PreCompact

PreCompact is a hook for Claude Code from fmind/dotfiles. Its token cost is not measured, scanned A, original, MIT.

A pre-compaction hook that runs a command before an agent's conversation context is shortened. Context compaction reduces old conversation detail so work can continue within the available space.

In plain words
What is it for?
Use it to connect context compaction with the session hook system from fmind/dotfiles.
Why use it?
It provides a defined point to run a session-related command before that information is compacted. The supplied configuration runs a `dot agent hook session grok` command.

Hook for Claude Code

Written for Claude Code: PreCompact hook event.

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 connect context compaction with the session hook system from fmind/dotfiles.

Compare 6 hooks from other repositories ↓
Install with agentmods
npx agentmods add hooks/fmind/dotfiles/pre-compact
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.

Clone the repo
git clone --depth 1 https://github.com/fmind/dotfiles

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/fmind/dotfiles/pre-compact/github.svg)](https://agentmods.dev/hooks/fmind/dotfiles/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/fmind/dotfiles/pre-compact"><img src="https://agentmods.dev/badge/hooks/fmind/dotfiles/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/fmind/dotfiles/pre-compact"><img src="https://agentmods.dev/badge/hooks/fmind/dotfiles/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 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 1mo 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

Copies of this mod

3 near-identical copies found in the catalogue:

  • SessionEnd — 91% identical, 2 lines differ
  • SubagentStop — 89% identical, 2 lines differ
  • Stop — 81% identical, 7 lines differ
dot_grok/hooks/hooks.json · 13 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "command": "dot agent hook session grok",
          "timeout": 30,
          "type": "command"
        }
      ]
    }
  ]
}
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. 1mo ago First seen · 13 lines scan A b55f82a67150

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository fmind/dotfiles (4 stars, last pushed 1mo 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. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.