diff --git a/backend/Dockerfile b/backend/Dockerfile
new file mode 100644
index 0000000..15cd020
--- /dev/null
+++ b/backend/Dockerfile
@@ -0,0 +1,25 @@
+# S0 minimal backend Dockerfile (OPS-25: pinned, not latest)
+FROM python:3.14.3-slim-bookworm
+
+WORKDIR /app
+
+# system deps minimal
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY backend/requirements.txt /app/requirements.txt
+RUN pip install --no-cache-dir --upgrade pip && \
+    pip install --no-cache-dir -r /app/requirements.txt
+
+COPY backend/ /app/backend/
+COPY .dockerignore /app/.dockerignore 2>/dev/null || true
+
+ENV PYTHONPATH=/app \
+    PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1
+
+# non-root? later; for S0 root ok
+EXPOSE 8000
+
+CMD ["uvicorn", "backend.app:app", "--host", "0.0.0.0", "--port", "8000", "--log-level", "info"]
diff --git a/backend/__init__.py b/backend/__init__.py
new file mode 100644
index 0000000..1502a60
--- /dev/null
+++ b/backend/__init__.py
@@ -0,0 +1,2 @@
+"""SlabUploader backend package (S0 foundation)."""
+__all__ = ["app", "db"]
diff --git a/backend/app.py b/backend/app.py
new file mode 100644
index 0000000..ff532fb
--- /dev/null
+++ b/backend/app.py
@@ -0,0 +1,163 @@
+"""S0 FastAPI app foundation (APP-30, APP-45, APP-55, APP-65, SETTINGS-10/25, OPS-25).
+Base /api/v1; health at /api/health (non-200 on storage not writable).
+Stdlib JSON logging with request_id from X-Request-Id (generate if absent).
+Startup guards refuse on bad WOO_BASE_URL or missing SLAB_AES_KEY.
+No secrets in logs. Minimal, no S1+.
+"""
+from __future__ import annotations
+
+import json
+import logging
+import os
+import sys
+import uuid
+from contextvars import ContextVar
+from pathlib import Path
+from typing import Any
+
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI, HTTPException, Request
+from fastapi.middleware.cors import CORSMiddleware
+from starlette.middleware.base import BaseHTTPMiddleware
+
+from .db import get_connection, init_db, probe_images_writable, probe_writable
+
+__version__ = "0.5.0-m3-s0"
+
+# --- Structured JSON logging (stdlib only) ---
+request_id_var: ContextVar[str] = ContextVar("request_id", default="")
+
+
+class _JsonFormatter(logging.Formatter):
+    """JSON lines; redacts any secret-looking content (APP-65)."""
+
+    def format(self, record: logging.LogRecord) -> str:
+        rid = getattr(record, "request_id", None) or request_id_var.get("")
+        msg = record.getMessage()
+        # Redact secrets: never log creds, keys, aes material
+        lower = msg.lower()
+        if any(k in lower for k in ("password", "api_key", "aes_key", "slab_aes_key", "woo_app_password", "inference_api_key")):
+            msg = "[REDACTED secret material]"
+        data: dict[str, Any] = {
+            "ts": self.formatTime(record, self.datefmt),
+            "level": record.levelname,
+            "logger": record.name,
+            "request_id": rid,
+            "msg": msg,
+        }
+        if record.exc_info:
+            data["exc"] = self.formatException(record.exc_info)
+        return json.dumps(data, ensure_ascii=False, separators=(",", ":"))
+
+
+def _configure_logging() -> None:
+    level = os.getenv("LOG_LEVEL", "INFO").upper()
+    handler = logging.StreamHandler(sys.stdout)
+    handler.setFormatter(_JsonFormatter())
+    root = logging.getLogger()
+    root.handlers.clear()
+    root.addHandler(handler)
+    root.setLevel(getattr(logging, level, logging.INFO))
+    # uvicorn access logs also json? for S0 keep simple; they inherit
+    logging.getLogger("uvicorn.access").setLevel(logging.WARNING)
+
+
+_configure_logging()
+logger = logging.getLogger("slab.backend")
+
+
+# --- Startup guards (refuse with clear message) ---
+def _enforce_startup_guards() -> None:
+    woo_url = os.getenv("WOO_BASE_URL")
+    if not woo_url:
+        msg = "SETTINGS-10: WOO_BASE_URL is required (https://...)"
+        logger.error(msg)
+        raise RuntimeError(msg)
+    if not woo_url.startswith("https://"):
+        msg = "SETTINGS-10: WOO_BASE_URL must start with https:// (got: " + woo_url[:8] + ")"
+        logger.error(msg)
+        raise RuntimeError(msg)
+    if not os.getenv("SLAB_AES_KEY"):
+        msg = "SETTINGS-25: SLAB_AES_KEY is required (32-byte base64 in env/compose)"
