fix missing tiers in previous part of webhook

[cathysarisky]

closes #29805

Currently, switching between tiers does not cause a webhook to fire. This makes it hard for an integration to detect plan changes without doing a full scan of members.

This PR makes sure that tiers are emitted, and provides a test for the corrected behavior.

AI disclosure: Fable helped find the code responsible for the bug and fix it.

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☁️ Nx Cloud last updated this comment at 2026-08-10 18:16:02 UTC

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 151d037 and 349e09f.

📒 Files selected for processing (2)

• ghost/core/core/server/services/webhooks/serialize.js
• ghost/core/test/unit/server/services/webhooks/serialize.test.js

🚧 Files skipped from review as they are similar to previous changes (2)

• ghost/core/test/unit/server/services/webhooks/serialize.test.js
• ghost/core/core/server/services/webhooks/serialize.js

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Walkthrough

The webhook serializer maps member products changes to the serialized tiers field when it builds previous data. Other keys keep their original names. A regression test verifies current and previous tier slugs for a paid-to-paid tier switch.

Fixed issue severity: Medium

Possibly related PRs

• TryGhost/Ghost#29814: This PR also changes webhooks/serialize.js and member webhook serializer tests to preserve previous paid-tier data.

Suggested reviewers: 9larsons

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the fix for missing tier data in webhook previous payloads.
Description check	✅ Passed	The description directly explains the tier-switch webhook bug and the regression test added to fix it.
Linked Issues check	✅ Passed	The serializer change and regression test satisfy issue #29805 by including the previous tier in member.edited webhooks.
Out of Scope Changes check	✅ Passed	The changes remain within scope and support the webhook serialization fix and its regression coverage.

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• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.45%. Comparing base (fadf960) to head (349e09f).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #29810      +/-   ##
==========================================
+ Coverage   75.41%   75.45%   +0.04%     
==========================================
  Files        1606     1605       -1     
  Lines      140372   140458      +86     
  Branches    17394    17423      +29     
==========================================
+ Hits       105859   105988     +129     
+ Misses      33464    33393      -71     
- Partials     1049     1077      +28     

Flag	Coverage Δ
e2e-tests	77.61% <100.00%> (+0.04%)	⬆️

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