After adding a new WhatsApp number, the n8n WhatsApp Cloud API node started returning 400 Bad Request / “Error validating client secret”. Direct Graph API calls with a System User Bearer token to POST https://graph.facebook.com/v20.0/<PHONE_NUMBER_ID>/messages return 200 OK, so Meta credentials and phone_number_id are correct. The failure appears specific to n8n’s WhatsApp node/credential type (expects OAuth Client ID/Secret), while WhatsApp Cloud actually uses Bearer tokens. Environment repocloud n8n WhatsApp Business Cloud API (Graph v20) ~840 nodes depend on the same WhatsApp credential Steps to Reproduce Add a new WhatsApp number to the WABA and generate a System User token with whatsapp_business_messaging + whatsapp_business_management. Configure the n8n WhatsApp node using the existing OAuth credential (App ID/Secret). Execute any send-message operation → 400 Bad Request / client secret error. Observed Behavior n8n WhatsApp node fails with OAuth/Client Secret validation errors. The same request with Bearer token via HTTP Request node or curl succeeds (200). Expected Behavior n8n WhatsApp integration should accept Bearer (System User) tokens for WhatsApp Cloud API and send messages successfully. What I’ve Tried Verified token scopes and validity (debug_token OK). Confirmed correct PHONE_NUMBER_ID and WABA mapping. Raw API test succeeds (200). Problem persists only inside n8n’s WhatsApp node using OAuth credential. Impact All ~840 automations tied to this credential are blocked. Manually converting each to HTTP Request is impractical. Request Guidance or a fix to use Bearer tokens with the built-in WhatsApp node (or a way to convert the existing OAuth credential to Bearer without breaking references), or update n8n to a version where the WhatsApp node supports Bearer auth.
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