+        logger.error(msg)
+        raise RuntimeError(msg)
+    # db/images envs are required by db.py on use; guards here only per spec
+
+
+_enforce_startup_guards()
+
+
+# --- Request ID middleware (threads X-Request-Id or generates) ---
+class RequestIdMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        rid = request.headers.get("X-Request-Id") or str(uuid.uuid4())
+        token = request_id_var.set(rid)
+        try:
+            response = await call_next(request)
+            response.headers["X-Request-Id"] = rid
+            return response
+        finally:
+            request_id_var.reset(token)
+
+
+# --- App ---
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    logger.info("startup: applying schema (idempotent)")
+    try:
+        init_db()
+        logger.info("startup: schema ready; db+images envs present")
+    except Exception:
+        logger.exception("startup failed")
+        raise
+    yield
+    # shutdown: reset conn for test isolation if needed
+    try:
+        from .db import _reset_for_tests
+        _reset_for_tests()
+    except Exception:
+        pass
+
+
+app = FastAPI(
+    title="SlabUploader",
+    version=__version__,
+    docs_url=None,
+    redoc_url=None,
+    lifespan=lifespan,
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=False,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+app.add_middleware(RequestIdMiddleware)
+
+
+@app.get("/api/health")
+async def health() -> dict[str, Any]:
+    """Health per APP-30/45: non-200 when db or image volume not writable (probe file)."""
+    db_ok = probe_writable()
+    img_ok = probe_images_writable()
+    if not (db_ok and img_ok):
+        logger.warning("health: storage not writable", extra={"request_id": request_id_var.get("")})
+        raise HTTPException(status_code=503, detail="storage not writable")
+    return {
+        "status": "ok",
+        "version": __version__,
+        "woo_reachable": False,  # S0 stub; S4 will implement real check
+    }
+
+
+@app.get("/api/v1/meta")
+async def meta() -> dict[str, Any]:
+    """Per API.md §3."""
+    return {"version": __version__}
+
+
+# expose for tests
+__all__ = ["app", "__version__"]
diff --git a/backend/db/__init__.py b/backend/db/__init__.py
new file mode 100644
index 0000000..a45b8a4
--- /dev/null
+++ b/backend/db/__init__.py
@@ -0,0 +1,98 @@
+"""S0 db factory package: stdlib sqlite3 ONLY. ... (same as before)"""
+from __future__ import annotations
+
+import os
+import sqlite3
+import threading
+from pathlib import Path
+from typing import Any
+
+DB_PATH_ENV = "SLAB_DB_PATH"
+IMAGES_DIR_ENV = "SLAB_IMAGES_DIR"
+SCHEMA_FILE = "schema.sql"
+
+_lock = threading.Lock()
+_conn: sqlite3.Connection | None = None
+_current_path: str | None = None
+
+
+def _get_schema_path() -> Path:
+    # backend/db/__init__.py -> backend/db/schema.sql
+    return Path(__file__).parent / SCHEMA_FILE
+
+
+def get_connection(db_path: str | None = None) -> sqlite3.Connection:
+    global _conn, _current_path
+    if db_path is None:
+        db_path = os.environ.get(DB_PATH_ENV)
+        if not db_path:
+            raise RuntimeError(f"{DB_PATH_ENV} env var is required")
+    db_path = str(Path(db_path).resolve())
+
+    with _lock:
+        if _conn is None or _current_path != db_path:
+            if _conn is not None:
+                _conn.close()
+            _conn = sqlite3.connect(db_path, check_same_thread=False)
+            _conn.row_factory = sqlite3.Row
+            _conn.execute("PRAGMA journal_mode=WAL")
+            _conn.execute("PRAGMA foreign_keys=ON")
+            _conn.execute("PRAGMA busy_timeout=5000")
+            _conn.execute("PRAGMA synchronous=NORMAL")
+            _current_path = db_path
+        return _conn
+
+
+def init_db(db_path: str | None = None) -> sqlite3.Connection:
+    conn = get_connection(db_path)
+    schema_path = _get_schema_path()
+    if not schema_path.exists():
+        raise FileNotFoundError(f"Schema not found: {schema_path}")
+    with open(schema_path, "r", encoding="utf-8") as f:
+        schema = f.read()
+    with _lock:
+        conn.executescript(schema)
+        conn.commit()
+    return conn
+
+
+def get_images_dir() -> Path:
+    img = os.environ.get(IMAGES_DIR_ENV)
+    if not img:
+        raise RuntimeError(f"{IMAGES_DIR_ENV} env var is required")
+    return Path(img).resolve()
+
+
+def probe_writable(conn: sqlite3.Connection | None = None) -> bool:
+    try:
+        c = conn or get_connection()
+        c.execute("SELECT 1").fetchone()
+        return True
+    except Exception:
+        return False
+
+
+def probe_images_writable() -> bool:
+    try:
+        img_dir = get_images_dir()
+        if not img_dir.exists():
+            img_dir.mkdir(parents=True, exist_ok=True)
+        probe = img_dir / ".health-probe"
+        probe.write_text("ok", encoding="utf-8")
+        probe.unlink(missing_ok=True)
+        return True
+    except Exception:
+        return False
+
+
+def _reset_for_tests() -> None:
+    """Close global conn so temp dirs can be cleaned on Windows (test only)."""
+    global _conn, _current_path
+    with _lock:
+        if _conn is not None:
+            try:
+                _conn.close()
+            except Exception:
+                pass
+            _conn = None
+            _current_path = None
diff --git a/backend/db/schema.sql b/backend/db/schema.sql
new file mode 100644
index 0000000..1037bf3
--- /dev/null
+++ b/backend/db/schema.sql
@@ -0,0 +1,157 @@
+-- SlabUploader SQLite schema (S0)
+-- Every table/column from docs/contracts/DATA-MODEL.md using CREATE TABLE IF NOT EXISTS
+-- Taxonomy tables exist but remain EMPTY (S4 populates). Stdlib sqlite3 only.
+-- Pragmas applied by db factory: journal_mode=WAL, foreign_keys=ON, busy_timeout=5000, synchronous=NORMAL
+
+PRAGMA foreign_keys = ON;
+
+-- 2. slabs
+CREATE TABLE IF NOT EXISTS slabs (
+    id TEXT PRIMARY KEY,
+    status TEXT NOT NULL DEFAULT 'draft' CHECK(status IN ('draft','calibrated','ready','publishing','published','failed')),
+    sku TEXT UNIQUE CHECK(length(sku) BETWEEN 3 AND 24),
+    length_in REAL,
+    thickness_in REAL,
+    sqft REAL,
+    bdft REAL,
+    width_min_in REAL,
+    width_max_in REAL,
+    width_avg_in REAL,
+    species_id INTEGER,
+    wood_category_ids TEXT,  -- JSON array of leaf ids
+    edge_type_term_id INTEGER,
+    figure_term_ids TEXT,    -- JSON array
+    grade_term_id INTEGER,
+    thickness_term_id INTEGER,
+    moisture_term_id INTEGER,
+    fig_tag_ids TEXT,        -- JSON array optional
+    feat_tag_ids TEXT,       -- JSON array optional
+    price REAL,
+    price_source TEXT CHECK(price_source IN ('recommendation','override') OR price_source IS NULL),
+    title TEXT,
+    short_description TEXT,
+    description TEXT,
+    content_source TEXT CHECK(content_source IN ('manual','llm','template') OR content_source IS NULL),
+    species_confidence REAL,
+    figure_confidence REAL,
+    grade_confidence REAL,
+    inference_status TEXT CHECK(inference_status IN ('inferring','done','failed') OR inference_status IS NULL),
+    calibration_photo_id TEXT,
+    client_rev INTEGER NOT NULL DEFAULT 1,
+    server_rev INTEGER NOT NULL DEFAULT 1,
+    woo_product_id INTEGER,
+    published_at TEXT,
+    deleted_at TEXT,
+    created_at TEXT NOT NULL,
+    updated_at TEXT NOT NULL,
+    FOREIGN KEY (species_id) REFERENCES woo_categories(id),
+    FOREIGN KEY (calibration_photo_id) REFERENCES slab_photos(id)
+);
+
+-- 3. slab_photos
+CREATE TABLE IF NOT EXISTS slab_photos (
+    id TEXT PRIMARY KEY,
+    slab_id TEXT NOT NULL,
+    seq INTEGER NOT NULL,
+    is_calibration INTEGER NOT NULL DEFAULT 0 CHECK(is_calibration IN (0,1)),
+    original_blob BLOB,
+    processed_blob BLOB,
+    width_px INTEGER,
+    height_px INTEGER,
+    created_at TEXT NOT NULL,
+    FOREIGN KEY (slab_id) REFERENCES slabs(id) ON DELETE CASCADE
+);
+
+-- 4. pricing_rules
+CREATE TABLE IF NOT EXISTS pricing_rules (
+    id INTEGER PRIMARY KEY,
+    species_id INTEGER NOT NULL UNIQUE,
+    price_per_bdft REAL NOT NULL,
+    created_at TEXT NOT NULL,
+    updated_at TEXT NOT NULL,
+    FOREIGN KEY (species_id) REFERENCES woo_categories(id)
+);
+
+-- 5. Taxonomy cache (empty at S0; columns chosen to support FKs + S4 sync; ambiguity resolved in learnings)
+CREATE TABLE IF NOT EXISTS woo_categories (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL,
+    slug TEXT NOT NULL UNIQUE,
