Hook Trigger Points

About 5 minutes

Those deciding where to attach hooks, those learning the common trigger points

Basic understanding of What Are Hooks

Hooks run logic automatically at set points. What becomes possible depends on which point is chosen.

The Common Trigger Points

graph LR
    Start["Session start"] --> Before["Before tool execution"]
    Before --> Exec["Tool execution"]
    Exec --> After["After tool execution"]
    After --> Resp["Before the response"]
    Resp --> End["Session end"]

Timing	What it enables	Example use
Session start	Injecting background information	Loading project conventions
Before tool execution	Blocking, or requesting approval	Blocking operations against production
After tool execution	Verifying, formatting, recording	Running tests after a change
Before the response	Inspecting the output	Checking for sensitive information
Session end	Wrap-up processing	Saving work logs, clearing temporary files

To Block, Use Before Execution

The highest-value point is immediately before tool execution. It is the only place where an operation can be prevented from running.

Abort when the target path falls outside the allowed scope
Request approval for delete operations
Stop when a connection to production is detected

Unlike an instruction, a hook operates as mechanism, so it keeps working even deep into long tasks.

To Verify, Use After Execution

Running verification immediately after a change keeps errors from carrying into the next step.

Run tests or syntax checks after a file changes
Confirm the output meets conventions
On failure, return the result to the AI so it corrects course immediately

This is also a way to enforce self-correction as mechanism rather than leaving it to the AI’s judgment.

To Supply Context, Use Session Start

When the same background gets repeated every time, load it automatically at session start: project conventions, terminology rules, and anything that should always apply.

Choose From the Goal

More trigger points is not better. Work backward from the purpose.

Goal	Point to choose
Prevent something dangerous	Before tool execution
Confirm the result is correct	After tool execution
Keep the baseline consistent	Session start
Inspect the output	Before the response

Summary

The main points are session start, before and after tool execution, before the response, and session end
Only the before-execution point can actually prevent an operation
Verification right after a change enforces self-correction as mechanism
Choose points from the goal rather than attaching hooks everywhere

Quiz

What Are Hooks

Hook Use Cases