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:

1. fuse-ai-pilot:explore-codebase - Check existing actions in src/actions/
2. fuse-ai-pilot:research-expert - Verify latest Actions docs via Context7/Exa
3. mcp__context7__query-docs - Get defineAction and ActionError examples

After implementation, run fuse-ai-pilot:sniper for validation.

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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

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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.

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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

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Best Practices

1. Always define input schema — Never skip Zod validation
2. Use ActionError for known errors — Standardized codes for client handling
3. accept: 'form' for HTML forms — Native form submission support
4. Progressive enhancement — Form works without JS, enhanced with it
5. Check ctx.cookies for auth — Throw UNAUTHORIZED when not logged in