+    parent_id INTEGER,
+    woo_id INTEGER
+);
+
+CREATE TABLE IF NOT EXISTS woo_attributes (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL,
+    slug TEXT NOT NULL UNIQUE,
+    woo_id INTEGER
+);
+
+CREATE TABLE IF NOT EXISTS woo_attribute_terms (
+    id INTEGER PRIMARY KEY,
+    attribute_id INTEGER NOT NULL,
+    name TEXT NOT NULL,
+    slug TEXT NOT NULL,
+    woo_id INTEGER,
+    FOREIGN KEY (attribute_id) REFERENCES woo_attributes(id)
+);
+
+CREATE TABLE IF NOT EXISTS woo_tags (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL,
+    slug TEXT NOT NULL UNIQUE,
+    woo_id INTEGER
+);
+
+-- 6. settings (key/value/value_enc per §6; secrets in value_enc = nonce||ciphertext)
+CREATE TABLE IF NOT EXISTS settings (
+    key TEXT PRIMARY KEY,
+    value TEXT,
+    value_enc TEXT
+);
+
+-- 7. prompts + prompt_revisions (append-only revisions)
+CREATE TABLE IF NOT EXISTS prompts (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL CHECK(name IN ('call1','call2')),
+    active_revision_id INTEGER,
+    created_at TEXT NOT NULL,
+    updated_at TEXT NOT NULL,
+    FOREIGN KEY (active_revision_id) REFERENCES prompt_revisions(id)
+);
+
+CREATE TABLE IF NOT EXISTS prompt_revisions (
+    id INTEGER PRIMARY KEY,
+    prompt_id INTEGER NOT NULL,
+    content TEXT NOT NULL,
+    content_hash TEXT NOT NULL,
+    created_at TEXT NOT NULL,
+    created_by TEXT,
+    FOREIGN KEY (prompt_id) REFERENCES prompts(id)
+);
+
+-- 8. sync_log (append-only)
+CREATE TABLE IF NOT EXISTS sync_log (
+    id INTEGER PRIMARY KEY,
+    slab_id TEXT,
+    woo_product_id INTEGER,
+    status TEXT NOT NULL CHECK(status IN ('success','failed')),
+    payload_hash TEXT,
+    message TEXT,
+    created_at TEXT NOT NULL
+);
+
+-- 9. inference_log (append-only audit)
+CREATE TABLE IF NOT EXISTS inference_log (
+    id INTEGER PRIMARY KEY,
+    slab_id TEXT,
+    call INTEGER NOT NULL CHECK(call IN (1,2)),
+    prompt_revision_id INTEGER,
+    model TEXT,
+    request_payload TEXT,
+    response_payload TEXT,
+    latency_ms INTEGER,
+    created_at TEXT NOT NULL,
+    FOREIGN KEY (prompt_revision_id) REFERENCES prompt_revisions(id)
+);
diff --git a/backend/requirements.txt b/backend/requirements.txt
new file mode 100644
index 0000000..20cb2c0
--- /dev/null
+++ b/backend/requirements.txt
@@ -0,0 +1,6 @@
+# S0 backend requirements (pinned, no ORM)
+fastapi==0.115.2
+uvicorn[standard]==0.30.6
+pytest==8.3.3
+httpx==0.27.2
+# stdlib only for sqlite3, logging, json, contextvars, threading
diff --git a/backend/tests/test_health_startup.py b/backend/tests/test_health_startup.py
new file mode 100644
index 0000000..f928c35
--- /dev/null
+++ b/backend/tests/test_health_startup.py
@@ -0,0 +1,73 @@
+"""TDD red tests for S0 health endpoint and startup guards (APP-30, APP-45, SETTINGS-10, SETTINGS-25)."""
+import importlib
+import os
+import tempfile
+from unittest.mock import patch
+
+import pytest
+from fastapi.testclient import TestClient
+
+import backend.db as db_mod
+
+
+def _reload_app():
+    import backend.app as app_mod
+    return importlib.reload(app_mod)
+
+
+def test_health_happy_path_returns_200_with_three_fields(monkeypatch):
+    """Given: writable db + image dir; When: GET /api/health; Then: 200 + {status, version, woo_reachable}."""
+    with tempfile.TemporaryDirectory() as tmp:
+        db_path = os.path.join(tmp, "test.db")
+        img_dir = os.path.join(tmp, "images")
+        os.mkdir(img_dir)
+        monkeypatch.setenv("SLAB_DB_PATH", db_path)
+        monkeypatch.setenv("SLAB_IMAGES_DIR", img_dir)
+        monkeypatch.setenv("WOO_BASE_URL", "https://example.com")
+        monkeypatch.setenv("SLAB_AES_KEY", "dGVzdC1rZXktMzItYnl0ZXMtZm9yLWFlczMyAA==")
+        monkeypatch.setenv("LOG_LEVEL", "INFO")
+        from backend.app import app
+        client = TestClient(app)
+        resp = client.get("/api/health")
+        assert resp.status_code == 200
+        body = resp.json()
+        assert set(body.keys()) == {"status", "version", "woo_reachable"}
+        assert body["status"] == "ok"
+        db_mod._reset_for_tests()
+
+
+def test_health_fails_non_200_when_image_dir_not_writable(monkeypatch):
