From e60734f3e71b052d51181fdaede72e10864f544a Mon Sep 17 00:00:00 2001
From: Abhimanyu Saharan <desk.abhimanyu@gmail.com>
Date: Thu, 12 Feb 2026 20:04:38 +0000
Subject: [PATCH] ci: add migration integrity gate for migration-relevant
 changes

---
 .github/workflows/ci.yml | 30 ++++++++++++++++++++++++++++++
 Makefile                 | 22 ++++++++++++++++++++++
 docs/03-development.md   | 22 +++++++++++++++++++++-
 3 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f17053e0..4dcf4890 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -62,6 +62,36 @@ jobs:
             nextjs-${{ runner.os }}-node-${{ steps.setup-node.outputs.node-version }}-
 
 
+
+      - name: Run migration integrity gate
+        run: |
+          set -euo pipefail
+
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            BASE_SHA="${{ github.event.pull_request.base.sha }}"
+            HEAD_SHA="${{ github.sha }}"
+            git fetch --no-tags --depth=1 origin "$BASE_SHA"
+          else
+            BASE_SHA="${{ github.event.before }}"
+            HEAD_SHA="${{ github.sha }}"
+          fi
+
+          CHANGED_FILES=$(git diff --name-only "$BASE_SHA" "$HEAD_SHA")
+          echo "Changed files:"
+          echo "$CHANGED_FILES"
+
+          if ! echo "$CHANGED_FILES" | grep -Eq '^backend/(app/models|db|migrations|alembic\.ini)'; then
+            echo "No migration-relevant backend changes detected; skipping migration gate."
+            exit 0
+          fi
+
+          if echo "$CHANGED_FILES" | grep -Eq '^backend/app/models/' && ! echo "$CHANGED_FILES" | grep -Eq '^backend/migrations/versions/'; then
+            echo "Model changes detected without a migration under backend/migrations/versions/."
+            exit 1
+          fi
+
+          make backend-migration-check
+
       - name: Run backend checks
         env:
           # Keep CI builds deterministic.
diff --git a/Makefile b/Makefile
index b64228ff..4ecffdc3 100644
--- a/Makefile
+++ b/Makefile
@@ -104,6 +104,28 @@ frontend-test: frontend-tooling ## Frontend tests (vitest)
 backend-migrate: ## Apply backend DB migrations (uses backend/migrations)
 	cd $(BACKEND_DIR) && uv run alembic upgrade head
 
+.PHONY: backend-migration-check
+backend-migration-check: ## Validate Alembic migrations on clean Postgres (upgrade head + single-head sanity)
+	@set -euo pipefail; \
+	CONTAINER_NAME="mc-migration-check-$$RANDOM"; \
+	docker run -d --rm --name $$CONTAINER_NAME -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=migration_ci -p 55432:5432 postgres:16 >/dev/null; \
+	cleanup() { docker rm -f $$CONTAINER_NAME >/dev/null 2>&1 || true; }; \
+	trap cleanup EXIT; \
+	for i in $$(seq 1 30); do \
+		if docker exec $$CONTAINER_NAME pg_isready -U postgres -d migration_ci >/dev/null 2>&1; then break; fi; \
+		sleep 1; \
+		if [ $$i -eq 30 ]; then echo "Postgres did not become ready"; exit 1; fi; \
+	done; \
+	cd $(BACKEND_DIR) && \
+		AUTH_MODE=local \
+		LOCAL_AUTH_TOKEN=ci-local-token-ci-local-token-ci-local-token-ci-local-token \
+		DATABASE_URL=postgresql+psycopg://postgres:postgres@localhost:55432/migration_ci \
+		uv run alembic upgrade head && \
+		AUTH_MODE=local \
+		LOCAL_AUTH_TOKEN=ci-local-token-ci-local-token-ci-local-token-ci-local-token \
+		DATABASE_URL=postgresql+psycopg://postgres:postgres@localhost:55432/migration_ci \
+		uv run alembic heads | grep -q "(head)"
+
 .PHONY: build
 build: frontend-build ## Build artifacts
 
diff --git a/docs/03-development.md b/docs/03-development.md
index 4949c0c3..b3e1417c 100644
--- a/docs/03-development.md
+++ b/docs/03-development.md
@@ -1,3 +1,23 @@
 # Development workflow
 
-Placeholder: see root `README.md` for current setup steps.
+## Migration integrity gate (CI)
+
+CI enforces a migration integrity gate to prevent merge-time schema breakages.
+
+### What it validates
+
+- Alembic migrations can apply from a clean Postgres database (`upgrade head`)
+- Alembic revision graph resolves to a head revision after migration apply
+- On migration-relevant PRs, CI also checks that model changes are accompanied by migration updates
+
+If any of these checks fails, CI fails and the PR is blocked.
+
+### Local reproduction
+
+From repo root:
+
+```bash
+make backend-migration-check
+```
+
+This command starts a temporary Postgres container, runs migration checks, and cleans up the container.