PostToolUse

A group of after-tool hooks that records agent activity after tools are used. Different hooks update a liveness heartbeat, track file reads, record writes, and create post-change information.

In plain words
What is it for?
Use it to run status updates after any tool call, track reads, process file changes, and generate change-related records after edits.
Why use it?
It makes session activity visible and keeps records up to date while the agent works. The heartbeat also shows whether the agent is still active.

Hook

Part of the c-brain plugin — 3 skills, 8 agents, 5 hooks shipped 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/yuno15-bb/c-brain/post-tool-use
Clone the repo
git clone --depth 1 https://github.com/Yuno15-bb/c-brain

Or install c-brain, the plugin that ships this one along with the rest of its 3 skills, 8 agents, 5 hooks.

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 70% copy Near-identical to another mod in the catalogue.
Security

Grade A, and why

PostToolUse 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.

Origin

This is a copy

70% identical to TaskCompleted — 39 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

hooks/hooks.json · 45 lines

What it actually says

{
  "PostToolUse": [
    {
      "_why": "SESSION LIVENESS. Every other PostToolUse entry matches a SLICE of the tools — Read for one, Write|Edit for the others — so a session spent in Bash, Grep or Task emitted no sign of life at all and the capsule hid the orb mid-work (measured: a status 654 s stale while the session never stopped). This one matches everything on purpose: the question is 'is Claude still working', and any tool running is the answer. It refreshes LIVENESS only, never the activity label.",
      "matcher": "*",
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/brain_status.py\" heartbeat",
          "timeout": 5
        }
      ]
    },
    {
      "matcher": "Write|Edit",
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/on_fiche_write.py\"",
          "timeout": 15
        }
      ]
    },
    {
      "matcher": "Read",
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/track_read.py\"",
          "timeout": 10
        }
      ]
    },
    {
      "matcher": "Write|Edit|MultiEdit|NotebookEdit",
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/companion/hooks/post_diff.py\"",
          "timeout": 8
        }
      ]
    }
  ]
}
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. 2d ago First seen · 45 lines scan A efa9006ff40e

Subscribe to this mod's changes

PostToolUse is a hook published in the GitHub repository Yuno15-bb/c-brain (2 stars, last pushed 8d ago), 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. It is 70% identical to TaskCompleted, differing in 39 lines, and is treated as a copy.