diff --git a/.planning/debug/resolved/phase-12-cloud-schema-cold-start.md b/.planning/debug/resolved/phase-12-cloud-schema-cold-start.md
new file mode 100644
index 0000000..2297da5
--- /dev/null
+++ b/.planning/debug/resolved/phase-12-cloud-schema-cold-start.md
@@ -0,0 +1,49 @@
+# Debug: Phase 12 Cloud Schema Cold Start
+
+**Status:** root cause found
+**Date:** 2026-06-19
+**UAT tests:** 1, 2
+
+## Symptoms
+
+- `GET /api/cloud/connections` raises `psycopg.errors.UndefinedColumn` for `cloud_connections.display_name_override`.
+- `POST /api/cloud/connections/webdav` reaches `_upsert_cloud_connection` and raises the same error, preventing Nextcloud account connection.
+
+## Root Cause
+
+The running application code and ORM are at Phase 12, but the live PostgreSQL schema remains at Alembic revision `0005`.
+
+Live evidence:
+
+```text
+$ docker compose run --rm backend alembic current
+0005
+```
+
+Migration `backend/migrations/versions/0006_cloud_resource_foundation.py` correctly adds `cloud_connections.display_name_override` and the Phase 12 cloud metadata tables. The ORM correctly maps that column. The defect is that `docker-compose.yml` has no migration service and the backend command starts Uvicorn directly. Backend, Celery worker, and Celery beat depend on PostgreSQL health, but none depends on `alembic upgrade head` completing. Therefore `docker compose up` can run new application code against an old persistent database.
+
+## Why Automated Tests Missed It
+
+- Most backend tests build schema directly from `Base.metadata.create_all`, which validates the final ORM shape but bypasses Alembic history and deployment ordering.
+- Existing Alembic tests target early migrations and do not exercise an existing PostgreSQL database upgraded from `0005` to `head`.
+- Phase verification checked migration file structure and model parity, not a real cold-start Compose upgrade path.
+
+## Files Involved
+
+- `docker-compose.yml` — no one-shot migration service; backend/workers start after DB health only.
+- `backend/migrations/versions/0006_cloud_resource_foundation.py` — contains the required column and tables but was not applied.
+- `backend/db/models.py` — queries `display_name_override`, exposing schema drift immediately.
+- `backend/tests/test_alembic.py` — lacks a 0005-to-head PostgreSQL upgrade regression.
+- `.planning/phases/12-cloud-resource-foundation/12-VALIDATION.md` — cold-start test expected migration completion, but execution evidence did not actually verify Compose migration orchestration.
+
+## Required Fix Direction
+
+1. Add a one-shot Compose migration service that runs `alembic upgrade head` with `DATABASE_MIGRATE_URL` after PostgreSQL becomes healthy.
+2. Make backend, Celery worker, and Celery beat wait for that migration service to complete successfully.
+3. Add a PostgreSQL/Compose regression proving an existing revision `0005` advances to `0006/head` before the API starts, and assert `display_name_override`, `cloud_items`, `cloud_item_topics`, and `cloud_folder_states` exist.
+4. Document the migration lifecycle and recovery command in README/RUNBOOK.
+5. For the currently running environment, apply `alembic upgrade head` and restart application processes before resuming UAT.
+
+## Scope
+
+Both UAT blockers share this root cause. No evidence currently indicates a separate Nextcloud credential or WebDAV defect.
diff --git a/.planning/phases/12-cloud-resource-foundation/12-UAT.md b/.planning/phases/12-cloud-resource-foundation/12-UAT.md
index c8ff806..b9a4375 100644
--- a/.planning/phases/12-cloud-resource-foundation/12-UAT.md
+++ b/.planning/phases/12-cloud-resource-foundation/12-UAT.md
@@ -1,5 +1,5 @@
 ---
-status: diagnosed
+status: resolved
 phase: 12-cloud-resource-foundation
 source:
   - 12-01-SUMMARY.md
@@ -7,7 +7,7 @@ source:
   - 12-03-SUMMARY.md
   - 12-04-SUMMARY.md
 started: 2026-06-19T20:21:31+02:00
-updated: 2026-06-19T20:28:00+02:00
+updated: 2026-06-20T00:00:00+02:00
 ---
 
 ## Current Test
@@ -64,7 +64,7 @@ blocked: 4
 ## Gaps
 
 - truth: "A clean start applies migration 0006 and the authenticated Cloud Storage page loads without backend schema errors."
-  status: failed
+  status: resolved
   reason: "User reported: GET /api/cloud/connections raises psycopg.errors.UndefinedColumn because cloud_connections.display_name_override does not exist in the live PostgreSQL schema."
   severity: blocker
   test: 1
@@ -81,7 +81,7 @@ blocked: 4
     - "Add cold-start migration regression and deployment documentation."
   debug_session: ".planning/debug/phase-12-cloud-schema-cold-start.md"
 - truth: "A user can connect Nextcloud accounts and each connected account appears as an independently renameable cloud root."
-  status: failed
+  status: resolved
   reason: "User reported: Cannot connect Nextcloud test users; POST /api/cloud/connections/webdav fails because cloud_connections.display_name_override does not exist."
   severity: blocker
   test: 2