docs(deploy): fallback UAT on Grok Bot computer :18181

When Tailscale cannot reach ubudual5060, Capture UAT serves from the
bot computer on :18181. Primary overnight remains :10881. Never touch
Ty local :18080 or legacy :10880.

.dockerignore

@@ -0,0 +1,10 @@
+.git
+backend
+frontend/node_modules
+frontend/dist
+frontend/.svelte-kit
+**/.DS_Store
+*.md
+!deploy/README.md
+.audit
+docs/archive

.gitignore

@@ -35,3 +35,11 @@ images/
 
 # Logs
 *.log
+
+# Playwright e2e (#65) — keep README; ignore churn
+frontend/tests/e2e/artifacts/*.png
+frontend/tests/e2e/artifacts/run-log.txt
+frontend/tests/e2e/test-results/
+frontend/tests/e2e/playwright-report/
+frontend/blob-report/
+frontend/playwright/.cache/

AGENTS.md

@@ -2,16 +2,21 @@
 
 ## Agent context
 
-Read this file and `docs/CAPTURE.md`.
-Implement Milestone 1 only. Specification: `docs/CAPTURE.md`.
-PRD: `docs/PRODUCT.md` for destination and field names. Do not implement Milestone 2, 3, or 4.
+Read this file, `docs/CAPTURE.md`, and `docs/PHOTOS.md`.
+Implement Milestone 2 only. Specification: `docs/PHOTOS.md`.
+PRD: `docs/PRODUCT.md` for destination and field names. Do not implement Milestone 3 or 4.
+Do not widen Milestone 2 into Complete-listing taxonomy, SKU, price, copy, or Woo create.
 
-## Milestone 1
+## Milestone 2
 
-Capture.
-Acceptance: on a phone, one real slab, approved mask, approved length-axis rectangle, user length and thickness, inventory PNG on screen, widths and board feet on screen.
+Photos.
+Acceptance: on a phone, batch of 1–N photos, user-picked calibration photo through Milestone 1 mask/axis/measure, every successful shot as a 3:4 transparent inventory PNG lined up, Milestone 1 numbers on screen, dimension-overlay copy of the calibration PNG present.
 
-Milestone 1 is inference-free. Background removal, rectangle, measurements, and PNG encode run in the browser as ordinary code. There is no inference URL and no model call in this milestone.
+Milestone 2 is inference-free. Batch mask/crop reuse and dimension overlays run in the browser as ordinary code. There is no inference URL and no model call in this milestone.
+
+## Milestone 1 (historical)
+
+Capture. Spec: `docs/CAPTURE.md`. Remains the calibration math and PNG contract Milestone 2 reuses.
 
 ## Invariants
 
@@ -26,3 +31,4 @@ Milestone 1 is inference-free. Background removal, rectangle, measurements, and
 - Create works with inference off.
 - Source below the PNG size floor requires a new photo.
 - Existing store SKU blocks create.
+- Dimension overlay orientation follows the user-approved length axis from Milestone 1.

README.md

@@ -7,6 +7,7 @@ Lists one-of-a-kind wood slabs on Whidbey Wood Store.
 | PRD | `docs/PRODUCT.md` |
 | Invariants and agent context | `AGENTS.md` |
 | Milestone 1 | `docs/CAPTURE.md` |
+| Milestone 2 | `docs/PHOTOS.md` |
 | Hosting | `deploy/` |
 
 Owner: Ty. Store: https://www.whidbeywoodstore.com/

deploy/INVENTORY.md

@@ -1,4 +1,35 @@
 # Host
 
-Record the machine and URL when a container is started.
+## Overnight Capture UAT (primary — when Tailscale is up)
+
+- Host: `ubudual5060` / Tailscale `100.64.0.9`
+- Container: `slabuploader-m2-overnight` (image `slabuploader-m2:overnight`) — or salvage rebuild of the same role
+- Port: **10881** → 80
+- URL: `http://100.64.0.9:10881`
+- Replaces prior overnight container `slabuploader-m1-overnight` (same port).
+
+## Fallback UAT — Grok Bot computer (when Tailscale to 5060 is down)
+
+Use this path for salvage / Capture UAT until the box can reach `100.64.0.9` again.
+
+- Host: Grok Bot computer (slab-m1 box)
+- Serve: static Capture build (`frontend` → `npm run build`, then `vite preview` or equivalent static server)
+- Port: **18181** (chosen so it never collides with Ty local on 5060)
+- Bind: `0.0.0.0:18181`
+- URL (from this box): `http://127.0.0.1:18181` — Ty reaches it via the bot computer / whatever path the app exposes; Tailscale IP of this box when mesh returns
+- Branch for salvage: `salvage-one-woo-draft` (cut from `m2-ds`)
+- Do **not** require Docker on the box for this fallback.
+
+When Tailscale is restored, prefer primary overnight `:10881` again and stop advertising the fallback as the main UAT URL.
+
+## Ty local Node/SvelteKit on 5060 (do not overwrite)
+
+- Host: `ubudual5060` / `100.64.0.9`
+- Container: `slabuploader-m1`
+- Port: **18080** → 80
+- URL: `http://100.64.0.9:18080`
+- **Never** recreate or remap this container for overnight or box-fallback UAT.
+- **Never** bind overnight or fallback UAT to **10880** either (legacy Ty local).
+
+Future overnight Capture deploys use a **separate** container name and an open **108XX** port other than Ty’s local ports.
 Do not put a host name in the product spec.

deploy/nginx-m1.conf

@@ -0,0 +1,17 @@
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # SPA: fall back to index.html for any path
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    location ~* \.(js|css|png|jpg|jpeg|svg|woff2?)$ {
+        expires 7d;
+        add_header Cache-Control "public";
+        try_files $uri =404;
+    }
+}

docs/CAPTURE.md

@@ -1,7 +1,7 @@
 # Milestone 1 — Capture
 
 Runs in the browser on phone and PC as ordinary client code.
-No inference URL. No model. No backend. Mask, rectangle, measurements, and PNG encode are deterministic functions of the photo and user inputs.
+No inference URL. No model. No backend. Mask, rectangle, measurements, crop, and PNG encode are deterministic functions of the photo and user inputs.
 
 Milestone 1 uses one reference photo. Further angles are later milestones.
 Milestone 1 ends when the user sees the inventory PNG and measurements. Milestone 2 is Review. Milestone 3 is Create. This file does not create a WooCommerce product.
@@ -33,9 +33,9 @@ Otherwise the app opens Add photo.
 3. User sets sheet Auto / Green / Black and sensitivity 0–100 (slider or minus / plus). App updates the control immediately. App recomputes the overlay 2.0 seconds after the last sensitivity change. User adjusts until only the slab remains, then approves. App blocks approve if the mask has no slab pixels; user retakes. The approved mask is the footprint for every later step.
 4. App draws the minimum-area bounding rectangle of the mask and the length axis on the long side of that rectangle. User rotates the axis if it does not follow the slab length, then approves the axis.
 5. User enters length `L` in inches (1/8 in steps) and thickness (1/8 in steps), then presses Calculate.
-6. App sets `scale = longest_axis_px / L`.
-7. App computes widths, sqft, and bdft from the mask, and writes the inventory PNG.
-8. User sees the PNG and the numbers. Milestone 1 stops here.
+6. App sets `scale = longest_axis_px / L` (mask/wood span along the approved direction ÷ user `L`; rectangle is direction only).
+7. App computes widths, sqft, and bdft from the mask. App crops the masked slab into a 3:4 portrait frame: slab centered, 90% fill at the widest and tallest points, background transparent. App writes that frame as an inventory PNG (`image/png`, 8-bit RGBA).
+8. User sees the transparent PNG and the numbers. Milestone 1 stops here.
 
 Calculate does not create a WooCommerce product.
 
@@ -53,13 +53,13 @@ One photo component is reused. Each state advances on approve. Back returns to t
 2. Add photo — camera or picker. One photo. Setup rules visible.
 3. Mask — background removal on that photo.
 4. Length axis — bounding rectangle and long-side axis on the same photo.
-5. Measure — length, thickness, Calculate, inventory PNG, widths, sqft, bdft. Milestone 1 stops here.
+5. Measure — length, thickness, Calculate, crop, inventory PNG, widths, sqft, bdft. Milestone 1 stops here.
 
