PreCompact

PreCompact is a hook for coding agents from Fmarzochi/EGC. Its token cost is not measured, scanned A, original, Apache-2.0.

A pre-compaction hook that runs specified Node.js commands before an agent's conversation context is shortened. A hook is an automatic action triggered at a particular point in the agent lifecycle.

In plain words
What is it for?
It is for connecting the pre-compaction event to the provided utility and hook-runner scripts.
Why use it?
It lets required preparation or cleanup happen before earlier conversation details are removed from the active context.

Hook

One of 8 entries in hooks.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/fmarzochi/egc/pre-compact
Clone the repo
git clone --depth 1 https://github.com/Fmarzochi/EGC

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/fmarzochi/egc/pre-compact.svg)](https://agentmods.dev/hooks/fmarzochi/egc/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/fmarzochi/egc/pre-compact"><img src="https://agentmods.dev/badge/hooks/fmarzochi/egc/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 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

PreCompact scanned grade A with 1 finding 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 yesterday.

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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

"command": "node -e \"const fs=require('fs');const path=require('path');const {spawnSync}=require('child_process');const raw=fs.readFileSync(0,'utf8');const rel=path.join('scripts','hooks','run-with-flags.js');const hasR
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

hooks/hooks.json · 38 lines

How it starts

The opening of the file, as written. The whole thing — 38 lines — stays where its author put it; the contents beside it link to each section on GitHub.

{
  "PreCompact": [
    {
      "matcher": "*",
      "hooks": [
        {
          "type": "command",
          "command": "node -e \"const p=require('path');const r=(()=>{var e=process.env.EGC_PLUGIN_ROOT||process.env.ECC_PLUGIN_ROOT||process.env.GEMINI_PLUGIN_ROOT;if(e&&e.trim())return e.trim();var p=require('path'),f=require('fs'),h=require('os').homedir(),d=p.join(h,'.gemini'),q=p.join('scripts','lib','utils.js');if(f.existsSync(p.join(d,q)))return d;for(var s of [['egc'],['egc@egc'],['marketplace','egc'],['everything-gemini'],['everything-gemini@everything-gemini'],['marketplace','everything-gemini']]){var l=p.join(d,'plugins',...s);if(f.existsSync(p.join(l,q)))return l}try{for(var g of ['egc','everything-gemini']){var b=p.join(d,'plugins','cache',g);for(var o of f.readdirSync(b,{withFileTypes:true})){if(!o.isDirectory())continue;for(var v of f.readdirSync(p.join(b,o.name),{withFileTypes:true})){if(!v.isDirectory())continue;var c=p.join(b,o.name,v.name);if(f.existsSync(p.join(c,q)))return c}}}}catch(x){}return d})();const s=p.join(r,'scripts/hooks/plugin-hook-bootstrap.js');process.env.GEMINI_PLUGIN_ROOT=r;process.argv.splice(1,0,s);require(s)\" node scripts/hooks/run-with-flags.js pre:compact scripts/hooks/pre-compact.js standard,strict"
        }
      ],
      "description": "Save state before context compaction",
      "id": "pre:compact"
    },
    {
      "matcher": "*",
      "hooks": [
        {
          "type": "command",
          "command": "node -e \"const fs=require('fs');const path=require('path');const {spawnSync}=require('child_process');const raw=fs.readFileSync(0,'utf8');const rel=path.join('scripts','hooks','run-with-flags.js');const hasRunnerRoot=candidate=>{const value=typeof candidate==='string'?candidate.trim():'';return value.length>0&&fs.existsSync(path.join(path.resolve(value),rel));};const root=(()=>{const envRoot=process.env.EGC_PLUGIN_ROOT||process.env.ECC_PLUGIN_ROOT||process.env.GEMINI_PLUGIN_ROOT||'';if(hasRunnerRoot(envRoot))

Read the full file on GitHub · 38 lines

Same file

What else hooks.json configures

This page is one entry in a file that holds 8. 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. yesterday First seen · 38 lines scan A aa33470d5c87

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository Fmarzochi/EGC (48 stars, last pushed today), 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 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.