PostToolUseFailure

PostToolUseFailure is a hook for Claude Code from hashgraph-online/hol-cigar. Its token cost is not measured, scanned A, a copy of SessionStart, Apache-2.0.

A tool-failure hook that runs a shell command after an agent tool call fails. A hook is an automatic action tied to a specific agent event.

In plain words
What is it for?
Use it to trigger the CIGAR check after a tool reports an error.
Why use it?
It lets the surrounding tool react to failed commands or other tool calls automatically.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

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 cigar plugin — 5 skills, 3 agents, 18 hooks, 1 MCP server shipped together

One of 18 entries in hooks.json — they are configured in one file and arrive together.

Good fit Use it to trigger the CIGAR check after a tool reports an…

Compare 6 hooks from other repositories ↓
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 hashgraph-online/hol-cigar
Claude Code
/plugin install cigar

Made for: Claude Code.

Or install cigar, the plugin that ships this one along with the rest of its 5 skills, 3 agents, 18 hooks, 1 MCP server.

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 PostToolUseFailure

README.md
[![agentmods](https://agentmods.dev/badge/hooks/hashgraph-online/hol-cigar/post-tool-use-failure.svg)](https://agentmods.dev/hooks/hashgraph-online/hol-cigar/post-tool-use-failure)
Your own site
<a href="https://agentmods.dev/hooks/hashgraph-online/hol-cigar/post-tool-use-failure"><img src="https://agentmods.dev/badge/hooks/hashgraph-online/hol-cigar/post-tool-use-failure.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. A grade says what 26 rules found in the file — not that it is safe.
Origin 89% copy Near-identical to another mod in the catalogue.
Security

Grade A, and why

PostToolUseFailure 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 6d 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

89% identical to SessionStart — 2 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.

adapters/claude-code/hooks/hooks.json · 20 lines

What it actually says

{
  "PostToolUseFailure": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "${CLAUDE_PLUGIN_ROOT}/bin/cigar-claude-hook",
          "args": [
            "run",
            "--plugin-root",
            "${CLAUDE_PLUGIN_ROOT}",
            "--plugin-data",
            "${CLAUDE_PLUGIN_DATA}"
          ],
          "timeout": 1
        }
      ]
    }
  ]
}
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. 6d ago First seen · 20 lines scan A c3e5617bd19a

Subscribe to this mod's changes

PostToolUseFailure is a hook published in the GitHub repository hashgraph-online/hol-cigar (8 stars, last pushed 4d 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 89% identical to SessionStart, differing in 2 lines, and is treated as a copy.