 ## Display
 
 Preview fits the device width. Height is capped so Mask and Measure controls stay on screen. Phone and PC use the same states.
 
-The preview is display only. Mask, rectangle, `scale`, sqft, and PNG encode use the source photo pixels, not the CSS size of the preview.
+The preview is display only. Mask, rectangle, crop, `scale`, sqft, and PNG encode use the source photo pixels, not the CSS size of the preview.
 
 ## Runtime
 
@@ -83,22 +83,34 @@ Mask work runs in the worker. The last good overlay stays visible while a pass r
 
 Approve is blocked when the mask has no slab pixels. User retakes.
 
-User approves the mask when only the slab remains. That mask is the footprint for Length axis, measurements, and the inventory PNG.
+User approves the mask when only the slab remains. That mask is the footprint for Length axis, crop, measurements, and the inventory PNG.
 
 ## Length axis
 
-On the same photo, draw the minimum-area bounding rectangle of the mask and the length axis on the long side of that rectangle. User rotates the axis if it does not follow the slab length, then approves the axis.
+On the same photo, keep the approved mask in view and draw the minimum-area bounding rectangle of the mask with the length axis on the long side of that rectangle. User rotates the rectangle (slider with minus and plus) until that direction follows the slab length, then approves the axis.
 
 ## Measure
 
 User enters length `L` in inches (1/8 in steps) and thickness (1/8 in steps), then presses Calculate.
 
-- `scale = longest_axis_px / L`
-- Widths: min, max, avg, sampled every 6 in along the approved length axis, perpendicular to it
+- `scale = longest_axis_px / L` where `longest_axis_px` is the mask/wood span along the approved length direction (slab pixels end-to-end on that axis), not the rectangle edge length. The rectangle sets direction only; user-entered `L` is wood end→end along that direction.
+- Widths: min, max, avg from samples taken every 6 in along the approved length axis, perpendicular to it, after dropping the first and last 6 in of the span (bulk widths, not tips). If `L ≤ 12 in` there are no interior stations and all three are 0.
 - `sqft = (mask_pixels / scale²) / 144` (2 decimals)
 - `bdft = sqft × thickness_in` (2 decimals)
+- Crop: 3:4 portrait, slab centered, 90% fill at the widest and tallest points, transparent background
+- File: inventory PNG, `image/png`, 8-bit RGBA, alpha kept
 
-User sees the inventory PNG and those numbers. Stop. Calculate does not create a WooCommerce product.
+User sees the transparent PNG and those numbers. Stop. Calculate does not create a WooCommerce product.
+
+## Crop
+
+On Calculate, the app builds the inventory image from the approved mask:
+
+1. Keep slab pixels from the source photo. Removed pixels are transparent.
+2. Place the slab in a 3:4 portrait frame, centered.
+3. Scale so the widest and tallest points of the slab fill 90% of the frame. Extra margin where the slab is narrower.
+4. After that crop, shorter side ≥ 800px when the source can supply it. Otherwise warn and require a new photo. No upscale from an undersized source.
+5. Encode as PNG with alpha.
 
 ## Device draft
 
@@ -121,8 +133,8 @@ The first inventory photo is the measurement reference. Later inventory photos u
 | Format | PNG, 8-bit RGBA (`image/png`) |
 | Alpha | Kept through encode and upload |
 | Aspect | 3:4 portrait |
-| Layout | Slab centered, 80% fill at the widest and tallest points |
-| Size | After crop, shorter side ≥ 1600px when the source can supply it |
+| Layout | Slab centered, 90% fill at the widest and tallest points |
+| Size | After crop, shorter side ≥ 800px when the source can supply it |
 
 Source below that floor: warn and require a new photo. No upscale from an undersized source.
 Editor preview of alpha is a light gray checkerboard. The storefront uses the theme background.

docs/PHOTOS.md

@@ -0,0 +1,75 @@
+# Milestone 2 — Photos
+
+Builds on Milestone 1. Spec for calibration math and inventory PNG properties: `docs/CAPTURE.md`.
+This milestone gets every photo of one slab background-removed and cropped store-ready.
+It does not fill Complete-listing taxonomy, SKU, price, or copy. It does not create a WooCommerce product.
+No inference URL. No model. Mask and crop for non-calibration shots reuse the approved calibration params as ordinary client code.
+
+## Goal
+
+Phone capture of one slab → a lined-up set of Woo-compatible inventory PNGs, plus Milestone 1 calibration numbers on the reference shot, plus one annotated copy of the calibration PNG with dimension overlays.
+
+## Use case
+
+1. User adds a batch of one or more photos of the same slab (Setup rules from Milestone 1: green or black sheet, top-down reference expectations still apply to the calibration choice).
+2. User selects which photo in the batch is the calibration photo.
+3. App runs the Milestone 1 workflow on that calibration photo only: Mask → Length axis → Measure (length `L`, thickness, Calculate).
+4. After Calculate, the app applies the approved mask sheet and sensitivity, and the same crop rules (3:4 portrait, 90% fill, transparent PNG, shorter-side floor), to every other photo in the batch.
+5. App adds a second copy of the calibration inventory PNG with dimension overlays burned in (see Dimension overlay).
+6. User sees Photos ready: inventory PNGs lined up in this order — clean calibration PNG, then the dimension-overlay copy of the calibration PNG, then the other batch photos in capture order — plus the Milestone 1 calibration details (widths, sqft, bdft, scale) presented as in Measure.
+
+A batch of one photo still works: that photo is the calibration photo; the end set is the clean PNG plus the dimension-overlay copy.
+
+## States (additions over Milestone 1)
+
+1. Batch — add one or more photos; continue when the batch has at least one.
+2. Pick calibration — user chooses which batch photo is the reference.
+3. Mask / Length axis / Measure — Milestone 1 states on the calibration photo only.
+4. Photos ready — lineup order: clean calibration PNG → dimension-overlay copy → other batch photos in capture order; plus Milestone 1 numbers.
+
+Device draft restores the last approved state, including the batch and which photo was calibration when those exist.
+
+## Apply to non-calibration photos
+
+For each non-calibration photo:
+
+- Reuse the approved Mask sheet (Auto / Green / Black) and sensitivity from the calibration photo. Do not re-open Mask controls for that photo in this milestone.
+- Run background removal with those params; compose inventory PNG with the same crop rules as Milestone 1 Calculate.
+- If a photo yields an empty mask or fails the PNG size floor, keep it out of the ready set and show a clear per-photo error; other photos still proceed.
+
+Scale, widths, sqft, and bdft stay tied to the calibration photo and user `L` / thickness. Non-calibration photos are visual inventory only.
+
+## Dimension overlay
+
+A second copy of the **calibration** inventory PNG is added to the collection. Overlays are black, large enough to read on phone and storefront.
+
+Orientation follows the **user-approved length axis** from Milestone 1 (not the upright edges of the photo).
+
+- **Length:** dimension graphic beside the wood on the right in axis-space (outside the slab edge along the length direction).
+- **Widths:** stations every 12 in along the approved length axis, starting 6 in from the **bottom** of the slab span, continuing while the station is not within 6 in of the top (stations at 6, 18, 30, … in inches along the axis while ≤ `L − 6`). Each width is drawn across the wood perpendicular to the length axis, with arrow tips on the left and right slab edges and the measurement text on that line.
+- **Bottom:** after the calibration photo’s EXIF orientation is applied, the bottom edge of that oriented photo establishes which end of the slab is bottom for width stations. Length-axis direction still follows the user-approved Milestone 1 axis; EXIF only picks which end is bottom vs top along that span.
+
+## Photos-ready order
+
+1. Clean calibration inventory PNG
+2. Dimension-overlay copy of the calibration PNG
+3. Remaining batch inventory PNGs in capture order
+
+The clean calibration PNG remains in the set. The annotated copy is extra.
+
+## Acceptance
+
+On a phone UAT build:
+
+- User can capture 1–N photos, pick calibration, complete Milestone 1 on that shot, and see every successful batch photo as a 3:4 transparent inventory PNG lined up.
+- Calibration measures match Milestone 1 presentation.
+- Dimension-overlay copy of the calibration PNG is present with black length and width graphics oriented to the approved axis; width stations start 6 in from EXIF-established bottom.
+- Lineup order is clean calibration → dimension overlay → other batch photos in capture order.
+- No Woo create. No inference URL.
+
+## Out of scope
+
+- Complete-listing fields (SKU, species, category, edge, figure, grade, thickness band, moisture, `fig-*` / `feat-*`, title, short title, description, price)
+- WooCommerce create (Milestone 3)
+- Inference / Assist (Milestone 4)
+- Changing Milestone 1 mask/axis/measure math except to reuse its outputs for batch apply and overlays

docs/PRODUCT.md

@@ -32,8 +32,9 @@ Store categories, attributes, and `fig-*` / `feat-*` tags are the filters. Measu
 
