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.
npx agentmods add skills/thethoughtagen/agentsync/hook-authoringnpx skills add TheThoughtagen/agentsync --skill hook-authoringgit clone --depth 1 https://github.com/TheThoughtagen/agentsyncWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00035 | $0.01137 |
| Opus 5 | $0.00017 | $0.00568 |
| Sonnet 5 | $0.00007 | $0.00227 |
| Haiku 4.5 | $0.00003 | $0.00114 |
Grade A, and why
hook-authoring 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 body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
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.
How it starts
The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hook Authoring Guide
File Format
Hooks are defined in .ai/hooks.toml using TOML. Each hook is grouped under an [[EventName]] section with an optional matcher field, and contains one or more [[EventName.hooks]] entries.
[[PreToolUse]]
matcher = "Bash"
[[PreToolUse.hooks]]
type = "command"
command = "bash .ai/scripts/validate-bash.sh"
timeout = 10
Valid Events
Shared Events (work in both Claude Code and Cursor via aisync translation)
| Event | Description |
|---|---|
PreToolUse |
Fires before a tool is invoked. Use matcher to target specific tools. |
PostToolUse |
Fires after a tool completes. Use matcher to target specific tools. |
Stop |
Fires when the agent stops (completes a response). |
SubagentStop |
Fires when a sub-agent stops. |
Claude Code Only (via aisync translation)
| Event | Description |
|---|---|
Notification |
Fires when a notification is sent. |
Cursor Only (via aisync translation)
| Event | Description |
|---|---|
PostToolUseFailure |
Fires when a tool invocation fails. |
SessionStart |
Fires when a new session begins. |
SessionEnd |
Fires when a session ends. |
BeforeShellExecution |
Fires before a shell command runs. |
AfterShellExecution |
Fires after a shell command completes. |
BeforeReadFile |
Fires before reading a file. |
AfterFileEdit |
Fires after a file is edited. |
BeforeSubmitPrompt |
Fires before a prompt is submitted. |
PreCompact |
Fires before context compaction. |
AfterAgentResponse |
Fires after the agent responds. |
AfterAgentThought |
Fires after an agent thought step. |
SubagentStart |
Fires when a sub-agent starts. |
BeforeMCPExecution |
Fires before an MCP tool call. |
AfterMCPExecution |
Fires after an MCP tool call completes. |
Note: Claude Code natively supports additional events (
SessionStart,SessionEnd,UserPromptSubmit,PreCompact) that aisync does not yet translate. When writing hooks for these events in.ai/hooks.toml, aisync will currently skip them during Claude Code translation. To use these events, configure them directly in.claude/settings.jsonor via a Claude Code plugin'shooks.json.
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 · 137 lines · 35 tokens per session scan A 9e2c9d74a17a
hook-authoring is a skill published in the GitHub repository TheThoughtagen/agentsync (2 stars, last pushed 5mo ago), licensed MIT. It adds 35 tokens to every session and 1,137 once invoked, about $0.0002 per session on Opus 5. 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.
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