Webhook Subscriptions

Webhook Subscriptions

Create dynamic webhook subscriptions so external services (GitHub, GitLab, Stripe, CI/CD, IoT sensors, monitoring tools) can trigger Hermes agent runs by POSTing events to a URL.

Setup (Required First)

The webhook platform must be enabled before subscriptions can be created. Check with:

hermes webhook list

If it says "Webhook platform is not enabled", set it up:

Option 1: Setup wizard

hermes gateway setup

Follow the prompts to enable webhooks, set the port, and set a global HMAC secret.

Option 2: Manual config

Add to ~/.hermes/config.yaml:

platforms:
  webhook:
    enabled: true
    extra:
      host: "0.0.0.0"
      port: 8644
      secret: "<generate-a-strong-secret>"

Option 3: Environment variables

Add to ~/.hermes/.env:

WEBHOOK_ENABLED=true
WEBHOOK_PORT=8644
WEBHOOK_SECRET=<generate-a-strong-secret>

After configuration, start (or restart) the gateway:

hermes gateway run
# Or if using systemd:
systemctl --user restart hermes-gateway

Verify it's running:

curl http://localhost:8644/health

Commands

All management is via the hermes webhook CLI command:

Create a subscription

hermes webhook subscribe <name> \
  --prompt "Prompt template with {payload.fields}" \
  --events "event1,event2" \
  --description "What this does" \
  --skills "skill1,skill2" \
  --deliver telegram \
  --deliver-chat-id "12345" \
  --secret "optional-custom-secret"

Returns the webhook URL and HMAC secret. The user configures their service to POST to that URL.

List subscriptions

hermes webhook list

Remove a subscription

hermes webhook remove <name>

Test a subscription

hermes webhook test <name>
hermes webhook test <name> --payload '{"key": "value"}'

Prompt Templates

Prompts support {dot.notation} for accessing nested payload fields:

• {issue.title} - GitHub issue title
• {pull_request.user.login} - PR author
• {data.object.amount} - Stripe payment amount
• {sensor.temperature} - IoT sensor reading

If no prompt is specified, the full JSON payload is dumped into the agent prompt.

Common Patterns

GitHub: new issues

hermes webhook subscribe github-issues \
  --events "issues" \
  --prompt "New GitHub issue #{issue.number}: {issue.title}\n\nAction: {action}\nAuthor: {issue.user.login}\nBody:\n{issue.body}\n\nPlease triage this issue." \
  --deliver telegram \
  --deliver-chat-id "-100123456789"

Then in GitHub repo Settings -> Webhooks -> Add webhook:

• Payload URL: the returned webhook_url
• Content type: application/json
• Secret: the returned secret
• Events: "Issues"

GitHub: PR reviews

hermes webhook subscribe github-prs \
  --events "pull_request" \
  --prompt "PR #{pull_request.number} {action}: {pull_request.title}\nBy: {pull_request.user.login}\nBranch: {pull_request.head.ref}\n\n{pull_request.body}" \
  --skills "github-code-review" \
  --deliver github_comment

Stripe: payment events

hermes webhook subscribe stripe-payments \
  --events "payment_intent.succeeded,payment_intent.payment_failed" \
  --prompt "Payment {data.object.status}: {data.object.amount} cents from {data.object.receipt_email}" \
  --deliver telegram \
  --deliver-chat-id "-100123456789"

CI/CD: build notifications

hermes webhook subscribe ci-builds \
  --events "pipeline" \
  --prompt "Build {object_attributes.status} on {project.name} branch {object_attributes.ref}\nCommit: {commit.message}" \
  --deliver discord \
  --deliver-chat-id "1234567890"

Generic monitoring alert

hermes webhook subscribe alerts \
  --prompt "Alert: {alert.name}\nSeverity: {alert.severity}\nMessage: {alert.message}\n\nPlease investigate and suggest remediation." \
  --deliver origin

Direct delivery (no agent, zero LLM cost)

For use cases where you just want to push a notification through to a user's chat - no reasoning, no agent loop - add --deliver-only. The rendered --prompt template becomes the literal message body and is dispatched directly to the target adapter.

Use this for:

• External service push notifications (Supabase/Firebase webhooks -> Telegram)
• Monitoring alerts that should forward verbatim
• Inter-agent pings where one agent is telling another agent's user something
• Any webhook where an LLM round trip would be wasted effort

hermes webhook subscribe antenna-matches \
  --deliver telegram \
  --deliver-chat-id "123456789" \
  --deliver-only \
  --prompt "New match: {match.user_name} matched with you!" \
  --description "Antenna match notifications"

The POST returns 200 OK on successful delivery, 502 on target failure - so upstream services can retry intelligently. HMAC auth, rate limits, and idempotency still apply.

Requires --deliver to be a real target (telegram, discord, slack, github_comment, etc.) - --deliver log is rejected because log-only direct delivery is pointless.

Security

• Each subscription gets an auto-generated HMAC-SHA256 secret (or provide your own with --secret)
• The webhook adapter validates signatures on every incoming POST
• Static routes from config.yaml cannot be overwritten by dynamic subscriptions
• Subscriptions persist to ~/.hermes/webhook_subscriptions.json

How It Works

1. hermes webhook subscribe writes to ~/.hermes/webhook_subscriptions.json
2. The webhook adapter hot-reloads this file on each incoming request (mtime-gated, negligible overhead)
3. When a POST arrives matching a route, the adapter formats the prompt and triggers an agent run
4. The agent's response is delivered to the configured target (Telegram, Discord, GitHub comment, etc.)

Troubleshooting

If webhooks aren't working:

1. Is the gateway running? Check with systemctl --user status hermes-gateway or ps aux | grep gateway
2. Is the webhook server listening? curl http://localhost:8644/health should return {"status": "ok"}
3. Check gateway logs: grep webhook ~/.hermes/logs/gateway.log | tail -20
4. Signature mismatch? Verify the secret in your service matches the one from hermes webhook list. GitHub sends X-Hub-Signature-256, GitLab sends X-Gitlab-Token.
5. Firewall/NAT? The webhook URL must be reachable from the service. For local development, use a tunnel (ngrok, cloudflared).
6. Wrong event type? Check --events filter matches what the service sends. Use hermes webhook test <name> to verify the route works.