 ## System seams
 
-Milestone 1 runs in the browser. No backend and no inference URL.
-Handoff is the device draft: source photo, approved mask, inventory PNG, length, thickness, widths, sqft, bdft.
+Milestones 1 and 2 run in the browser. No backend and no inference URL.
+Milestone 1 handoff is the device draft: source photo, approved mask, inventory PNG, length, thickness, widths, sqft, bdft.
+Milestone 2 extends the draft with the photo batch, calibration choice, per-photo inventory PNGs, and the dimension-overlay calibration copy.
 Milestone 3 uses FastAPI as the Woo client. Store credentials stay on the server.
 
 ## Create
@@ -49,7 +50,7 @@ Work is split into four milestones. Each milestone is done when its acceptance c
 
 ### Milestone 1 — Capture
 
-Spec: `docs/CAPTURE.md`. Current work.
+Spec: `docs/CAPTURE.md`. Done historically; handoff into Milestone 2.
 
 User stories:
 - Photograph a slab on a green or black sheet and remove the background.
@@ -58,10 +59,12 @@ User stories:
 
 Acceptance: inventory PNG and measurements visible on a phone. No Woo create.
 
-### Milestone 2 — Review
+### Milestone 2 — Photos
 
-Remaining listing fields in the app.
-Acceptance: every field in Complete listing is filled or proposed and editable.
+Spec: `docs/PHOTOS.md`. Current work.
+
+Batch photos of one slab, pick calibration, run Milestone 1 on that reference, apply the same mask params and crop to the rest, preview all inventory PNGs lined up, plus a dimension-overlay copy of the calibration PNG.
+Acceptance: on a phone, 1–N store-ready inventory PNGs for the slab (including dimension overlay on the calibration copy) with Milestone 1 measures visible. No Woo create. No Complete-listing taxonomy in this milestone.
 
 ### Milestone 3 — Create
 

frontend/Dockerfile

@@ -0,0 +1,13 @@
+# Build the static app, then serve only the built artifacts.
+# Build context is the repo root: `docker build -f frontend/Dockerfile .`
+FROM node:20-slim AS build
+WORKDIR /app
+COPY frontend/package.json frontend/package-lock.json* ./
+RUN npm install --no-audit --no-fund
+COPY frontend/ ./
+RUN npm run build
+
+FROM nginx:1.27-alpine
+COPY deploy/nginx-m1.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /app/dist /usr/share/nginx/html
+EXPOSE 80

frontend/index.html

@@ -0,0 +1,16 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
+    <title>SlabUploader — Capture</title>
+    <style>
+      html, body { margin: 0; padding: 0; background: #111; }
+      #app { display: block; }
+    </style>
+  </head>
+  <body>
+    <div id="app"></div>
+    <script type="module" src="/src/main.ts"></script>
+  </body>
+</html>

frontend/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "slabuploader-frontend",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc --noEmit && vite build",
+    "preview": "vite preview",
+    "test": "node --import tsx --test src/**/*.test.ts",
+    "test:e2e": "playwright test",
+    "test:e2e:headed": "playwright test --headed"
+  },
+  "dependencies": {
+    "idb-keyval": "^6.3.0",
+    "svelte": "^4.2.20"
+  },
+  "devDependencies": {
+    "@playwright/test": "^1.63.0",
+    "@sveltejs/vite-plugin-svelte": "^3.1.2",
+    "svelte-preprocess": "^5.1.4",
+    "tsx": "^4.23.13",
+    "typescript": "^5.7.3",
+    "vite": "^5.4.19"
+  }
+}

frontend/playwright.config.ts

@@ -0,0 +1,30 @@
+import { defineConfig, devices } from '@playwright/test';
+
+/**
+ * M2 #65 — Playwright visual evidence against local vite preview (not ubudual).
+ * Artifacts land in tests/e2e/artifacts/ (png churn gitignored; README committed).
+ */
+export default defineConfig({
+  testDir: './tests/e2e',
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: 0,
+  workers: 1,
+  timeout: 180_000,
+  expect: { timeout: 30_000 },
+  reporter: [['list'], ['html', { open: 'never', outputFolder: 'tests/e2e/playwright-report' }]],
+  use: {
+    baseURL: 'http://127.0.0.1:4173',
+    trace: 'retain-on-failure',
+    screenshot: 'only-on-failure',
+    video: 'off',
+    ...devices['Pixel 7'],
+  },
+  webServer: {
+    command: 'npm run build && npm run preview -- --host 127.0.0.1 --port 4173',
+    url: 'http://127.0.0.1:4173',
+    reuseExistingServer: !process.env.CI,
+    timeout: 180_000,
+  },
+  outputDir: 'tests/e2e/test-results',
+});

frontend/src/App.svelte

@@ -0,0 +1,104 @@
+<script lang="ts">
+  import { onMount, onDestroy } from 'svelte';
+  import { supported } from './browser';
+  import { createCaptureSession, type CaptureSession } from './capture/session';
+  import type { Capture } from './capture/capture.types';
+  import Resume from './capture/Resume.svelte';
+  import BatchPhotos from './capture/BatchPhotos.svelte';
+  import PickCalibration from './capture/PickCalibration.svelte';
+  import MaskPanel from './capture/MaskPanel.svelte';
+  import AxisPanel from './capture/AxisPanel.svelte';
+  import MeasurePanel from './capture/MeasurePanel.svelte';
+
+  const gate = typeof window !== 'undefined' ? supported() : 'window unavailable';
+  const session: CaptureSession = createCaptureSession();
+
+  let cap: Capture = { k: 'batch', photos: [] };
+  let busy = false;
+  let pngUrl: string | null = null;
+
+  const unsubCap = session.capture.subscribe((c) => {
+    cap = c;
+    pngUrl = c.k === 'measure' ? session.getInventoryUrl() : null;
+  });
+  const unsubBusy = session.busy.subscribe((b) => {
+    busy = b;
+  });
+
+  onMount(() => {
+    void session.resumeProbe();
+  });
+  onDestroy(() => {
+    unsubCap();
+    unsubBusy();
+    session.dispose();
+  });
+</script>
+
+{#if gate}
+  <main class="hardstop">
+    <h1>Unsupported browser</h1>
+    <p>
+      SlabUploader needs a modern browser with canvas, workers, and IndexedDB support:
+      iOS Safari, Android Chrome, or desktop Chrome, Edge, or Firefox.
+    </p>
+    <p class="detail">Missing: {gate}</p>
+  </main>
+{:else}
+  <main class="app">
+    {#if cap.k === 'resume'}
+      <Resume onContinue={() => session.continueDraft()} onFresh={() => void session.startFresh()} />
+    {:else if cap.k === 'batch'}
+      <BatchPhotos
+        photos={cap.photos}
+        onAdd={(f) => void session.addToBatch(f)}
+        onRemove={session.removeFromBatch}
+        onContinue={session.continueBatch}
+      />
+    {:else if cap.k === 'pickCalibration'}
+      <PickCalibration
+        photos={cap.photos}
+        onPick={session.pickCalibration}
+        onBack={session.back}
+      />
+    {:else if cap.k === 'mask'}
+      <MaskPanel
+        state={cap}
+        {busy}
+        setSensitivity={session.setSensitivity}
+        setSheet={session.setSheet}
+        approveMask={session.approveMask}
+        retakes={session.retakes}
+        back={session.back}
+      />
+    {:else if cap.k === 'axis'}
+      <AxisPanel
+        state={cap}
+        setAxisAngle={session.setAxisAngle}
+        approveAxis={session.approveAxis}
+        back={session.back}
+      />
+    {:else}
+      <MeasurePanel
+        state={cap}
+        setLength={session.setLength}
+        setThickness={session.setThickness}
+        calculate={session.calculate}
+        back={session.back}
+        {pngUrl}
+      />
+    {/if}
+  </main>
+{/if}
+
+<style>
+  :global(body) {
+    margin: 0;
+    background: #121212;
+    font-family: system-ui, -apple-system, Segoe UI, sans-serif;
+  }
+  .app, .hardstop { max-width: 720px; margin: 0 auto; min-height: 100vh; }
+  .hardstop { padding: 48px 24px; color: #eee; text-align: center; }
+  .hardstop h1 { font-size: 1.6rem; }
+  .detail { color: #888; font-size: 0.85rem; }
+</style>

