Google Chat Messages

Send messages to Google Chat spaces via incoming webhooks. Produces text messages, rich cards (cardsV2), and threaded replies.

What You Produce

• Text messages with Google Chat formatting
• Rich card messages (cardsV2) with headers, sections, widgets
• Threaded conversations
• Reusable webhook sender utility

Workflow

Step 1: Get Webhook URL

In Google Chat:

1. Open a Space > click space name > Manage webhooks
2. Create webhook (name it, optionally add avatar URL)
3. Copy the webhook URL

Store the URL as an environment variable or in your secrets manager — never hardcode.

Step 2: Choose Message Type

Need	Type	Complexity
Simple notification	Text message	Low
Structured info (status, digest)	Card message (cardsV2)	Medium
Ongoing updates	Threaded replies	Medium
Action buttons (open URL)	Card with buttonList	Medium

Step 3: Send the Message

Use assets/webhook-sender.ts for the sender utility. Use assets/card-builder.ts for structured card construction.

Text Formatting

Google Chat does NOT use standard Markdown.

Format	Syntax	Example
Bold	*text*	*important*
Italic	_text_	_emphasis_
Strikethrough	~text~	~removed~
Monospace	`text`	`code`
Code block	```text```	Multi-line code
Link	<url|text>	<https://example.com|Click here>
Mention user	<users/USER_ID>	<users/123456>
Mention all	<users/all>	<users/all>

Not supported: **double asterisks**, headings (###), blockquotes, tables, images inline.

Text Message Example

await sendText(webhookUrl, '*Build Complete*\n\nBranch: `main`\nStatus: Passed\n<https://ci.example.com/123|View Build>');

cardsV2 Structure

Cards use the cardsV2 format (recommended over legacy cards).

const message = {
  cardsV2: [{
    cardId: 'unique-id',
    card: {
      header: {
        title: 'Card Title',
        subtitle: 'Optional subtitle',
        imageUrl: 'https://example.com/icon.png',
        imageType: 'CIRCLE'  // or 'SQUARE'
      },
      sections: [{
        header: 'Section Title',  // optional
        widgets: [
          // widgets go here
        ]
      }]
    }
  }]
};

Widget Types

Text paragraph — formatted text block:

{ textParagraph: { text: '*Bold* and _italic_ text' } }

Decorated text — label + value with optional icon:

{
  decoratedText: {
    topLabel: 'Status',
    text: 'Deployed',
    startIcon: { knownIcon: 'STAR' }
  }
}

Button list — action buttons:

{
  buttonList: {
    buttons: [{
      text: 'View Dashboard',
      onClick: { openLink: { url: 'https://dashboard.example.com' } }
    }]
  }
}

Image — standalone image:

{ image: { imageUrl: 'https://example.com/chart.png', altText: 'Usage chart' } }

Divider — horizontal separator:

{ divider: {} }

See references/widget-reference.md for all widget types with full examples. See references/icon-list.md for all available knownIcon values.

Threading

Thread messages together using threadKey:

// First message — creates thread
const response = await sendCard(webhookUrl, card, {
  threadKey: 'deploy-2026-02-16'
});

// Reply to thread — append &messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD
const threadUrl = `${webhookUrl}&messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD`;
await sendCard(threadUrl, replyCard, {
  threadKey: 'deploy-2026-02-16'
});

The threadKey is a client-assigned string. Use consistent keys for related messages (e.g., deploy-{date}, alert-{id}).

Common Patterns

Notification Card

import { buildCard, sendCard } from './assets/card-builder';
import { sendWebhook } from './assets/webhook-sender';

const card = buildCard({
  cardId: 'deploy-notification',
  title: 'Deployment Complete',
  subtitle: 'production - v2.1.0',
  imageUrl: 'https://example.com/your-icon.png',
  sections: [{
    widgets: [
      { decoratedText: { topLabel: 'Environment', text: 'Production' } },
      { decoratedText: { topLabel: 'Version', text: 'v2.1.0' } },
      { decoratedText: { topLabel: 'Status', text: '*Healthy*', startIcon: { knownIcon: 'STAR' } } },
      { buttonList: { buttons: [{ text: 'View Deployment', onClick: { openLink: { url: 'https://dash.example.com' } } }] } }
    ]
  }]
});

Digest Card (Weekly Summary)

const digest = buildCard({
  cardId: 'weekly-digest',
  title: 'Weekly Summary',
  subtitle: `${count} updates this week`,
  sections: [
    {
      header: 'Highlights',
      widgets: items.map(item => ({
        decoratedText: { text: item.title, bottomLabel: item.date }
      }))
    },
    {
      widgets: [{
        buttonList: {
          buttons: [{ text: 'View All', onClick: { openLink: { url: dashboardUrl } } }]
        }
      }]
    }
  ]
});

Simple Text Alert

await sendText(webhookUrl, `*Alert*: CPU usage above 90% on \`worker-prod-1\`\n<${alertUrl}|View Alert>`);

Error Prevention

Mistake	Fix
**bold** in text	Use *bold* (single asterisks)
[text](url) links	Use <url|text> format
Missing cardsV2 wrapper	Wrap card in { cardsV2: [{ cardId, card }] }
Thread replies not threading	Append &messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD to webhook URL
Webhook returns 400	Check JSON structure — common issue is missing text or cardsV2 at top level
Card not showing	Ensure sections has at least one widget

Asset Files

File	Purpose
assets/types.ts	TypeScript type definitions for cardsV2
assets/card-builder.ts	Utility to build card messages
assets/webhook-sender.ts	POST to webhook with error handling