PreCompact

PreCompact is a hook for Claude Code from shyftlabs/continuum. Its token cost is not measured, scanned A, original, Apache-2.0.

Hooks that run project scripts before the agent's conversation context is shortened, either manually or automatically. Context is the information the agent can currently refer to.

In plain words
What is it for?
Use them to preserve state, summarize work, or run session-end processing before context is compacted.
Why use it?
They provide a chance to save session information before older context is removed.

Hook for Claude Code

One of 11 entries in settings.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/shyftlabs/continuum/pre-compact
Clone the repo
git clone --depth 1 https://github.com/shyftlabs/continuum

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/shyftlabs/continuum/pre-compact.svg)](https://agentmods.dev/hooks/shyftlabs/continuum/pre-compact)
Your own site
<a href="https://agentmods.dev/hooks/shyftlabs/continuum/pre-compact"><img src="https://agentmods.dev/badge/hooks/shyftlabs/continuum/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 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.

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

1 near-identical copy found in the catalogue:

.claude/settings.json · 32 lines

What it actually says

{
  "PreCompact": [
    {
      "matcher": "manual",
      "hooks": [
        {
          "type": "command",
          "command": "sh -c 'exec node \"${CLAUDE_PROJECT_DIR:-.}/.claude/helpers/hook-handler.cjs\" compact-manual'"
        },
        {
          "type": "command",
          "command": "sh -c 'exec node \"${CLAUDE_PROJECT_DIR:-.}/.claude/helpers/hook-handler.cjs\" session-end'",
          "timeout": 5000
        }
      ]
    },
    {
      "matcher": "auto",
      "hooks": [
        {
          "type": "command",
          "command": "sh -c 'exec node \"${CLAUDE_PROJECT_DIR:-.}/.claude/helpers/hook-handler.cjs\" compact-auto'"
        },
        {
          "type": "command",
          "command": "sh -c 'exec node \"${CLAUDE_PROJECT_DIR:-.}/.claude/helpers/hook-handler.cjs\" session-end'",
          "timeout": 6000
        }
      ]
    }
  ]
}
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 · 32 lines scan A af727243ae06

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository shyftlabs/continuum (84 stars, last pushed yesterday), 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 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.