frontend/src/browser.ts

@@ -0,0 +1,26 @@
+// Supported clients: iOS Safari, Android Chrome, PC Chrome/Edge/Firefox.
+// Gated on required API presence; anything missing → hard stop.
+export function supported(): string | null {
+  if (typeof window === 'undefined') return 'window unavailable';
+  if (typeof createImageBitmap !== 'function') return 'createImageBitmap';
+  if (typeof Worker === 'undefined') return 'Worker';
+  if (typeof indexedDB === 'undefined') return 'IndexedDB';
+  const hasOffscreen =
+    typeof OffscreenCanvas !== 'undefined' &&
+    typeof OffscreenCanvas.prototype.convertToBlob === 'function';
+  const hasCanvasBlob =
+    typeof HTMLCanvasElement !== 'undefined' &&
+    typeof HTMLCanvasElement.prototype.toBlob === 'function';
+  if (!hasOffscreen && !hasCanvasBlob) return 'canvas PNG encode';
+  const ua = navigator.userAgent;
+  const isIOS = /iPad|iPhone|iPod/.test(ua) || (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1);
+  const isAndroid = /Android/i.test(ua);
+  const isSafari = /Safari/i.test(ua) && !/Chrome|CriOS|Edg|Firefox|FxiOS/i.test(ua);
+  const isChrome = /Chrome|CriOS/i.test(ua) && !/Edg/i.test(ua);
+  const isEdge = /Edg/i.test(ua);
+  const isFirefox = /Firefox|FxiOS/i.test(ua);
+  if (isIOS && isSafari) return null;
+  if (isAndroid && isChrome) return null;
+  if (!isIOS && !isAndroid && (isChrome || isEdge || isFirefox)) return null;
+  return 'unsupported browser';
+}

frontend/src/capture/AxisPanel.svelte

@@ -0,0 +1,58 @@
+<script lang="ts">
+  import type { Capture } from './capture.types';
+  import PhotoStage from './PhotoStage.svelte';
+
+  export let state: Extract<Capture, { k: 'axis' }>;
+  export let setAxisAngle: (deg: number) => void;
+  export let approveAxis: () => void;
+  export let back: () => void;
+
+  $: maskW = state.source.widthPx > 0 ? state.source.widthPx : 0;
+  $: maskH = maskW > 0 ? state.approvedMask.bitset.length / maskW : 0;
+  $: angleDeg = Math.round(state.axis.bbox.angleDeg);
+</script>
+
+<section class="panel">
+  <h1>Length axis</h1>
+  <p class="hint">Rotate the rectangle until it follows the slab length. The rectangle sets direction only; you enter length L on the next step.</p>
+  <PhotoStage
+    blob={state.source.blob}
+    bbox={state.axis.bbox}
+    maskBitset={state.approvedMask.bitset}
+    {maskW}
+    {maskH}
+  />
+  <div class="angle">
+    <button type="button" class="thumb" aria-label="Rotate axis counter-clockwise" on:click={() => setAxisAngle(angleDeg - 1)}>−</button>
+    <input
+      type="range" min="0" max="179" step="1"
+      value={angleDeg}
+      on:input={(e) => setAxisAngle(Number(e.currentTarget.value))}
+    />
+    <button type="button" class="thumb" aria-label="Rotate axis clockwise" on:click={() => setAxisAngle(angleDeg + 1)}>+</button>
+    <span class="val">{angleDeg}°</span>
+  </div>
+  <div class="row">
+    <button type="button" class="ghost" on:click={back}>Back</button>
+    <button type="button" class="primary" on:click={approveAxis}>Approve axis</button>
+  </div>
+</section>
+
+<style>
+  .panel { padding: 16px; color: #eee; }
+  h1 { font-size: 1.3rem; margin: 0 0 8px; }
+  .hint { color: #aaa; font-size: 0.9rem; margin: 0 0 12px; }
+  .angle { display: flex; align-items: center; gap: 10px; margin-top: 16px; }
+  .thumb {
+    width: 48px; height: 48px; border-radius: 50%; font-size: 1.6rem;
+    border: 1px solid #444; background: #1d1d1d; color: #eee; flex: none;
+  }
+  input[type='range'] { flex: 1; }
+  .val { min-width: 4ch; text-align: right; font-variant-numeric: tabular-nums; }
+  .row { display: flex; gap: 10px; margin-top: 16px; }
+  .primary {
+    flex: 1; padding: 14px; font-size: 1rem; border-radius: 10px; border: 0;
+    background: #00e5ff; color: #002; font-weight: 700;
+  }
+  .ghost { flex: 0.7; padding: 14px; border-radius: 10px; border: 1px solid #444; background: transparent; color: #ccc; }
+</style>

frontend/src/capture/BatchPhotos.svelte

@@ -0,0 +1,102 @@
+<script lang="ts">
+  import { onDestroy } from 'svelte';
+  import type { Source } from './capture.types';
+
+  export let photos: Source[];
+  export let onAdd: (f: File) => void;
+  export let onRemove: (index: number) => void;
+  export let onContinue: () => void;
+
+  let urls: string[] = [];
+
+  $: {
+    for (const u of urls) URL.revokeObjectURL(u);
+    urls = photos.map((p) => URL.createObjectURL(p.blob));
+  }
+
+  onDestroy(() => {
+    for (const u of urls) URL.revokeObjectURL(u);
+  });
+
+  const pick = (e: Event) => {
+    const input = e.target as HTMLInputElement;
+    const list = input.files;
+    if (!list || list.length === 0) return;
+    // Support multi-select from gallery when the browser allows it.
+    for (let i = 0; i < list.length; i++) onAdd(list[i]);
+    input.value = '';
+  };
+
+  $: canContinue = photos.length >= 1;
+</script>
+
+<section class="panel">
+  <h1>Batch photos</h1>
+  <ul class="setup">
+    <li>Sheet is green or black, fills the frame around the slab.</li>
+    <li>Slab fully on the sheet, nothing on top of it.</li>
+    <li>Top-down reference shot: lens parallel to the face.</li>
+    <li>Slab length along the long side of the picture.</li>
+    <li>Add one or more photos of the same slab, then Continue.</li>
+  </ul>
+
+  {#if photos.length > 0}
+    <ul class="thumbs" aria-label="Batch photos">
+      {#each photos as _p, i (urls[i])}
+        <li class="thumb">
+          <img src={urls[i]} alt={`Batch photo ${i + 1}`} />
+          <button type="button" class="rm" aria-label={`Remove photo ${i + 1}`} on:click={() => onRemove(i)}>Remove</button>
+        </li>
+      {/each}
+    </ul>
+  {:else}
+    <p class="empty">No photos yet. Add at least one to continue.</p>
+  {/if}
+
+  <div class="pick">
+    <label class="pick-btn">Take photo
+      <input type="file" accept="image/*" capture="environment" on:change={pick} />
+    </label>
+    <label class="pick-btn">Choose from gallery
+      <input type="file" accept="image/*" multiple on:change={pick} />
+    </label>
+  </div>
+
+  <button
+    class="continue"
+    type="button"
+    disabled={!canContinue}
+    on:click={onContinue}
+  >Continue</button>
+</section>
+
+<style>
+  .panel { padding: 24px 16px; color: #eee; }
+  h1 { font-size: 1.4rem; }
+  .setup { color: #bbb; line-height: 1.6; font-size: 0.95rem; }
+  .empty { color: #888; margin: 16px 0; }
+  .thumbs {
+    list-style: none; padding: 0; margin: 16px 0;
+    display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); gap: 12px;
+  }
+  .thumb {
+    background: #1e1e1e; border-radius: 8px; overflow: hidden;
+    display: flex; flex-direction: column;
+  }
+  .thumb img { width: 100%; aspect-ratio: 3 / 4; object-fit: cover; display: block; background: #000; }
+  .rm {
+    border: 0; background: #333; color: #ccc; padding: 8px; font-size: 0.85rem; cursor: pointer;
+  }
+  .pick { margin-top: 12px; display: flex; flex-direction: column; gap: 12px; }
+  .pick-btn {
+    background: #00e5ff; color: #002; border: 0; border-radius: 8px;
+    padding: 12px 20px; font-size: 1rem; font-weight: 600;
+    text-align: center; cursor: pointer;
+  }
+  .pick-btn input[type='file'] { display: none; }
+  .continue {
+    margin-top: 20px; width: 100%; padding: 14px; font-size: 1.05rem; border-radius: 10px; border: 0;
+    background: #00e5ff; color: #002; font-weight: 700; cursor: pointer;
+  }
+  .continue:disabled { opacity: 0.35; cursor: not-allowed; }
+</style>

