A pre-compaction hook that saves a short factual checkpoint before the agent’s conversation context is shortened. It then allows a later session-start step to restore the recent context.

Use it to preserve a checkpoint in `.harness/last-checkpoint.md` before context compaction; it runs automatically and does not use an AI subagent.

It reduces the chance of losing the user’s original request and recent work when the conversation becomes too large.

PreCompact — Hook by andrewcigan

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/andrewcigan/vibe-dev-plugin/pre-compact

Clone the repo

git clone --depth 1 https://github.com/andrewcigan/vibe-dev-plugin

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 2d 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 · 15 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PLUGIN_ROOT}/hooks/pre-compact.sh\"",
          "timeout": 30
        }
      ],
      "description": "Vibe Dev: PreCompact-хук M2 (v7, автопамять). Перед сжатием контекста — extractive-слепок транскрипта (первая просьба пользователя + последние просьбы + хвост хода) в .harness/last-checkpoint.md; SessionStart-бриф C1 восстанавливает контекст после компакции. Пишет ФАКТЫ, НЕ статус «готово». Без LLM/субагента, всегда exit 0 (fail-open). Событие подтверждено живым прогоном 2026-07-02 на 2.1.170. Активно во всех профилях (слепок безвреден).",
      "id": "vibe:pre-compact"
    }
  ]
}

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.

2d ago First seen · 15 lines scan A b73eb1d09c56

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository andrewcigan/vibe-dev-plugin (5 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.

ai-agents claude-code claude-code-plugin harness vibe-coding

PreCompact

Getting it into your agent

Grade A, and why

Nothing flagged

What it actually says

What this file has done since we first saw it

Other hooks, from other repositories

SessionStart

PostToolUse

Stop

UserPromptSubmit

SessionStart

PostToolUse