agentmods.dev

SubagentStart

A hook that runs when a coding subagent starts. It executes a local JavaScript program with Bun, a JavaScript runtime.

In plain words
What is it for?
Use it for the startup behavior defined by the local bin.mjs program.
Why use it?
It can perform the configured startup action automatically whenever a subagent begins.

Hook

1 13d ago A scan tokens not measured no licence
View the source file fusengine/codex
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/fusengine/codex/subagent-start
Clone the repo
git clone --depth 1 https://github.com/fusengine/codex
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 unknown No closer match found in the catalogue.
Security

Grade A, and why

SubagentStart 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.

plugins/ai-pilot/hooks/hooks.json · 13 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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 · 13 lines scan A 36162b99d5a8

Subscribe to this mod's changes

SubagentStart is a hook published in the GitHub repository fusengine/codex (1 stars, last pushed 13d ago), with no licence file. 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.

Building agentsLanguagesagent-skillsagents-mdai-agentsbunclicodex-cli
Related

Other hooks, from other repositories

SubagentStart

Runs when a subagent starts, running trce spool --harness codex-cli --event SubagentStart. From assimovt/trce-cli.

assimovt/trce-cli · not measured

SubagentStop

Runs when a subagent finishes, running trce spool --harness codex-cli --event SubagentStop. From assimovt/trce-cli.

assimovt/trce-cli · not measured

UserPromptSubmit

Runs when you submit a prompt, before the agent sees it, executing behavior-feedback.sh, prompt-submit.sh and subagent-stance.sh (3 commands). From tdwhere123/do-it.

tdwhere123/do-it · not measured

SubagentStart

Runs when a subagent starts, executing stop-that-shit-claude.cjs via node. From lennney/stop-that-shit.

lennney/stop-that-shit · not measured

SessionStart

Runs when a session starts, running trce spool --harness codex-cli --event SessionStart. From assimovt/trce-cli.

assimovt/trce-cli · not measured

UserPromptSubmit

Runs when you submit a prompt, before the agent sees it, running trce spool --harness codex-cli --event UserPromptSubmit. From assimovt/trce-cli.

assimovt/trce-cli · not measured