PreCompact

PreCompact is a hook for Claude Code from MauricioVieiraBraga/briefspec. Its token cost is not measured, scanned A, a copy of PreCompact, MIT.

A pre-compaction hook that runs a shell command before the agent's conversation context is shortened. It calls a briefspec check script.

In plain words
What is it for?
Use it to run the briefspec check before context compaction.
Why use it?
It can check the session before older context is compressed, helping catch issues at that transition.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the briefspec plugin — 2 skills, 5 hooks shipped together

One of 5 entries in hooks.json upstream. Installing this one merges just its entry into your config; the other 4 are separate, each on its own page.

Good fit Use it to run the briefspec check before context compaction.

Compare 6 hooks from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add MauricioVieiraBraga/briefspec
Claude Code
/plugin install briefspec

Made for: Claude Code.

Or install briefspec, the plugin that ships this one along with the rest of its 2 skills, 5 hooks.

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/mauriciovieirabraga/briefspec/pre-compact/github.svg)](https://agentmods.dev/hooks/mauriciovieirabraga/briefspec/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/mauriciovieirabraga/briefspec/pre-compact"><img src="https://agentmods.dev/badge/hooks/mauriciovieirabraga/briefspec/pre-compact/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for PreCompact

Your own site · 80×15
<a href="https://agentmods.dev/hooks/mauriciovieirabraga/briefspec/pre-compact"><img src="https://agentmods.dev/badge/hooks/mauriciovieirabraga/briefspec/pre-compact.svg" alt="Reviewed on agentmods" width="80" 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. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod 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 10d 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.

Origin

This is a copy

100% identical to PreCompact — 0 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 · 13 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/scripts/briefspec-hook\" --provider auto --event PreCompact",
          "timeout": 10
        }
      ]
    }
  ]
}
Same file

What else hooks.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. 10d ago First seen · 13 lines scan A c747080528c9

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository MauricioVieiraBraga/briefspec (2 stars, last pushed 29d 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 0 findings. It is 100% identical to PreCompact, differing in 0 lines, and is treated as a copy.