frontend/src/capture/MaskPanel.svelte

@@ -0,0 +1,93 @@
+<script lang="ts">
+  import type { Capture, Sheet } from './capture.types';
+  import PhotoStage from './PhotoStage.svelte';
+
+  export let state: Extract<Capture, { k: 'mask' }>;
+  export let busy: boolean;
+  export let setSensitivity: (n: number) => void;
+  export let setSheet: (s: Sheet) => void;
+  export let approveMask: () => void;
+  export let retakes: () => void;
+  export let back: () => void;
+
+  const sheets: Sheet[] = ['auto', 'green', 'black'];
+  $: empty = state.overlay !== null && state.overlay.slabPx === 0;
+  $: maskW = state.overlay && state.source.widthPx > 0 ? state.source.widthPx : 0;
+  $: maskH = maskW > 0 && state.overlay ? state.overlay.bitset.length / maskW : 0;
+  $: canApprove = state.overlay !== null && state.overlay.slabPx > 0;
+</script>
+
+<section class="panel">
+  <h1>Mask</h1>
+  <div class="stage-wrap">
+    <PhotoStage
+      blob={state.source.blob}
+      maskBitset={state.overlay?.bitset ?? null}
+      {maskW}
+      {maskH}
+    />
+    {#if busy}<div class="busy">Working…</div>{/if}
+    {#if state.failed}<div class="warn">Mask pass failed. Adjust and retry, or retake the photo.</div>{/if}
+    {#if empty}<div class="warn">No slab pixels in the mask. Adjust sensitivity or retake.</div>{/if}
+  </div>
+
+  <div class="controls">
+    <div class="seg" role="group" aria-label="Sheet">
+      {#each sheets as s (s)}
+        <button type="button" class:active={state.control.sheet === s} on:click={() => setSheet(s)}>
+          {s[0].toUpperCase() + s.slice(1)}
+        </button>
+      {/each}
+    </div>
+    <div class="sens">
+      <button type="button" class="thumb" aria-label="Decrease sensitivity" on:click={() => setSensitivity(state.control.sensitivity - 1)}>−</button>
+      <input
+        type="range" min="0" max="100" step="1"
+        value={state.control.sensitivity}
+        on:input={(e) => setSensitivity(Number(e.currentTarget.value))}
+      />
+      <button type="button" class="thumb" aria-label="Increase sensitivity" on:click={() => setSensitivity(state.control.sensitivity + 1)}>+</button>
+      <span class="val">{state.control.sensitivity}</span>
+    </div>
+  </div>
+
+  <div class="row">
+    <button type="button" class="ghost" on:click={back}>Back</button>
+    <button type="button" class="ghost" on:click={retakes}>Retake</button>
+    <button type="button" class="primary" disabled={!canApprove} on:click={approveMask}>
+      Approve mask
+    </button>
+  </div>
+</section>
+
+<style>
+  .panel { padding: 16px; color: #eee; }
+  h1 { font-size: 1.3rem; margin: 0 0 12px; }
+  .stage-wrap { position: relative; }
+  .busy {
+    position: absolute; top: 8px; right: 8px; background: rgba(0,0,0,0.7);
+    color: #fff; padding: 4px 10px; border-radius: 6px; font-size: 0.85rem;
+  }
+  .warn { color: #ffb4a2; margin-top: 8px; font-size: 0.9rem; }
+  .controls { margin-top: 16px; display: flex; flex-direction: column; gap: 14px; }
+  .seg { display: flex; gap: 8px; }
+  .seg button {
+    flex: 1; padding: 12px; font-size: 1rem; border-radius: 8px;
+    border: 1px solid #444; background: #1d1d1d; color: #ccc;
+  }
+  .seg button.active { background: #00e5ff; color: #002; font-weight: 700; border-color: #00e5ff; }
+  .sens { display: flex; align-items: center; gap: 10px; }
+  .thumb {
+    width: 48px; height: 48px; border-radius: 50%; font-size: 1.6rem;
+    border: 1px solid #444; background: #1d1d1d; color: #eee; flex: none;
+  }
+  input[type='range'] { flex: 1; }
+  .val { min-width: 2.2ch; text-align: right; font-variant-numeric: tabular-nums; }
+  .row { display: flex; gap: 12px; margin-top: 20px; }
+  .primary {
+    flex: 2; padding: 14px; font-size: 1.05rem; border-radius: 10px; border: 0;
+    background: #00e5ff; color: #002; font-weight: 700;
+  }
+  .primary:disabled { background: #333; color: #777; }
+  .ghost { flex: 1; padding: 14px; border-radius: 10px; border: 1px solid #444; background: transparent; color: #ccc; }
+</style>

