GitHub Fork PR Opened Notification to Slack
Use the Github integration by MagicBell to setup a workflow when pull_request_target triggers in Github.
Connect Github to MagicBell to receive events and trigger workflows. This guide uses the MagicBell CLI.
Add the Github integration
Save your Github webhook signing secret in MagicBell. See GitHub webhooks.
magicbell integration save_github \
--data '{"webhook_signing_secret":"your_secret_here"}'Copy the ID from the response and use it to build your webhook URL:
https://api.magicbell.com/v2/integrations/github/webhooks/incoming/{id}Setup the webhook
- Setup a webhook in Github with the URL from the last step.
- Select the pull_request_target event.
- If you already have a webhook configured, make sure it includes this event.
Add a workflow
Create a workflow that triggers automatically when Github sends this event.
Workflow key
Use this key to trigger the workflow when Github sends a pull_request_target event:
integration.github.pull_request_targetFilter by action: GitHub sends the event type in the header and the action in the payload body. Use an if condition to filter for the opened action:
"if": "payload.action == 'opened'"Example workflow
Handle pull requests from forks that trigger workflows in the target repository.
{
"key": "integration.github.pull_request_target.opened",
"steps": [
{
"command": "broadcast",
"input": {
"action_url": "{{payload.pull_request.html_url}}",
"content": "{{payload.pull_request.author_association}} {{payload.sender.login}} opened PR from fork {{payload.pull_request.head.repo.full_name}}. Review carefully before running workflows.",
"overrides": {
"providers": {
"slack": {}
}
},
"recipients": [
{
"external_id": "maintainers"
}
],
"title": "External PR #{{payload.number}}: {{payload.pull_request.title}}"
}
}
]
}Save with the CLI
Use the MagicBell CLI to save this workflow to your project. You can also use the Workflows API endpoint instead.
magicbell workflow save \
--data '{"key":"integration.github.pull_request_target.opened","steps":[{"command":"broadcast","input":{"action_url":"{{payload.pull_request.html_url}}","content":"{{payload.pull_request.author_association}} {{payload.sender.login}} opened PR from fork {{payload.pull_request.head.repo.full_name}}. Review carefully before running workflows.","overrides":{"providers":{"slack":{}}},"recipients":[{"external_id":"maintainers"}],"title":"External PR #{{payload.number}}: {{payload.pull_request.title}}"}}]}'Event payload
Sample payload for the pull_request_target event. Use liquid templates to access fields in your workflow.
{
"action": "opened",
"number": 42,
"organization": {
"avatar_url": "https://avatars.githubusercontent.com/u/111111?v=4",
"description": "Building great software",
"id": 111111,
"login": "acme",
"node_id": "MDEyOk9yZ2FuaXphdGlvbjExMTExMQ==",
"url": "https://api.github.com/orgs/acme"
},
"pull_request": {
"active_lock_reason": null,
"assignee": null,
"assignees": [],
"author_association": "FIRST_TIME_CONTRIBUTOR",
"auto_merge": null,
"base": {
"label": "acme:main",
"ref": "main",
"repo": {
"fork": false,
"full_name": "acme/project",
"id": 987654321,
"name": "project",
"node_id": "MDEwOlJlcG9zaXRvcnk5ODc2NTQzMjE=",
"private": false
},
"sha": "def789012345678901234567890abcdef12345678",
"user": {
"avatar_url": "https://avatars.githubusercontent.com/u/111111?v=4",
"html_url": "https://github.com/acme",
"id": 111111,
"login": "acme",
"type": "Organization"
}
},
"body": "This PR adds a new feature. Submitted from a forked repository.",
"closed_at": null,
"comments_url": "https://api.github.com/repos/acme/project/issues/42/comments",
"commits_url": "https://api.github.com/repos/acme/project/pulls/42/commits",
"created_at": "2025-01-16T18:00:00Z",
"diff_url": "https://github.com/acme/project/pull/42.diff",
"draft": false,
"head": {
"label": "external-contributor:feature-branch",
"ref": "feature-branch",
"repo": {
"fork": true,
"full_name": "external-contributor/project",
"id": 111222333,
"name": "project",
"node_id": "MDEwOlJlcG9zaXRvcnkxMTEyMjIzMzM=",
"private": false
},
"sha": "abc123def456789012345678901234567890abcd",
"user": {
"avatar_url": "https://avatars.githubusercontent.com/u/789012?v=4",
"html_url": "https://github.com/external-contributor",
"id": 789012,
"login": "external-contributor",
"node_id": "MDQ6VXNlcjc4OTAxMg==",
"type": "User"
}
},
"html_url": "https://github.com/acme/project/pull/42",
"id": 123456789,
"issue_url": "https://api.github.com/repos/acme/project/issues/42",
"labels": [],
"locked": false,
"merge_commit_sha": null,
"merged_at": null,
"node_id": "PR_kwDOABC123",
"number": 42,
"patch_url": "https://github.com/acme/project/pull/42.patch",
"requested_reviewers": [],
"requested_teams": [],
"review_comment_url": "https://api.github.com/repos/acme/project/pulls/comments{/number}",
"review_comments_url": "https://api.github.com/repos/acme/project/pulls/42/comments",
"state": "open",
"statuses_url": "https://api.github.com/repos/acme/project/statuses/abc123",
"title": "External contribution: Add new feature",
"updated_at": "2025-01-16T18:00:00Z",
"url": "https://api.github.com/repos/acme/project/pulls/42",
"user": {
"avatar_url": "https://avatars.githubusercontent.com/u/789012?v=4",
"html_url": "https://github.com/external-contributor",
"id": 789012,
"login": "external-contributor",
"node_id": "MDQ6VXNlcjc4OTAxMg==",
"type": "User"
}
},
"repository": {
"default_branch": "main",
"full_name": "acme/project",
"html_url": "https://github.com/acme/project",
"id": 987654321,
"name": "project",
"node_id": "MDEwOlJlcG9zaXRvcnk5ODc2NTQzMjE=",
"owner": {
"avatar_url": "https://avatars.githubusercontent.com/u/111111?v=4",
"html_url": "https://github.com/acme",
"id": 111111,
"login": "acme",
"node_id": "MDEyOk9yZ2FuaXphdGlvbjExMTExMQ==",
"type": "Organization"
},
"private": false
},
"sender": {
"avatar_url": "https://avatars.githubusercontent.com/u/789012?v=4",
"html_url": "https://github.com/external-contributor",
"id": 789012,
"login": "external-contributor",
"node_id": "MDQ6VXNlcjc4OTAxMg==",
"type": "User"
}
}