docs: add 4 new Learning Hub articles for agents, MCP, hooks, coding agent

Add four high-priority articles identified by gap analysis against
nishanil/copilot-guide:

- Building Custom Agents: personas, tools, MCP integration, patterns
- Understanding MCP Servers: what MCP is, configuration, agent usage
- Automating with Hooks: lifecycle events, hooks.json, practical examples
- Using the Copilot Coding Agent: setup steps, issue assignment, PR workflow

Update index.astro fundamentalsOrder to include all 10 articles.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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2026-02-26 12:34:12 +11:00
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---
title: 'Automating with Hooks'
description: 'Learn how to use hooks to automate lifecycle events like formatting, linting, and governance checks during Copilot agent sessions.'
authors:
- GitHub Copilot Learning Hub Team
lastUpdated: '2026-02-26'
estimatedReadingTime: '8 minutes'
tags:
- hooks
- automation
- fundamentals
relatedArticles:
- ./building-custom-agents.md
- ./what-are-agents-skills-instructions.md
prerequisites:
- Basic understanding of GitHub Copilot agents
---
Hooks let you run automated scripts at key moments during a Copilot agent session—when a session starts, when the user submits a prompt, or when the agent is about to commit code. They're the glue between Copilot's AI capabilities and your team's existing tooling: linters, formatters, governance scanners, and notification systems.
This article explains how hooks work, how to configure them, and practical patterns for common automation needs.
## What Are Hooks?
Hooks are shell commands or scripts that run automatically in response to lifecycle events during a Copilot agent session. They execute outside the AI model—they're deterministic, repeatable, and under your full control.
**Key characteristics**:
- Hooks run as shell commands on the user's machine
- They execute synchronously—the agent waits for them to complete
- They can block actions (e.g., prevent commits that fail linting)
- They're defined in a `hooks.json` configuration file
- They can include bundled scripts for complex logic
### When to Use Hooks vs Other Customizations
| Use Case | Best Tool |
|----------|-----------|
| Run a linter after every code change | **Hook** |
| Teach Copilot your coding standards | **Instruction** |
| Automate a multi-step workflow | **Skill** or **Agent** |
| Scan prompts for sensitive data | **Hook** |
| Format code before committing | **Hook** |
| Generate tests for new code | **Skill** |
Hooks are ideal for **deterministic automation** that must happen reliably—things you don't want to depend on the AI remembering to do.
## Anatomy of a Hook
Each hook in this repository is a folder containing:
```
hooks/
└── my-hook/
├── README.md # Documentation with frontmatter
├── hooks.json # Hook configuration
└── scripts/ # Optional bundled scripts
└── check.sh
```
### README.md
The README provides metadata and documentation:
```markdown
---
name: 'Auto Format'
description: 'Automatically formats code using project formatters before commits'
tags: ['formatting', 'code-quality']
---
# Auto Format
Runs your project's configured formatter (Prettier, Black, gofmt, etc.)
automatically before the agent commits changes.
## Setup
1. Ensure your formatter is installed and configured
2. Copy the hooks.json to your `.copilot/hooks.json`
3. Adjust the formatter command for your project
```
### hooks.json
The configuration defines which events trigger which commands:
```json
{
"version": 1,
"hooks": {
"copilotAgentCommit": [
{
"type": "command",
"bash": "npx prettier --write .",
"cwd": ".",
"timeoutSec": 30
}
]
}
}
```
## Hook Events
Hooks can trigger on several lifecycle events:
| Event | When It Fires | Common Use Cases |
|-------|---------------|------------------|
| `sessionStart` | Agent session begins | Initialize logging, check prerequisites |
| `sessionEnd` | Agent session ends | Clean up temp files, send notifications |
| `userPromptSubmitted` | User sends a message | Scan for sensitive data, log for governance |
| `copilotAgentCommit` | Agent is about to commit | Format code, run linters, validate changes |
### Event Configuration
Each hook entry supports these fields:
```json
{
"type": "command",
"bash": "./scripts/my-check.sh",
"cwd": ".",
"timeoutSec": 10,
"env": {
"CUSTOM_VAR": "value"
}
}
```
**type**: Always `"command"` for shell-based hooks.
**bash**: The command or script to execute. Can be inline or reference a script file.
**cwd**: Working directory for the command. Use `"."` for the repository root.
**timeoutSec**: Maximum execution time. The hook is killed if it exceeds this limit.
**env**: Additional environment variables passed to the command.
## Practical Examples
### Auto-Format Before Commit
Ensure all code is formatted before the agent commits:
