{ "name": "LinkedIn published to Bluesky + Threads cross-post", "nodes": [ { "parameters": { "content": "## LinkedIn → Bluesky + Threads cross-post\n\nWhen a LinkedIn post publishes, Posta fires an outbound webhook. This workflow verifies it, fetches the published caption, compresses it per network with an LLM, and creates **draft** Bluesky and Threads versions for you to review.\n\n### Setup\n\n- [ ] Point a Posta **outbound webhook** at the `Posta webhook` node's URL, scoped to `post.published` on LinkedIn (Posta dashboard → Webhooks)\n- [ ] Set `POSTA_WEBHOOK_SECRET` in n8n env (the signing secret from the webhook endpoint)\n- [ ] Add **Header Auth** credentials: `Posta API` (`Authorization: Bearer posta_…`) and `OpenAI API` (`Authorization: Bearer sk-…`)\n- [ ] Set your Bluesky and Threads Posta account ids on the two Create-post nodes\n- [ ] Set `SLACK_WEBHOOK_URL` in n8n env for the review ping (or delete the Slack node)\n\n### Signature scheme\n\nPosta signs `HMAC-SHA256(secret, \"{X-Posta-Timestamp}.{rawBody}\")` and sends it as `X-Posta-Signature`. The Code node verifies exactly that (constant-time, raw body).", "height": 620, "width": 480 }, "type": "n8n-nodes-base.stickyNote", "typeVersion": 1, "position": [ -1120, -120 ], "id": "b1000000-0000-4000-9000-000000000001", "name": "Sticky Overview" }, { "parameters": { "httpMethod": "POST", "path": "posta-linkedin-published", "options": { "rawBody": true } }, "type": "n8n-nodes-base.webhook", "typeVersion": 2, "position": [ -580, 160 ], "id": "b1000000-0000-4000-9000-000000000002", "name": "Posta webhook", "webhookId": "posta-linkedin-published" }, { "parameters": { "jsCode": "// Verify Posta's HMAC signature over `{timestamp}.{rawBody}` (constant-time),\n// then emit the parsed payload. Throws (stops the run) if verification fails.\nconst crypto = require('crypto');\nconst item = $input.first();\nconst headers = item.json.headers || {};\nconst sig = headers['x-posta-signature'];\nconst ts = headers['x-posta-timestamp'];\nif (!sig || !ts) throw new Error('Missing X-Posta-Signature / X-Posta-Timestamp');\n\n// Raw body (the Webhook node has Raw Body enabled -> binary 'data').\nconst raw = item.binary && item.binary.data\n ? Buffer.from(item.binary.data, 'base64').toString('utf8')\n : JSON.stringify(item.json.body);\n\nconst secret = $env.POSTA_WEBHOOK_SECRET;\nif (!secret) throw new Error('Set POSTA_WEBHOOK_SECRET in n8n env');\n\nconst expected = crypto.createHmac('sha256', secret).update(`${ts}.${raw}`).digest('hex');\nconst a = Buffer.from(sig);\nconst b = Buffer.from(expected);\nif (a.length !== b.length || !crypto.timingSafeEqual(a, b)) {\n throw new Error('Bad signature');\n}\nreturn [{ json: JSON.parse(raw) }];" }, "type": "n8n-nodes-base.code", "typeVersion": 2, "position": [ -340, 160 ], "id": "b1000000-0000-4000-9000-000000000003", "name": "Verify signature" }, { "parameters": { "url": "=https://api.getposta.app/v1/posts/{{ $json.data.post.id }}", "authentication": "genericCredentialType", "genericAuthType": "httpHeaderAuth", "options": {} }, "type": "n8n-nodes-base.httpRequest", "typeVersion": 4.2, "position": [ -100, 160 ], "id": "b1000000-0000-4000-9000-000000000004", "name": "Get LinkedIn post", "credentials": { "httpHeaderAuth": { "name": "Posta API" } } }, { "parameters": { "method": "POST", "url": "https://api.openai.com/v1/chat/completions", "authentication": "genericCredentialType", "genericAuthType": "httpHeaderAuth", "sendBody": true, "specifyBody": "json", "jsonBody": "={{ JSON.stringify({\n model: 'gpt-4o-mini',\n response_format: { type: 'json_object' },\n messages: [\n { role: 'system', content: 'Rewrite a LinkedIn post for other networks. Return JSON {\"bluesky\": string <=300 chars, \"threads\": string <=500 chars}. Keep links, drop the LinkedIn-flavored opener, keep the technical specifics.' },\n { role: 'user', content: $json.caption || ($json.post && $json.post.caption) || '' }\n ]\n}) }}", "options": {} }, "type": "n8n-nodes-base.httpRequest", "typeVersion": 4.2, "position": [ 140, 160 ], "id": "b1000000-0000-4000-9000-000000000005", "name": "Compress per network", "credentials": { "httpHeaderAuth": { "name": "OpenAI API" } } }, { "parameters": { "jsCode": "// Parse the model's JSON content into top-level fields.\nconst content = $json.choices[0].message.content;\nconst parsed = JSON.parse(content);\nreturn [{ json: { bluesky: parsed.bluesky, threads: parsed.threads } }];" }, "type": "n8n-nodes-base.code", "typeVersion": 2, "position": [ 380, 160 ], "id": "b1000000-0000-4000-9000-000000000006", "name": "Parse variants" }, { "parameters": { "socialAccountIds": "REPLACE_BLUESKY_ACCOUNT_ID", "caption": "={{ $json.bluesky }}", "additionalFields": {}, "platformConfigurations": {} }, "type": "n8n-nodes-posta.posta", "typeVersion": 1, "position": [ 640, 60 ], "id": "b1000000-0000-4000-9000-000000000007", "name": "Create Bluesky draft", "credentials": { "postaApi": { "name": "Posta account" } } }, { "parameters": { "socialAccountIds": "REPLACE_THREADS_ACCOUNT_ID", "caption": "={{ $json.threads }}", "additionalFields": {}, "platformConfigurations": {} }, "type": "n8n-nodes-posta.posta", "typeVersion": 1, "position": [ 640, 260 ], "id": "b1000000-0000-4000-9000-000000000008", "name": "Create Threads draft", "credentials": { "postaApi": { "name": "Posta account" } } }, { "parameters": { "method": "POST", "url": "={{ $env.SLACK_WEBHOOK_URL }}", "sendBody": true, "specifyBody": "json", "jsonBody": "={{ JSON.stringify({ text: 'Cross-post drafts ready for review:\\n• Bluesky: https://getposta.app/app/posts/' + $('Create Bluesky draft').item.json.id + '\\n• Threads: https://getposta.app/app/posts/' + $('Create Threads draft').item.json.id }) }}", "options": {} }, "type": "n8n-nodes-base.httpRequest", "typeVersion": 4.2, "position": [ 900, 160 ], "id": "b1000000-0000-4000-9000-000000000009", "name": "Slack review ping" } ], "pinData": {}, "connections": { "Posta webhook": { "main": [ [ { "node": "Verify signature", "type": "main", "index": 0 } ] ] }, "Verify signature": { "main": [ [ { "node": "Get LinkedIn post", "type": "main", "index": 0 } ] ] }, "Get LinkedIn post": { "main": [ [ { "node": "Compress per network", "type": "main", "index": 0 } ] ] }, "Compress per network": { "main": [ [ { "node": "Parse variants", "type": "main", "index": 0 } ] ] }, "Parse variants": { "main": [ [ { "node": "Create Bluesky draft", "type": "main", "index": 0 }, { "node": "Create Threads draft", "type": "main", "index": 0 } ] ] }, "Create Bluesky draft": { "main": [ [ { "node": "Slack review ping", "type": "main", "index": 0 } ] ] } }, "active": false, "settings": { "executionOrder": "v1" }, "meta": { "templateCredsSetupCompleted": true }, "tags": [ { "name": "socialmedia" }, { "name": "posta" }, { "name": "webhook" } ] }