diff --git a/.env.example b/.env.example
index e0d6daed..cbe4517b 100644
--- a/.env.example
+++ b/.env.example
@@ -96,6 +96,14 @@ TIER4_CPU_SHARES=4096          # Full-host tier CPU (default 4096 = 4 CPU; previ
 TELEGRAM_BOT_TOKEN=            # Telegram Bot API token (talk to @BotFather). Used as default for new Telegram channels.
 DISCORD_WEBHOOK_URL=           # Discord Incoming Webhook URL (Server → Channel → Integrations → Webhooks). Used by Community Manager workspace.
 
+# CI/CD Slack notifications (issue #624)
+# Add SLACK_CI_WEBHOOK_URL as a GitHub Actions secret (repo Settings → Secrets → Actions).
+# When set, CI failures in platform-build, canvas-build, python-lint, shellcheck,
+# and e2e-api workflows post an alert to the configured #ci-alerts Slack channel.
+# Obtain: Slack App → Incoming Webhooks → Add to channel → copy URL.
+# Leave unset to disable (jobs skip silently — no build failure).
+SLACK_CI_WEBHOOK_URL=          # https://hooks.slack.com/services/...
+
 # Langfuse (optional observability)
 LANGFUSE_HOST=http://langfuse-web:3000
 LANGFUSE_PUBLIC_KEY=