docs: activity log — chat participant fix revert (v2.8.73) + template validation (frontend v2.8.80)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

09 - Audits/Activity Log.md

@@ -1104,4 +1104,23 @@ template fields can now be left empty end-to-end.
 
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+### 2026-06-04 — backend v2.8.72→v2.8.73 (chat participant fix reverted) + frontend v2.8.80 (template validation visibility)
+
+**Backend chat — attempted + reverted.** v2.8.72 tried to canonicalize chat
+participant ids (userRepo.findById) so a buyer (marketplace uuid for the seller)
+and seller (legacy ObjectId session) would share one direct thread. It backfired:
+findById returns an id format (Mongo ObjectId / PG uuid) that no longer matches
+the session JWT id, so the membership check rejected everyone ("User is not a
+participant"). v2.8.73 reverts to storing ids as passed (restores chat access).
+**Open issue:** buyer↔seller messages still don't cross — they land in separate
+direct conversations because the seller is referenced by a uuid while the session
+id is a legacy ObjectId (users in Mongo, chats in Postgres). Needs a correct
+uuid→legacyObjectId resolution (via marketplace id_map), not the session-breaking
+findById path. Deferred for a careful fix.
+**Frontend v2.8.80:** template-form onInvalid now expands all collapsed accordion
+sections and toasts the actual nested error messages, so validation errors are
+visible under their fields instead of only in the console.
+
+---
+
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