# CI/CD Target Architecture

## Goal

This document describes the canonical release path for Nexus.

The release model is now:

1. PRs are validated by CI before merge.
2. Every push to `main` publishes immutable `app` and `migrator` images.
3. Staging and production promote the exact same `sha-<commit>` tag.
4. The host deploys only from images and runtime env files.
5. A deployment is successful only after `GET /api/ready` passes.

## Canonical Flow

### 1. Pull Request Validation

The main [ci.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/ci.yml) workflow remains the merge gate for:

- architecture guardrails
- typecheck
- lint
- unit tests
- build
- E2E

### 2. Automatic Image Release

[release-image.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/release-image.yml) now runs automatically on every push to `main` and can still be started manually for rebuilds or tag overrides.

It publishes two images from [Dockerfile.prod](/home/hartmut/Documents/Copilot/nexus/Dockerfile.prod):

- `ghcr.io/<owner>/<repo>-app:sha-<commit>`
- `ghcr.io/<owner>/<repo>-migrator:sha-<commit>`

### 3. Staging Promotion

[deploy-staging.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/deploy-staging.yml) copies the canonical deploy bundle to the staging host:

- [docker-compose.prod.yml](/home/hartmut/Documents/Copilot/nexus/docker-compose.prod.yml)
- [tooling/deploy/deploy-compose.sh](/home/hartmut/Documents/Copilot/nexus/tooling/deploy/deploy-compose.sh)
- the rest of [tooling/deploy](/home/hartmut/Documents/Copilot/nexus/tooling/deploy/README.md)

GitHub Actions also writes a short-lived `deploy.env` containing `APP_IMAGE`, `MIGRATOR_IMAGE`, and the host port.

### 4. Host-Side Deployment

On the target host, [deploy-compose.sh](/home/hartmut/Documents/Copilot/nexus/tooling/deploy/deploy-compose.sh):

1. loads `.env.production` and `deploy.env`
2. validates the rendered compose file
3. pulls the immutable `app` and `migrator` images
4. starts PostgreSQL and Redis
5. runs Prisma migrations through the dedicated `migrator` image
6. starts the new `app` container
7. waits for `GET /api/ready`

The host does not build application code from Git anymore.

### 5. Production Promotion

[deploy-prod.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/deploy-prod.yml) repeats the exact staging flow with the same image tag after staging acceptance.

That keeps staging and production on the same artifact instead of rebuilding.

## Required Infrastructure

### Minimum

- GitHub repository with Actions enabled
- GHCR or another container registry
- one Linux host with Docker Engine and Docker Compose v2
- PostgreSQL
- Redis
- SSH access from GitHub Actions to the host
- reverse proxy or load balancer in front of the app

### Recommended

- separate staging and production hosts
- GitHub Environments for `staging` and `production`
- required approval for the `production` environment
- monitoring on `/api/health` and `/api/ready`
- PostgreSQL backup and restore drills

## Runtime Configuration

The canonical host-side inputs are:

- [docker-compose.prod.yml](/home/hartmut/Documents/Copilot/nexus/docker-compose.prod.yml)
- `.env.production`
- `deploy.env`

`.env.production` holds long-lived runtime configuration and secrets. The example file is [tooling/deploy/.env.production.example](/home/hartmut/Documents/Copilot/nexus/tooling/deploy/.env.production.example).

`deploy.env` is short-lived deployment metadata. The example file is [tooling/deploy/deploy.env.example](/home/hartmut/Documents/Copilot/nexus/tooling/deploy/deploy.env.example).

Important invariants:

- `RATE_LIMIT_BACKEND=redis` should stay explicit in release environments
- runtime AI, SMTP, and anonymization secrets belong to the host or platform secret layer
- admin settings are for verification and legacy-secret cleanup, not for secret rotation

## Database Policy

Release environments must run migrations through the `migrator` image, which executes:

```bash
pnpm --filter @nexus/db db:migrate:deploy
```

`db:push` remains a local-development tool, not a production rollout mechanism.

## Rollback Model

Rollback is image-based:

1. choose the previous healthy `sha-<commit>` tag
2. redeploy staging or production with that tag
3. confirm `GET /api/ready`

This assumes schema changes follow backwards-compatible expand-and-contract rollout rules.

## Production Update Summary

The standard production update is:

1. merge to `main` after CI is green
2. let [release-image.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/release-image.yml) publish `sha-<commit>` images
3. deploy that tag to staging through [deploy-staging.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/deploy-staging.yml)
4. validate staging
5. promote the same tag through [deploy-prod.yml](/home/hartmut/Documents/Copilot/nexus/.github/workflows/deploy-prod.yml)

The important property is artifact identity: staging and production run the same image, not two separate builds.
