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PreCompact

PreCompact is a hook for coding agents from yanfeid/claude-amber. Its token cost is not measured, scanned A, original, MIT.

A session hook that runs a Node.js checkpoint script before the agent's conversation context is shortened. The context is the information the agent can currently remember.

In plain words
What is it for?
Use it for automatic pre-compaction checkpoints in agent sessions.
Why use it?
It preserves a checkpoint before context reduction, helping work continue with a saved state instead of losing important progress.

Hook

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 amber plugin — 4 skills, 3 hooks shipped together

One of 3 entries in hooks.json — they are configured in one file and arrive together.

not rated 2 2mo ago A scan tokens not measured original MIT
View the source file yanfeid/claude-amber
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 yanfeid/claude-amber
Claude Code
/plugin install amber

Or install amber, the plugin that ships this one along with the rest of its 4 skills, 3 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/yanfeid/claude-amber/pre-compact.svg)](https://agentmods.dev/hooks/yanfeid/claude-amber/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/yanfeid/claude-amber/pre-compact"><img src="https://agentmods.dev/badge/hooks/yanfeid/claude-amber/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.

hooks/hooks.json · 14 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "node \"${CLAUDE_PLUGIN_ROOT}/hooks/scripts/checkpoint.js\"",
          "timeout": 20,
          "statusMessage": "Amber: sealing checkpoint before compaction"
        }
      ]
    }
  ]
}
Same file

What else hooks.json configures

This page is one entry in a file that holds 3. 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 15a5177b73cd

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository yanfeid/claude-amber (2 stars, last pushed 2mo 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.

ai-memoryclaudeclaude-codeclaude-code-plugincontext-engineeringhooks
Related

Other hooks, from other repositories

PreCompact

Runs before the context is compacted, executing on_pre_compact.sh. From atomicstrata/atomicmemory.

atomicstrata/atomicmemory · not measured

PreToolUse

Runs before the agent uses a tool for Write and Edit tool calls, executing block_memory_write.sh. From atomicstrata/atomicmemory.

atomicstrata/atomicmemory · not measured

PostCompact

Runs after the context is compacted, executing on_post_compact.sh. From atomicstrata/atomicmemory.

atomicstrata/atomicmemory · not measured

TaskCompleted

Runs when a task is marked completed, executing on_task_completed.sh. From atomicstrata/atomicmemory.

atomicstrata/atomicmemory · not measured

Stop

Runs when the agent finishes a response, running claude-memes hook stop. From ShovalBenjer/claude-memes-skills.

ShovalBenjer/claude-memes-skills · not measured

PostToolUse

Runs after a tool call finishes for Grep tool calls, executing g2-fallback.py via python3. From pluto2060/CTX.

pluto2060/CTX · not measured