PreCompact

PreCompact is a hook for Claude Code from go-to-k/cdkd. Its token cost is not measured, scanned A, original, Apache-2.0.

A pre-compaction hook that runs a short shell command before the agent’s conversation context is shortened. It adds a reminder to record current work, unresolved issues, and next actions.

In plain words
What is it for?
Use it to prompt the agent to update its task notes before context compaction.
Why use it?
It helps preserve important working notes when the conversation is about to lose older context.

Hook for Claude Code

One of 5 entries in settings.json — they are configured in one file and arrive together.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add hooks/go-to-k/cdkd/pre-compact
Clone the repo
git clone --depth 1 https://github.com/go-to-k/cdkd

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for PreCompact

README.md
[![agentmods](https://agentmods.dev/badge/hooks/go-to-k/cdkd/pre-compact.svg)](https://agentmods.dev/hooks/go-to-k/cdkd/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/go-to-k/cdkd/pre-compact"><img src="https://agentmods.dev/badge/hooks/go-to-k/cdkd/pre-compact.svg" alt="Measured on agentmods" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured Not applicable: nothing here is loaded into a session.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

PreCompact scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the commands this hook runs, not an audit. A hook is shell that executes on your machine at the event it names, which is why every command in it is printed with what was found.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/settings.json · 14 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "printf '{\"hookSpecificOutput\": {\"hookEventName\": \"PreCompact\", \"additionalContext\": \"Before compaction: record current work state, unresolved issues, and next actions into TodoWrite before compacting.\"}}'",
          "timeout": 5,
          "statusMessage": "Preparing for context compaction..."
        }
      ]
    }
  ]
}
Same file

What else settings.json configures

This page is one entry in a file that holds 5. Installing the file brings all of them; each is measured and scanned on its own page.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 14 lines scan A c3a9a463d771

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository go-to-k/cdkd (122 stars, last pushed yesterday), licensed Apache-2.0. Its token cost is not measured: a hook is shell that never enters the context. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.