+    """Given: image dir not writable; When: GET /api/health; Then: non-200 (probes health file per DATA-MODEL §1)."""
+    with tempfile.TemporaryDirectory() as tmp:
+        db_path = os.path.join(tmp, "test.db")
+        img_dir = os.path.join(tmp, "images")
+        os.mkdir(img_dir)
+        monkeypatch.setenv("SLAB_DB_PATH", db_path)
+        monkeypatch.setenv("SLAB_IMAGES_DIR", img_dir)
+        monkeypatch.setenv("WOO_BASE_URL", "https://example.com")
+        monkeypatch.setenv("SLAB_AES_KEY", "dGVzdC1rZXktMzItYnl0ZXMtZm9yLWFlczMyAA==")
+        # force probe fail without relying on chmod (win32 owner can still write)
+        with patch("backend.app.probe_images_writable", return_value=False):
+            from backend.app import app
+            client = TestClient(app)
+            resp = client.get("/api/health")
+            assert resp.status_code != 200
+            db_mod._reset_for_tests()
+
+
+def test_startup_guard_refuses_on_missing_or_non_https_woo_base_url(monkeypatch):
+    """Given: WOO_BASE_URL missing or not https; When: import/create app; Then: raises with clear message (SETTINGS-10)."""
+    monkeypatch.delenv("WOO_BASE_URL", raising=False)
+    with pytest.raises(RuntimeError, match="WOO_BASE_URL"):
+        _reload_app()
+    monkeypatch.setenv("WOO_BASE_URL", "http://insecure.example.com")
+    with pytest.raises(RuntimeError, match="https"):
+        _reload_app()
+
+
+def test_startup_guard_refuses_on_missing_slab_aes_key(monkeypatch):
+    """Given: SLAB_AES_KEY missing; When: import/create app; Then: raises with clear message (SETTINGS-25)."""
+    monkeypatch.setenv("WOO_BASE_URL", "https://example.com")
+    monkeypatch.delenv("SLAB_AES_KEY", raising=False)
+    with pytest.raises(RuntimeError, match="SLAB_AES_KEY"):
+        _reload_app()
diff --git a/backend/tests/test_schema.py b/backend/tests/test_schema.py
new file mode 100644
index 0000000..dc9ce13
--- /dev/null
+++ b/backend/tests/test_schema.py
@@ -0,0 +1,46 @@
+"""TDD red test for S0 schema load (DATA-MODEL.md contract)."""
+import os
+import sqlite3
+import tempfile
+
+import pytest
+
+
+SCHEMA_PATH = os.path.join(os.path.dirname(__file__), "..", "db", "schema.sql")
+
+
+def test_schema_loads_cleanly_and_all_tables_exist():
+    """Given: schema.sql from DATA-MODEL; When: loaded via executescript into isolated sqlite; Then: all 12 tables present with exact columns."""
+    expected_tables = {
+        "slabs",
+        "slab_photos",
+        "pricing_rules",
+        "woo_categories",
+        "woo_attributes",
+        "woo_attribute_terms",
+        "woo_tags",
+        "settings",
+        "prompts",
+        "prompt_revisions",
+        "sync_log",
+        "inference_log",
+    }
+    with tempfile.TemporaryDirectory() as tmp:
+        db_path = os.path.join(tmp, "isolated.db")
+        assert os.path.exists(SCHEMA_PATH), "schema.sql must exist for test"
+        with open(SCHEMA_PATH, "r", encoding="utf-8") as f:
+            schema_sql = f.read()
+        conn = sqlite3.connect(db_path)
+        try:
+            conn.executescript(schema_sql)
+            conn.commit()
+            rows = conn.execute(
+                "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%'"
+            ).fetchall()
+            actual = {r[0] for r in rows}
+            assert expected_tables.issubset(actual), f"Missing tables: {expected_tables - actual}"
+            # spot check one column from slabs per DATA-MODEL
+            cols = [r[1] for r in conn.execute("PRAGMA table_info(slabs)").fetchall()]
+            assert "id" in cols and "status" in cols and "client_rev" in cols
+        finally:
+            conn.close()
diff --git a/docs/contracts/API.md b/docs/contracts/API.md
index aec9d41..857f77d 100644
--- a/docs/contracts/API.md
+++ b/docs/contracts/API.md
@@ -75,7 +75,7 @@ There is no `412 validation_module_stale` path.
 Multipart create of a calibrated draft. Returns `201` with the slab at `status: "calibrated"`.
 Stores the client-sent derived numbers and never recomputes them. Auto-runs Call 1 only when
 `inference_enabled` is true; inferred values persist only at confidence ≥ 0.7. `409 duplicate_sku`
-if the SKU already exists.
+if the SKU already exists. Cites APP-20, CAPTURE-135, METADATA-45, PUBLISH-15.
 