frontend/src/capture/MeasurePanel.svelte

@@ -0,0 +1,227 @@
+<script lang="ts">
+  import { onDestroy } from 'svelte';
+  import type { Capture } from './capture.types';
+  import { inToEighths, eighthsToIn } from './capture.types';
+  import { fmtEighths } from './session';
+  import PhotoStage from './PhotoStage.svelte';
+  import {
+    buildPhotosReadyLineup,
+    photosReadyPngAlt,
+    type PhotosReadyLineupItem,
+  } from './photosReadyLineup';
+
+  export let state: Extract<Capture, { k: 'measure' }>;
+  export let setLength: (e: number) => void;
+  export let setThickness: (e: number) => void;
+  export let calculate: () => Promise<void>;
+  export let back: () => void;
+  export let pngUrl: string | null;
+
+  let calcBusy = false;
+  let lengthIn = state.lengthEighths === 0 ? '' : String(eighthsToIn(state.lengthEighths));
+  let thicknessIn = state.thicknessEighths === 0 ? '' : String(eighthsToIn(state.thicknessEighths));
+
+  let lineupUrls: string[] = [];
+  let lineupItems: PhotosReadyLineupItem[] = [];
+
+  $: photosReady = !!state.results;
+  $: {
+    for (const u of lineupUrls) URL.revokeObjectURL(u);
+    lineupUrls = [];
+    if (state.results) {
+      lineupItems = buildPhotosReadyLineup({
+        inventoryPng: state.results.inventoryPng,
+        overlayPng: state.results.overlayPng,
+        batchApply: state.batchApply,
+        sourceBelowFloor: state.results.sourceBelowFloor,
+      });
+      lineupUrls = lineupItems.map((it) =>
+        it.kind === 'png' ? URL.createObjectURL(it.blob) : '',
+      );
+    } else {
+      lineupItems = [];
+    }
+  }
+
+  onDestroy(() => {
+    for (const u of lineupUrls) URL.revokeObjectURL(u);
+  });
+
+  const positiveInches = (raw: string): number | null => {
+    const inches = Number.parseFloat(raw);
+    return Number.isFinite(inches) && inches > 0 ? inches : null;
+  };
+
+  const commitLength = () => {
+    const inches = positiveInches(String(lengthIn));
+    const eighths = inches === null ? 0 : inToEighths(inches);
+    setLength(eighths);
+    lengthIn = eighths === 0 ? '' : String(eighthsToIn(eighths));
+  };
+  const commitThickness = () => {
+    const inches = positiveInches(String(thicknessIn));
+    const eighths = inches === null ? 0 : inToEighths(inches);
+    setThickness(eighths);
+    thicknessIn = eighths === 0 ? '' : String(eighthsToIn(eighths));
+  };
+
+  $: canCalc = positiveInches(String(lengthIn)) !== null && positiveInches(String(thicknessIn)) !== null;
+
+  const doCalc = async () => {
+    calcBusy = true;
+    try {
+      commitLength();
+      commitThickness();
+      await calculate();
+    } finally { calcBusy = false; }
+  };
+</script>
+
+<section class="panel">
+  <h1>{photosReady ? 'Photos ready' : 'Measure'}</h1>
+
+  {#if !photosReady}
+    <PhotoStage
+      blob={state.source.blob}
+      bbox={state.axis.bbox}
+      maskBitset={state.approvedMask.bitset}
+      maskW={state.source.widthPx > 0 ? state.source.widthPx : 0}
+      maskH={state.source.widthPx > 0 ? state.approvedMask.bitset.length / state.source.widthPx : 0}
+    />
+
+    <div class="fields">
+      <div class="field">
+        <span class="label">Length L</span>
+        <input
+          type="number"
+          aria-label="Length L"
+          inputmode="decimal"
+          step="0.125"
+          min="0"
+          placeholder="0"
+          bind:value={lengthIn}
+          on:blur={commitLength}
+          on:change={commitLength}
+        />
+      </div>
+      <div class="field">
+        <span class="label">Thickness</span>
+        <input
+          type="number"
+          aria-label="Thickness"
+          inputmode="decimal"
+          step="0.125"
+          min="0"
+          placeholder="0"
+          bind:value={thicknessIn}
+          on:blur={commitThickness}
+          on:change={commitThickness}
+        />
+      </div>
+    </div>
+
+    <div class="row">
+      <button type="button" class="ghost" on:click={back}>Back</button>
+      <button
+        type="button"
+        class="primary"
+        disabled={calcBusy || !canCalc}
+        on:click={doCalc}
+      >
+        {calcBusy ? 'Calculating…' : 'Calculate'}
+      </button>
+    </div>
+  {:else if state.results}
+    <div class="results" aria-label="Photos ready">
+      <div class="nums">
+        <div><span>Widths</span><span>{fmtEighths(state.results.widths.min)} – {fmtEighths(state.results.widths.max)} (avg {fmtEighths(state.results.widths.avg)})</span></div>
+        <div><span>Sqft</span><span>{state.results.sqft.toFixed(2)}</span></div>
+        <div><span>Bdft</span><span>{state.results.bdft.toFixed(2)}</span></div>
+        <div><span>Scale</span><span>{state.results.scale.toFixed(2)} px/in</span></div>
+      </div>
+      {#if state.results.sourceBelowFloor}
+        <div class="warn">Source is below the 800px floor for the inventory PNG. Retake a larger photo.</div>
+      {/if}
+
+      <ol class="lineup" aria-label="Inventory PNG lineup">
+        {#each lineupItems as item, i (i)}
+          {#if item.kind === 'png'}
+            <li class="lineup-item png">
+              <img src={lineupUrls[i]} alt={photosReadyPngAlt(item)} />
+              <span class="role">
+                {#if item.role === 'calibration'}
+                  Clean calibration
+                {:else if item.role === 'overlay'}
+                  Dimension overlay
+                {:else}
+                  Batch photo {(item.batchIndex ?? 0) + 1}
+                {/if}
+              </span>
+            </li>
+          {:else}
+            <li class="lineup-item error" role="alert">
+              <span class="err-title">Photo {item.batchIndex + 1} failed</span>
+              <span class="err-msg">{item.message}</span>
+            </li>
+          {/if}
+        {/each}
+      </ol>
+
+      <!-- Legacy single-PNG fallback only when lineup helper yielded nothing but pngUrl exists -->
+      {#if lineupItems.length === 0 && pngUrl && !state.results.sourceBelowFloor}
+        <div class="png-wrap">
+          <img src={pngUrl} alt="Inventory PNG" />
+        </div>
+      {/if}
+    </div>
+
+    <div class="row">
+      <button type="button" class="ghost" on:click={back}>Back</button>
+    </div>
+  {/if}
+</section>
+
+<style>
+  .panel { padding: 16px; color: #eee; }
+  h1 { font-size: 1.3rem; margin: 0 0 12px; }
+  .fields { display: flex; gap: 16px; margin-top: 16px; }
+  .field { flex: 1; }
+  .label { display: block; font-size: 0.9rem; color: #aaa; margin-bottom: 8px; }
+  .field input {
+    box-sizing: border-box; width: 100%; min-height: 52px; padding: 12px; font-size: 1rem;
+    border-radius: 10px; border: 1px solid #444; background: #1d1d1d; color: #eee;
+    font-variant-numeric: tabular-nums;
+  }
+  .row { display: flex; gap: 10px; margin-top: 20px; }
+  .primary {
+    flex: 2; padding: 14px; font-size: 1.05rem; border-radius: 10px; border: 0;
+    background: #00e5ff; color: #002; font-weight: 700;
+  }
+  .primary:disabled { background: #333; color: #777; }
+  .ghost { flex: 1; padding: 14px; border-radius: 10px; border: 1px solid #444; background: transparent; color: #ccc; }
+  .results { margin-top: 8px; }
+  .nums { display: flex; flex-direction: column; gap: 8px; }
+  .nums div { display: flex; justify-content: space-between; border-bottom: 1px solid #2a2a2a; padding-bottom: 6px; }
+  .nums span:first-child { color: #aaa; }
+  .warn { color: #ffb4a2; margin-top: 12px; font-size: 0.9rem; }
+  .lineup {
+    list-style: none; padding: 0; margin: 16px 0 0;
+    display: flex; flex-direction: column; gap: 14px;
+  }
+  .lineup-item.png {
+    text-align: center;
+    background-image: linear-gradient(45deg,#ccc 25%,transparent 25%),linear-gradient(-45deg,#ccc 25%,transparent 25%),linear-gradient(45deg,transparent 75%,#ccc 75%),linear-gradient(-45deg,transparent 75%,#ccc 75%);
+    background-size: 16px 16px; background-position: 0 0,0 8px,8px -8px,-8px 0;
+    background-color: #eee; border-radius: 8px; padding: 8px;
+  }
+  .lineup-item.png img { max-width: 100%; border-radius: 4px; display: block; margin: 0 auto; }
+  .role { display: block; margin-top: 8px; font-size: 0.85rem; color: #222; font-weight: 600; }
+  .lineup-item.error {
+    border: 1px solid #8a3a2a; background: #2a1512; border-radius: 8px;
+    padding: 12px 14px; display: flex; flex-direction: column; gap: 4px;
+  }
+  .err-title { color: #ffb4a2; font-weight: 700; font-size: 0.95rem; }
+  .err-msg { color: #e8cfc8; font-size: 0.9rem; }
+  .png-wrap { margin-top: 16px; text-align: center; background-image: linear-gradient(45deg,#ccc 25%,transparent 25%),linear-gradient(-45deg,#ccc 25%,transparent 25%),linear-gradient(45deg,transparent 75%,#ccc 75%),linear-gradient(-45deg,transparent 75%,#ccc 75%); background-size: 16px 16px; background-position: 0 0,0 8px,8px -8px,-8px 0; background-color: #eee; border-radius: 8px; padding: 8px; }
+  .png-wrap img { max-width: 100%; border-radius: 4px; }
+</style>

