Webhook receiver — setup and run replay

What this accomplishes

How to trigger Miton workflows via authenticated webhooks and use the run inspector to replay steps.

Miton includes a local webhook receiver that listens for incoming HTTP events and triggers workflows. The receiver runs on 127.0.0.1:7733 — loopback only, no public exposure by default.

Current availability

This page documents behaviour verified in Miton development builds. Miton is still pre-release and is not publicly downloadable; invited beta users will receive a signed desktop build with automatic updates.

Before you start

• A Miton development build and an active project.
• A connected cloud or local model, plus any credentials or local runtime required by this task.

Setting up a webhook trigger

Step 1 — Add a webhook trigger to your workflow

In the Workflow Surface, click + Trigger → Webhook. Miton generates a unique path for this workflow:

http://127.0.0.1:7733/hooks/<workflow-id>

Step 2 — Get the signing secret

Click Show secret in the trigger card. Copy the HMAC-SHA256 signing secret.

Step 3 — Configure your sender

Configure whatever is sending the webhook to:

1. POST to http://127.0.0.1:7733/hooks/<workflow-id>
2. Include the X-Hub-Signature-256 header with the HMAC-SHA256 signature of the request body

The signature format is:

X-Hub-Signature-256: sha256=<hex-digest>

Miton rejects any request with a missing or invalid signature.

Exposing the webhook to the internet

The receiver is localhost-only by default. To receive webhooks from a remote sender (e.g. GitHub webhooks, a third-party service), you need to expose the port:

• Use a tunnel tool (e.g. ngrok http 7733) during development
• On a machine with a static IP, port-forward 7733 in your router/firewall

Miton does not manage the tunnel. This is a network configuration you control.

Run inspector

Every webhook-triggered run appears in the Run Inspector. To open it:

1. Open the Workflow Surface
2. Select your workflow
3. Click Run history in the right panel

The Run Inspector shows two levels of history:

Run level

Step level

Click any run to expand its steps. Each step shows:

• Input — the data passed to this node
• Output — the data the node returned
• Duration — time for this step
• Cost — token cost (AI nodes only)
• Error — the error message and stack trace (failed steps only)

Replaying a step

To re-run a single step without triggering the whole workflow:

1. Open the Run Inspector → expand the run → click the step you want to replay
2. Click Replay step
3. The step re-runs with its original input. The output updates in the inspector.

This is useful for debugging: if a downstream step failed due to a transient error, replay it without re-fetching the trigger data or re-running expensive upstream AI nodes.

Signature verification details

Miton uses HMAC-SHA256 to authenticate webhook requests:

signature = HMAC-SHA256(secret, request_body_bytes)
header = "sha256=" + hex(signature)

The comparison is constant-time to prevent timing attacks. Requests with no signature header, an invalid format, or a bad signature return HTTP 401 with no body.

What success looks like

How to trigger Miton workflows via authenticated webhooks and use the run inspector to replay steps. The result remains attached to the active project when you move to another workspace.

Common failures and recovery

• Confirm the correct project and model are active.
• Read the exact error and the requested permission before retrying.
• Retry only the failed step so completed project work remains intact.

Related next action

• Workflow getting started — building your first workflow
• Security & Permissions — permission policies for workflow execution