 `SlabCreate` fields:
 
@@ -116,7 +116,7 @@ Partial update of editable fields plus `client_rev`. Stores client-sent derived
 not recompute them. Checks run in order: `409 revision_conflict`, then `409 duplicate_sku` (SKU
 field actions `edit_sku` / `open_existing`), then `422 stale_field` (current options included).
 `status` becomes `ready` only when the full required set is present; it is server-derived and a
-client never sets it.
+client never sets it. Cites APP-20, REVIEW-40, PUBLISH-15, PUBLISH-20.
 
 ### `DELETE /api/v1/slabs/{id}`
 Soft delete of unpublished drafts only (sets `deleted_at`); `204`. Deleted rows are excluded from
@@ -141,7 +141,7 @@ Runs Call 2 on user action only. Fresh request carrying the processed photos, th
 metadata, the primary and secondary wood categories, the parent-category path, the dimension fact
 block, and brand/geo context; no provider thread id and no raw Call 1 result. Requires
 `test-inference` `ok`. Returns `202`; the client polls. The model writes the long description only
-and never touches dimensions.
+and never touches dimensions. Cites METADATA-55, METADATA-65.
 
 Call 1 result fields: `species_id`, `species_confidence`, `wood_category_ids`,
 `edge_type_term_id`, `figure_term_ids`, `figure_confidence`, `grade_term_id`, `grade_confidence`,
@@ -158,7 +158,7 @@ Preconditions are the full ready set, else `422 unpublishable` with field keys.
 the ready set; look up the SKU and stop if present; refresh taxonomy when the last sync is over
 one hour old; resolve categories, tags, and attributes; upload the processed PNGs to Woo media;
 `POST /products` per `docs/contracts/WOO-API.md`; finalize. `SLAB-UAT-*` always creates a draft.
-Returns `202`; the client polls.
+Returns `202`; the client polls. Cites PUBLISH-5, PUBLISH-10, PUBLISH-15, PUBLISH-25.
 