```json
{
"version": 1,
"hooks": {
"copilotAgentCommit": [
{
"type": "command",
"bash": "npx prettier --write . && git add -A",
"cwd": ".",
"timeoutSec": 30
}
]
}
}
```
### Lint Check Before Commit
Run ESLint and block the commit if there are errors:
```json
{
"version": 1,
"hooks": {
"copilotAgentCommit": [
{
"type": "command",
"bash": "npx eslint . --max-warnings 0",
"cwd": ".",
"timeoutSec": 60
}
]
}
}
```
If the lint command exits with a non-zero status, the commit is blocked.
### Governance Audit
Scan user prompts for potential security threats and log session activity:
```json
{
"version": 1,
"hooks": {
"sessionStart": [
{
"type": "command",
"bash": ".github/hooks/governance-audit/audit-session-start.sh",
"cwd": ".",
"timeoutSec": 5
}
],
"userPromptSubmitted": [
{
"type": "command",
"bash": ".github/hooks/governance-audit/audit-prompt.sh",
"cwd": ".",
"env": {
"GOVERNANCE_LEVEL": "standard",
"BLOCK_ON_THREAT": "false"
},
"timeoutSec": 10
}
],
"sessionEnd": [
{
"type": "command",
"bash": ".github/hooks/governance-audit/audit-session-end.sh",
"cwd": ".",
"timeoutSec": 5
}
]
}
}
```
This pattern is useful for enterprise environments that need to audit AI interactions for compliance.
### Notification on Session End
Send a Slack or Teams notification when an agent session completes:
```json
{
"version": 1,
"hooks": {
"sessionEnd": [
{
"type": "command",
"bash": "curl -X POST \"$SLACK_WEBHOOK_URL\" -H 'Content-Type: application/json' -d '{\"text\": \"Copilot agent session completed\"}'",
"cwd": ".",
"env": {
"SLACK_WEBHOOK_URL": "${input:slackWebhook}"
},
"timeoutSec": 5
}
]
}
}
```
## Writing Hook Scripts
For complex logic, use bundled scripts instead of inline bash commands:
```bash
#!/usr/bin/env bash
# scripts/pre-commit-check.sh
set -euo pipefail
echo "Running pre-commit checks..."
# Format code
npx prettier --write .
# Run linter
npx eslint . --fix
# Run type checker
npx tsc --noEmit
# Stage any formatting changes
git add -A
echo "Pre-commit checks passed ✅"
```
**Tips for hook scripts**:
- Use `set -euo pipefail` to fail fast on errors
- Keep scripts focused—one responsibility per script
- Make scripts executable: `chmod +x scripts/pre-commit-check.sh`
- Test scripts manually before adding them to hooks.json
- Use reasonable timeouts—formatting a large codebase may need 30+ seconds
## Best Practices
- **Keep hooks fast**: Hooks run synchronously, so slow hooks delay the agent. Set tight timeouts and optimize scripts.
- **Use non-zero exit codes to block**: If a hook exits with a non-zero code, the triggering action is blocked. Use this for must-pass checks.
- **Bundle scripts in the hook folder**: Keep related scripts alongside the hooks.json for portability.
- **Document setup requirements**: If hooks depend on tools being installed (Prettier, ESLint), document this in the README.
- **Test locally first**: Run hook scripts manually before relying on them in agent sessions.
- **Layer hooks, don't overload**: Use multiple hook entries for independent checks rather than one monolithic script.
## Common Questions
**Q: Where do I put hooks.json?**
A: Place it at `.copilot/hooks.json` in your repository root. This makes hooks available to all team members.
**Q: Can hooks access the user's prompt text?**
A: Yes, for `userPromptSubmitted` events the prompt content is available to the hook script via environment variables. See the [GitHub Copilot hooks documentation](https://docs.github.com/en/copilot/how-tos/use-copilot-agents/coding-agent/use-hooks) for details.
**Q: What happens if a hook times out?**
A: The hook is terminated and the agent continues. Set `timeoutSec` appropriately for your scripts.
**Q: Can I have multiple hooks for the same event?**
A: Yes. Hooks for the same event run in the order they appear in the array. If any hook fails (non-zero exit), subsequent hooks for that event may be skipped.
**Q: Do hooks work with the Copilot coding agent?**
A: Yes. Hooks are especially valuable with the coding agent because they provide deterministic guardrails for autonomous operations. See [Using the Copilot Coding Agent](../learning-hub/using-copilot-coding-agent/) for details.
## Next Steps
- **Explore Examples**: Browse the [Hooks Directory](../hooks/) for ready-to-use hook configurations
- **Build Agents**: [Building Custom Agents](../learning-hub/building-custom-agents/) — Create agents that complement hooks
- **Automate Further**: [Using the Copilot Coding Agent](../learning-hub/using-copilot-coding-agent/) — Run hooks in autonomous agent sessions
---