really interested to see it.

   👍React with 👍1Reacted by Jannis Mainczyk

   🎉React with 🎉1Reacted by Brian Bowden
5. DuaneNielsen commented on Aug 27, 2025

   

   DuaneNielsen

   on Aug 27, 2025

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   Agree with this 100%. We need much better context management options that the current auto-compact. I have not heard anyone do anything but complain about this feature! I understand it's a cost savings thing, and anthropic is having some serious problems sustaining the current paradigm.. as the ever shrinking quotas reveal.. but auto-compaction is not a good solution. This Enhancement Request and suggestions by @coygeek offers much more useful solution... putting tools into the the community's hands to find the solution to a problem that 100% of the users experience.
6. BEN-50763 commented on Sep 7, 2025

   

   BEN-50763

   on Sep 7, 2025

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   This is a brilliant suggestion.

   My current approach is to have claude output its progress on the current task to a current_task.md file. When it reaches 90% context, it tell it to update this, then I clear or compact, and have it read this as a first action afterwards.

   If we could automate the flow so:

   At 90%: update current_task.md, clear/compact with specific message
   Post clear/compact: force read of current_task.md and continue with work
7. github-actions commented on Dec 5, 2025

   

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