Introduction

An app migration can move the site successfully while incoming webhooks still post to the old domain. The main website may already load from the new platform and manual API tests may pass, but third-party services keep delivering event callbacks to the legacy endpoint because their saved webhook URL was never updated. This creates a situation where automated integrations appear broken while the main application works correctly.

Treat this as an external-callback target problem instead of a general application outage. Start by checking the exact webhook destination configured in the sending platform, because many post-migration failures come from vendor-side callback URLs that remain pinned to the previous domain long after the site itself moves. This issue is particularly common with payment processors (Stripe, PayPal), messaging platforms (Slack, Discord), and CI/CD systems that store webhook URLs independently.

The problem frequently appears after domain migrations, API version upgrades, or when moving between different hosting platforms that use different URL structures. Organizations often remember to update DNS and application configuration but forget that external services have their own stored callback URLs that need manual updates.

Symptoms

  • Webhooks still post to the old domain after migration, visible in server logs or provider dashboards
  • Manual requests to the new endpoint work, but third-party event delivery still fails
  • Provider delivery logs show attempts against the previous hostname or URL path
  • Some integrations work after cutover while one vendor or service still hits the legacy domain
  • Events appear delayed, duplicated, or missing because callbacks go to the wrong destination
  • The issue started after domain migration, app cutover, or API endpoint replacement
  • Webhook secret validation fails because signatures are computed for a different endpoint
  • Payment notifications, chat bot commands, or CI/CD notifications stop working
  • Error logs show 404 or connection refused errors from old webhook endpoint attempts

Common Causes

  • The webhook sender still stores the old callback URL in its configuration
  • The new app moved to a different hostname, path, or routing pattern than the previous environment (e.g., /api/v1/webhook vs /webhook)
  • One vendor integration was excluded from the migration checklist and never updated
  • Legacy redirects, proxies, or expired certificates on the old domain hide the real callback failure
  • Teams validated interactive app traffic but not inbound webhook destinations from third-party systems
  • More than one webhook endpoint exists (different event types), and only part of the integration was updated
  • Webhook signing secrets were regenerated but not updated in the external service
  • Environment-specific webhook URLs (staging vs production) were swapped incorrectly

Step-by-Step Fix

  1. 1.Identify the exact webhook sender and event flow that still fails, because you need the real external delivery path before changing application routing. Determine which third-party service (Stripe, Slack, GitHub, etc.) is delivering the webhook.
  2. 2.Check the saved callback URL in the sending platform's configuration dashboard and record the full hostname and path it uses, because webhook problems after migration usually start with one vendor-side endpoint that still points to the previous domain.
  3. 3.Compare that configured URL with the intended post-migration endpoint, because the new app may use a different hostname, path, or versioned route than the old system. Note any differences in protocol (http vs https), port, or path structure.
  4. 4.Review delivery logs or recent failed webhook attempts from the sender's dashboard, because they usually confirm whether requests still target the retired domain or another stale endpoint. Look for 404, 503, or timeout errors.
  5. 5.Update the webhook URL at the actual source of delivery (the external service's dashboard) rather than relying on redirects, because callback traffic should point directly at the supported live endpoint after migration. Also update any webhook signing secrets if they changed.
  6. 6.Retest with a new event (trigger a payment, send a test notification) or provider resend after the change, because one corrected setting is not proven until the external service actually delivers to the new domain successfully.
  7. 7.Verify the new endpoint processes the webhook successfully and no longer depends on the old hostname, because successful network delivery alone does not confirm application-level recovery. Check that the webhook payload is processed correctly.
  8. 8.Review related integrations from the same vendor or workflow if multiple webhook endpoints exist (e.g., separate URLs for different event types), because migrations often miss one callback while another appears fixed.
  9. 9.Document every third-party callback URL updated during the cutover, because webhook destinations are easy to overlook in future app migrations and the same issue will recur without tracking.

Verification

Confirm the fix is complete:

  1. 1.Trigger a test event from the webhook sender and verify it arrives at the new endpoint
  2. 2.Check server logs to confirm the webhook came to the new domain
  3. 3.Verify the application processes the webhook payload correctly
  4. 4.Check that no more requests hit the old endpoint by monitoring old server logs
  5. 5.Test all event types if the integration uses multiple webhook endpoints

Prevention

To avoid this issue in future migrations:

  • Create an inventory of all webhook integrations including callback URLs before migration
  • Include webhook URL updates in the migration checklist as mandatory steps
  • Use consistent webhook path patterns that survive migrations (e.g., /api/webhooks/stripe)
  • Consider keeping the old domain temporarily with a redirect while webhook configs are updated
  • Document webhook signing secrets and update them alongside callback URLs
  • Set up monitoring for incoming webhook requests to detect delivery failures quickly
  • Test all webhook integrations explicitly after migration, not just main application functionality
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