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+---
+plan: 06-04
+phase: 06-performance-production-hardening
+status: partial
+completed_at: 2026-06-04
+commits:
+  - 3788226
+checkpoint_pending: task-3-human-verify
+---
+
+# Plan 06-04: Container Hardening
+
+## What was built (Tasks 1 & 2)
+
+### backend/Dockerfile — multi-stage with appuser
+
+Replaced the single-stage root-running Dockerfile with a two-stage build:
+
+**Stage 1 `AS builder`:**
+- `FROM python:3.12-slim AS builder`
+- Installs `gcc` (build-only dep, discarded after this stage) with `--no-install-recommends`
+- Runs `pip install --no-cache-dir --prefix=/install -r requirements.txt`
+
+**Stage 2 `AS runtime`:**
+- `FROM python:3.12-slim AS runtime`
+- Installs runtime apt deps (tesseract-ocr, libgl1, libglib2.0-0) with `--no-install-recommends`
+- `COPY --from=builder /install /usr/local` (copies compiled packages, discards builder)
+- Creates `appgroup` gid=1000 and `appuser` uid=1000 (no login shell, no home dir)
+- `COPY --chown=appuser:appgroup . .`
+- `USER appuser`
+- `CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]` (no `--reload`)
+
+### docker-compose.yml — runtime hardening
+
+Added to **backend** and **celery-worker** services (not celery-beat):
+
+```yaml
+read_only: true
+tmpfs:
+  - "/tmp:mode=1777"
+cap_drop:
+  - ALL
+security_opt:
+  - "no-new-privileges:true"
+```
+
+Added comment before celery-beat:
+```yaml
+# celery-beat: NOT hardened — writes celerybeat-schedule to working directory (Phase 6 Pitfall 7).
+```
+
+Existing bind mounts (`./backend:/app`), env vars, healthchecks, and Loki logging labels preserved.
+
+## Static verification (Tasks 1 & 2 acceptance criteria)
+
+| Check | Result |
+|-------|--------|
+| `FROM python:3.12-slim AS builder` | 1 ✓ |
+| `FROM python:3.12-slim AS runtime` | 1 ✓ |
+| `USER appuser` | 1 ✓ |
+| `useradd --uid 1000` | 1 ✓ |
+| `COPY --from=builder` | 1 ✓ |
+| `--no-install-recommends` occurrences | 2 ✓ |
+| `tesseract-ocr` in runtime only | 1 ✓ |
+| `--reload` in Dockerfile | 0 ✓ |
+| `docker compose config --quiet` | exit 0 ✓ |
+| `read_only: true` in backend block | 1 ✓ |
+| `/tmp:mode=1777` in backend block | 1 ✓ |
+| `no-new-privileges:true` in backend block | 1 ✓ |
+| `read_only: true` in celery-worker block | 1 ✓ |
+| hardening keys in celery-beat block | 0 ✓ |
+| `./backend:/app` bind mount preserved | 1 ✓ |
+
+## Task 3: Human smoke test (PENDING)
+
+Docker daemon was not running at execution time. Task 3 requires:
+1. `docker compose up -d --build` (rebuilds with new Dockerfile)
+2. `docker compose exec -T backend id` → must show uid=1000(appuser)
+3. `docker compose exec -T backend sh -c 'touch /readonly_probe 2>&1 || echo "rootfs is read-only"'`
+4. `docker compose exec -T backend sh -c 'touch /tmp/ok && ls -la /tmp/ok'`
+5. Same checks on celery-worker
+6. Confirm celery-beat is writable (intentionally)
+7. End-to-end upload test (proves tempfile.NamedTemporaryFile works under hardened runtime)
+
+Human responds "approved" to advance to Wave 3 (06-06).
+
+## Satisfaction of requirements
+- D-07 (multi-stage non-root image): ✓ Tasks 1 & 2 complete
+- D-08 (read-only rootfs + tmpfs): ✓ Tasks 1 & 2 complete
+- D-09 (cap_drop ALL + no-new-privileges): ✓ Tasks 1 & 2 complete
+- Runtime verification (Task 3): PENDING human checkpoint