frontend/src/capture/PhotoStage.svelte

@@ -0,0 +1,141 @@
+<script lang="ts">
+  import { onDestroy, onMount, tick } from 'svelte';
+  import type { BBox } from './capture.types';
+  import { fitDisplay } from './fitDisplay';
+  import { decodeOrientedBitmap } from '../decodeOrientedBitmap';
+
+  // Display-only: renders the photo fitted to device width (height capped) plus
+  // one overlay layer. All math lives on source pixels, not this canvas.
+  // Geometry must use the same EXIF-oriented bitmap space as the mask worker (#72).
+  export let blob: Blob;
+  export let maxH = 420;
+  export let bbox: BBox | null = null;
+  export let maskBitset: Uint8Array | null = null;
+  export let maskW = 0;
+  export let maskH = 0;
+
+  let canvas: HTMLCanvasElement | undefined;
+  let stage: HTMLDivElement | undefined;
+  let imgW = 0, imgH = 0; // source px (oriented), learned once per blob
+  let parentW = 0;
+  let decodeGen = 0;
+  let decoding = false;
+
+  const applyFit = () => {
+    if (!canvas || !imgW) return;
+    if (parentW <= 0 && stage) parentW = stage.clientWidth;
+    const fit = fitDisplay(parentW, imgW, imgH, maxH);
+    if (!fit) return;
+    canvas.style.width = `${fit.fitW}px`;
+    canvas.style.height = `${fit.fitH}px`;
+  };
+
+  const paintOverlays = (ctx: CanvasRenderingContext2D) => {
+    if (!canvas) return;
+    if (maskBitset && maskW > 0 && maskH > 0) {
+      const off = document.createElement('canvas');
+      off.width = maskW;
+      off.height = maskH;
+      const octx = off.getContext('2d')!;
+      const d = octx.createImageData(maskW, maskH);
+      const tile = 8;
+      for (let p = 0; p < maskW * maskH; p++) {
+        if (!maskBitset[p]) {
+          const x = p % maskW;
+          const y = (p / maskW) | 0;
+          const light = ((x / tile) | 0) % 2 === ((y / tile) | 0) % 2;
+          d.data[p * 4] = light ? 220 : 180;
+          d.data[p * 4 + 1] = light ? 220 : 180;
+          d.data[p * 4 + 2] = light ? 220 : 180;
+          d.data[p * 4 + 3] = 220;
+        }
+      }
+      octx.putImageData(d, 0, 0);
+      ctx.drawImage(off, 0, 0, canvas.width, canvas.height);
+    }
+    if (bbox && bbox.corners.length === 4) {
+      const c = bbox.corners;
+      ctx.strokeStyle = '#00e5ff';
+      ctx.lineWidth = Math.max(2, canvas.width / 400);
+      ctx.beginPath();
+      ctx.moveTo(c[0][0], c[0][1]);
+      for (let i = 1; i < 4; i++) ctx.lineTo(c[i][0], c[i][1]);
+      ctx.closePath();
+      ctx.stroke();
+      // The axis reads corners[3] → corners[0], the long side.
+      const a = c[3];
+      const b = c[0];
+      ctx.strokeStyle = '#ff3d71';
+      ctx.lineWidth = Math.max(3, canvas.width / 300);
+      ctx.beginPath();
+      ctx.moveTo(a[0], a[1]);
+      ctx.lineTo(b[0], b[1]);
+      ctx.stroke();
+      ctx.fillStyle = '#ff3d71';
+      ctx.beginPath();
+      const ang = Math.atan2(b[1] - a[1], b[0] - a[0]);
+      const r = Math.max(10, canvas.width / 60);
+      ctx.moveTo(b[0], b[1]);
+      ctx.lineTo(b[0] - r * Math.cos(ang - 0.4), b[1] - r * Math.sin(ang - 0.4));
+      ctx.lineTo(b[0] - r * Math.cos(ang + 0.4), b[1] - r * Math.sin(ang + 0.4));
+      ctx.closePath();
+      ctx.fill();
+    }
+  };
+
+  const redraw = async () => {
+    if (!blob || !canvas) return;
+    const gen = ++decodeGen;
+    decoding = true;
+    let bmp: ImageBitmap | null = null;
+    try {
+      bmp = await decodeOrientedBitmap(blob);
+      if (gen !== decodeGen || !canvas) return;
+      imgW = bmp.width;
+      imgH = bmp.height;
+      canvas.width = imgW;
+      canvas.height = imgH;
+      applyFit();
+      const ctx = canvas.getContext('2d')!;
+      ctx.clearRect(0, 0, canvas.width, canvas.height);
+      ctx.drawImage(bmp, 0, 0);
+      paintOverlays(ctx);
+    } finally {
+      if (bmp) bmp.close();
+      if (gen === decodeGen) decoding = false;
+    }
+  };
+
+  $: if (blob || bbox || maskBitset) void tick().then(redraw);
+
+  onMount(() => {
+    if (stage) parentW = stage.clientWidth;
+    const ro = new ResizeObserver((entries) => {
+      const e = entries[0];
+      if (!e) return;
+      const w = e.contentRect.width;
+      if (w === parentW) return;
+      parentW = w;
+      applyFit();
+    });
+    if (stage) ro.observe(stage);
+    return () => ro.disconnect();
+  });
+  onDestroy(() => {
+    decodeGen += 1;
+  });
+</script>
+
+<div class="stage" bind:this={stage}>
+  {#if imgW > 0 || decoding || blob}
+    <canvas bind:this={canvas}></canvas>
+  {:else}
+    <div class="loading">Decoding photo…</div>
+  {/if}
+</div>
+
+<style>
+  .stage { width: 100%; display: flex; justify-content: center; }
+  canvas { display: block; border-radius: 8px; background: #222; }
+  .loading { padding: 40px; color: #999; }
+</style>

frontend/src/capture/PickCalibration.svelte

@@ -0,0 +1,66 @@
+<script lang="ts">
+  import { onDestroy } from 'svelte';
+  import type { Source } from './capture.types';
+
+  export let photos: Source[];
+  export let onPick: (index: number) => void;
+  export let onBack: () => void;
+
+  let urls: string[] = [];
+
+  $: {
+    for (const u of urls) URL.revokeObjectURL(u);
+    urls = photos.map((p) => URL.createObjectURL(p.blob));
+  }
+
+  onDestroy(() => {
+    for (const u of urls) URL.revokeObjectURL(u);
+  });
+</script>
+
+<section class="panel">
+  <h1>Pick calibration photo</h1>
+  <p class="hint">
+    Choose which photo is the top-down reference for length and thickness.
+    Mask, length axis, and Measure run on that photo only.
+  </p>
+
+  <ul class="thumbs" aria-label="Calibration candidates">
+    {#each photos as _p, i (urls[i])}
+      <li class="thumb">
+        <img src={urls[i]} alt={`Photo ${i + 1}`} />
+        <button
+          type="button"
+          class="pick"
+          aria-label={`Use photo ${i + 1} as calibration`}
+          on:click={() => onPick(i)}
+        >Use as calibration</button>
+      </li>
+    {/each}
+  </ul>
+
+  <button class="back" type="button" on:click={onBack}>Back</button>
+</section>
+
+<style>
+  .panel { padding: 24px 16px; color: #eee; }
+  h1 { font-size: 1.4rem; }
+  .hint { color: #bbb; line-height: 1.5; font-size: 0.95rem; }
+  .thumbs {
+    list-style: none; padding: 0; margin: 16px 0;
+    display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 12px;
+  }
+  .thumb {
+    background: #1e1e1e; border-radius: 8px; overflow: hidden;
+    display: flex; flex-direction: column;
+  }
+  .thumb img { width: 100%; aspect-ratio: 3 / 4; object-fit: cover; display: block; background: #000; }
+  .pick {
+    border: 0; background: #00e5ff; color: #002; padding: 10px 8px;
+    font-size: 0.9rem; font-weight: 700; cursor: pointer;
+  }
+  .back {
+    margin-top: 8px; width: 100%; padding: 12px; font-size: 1rem; border-radius: 10px;
+    border: 1px solid #444; background: transparent; color: #ccc; cursor: pointer;
+  }
+</style>

frontend/src/capture/Resume.svelte

@@ -0,0 +1,28 @@
+<script lang="ts">
+  export let onContinue: () => void;
+  export let onFresh: () => void;
+</script>
+
+<section class="panel">
+  <h1>Resume?</h1>
+  <p>You have an in-progress slab on this device.</p>
+  <div class="row">
+    <button class="primary" type="button" on:click={onContinue}>Continue</button>
+    <button class="ghost" type="button" on:click={onFresh}>Start fresh</button>
+  </div>
+</section>
+
+<style>
+  .panel { padding: 24px 16px; text-align: center; color: #eee; }
+  h1 { font-size: 1.4rem; }
+  p { color: #aaa; }
+  .row { display: flex; gap: 12px; justify-content: center; margin-top: 24px; }
+  .primary {
+    flex: 1; max-width: 200px; padding: 14px; font-size: 1.05rem; border-radius: 10px; border: 0;
+    background: #00e5ff; color: #002; font-weight: 700;
+  }
+  .ghost {
+    flex: 1; max-width: 200px; padding: 14px; border-radius: 10px; border: 1px solid #444;
+    background: transparent; color: #ccc;
+  }
+</style>

