The Opportunity Radar generates a detailed markdown report every week. Until now, it lived in a private repo. This week we added a newsletter worker that reads that report and sends it as a formatted email via Resend — zero new infrastructure, Friday morning, automatically.

The Problem

The Radar was already producing content like this:

| 排名 | 产品机会 | 分类 | 优先级 |
| 1 | XingAI Opportunity Radar Newsletter | New Opportunities | Build Now |
| 2 | Personal AI Memory OS | New Opportunities | Build Now |

The problem wasn't content. It was distribution. A great analysis that only the author reads is not a product.

The Solution: One Script, One Cron Job

docs/issues/2026-07-03.md
         ↓
newsletter_worker.py
  load_latest_issue()        → read most recent .md file
  extract_top_opportunities() → parse opportunity table (regex)
  extract_key_signals()       → parse signal table (regex)
  format_newsletter_html()    → HTML email template
  format_newsletter_text()    → plain-text fallback
  send_via_resend()           → POST https://api.resend.com/emails

No database. No new service. No Substack API (it doesn't exist). Just a Python script that runs weekly via GitHub Actions.

The --dry-run Flag

Before sending to subscribers, preview locally:

python workers/newsletter_worker.py --dry-run
# [DRY RUN] Would send newsletter:
#   From: radar@xingai.app
#   To:   (NEWSLETTER_TO not set)
#   Subject: 🛰️ XingAI Opportunity Radar — 2026-07-03
#
# --- TEXT PREVIEW ---
# XingAI Opportunity Radar — 2026-07-03
# ==================================================
# TOP OPPORTUNITIES THIS WEEK
# 1. XingAI Opportunity Radar Newsletter [New Opportunities] → Build Now
# ...

The dry-run output is also what CI validates — the cron workflow runs --dry-run on every PR to confirm the parser doesn't break.

Why Resend, Not Mailchimp or Substack

	Resend	Mailchimp	Substack
API	Simple REST	Complex	No publishing API
Free tier	3k/month	500 contacts	Unlimited but manual
Unsubscribe handling	Automatic (Audiences)	Automatic	Automatic
Developer setup	10 min	1–2 hours	Manual only

Resend wins on simplicity. The API is one POST call. Audience management handles unsubscribes. Domain verification takes 10 minutes. No UI required.

GitHub Actions Cron

# .github/workflows/newsletter.yml
on:
  schedule:
    - cron: '0 17 * * 5'  # Friday 9am PT (17:00 UTC)

jobs:
  send-newsletter:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with: { python-version: '3.12' }
      - run: pip install httpx
      - run: python workers/newsletter_worker.py
        env:
          RESEND_API_KEY: ${{ secrets.RESEND_API_KEY }}
          NEWSLETTER_FROM: radar@xingai.app
          NEWSLETTER_TO: ${{ secrets.NEWSLETTER_AUDIENCE_ID }}

Related ADR: Opportunity Radar ADR-002