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PostToolUseFailure

PostToolUseFailure is a hook for coding agents from ArdurAI/ardur. Its token cost is not measured, scanned A, a copy of SessionStart, MIT.

A failure hook is an automatic command that runs when a tool call fails. It runs a shell check after the failure.

In plain words
What is it for?
It is for running a predefined shell script after failed tool calls and checking what went wrong.
Why use it?
It helps inspect or respond to tool errors automatically, instead of leaving every failure for manual follow-up.

Hook

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 ardur-claude-code-hook plugin — 5 hooks shipped together

One of 5 entries in hooks.json — they are configured in one file and arrive together.

not rated 2 4d ago A scan tokens not measured copy · 64% MIT
View the source file ArdurAI/ardur
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 ArdurAI/ardur
Claude Code
/plugin install ardur-claude-code-hook

Or install ardur-claude-code-hook, the plugin that ships this one along with the rest of its 5 hooks.

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/ardurai/ardur/post-tool-use-failure.svg)](https://agentmods.dev/hooks/ardurai/ardur/post-tool-use-failure)
Your own site
<a href="https://agentmods.dev/hooks/ardurai/ardur/post-tool-use-failure"><img src="https://agentmods.dev/badge/hooks/ardurai/ardur/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. Scan, not verified.
Origin 64% 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 5d 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

64% identical to SessionStart — 8 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.

plugins/claude-code/hooks/hooks.json · 13 lines

What it actually says

{
  "PostToolUseFailure": [
    {
      "matcher": ".*",
      "hooks": [
        {
          "type": "command",
          "command": "${CLAUDE_PLUGIN_ROOT}/hooks/post_tool_use_failure"
        }
      ]
    }
  ]
}
Same file

What else hooks.json configures

This page is one entry in a file that holds 5. Installing the file brings all of them; each is measured and scanned on its own page.

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. 5d ago First seen · 13 lines scan A d4d3934d32aa

Subscribe to this mod's changes

PostToolUseFailure is a hook published in the GitHub repository ArdurAI/ardur (2 stars, last pushed 4d 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. It is 64% identical to SessionStart, differing in 8 lines, and is treated as a copy.

AI Safetyagent-governanceai-agentsai-governanceopen-sourceruntime-security
Related

Other hooks, from other repositories

UserPromptSubmit

Runs when you submit a prompt, before the agent sees it, executing consent_gate_grant.mjs via node. From friedbotstudio/baseline.

friedbotstudio/baseline · not measured

SessionStart

Runs when a session starts, executing asif-hook-tap.sh via bash with --name. From nxtg-ai/forge-plugin.

nxtg-ai/forge-plugin · not measured

SessionStart

Runs when a session starts, executing prune_scratchpad.py via uv with --init. From EndogenAI/dogma.

EndogenAI/dogma · not measured

PostToolUse

Runs after a tool call finishes for Write, Edit, MultiEdit and Bash tool calls, executing lint_runner.mjs, test_runner.mjs and phase_timer.mjs via node (4 commands). From friedbotstudio/baseline.

friedbotstudio/baseline · not measured

SessionEnd

Runs when a session ends for clear, prompt_input_exit, logout, resume, bypass_permissions_disabled and other tool calls, running an inline shell check. From QORIS-AI/knox.

QORIS-AI/knox · not measured

SubagentStart

Runs when a subagent starts, running an inline shell check. From QORIS-AI/knox.

QORIS-AI/knox · not measured