 - Success: `woo_product_id` set and returned on the terminal poll, photos purged, the local working
   slab row discarded, device draft cleared. Nothing is deleted from WooCommerce.
@@ -187,6 +187,8 @@ One flat `price_per_bdft` per species leaf, no tiers.
 
 ## 10. Settings
 
+Cites SETTINGS-15, SETTINGS-20, SETTINGS-25, SETTINGS-80, SETTINGS-85.
+
 - `GET /api/v1/settings` → `SettingsView` with secrets masked.
 - `PUT /api/v1/settings` — partial update. `woo_base_url` is not writable; the server rejects the
   write. Woo credentials are write-only and stored AES-GCM. Inference base URL and key are
diff --git a/docs/contracts/DATA-MODEL.md b/docs/contracts/DATA-MODEL.md
index cbbe405..45277b3 100644
--- a/docs/contracts/DATA-MODEL.md
+++ b/docs/contracts/DATA-MODEL.md
@@ -104,6 +104,8 @@ successful publish.
 
 ## 5. Taxonomy cache
 
+Cites METADATA-5, SETTINGS-50, SETTINGS-51, SETTINGS-55.
+
 - `woo_categories` — species and wood-category leaves only; parents group and are never assigned.
 - `woo_attributes` / `woo_attribute_terms` — exactly the five locked attributes Edge Type, Figure,
   Grade, Thickness, Moisture, with their terms.
@@ -148,6 +150,8 @@ revision it used (`METADATA-66`).
 
 ## 8. `sync_log`
 
+Cites PUBLISH-25, PUBLISH-30.
+
 Append-only; never deleted on publish. Columns: `id`, `slab_id`, `woo_product_id`, `status`
 (`success` | `failed`), `payload_hash` (sha256 of the outbound payload), `message`, `created_at`.
 
