agentmods.dev

PreCompact

A pre-compaction hook that runs a Python script before an agent’s conversation context is shortened.

In plain words
What is it for?
Use it to run the referenced plugin’s pre-compaction routine before the session loses older context.
Why use it?
It provides a place to perform preparation before context is compacted, without requiring a manual command.

Hook

0 14d ago A scan tokens not measured original MIT
View the source file Substrate-memory/codex-substrate-memory
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/substrate-memory/codex-substrate-memory/pre-compact
Clone the repo
git clone --depth 1 https://github.com/Substrate-memory/codex-substrate-memory
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.

hooks/hooks.json · 14 lines

What it actually says

{
  "PreCompact": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${PLUGIN_ROOT}/scripts/plugin_runtime.py\" hook PreCompact",
          "timeout": 15,
          "commandWindows": "py -3 \"${PLUGIN_ROOT}/scripts/plugin_runtime.py\" hook PreCompact"
        }
      ]
    }
  ]
}
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 · 14 lines scan A a9c12efa89ce

Subscribe to this mod's changes

PreCompact is a hook published in the GitHub repository Substrate-memory/codex-substrate-memory (0 stars, last pushed 14d 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.

LanguagesMemory and context
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