Astro Actions Expert
Type-safe server functions with automatic validation, standardized errors, and progressive enhancement.
Agent Workflow (MANDATORY)
Before ANY implementation, use TeamCreate to spawn 3 agents:
- fuse-ai-pilot:explore-codebase - Check existing actions in
src/actions/ - fuse-ai-pilot:research-expert - Verify latest Actions docs via Context7/Exa
- mcp__context7__query-docs - Get defineAction and ActionError examples
After implementation, run fuse-ai-pilot:sniper for validation.
Overview
When to Use
- Handling form submissions with server-side validation
- Creating type-safe backend mutations without API boilerplate
- Building progressive enhancement (works without JS)
- Replacing API endpoints for client-server communication
Why Astro Actions
| Feature | Benefit |
|---------|---------|
| defineAction() | Type-safe server function definition |
| Zod validation | Automatic JSON and FormData parsing |
| ActionError | Standardized error codes and messages |
| accept: 'form' | Direct HTML form submission support |
| Progressive enhancement | Works without JavaScript enabled |
| astro:actions | Client import for type-safe calls |
Core Concepts
Action Structure
All actions live in src/actions/index.ts and export a server object:
// src/actions/index.ts
import { defineAction } from 'astro:actions';
import { z } from 'astro/zod';
export const server = {
myAction: defineAction({ /* ... */ })
}
Accept Modes
| Mode | Description |
|------|-------------|
| accept: 'json' (default) | Parses JSON request body |
| accept: 'form' | Parses HTML FormData directly |
Error Codes
Standard HTTP-aligned codes: UNAUTHORIZED, FORBIDDEN, NOT_FOUND, BAD_REQUEST, INTERNAL_SERVER_ERROR, CONFLICT, TOO_MANY_REQUESTS.
Reference Guide
| Need | Reference | |------|-----------| | Concepts & architecture | overview.md | | defineAction patterns | defining-actions.md | | ActionError handling | error-handling.md | | HTML form integration | forms.md | | Progressive enhancement | progressive-enhancement.md | | Contact form template | templates/contact-form.md | | JSON action template | templates/json-action.md |
Best Practices
- Always define
inputschema — Never skip Zod validation - Use
ActionErrorfor known errors — Standardized codes for client handling accept: 'form'for HTML forms — Native form submission support- Progressive enhancement — Form works without JS, enhanced with it
- Check
ctx.cookiesfor auth — ThrowUNAUTHORIZEDwhen not logged in