SlabUploader/docs/ARCHITECTURE.md

Architecture

Status: SPEC · 2026-08-27 · SlabUploader
Locked so far: topology C (hybrid), swimlane, what-runs-where. Remaining sections TBD.

Companion: PRD (root), TECH-SPEC-PIPELINE.md.

1. Topology (hybrid)

Phone does the happy-path pipeline (mask, length axis, sqft/bdft, 3:4 PNG).
FastAPI stores drafts, runs U2Net only on demand, proxies inference, talks to Woo.
reverse proxy terminates HTTPS.

phone (SvelteKit)
  capture, mask, sliders, length axis, sqft/bdft, 3:4 PNG
  if mask still bad → POST one photo → FastAPI U2Net → mask back → user continues

server
  reverse proxy → frontend (static)
        → fastapi : store, settings, prompts, taxonomy, Woo, inference proxy, U2Net

• Happy path never leaves the phone.
• U2Net is explicit “Try harder” (or coverage failure), not every slab.
• Woo + LLM keys stay on the server. Browser does not call Woo or the vision endpoint directly.

2. Swimlane

flowchart TB
  subgraph Phone["Phone — SvelteKit"]
    P1[New Wood: 1–5 photos]
    P2[BG overlay + sheet / sensitivity / edge / feather]
    P3{Edge OK?}
    P4[Length axis overlay — rotate / confirm]
    P5[User length + thickness + SKU]
    P6[sqft, bdft, 6in widths, 3:4 PNGs]
    P7[Review Call 1 fields]
    P8[Tap Generate text]
    P9[Review title / desc — publish]
  end

  subgraph API["server — FastAPI"]
    A1[U2Net: one photo in, mask out]
    A2[Store draft: originals + PNGs + numbers]
    A3[Call 1 proxy — vision]
    A4[Call 2 proxy — text]
    A5[Woo: taxonomy, SKU check, create product]
  end

  subgraph LLM["Your OpenAI-compatible endpoint"]
    L1[Wood expert — all photos at 1024]
    L2[Title / desc / short desc]
  end

  subgraph Woo["WooCommerce store"]
    W1[Categories / attributes / fig-* tags]
    W2[New product live or draft per setting]
  end

  P1 --> P2 --> P3
  P3 -->|no — Try harder| A1
  A1 --> P2
  P3 -->|no — Retake| P1
  P3 -->|yes| P4 --> P5 --> P6
  P6 --> A2
  A2 --> A3 --> L1 --> A3 --> P7
  P7 --> P8 --> A4 --> L2 --> A4 --> P9
  P9 --> A5
  A5 --> W1
  A5 --> W2

3. Clarifications

1. Happy path stays on the phone through PNG + numbers. FastAPI is idle until the user has a confirmed mask (or taps Try harder).
2. Try harder is U2Net on one photo (the one on screen). Mask comes back; sliders still apply. Not a full re-pipeline on the server.
3. Draft upload sends originals + processed PNGs + length/thickness/SKU/sqft/bdft/widths. Originals are needed if Call 1 or a later retry must not depend on the tab still being open. After successful Woo publish, server deletes both.
4. Call 1 is server-side so the vision key never sits in the browser. Body: all originals downscaled to 1024 + Woo taxonomy snapshot + SKU/length/thickness. Timeout 45s → error + retry on the phone. User must curate before Call 2.
5. Call 2 does not auto-fire. User taps Generate text. Server sends curated Call 1 + deterministic numbers + brand/GEO + prompt.
6. Woo is only FastAPI. Browser never sees the App Password. Duplicate SKU → stop, show error, no edit-same-SKU in MVP.
7. Settings (species $/bdft, prompts, endpoint, Woo, publish status) live on the server; the phone is just the form.

4. What runs where

Job	Where
Camera, 1-5 photos	Client
Sheet detect, chroma-key / black threshold, sliders, flood-fill	Client
U2Net	Server, on demand
Length axis overlay, 6" widths, sqft, bdft	Client
3:4 PNG, 80% fill	Client
Draft + originals + processed PNGs	Server (after user continues)
Species $/bdft, Woo creds, prompts, brand/GEO	Server
Call 1 (vision, all photos @1024)	Server proxy
Call 2 (title/desc)	Server proxy, after Call 1 curation
Woo taxonomy sync + publish	Server

5. Secrets and settings

Server-side only (never in browser JS):

1. WooCommerce consumer key + consumer secret (App Password). Server uses HTTP Basic Auth to call /wp-json/wc/v3/. Stored encrypted at rest in SQLite (AES-GCM).
2. Inference endpoint base URL + API key. Stored encrypted. Server proxies all inference calls.
3. AES master key. Env var on server, never in the DB.

Browser-side (no secrets):

1. User preferences: sheet mode, sensitivity, edge offset, feather. Persisted in localStorage, reset-to-default available.
2. Species list with $/bdft. Read from server settings sync.
3. Taxonomy snapshot (categories, attributes, tags). Read from server. No auth needed.

Flow:

1. User enters Woo credentials in Settings UI on the phone.
2. Browser POSTs them to /api/settings on FastAPI. Server stores encrypted.
3. Server syncs taxonomy from Woo, caches in SQLite.
4. Client reads taxonomy from /api/admin/taxonomy — no auth needed.
5. All Woo calls go server-to-woo. Browser never calls Woo REST directly.

This is the canonical WooCommerce App Password integration pattern. Browser-to-Woo REST requires CORS configuration on the Woo site, which is not under your control.

6. Status machine

draft → calibrated → ready → publishing → published
         │              │                ↑
         └→ failed  ────┴────────────────┘ (woo_product_id set)
any → failed (with error)

1. draft — user took photos, no mask confirmed yet.
2. calibrated — user confirmed the BG edge, confirmed length axis, entered length/thickness/SKU. Client computed sqft/bdft/widths. Draft uploaded to server.
3. ready — all mandatory fields populated (species, wood category, edge type, figure, grade, thickness, price, title/desc/short desc, at least one photo). Values can come from Call 1, manual entry, or a mix. Inference is optional; the user can fill everything by hand and go straight to ready.
4. publishing — Woo create in flight. Poll for result.
5. published — Woo product created, woo_product_id stored. Images purged.
6. failed — pipeline, inference, or publish error. Error detail stored. Retry available.

Call 1 and Call 2 are assist-only. They do not gate the flow. If the user skips inference, the path is: calibrated → ready → publishing → published.