@@ -158,5 +162,7 @@ Append-only audit. Columns: `id`, `slab_id`, `call` (1 | 2), `prompt_revision_id
 
 ## 10. Status transitions
 
+Cites APP-5.
+
 `draft` → `calibrated` → `ready` → `publishing` → `published`, with `failed` reachable from any
 step and retryable. `calibrated` is set when the draft uploads; `ready` requires the full set.
diff --git a/docs/contracts/PROMPTS.md b/docs/contracts/PROMPTS.md
index daa16b9..6c4e570 100644
--- a/docs/contracts/PROMPTS.md
+++ b/docs/contracts/PROMPTS.md
@@ -39,6 +39,8 @@ The interface is reachable on the trusted network only until it is authenticated
 
 ## 3. Call 1 — vision classification
 
+Cites METADATA-35, METADATA-40, METADATA-45, METADATA-50.
+
 **When.** Runs automatically after a calibrated draft uploads only when `inference_enabled` is
 true; also on demand or retry. With inference off it is skipped and the fields are filled by hand.
 
diff --git a/docs/contracts/UX.md b/docs/contracts/UX.md
index 7f344ef..8881014 100644
--- a/docs/contracts/UX.md
+++ b/docs/contracts/UX.md
@@ -11,10 +11,10 @@ Status: SPEC · 2026-09-18. Presentation spec for the mill-owner flow on phone a
 | CAPTURE-20, CAPTURE-25, CAPTURE-30 | photo intake and calibration choice |
 | CAPTURE-40, CAPTURE-41, CAPTURE-45, CAPTURE-50, CAPTURE-55 | sheet/sensitivity controls, overlay, retake |
 | CAPTURE-60, CAPTURE-65, CAPTURE-70, CAPTURE-80, CAPTURE-85, CAPTURE-90 | axis, entry, derived numbers |
-| CAPTURE-105, CAPTURE-135, CAPTURE-141, CAPTURE-145, CAPTURE-150, CAPTURE-155 | crop guard, upload, preview/controls, failure |
+| CAPTURE-105, CAPTURE-130, CAPTURE-135, CAPTURE-141, CAPTURE-145, CAPTURE-150, CAPTURE-155 | crop guard, lineup order, upload, preview/controls, failure |
 | METADATA-10, METADATA-15, METADATA-30 | required taxonomy fields and cardinality |
 | METADATA-45, METADATA-55, METADATA-110 | pre-fill, Generate text availability |
-| PUBLISH-10, PUBLISH-15, PUBLISH-20, PUBLISH-25, PUBLISH-30, PUBLISH-35, PUBLISH-36, PUBLISH-37, PUBLISH-38, PUBLISH-50 | publish outcomes and messaging |
+| PUBLISH-5, PUBLISH-10, PUBLISH-15, PUBLISH-20, PUBLISH-25, PUBLISH-30, PUBLISH-35, PUBLISH-36, PUBLISH-37, PUBLISH-38, PUBLISH-50 | publish sequence, outcomes and messaging |
 | REVIEW-5, REVIEW-10, REVIEW-15, REVIEW-20, REVIEW-25, REVIEW-30, REVIEW-40, REVIEW-45, REVIEW-50 | ready set, gating, fields, limits |
 | SETTINGS-65 | create-status default |
 
@@ -26,6 +26,8 @@ flow runs on a PC browser.
 
 ## 2. Capture
 
+Cites CAPTURE-20, CAPTURE-25, CAPTURE-40, CAPTURE-130.
+
 1. **Photos.** Take one or more photos; the first is top-down with the lens parallel to the broad
    face. The owner chooses which photo is the calibration photo.
 2. **Mask overlay and controls.** The app draws the mask on the source photo. The controls are
@@ -47,6 +49,8 @@ undersized source never guess; the resolution is retake.
 
 ## 3. Review
 
+Cites REVIEW-5, REVIEW-15, REVIEW-20, METADATA-45.
+
 - **Vision pre-fill.** At or above the threshold (default 0.7) a field is pre-filled and shown
   with an "AI" badge; below it the field starts empty. The badge is presentation only and clears
   on edit.
@@ -63,6 +67,8 @@ undersized source never guess; the resolution is retake.
 
 ## 4. Publish
 
+Cites PUBLISH-5, PUBLISH-10, PUBLISH-15, PUBLISH-25.
+
 - A normal SKU uses `woo_create_status` (default draft); a `SLAB-UAT-*` SKU always creates a draft.
   "Published" means the store create succeeded, not that it is live.
 - **Success.** The local draft and photos are gone; the store product reference is shown.