Instagram integration: token exchange fails with "Unsupported request - method type: get"

[adamh123-git]

Bug Description

When completing the Instagram OAuth flow, the token exchange step fails with an instagram_token_request_error. Instagram's token endpoint (https://api.instagram.com/oauth/access_token) only accepts POST requests, but it appears Nango is sending a GET request during the token exchange.

Error

AuthError: {
"name": "Error",
"message": "An unhandled error of type 'instagram_token_request_error' with payload '"{ "message": "Request failed with status code 400", "name": "AxiosError", "provider_error_payload": { "message": "Unsupported request - method type: get" } }"' has occurred"
}

Steps to Reproduce

1. Configure an instagram integration with valid Instagram App ID and Secret (from the Meta Developer Portal "Manage message & content on Instagram" use case)
2. Create a connect session and initiate nango.auth('instagram') from the frontend SDK
3. Complete the Instagram OAuth consent screen
4. Token exchange fails with the above error

Expected Behavior

Nango should send a POST request to Instagram's token endpoint (https://api.instagram.com/oauth/access_token) with client_id, client_secret, grant_type, redirect_uri, and code as form-encoded body parameters.

Environment

• Nango Frontend SDK: @nangohq/frontend (latest via CDN)
• Integration: instagram (built-in)
• Instagram API: Instagram Basic Display / Instagram Login

[linear]

NAN-4868