PreCompact

A hook that runs before the agent's conversation is shortened to make room for more context. It executes a local hook-orchestrator script.

In plain words
What is it for?
Use it in projects that need hook-orchestrator.mjs to run on every pre-compaction event.
Why use it?
It lets the project's configured hook system perform its preparation work before earlier context is compacted.

Hook

Part of the triflux plugin — 29 skills, 1 agent, 12 hooks shipped 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/tellang/triflux/pre-compact
Clone the repo
git clone --depth 1 https://github.com/tellang/triflux

Or install triflux, the plugin that ships this one along with the rest of its 29 skills, 1 agent, 12 hooks.

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 92% copy Near-identical to another mod 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 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.

Runs shell commandslowCapability

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

"command": "node -e \"const fs=require('node:fs'),os=require('node:os'),path=require('node:path'),cp=require('node:child_process');const roots=[];try{roots.push(fs.readFileSync(path.join(os.homedir(),'.claude','scripts',
Origin

This is a copy

92% identical to SessionStart — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

hooks/hooks.json · 14 lines

What it actually says

{
  "PreCompact": [
    {
      "matcher": "*",
      "hooks": [
        {
          "type": "command",
          "command": "node -e \"const fs=require('node:fs'),os=require('node:os'),path=require('node:path'),cp=require('node:child_process');const roots=[];try{roots.push(fs.readFileSync(path.join(os.homedir(),'.claude','scripts','.tfx-pkg-root'),'utf8').trim())}catch{}roots.push(process.env.PLUGIN_ROOT,process.env.CLAUDE_PLUGIN_ROOT);try{roots.push(cp.execFileSync('git',['rev-parse','--show-toplevel'],{encoding:'utf8',stdio:['ignore','pipe','ignore']}).trim())}catch{}roots.push(process.cwd());const root=roots.find(r=>r&&fs.existsSync(path.join(r,'hooks','hook-orchestrator.mjs')));if(!root){console.error('[triflux hook] cannot locate hooks/hook-orchestrator.mjs');process.exit(1)}const child=cp.spawnSync(process.execPath,[path.join(root,'hooks','hook-orchestrator.mjs')],{stdio:'inherit',env:process.env,windowsHide:true});process.exit(child.status??(child.signal?1:0));\"",
          "timeout": 5
        }
      ]
    }
  ]
}
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 5309bcc7826d

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository tellang/triflux (7 stars, last pushed 12d ago), licensed MIT. 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). It is 92% identical to SessionStart, differing in 4 lines, and is treated as a copy.