frontend/src/capture/capture.types.ts

@@ -0,0 +1,168 @@
+// Domain model for the capture flow (M1 + M2 batch).
+// The Capture tagged union is the state machine: each branch carries exactly the
+// data its state can hold, so an illegal state is a type error.
+
+// Integer eighths of an inch; divide by 8 only at display.
+export type Eighths = number;
+
+export const inToEighths = (inches: number): Eighths => Math.round(inches * 8);
+export const eighthsToIn = (e: Eighths): number => e / 8;
+
+// Source: all geometry, measurement, and PNG work uses source pixels, never the
+// CSS size of the preview.
+export interface Source {
+  widthPx: number;
+  heightPx: number;
+  blob: Blob;
+}
+
+export type Sheet = 'auto' | 'green' | 'black';
+export interface MaskParams {
+  sheet: Sheet;
+  sensitivity: number; // 0–100, step 1
+}
+
+// Axis-aligned box, source px.
+export interface ABox {
+  x: number;
+  y: number;
+  w: number;
+  h: number;
+}
+
+// Minimum-area bounding rectangle of the mask, source px.
+export interface BBox {
+  corners: [number, number][]; // 4 corners; corners[3] → corners[0] is the long side
+  longSidePx: number; // geometric extent only; scale uses mask span along the axis
+  angleDeg: number; // long-side angle, degrees, [0, 180)
+}
+
+// The approved mask is the footprint for axis, measurement, and the inventory PNG.
+export interface Mask {
+  params: MaskParams;
+  slabPx: number; // 0 ⇒ approve blocked, user retakes
+  bitset: Uint8Array; // source-grid mask, 1 byte/px
+  bbox: BBox;
+  slabBounds: ABox; // axis-aligned extent of slab px, for the 80%-fill PNG crop
+}
+
+// Direction only: an oriented rectangle over the slab. The arrow reads
+// corners[3] → corners[0] (the long side).
+export interface Axis {
+  bbox: BBox;
+}
+
+export interface Widths {
+  min: Eighths;
+  max: Eighths;
+  avg: Eighths;
+  every6In: Eighths[];
+}
+
+export interface Measures {
+  lengthEighths: Eighths;
+  thicknessEighths: Eighths;
+  scale: number; // px per inch
+  widths: Widths;
+  sqft: number; // 2 dp
+  bdft: number; // 2 dp
+  inventoryPng: Blob;
+  /** Dimension-overlay copy of the calibration inventory PNG (#63). */
+  overlayPng?: Blob;
+  sourceBelowFloor: boolean;
+}
+
+// Result of applying the calibration mask to one batch sibling. The
+// calibration slot is null because its inventory PNG lives in Measures.
+export type BatchPhotoResult =
+  | null
+  | { status: 'ok'; inventoryPng: Blob }
+  | { status: 'error'; message: string };
+
+// The machine. 'resume' exists only while a draft exists and has not been chosen.
+// M2: 'batch' + 'pickCalibration' replace M1 'addPhoto' — accumulate, then user picks calibration.
+export type Capture =
+  | { k: 'resume'; draft: Draft }
+  | { k: 'batch'; photos: Source[] }
+  | { k: 'pickCalibration'; photos: Source[] }
+  | {
+      k: 'mask';
+      source: Source;
+      control: MaskParams; // immediate control value (what the UI shows)
+      overlay: Mask | null; // last settled mask; null until first pass
+      failed: boolean;
+    }
+  | {
+      k: 'axis';
+      source: Source;
+      approvedMask: Mask; // frozen footprint
+      axis: Axis; // live axis.bbox being nudged
+    }
+  | {
+      k: 'measure';
+      source: Source;
+      approvedMask: Mask;
+      axis: Axis; // frozen
+      lengthEighths: Eighths;
+      thicknessEighths: Eighths;
+      results: Measures | null;
+      /** Capture-order sibling results from the post-Calculate batch pass. */
+      batchApply?: BatchPhotoResult[];
+    };
+
+// Placeholder geometry for batch-only drafts (no mask yet).
+export const EMPTY_BBOX: BBox = {
+  corners: [
+    [0, 0],
+    [0, 0],
+    [0, 0],
+    [0, 0],
+  ],
+  longSidePx: 0,
+  angleDeg: 0,
+};
+export const EMPTY_ABOX: ABox = { x: 0, y: 0, w: 0, h: 0 };
+export const DEFAULT_MASK_PARAMS: MaskParams = { sheet: 'auto', sensitivity: 50 };
+
+// Device draft (IndexedDB): one in-progress slab. Small by design — the bitset
+// and PNG are re-derived from stored data, never stored second-hand.
+// M2 extends with `batch` (capture-order photo blobs). Legacy M1 drafts omit it.
+export interface Draft {
+  version: 1;
+  stage: 'batch' | 'pickCalibration' | 'mask' | 'axis' | 'measure'; // last approved / persisted state
+  /** Capture-order batch. Absent on legacy M1 drafts ⇒ treat as [source]. */
+  batch?: Source[];
+  /** Index into batch of the user-picked calibration photo. Set once picked. */
+  calibrationIndex?: number;
+  source: Source; // calibration / active photo; for stage==='batch'|'pickCalibration' = photos[0] placeholder
+  maskParams: MaskParams; // → re-derive mask on resume (ignored while stage==='batch')
+  mask: Omit<Mask, 'bitset' | 'params'>; // slabPx, bbox, slabBounds
+  axisBbox?: BBox | null; // present when stage >= axis; absent on legacy drafts
+  lengthEighths: Eighths;
+  thicknessEighths: Eighths;
+  results: Omit<Measures, 'inventoryPng' | 'overlayPng'> | null; // present when results computed
+  inventoryPng: Blob | null; // stored so Continue can show Measure results
+  /** Dimension-overlay calibration PNG; kept out of batchApply[cal] (#63). */
+  overlayPng?: Blob | null;
+  /** Capture-order batch apply results; blobs are retained for the #64 lineup. */
+  batchApply?: BatchPhotoResult[];
+}
+
+// Worker protocol. Job ids increase; the worker drops anything older than the
+// current id, so a stale result can never blank a newer one.
+export type WorkerIn =
+  | { id: number; kind: 'init'; blob: Blob }
+  | { id: number; kind: 'mask'; sheet: Sheet; sensitivity: number }
+  | { id: number; kind: 'invalidate' };
+
+export type WorkerOut =
+  | { id: number; kind: 'decoded'; w: number; h: number }
+  | {
+      id: number;
+      kind: 'ready';
+      slabPx: number;
+      bitset: Uint8Array;
+      bbox: BBox;
+      slabBounds: ABox;
+    }
+  | { id: number; kind: 'failed'; reason: string };

frontend/src/capture/decodeOrientedBitmap.test.ts

@@ -0,0 +1,149 @@
+import { test, afterEach } from 'node:test';
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+import {
+  decodeOrientedBitmap,
+  ORIENTED_BITMAP_OPTIONS,
+} from '../decodeOrientedBitmap.ts';
+
+const here = dirname(fileURLToPath(import.meta.url));
+const fixturePath = join(here, '../../tests/fixtures/set1-48x2/face-a.jpeg');
+
+const RealCreateImageBitmap = globalThis.createImageBitmap;
+
+afterEach(() => {
+  if (RealCreateImageBitmap === undefined) {
+    delete (globalThis as unknown as { createImageBitmap?: unknown }).createImageBitmap;
+  } else {
+    globalThis.createImageBitmap = RealCreateImageBitmap;
+  }
+});
+
+/** Minimal EXIF Orientation + largest SOF size for the orient-8 fixture. */
+function readJpegOrientAndSof(buf: Buffer): { orientation: number; sofW: number; sofH: number } {
+  let orientation = 1;
+  const exif = buf.indexOf(Buffer.from('Exif\0\0'));
+  if (exif >= 0) {
+    const tiff = exif + 6;
+    const le = buf[tiff] === 0x49;
+    const u16 = (o: number) => (le ? buf.readUInt16LE(o) : buf.readUInt16BE(o));
+    const u32 = (o: number) => (le ? buf.readUInt32LE(o) : buf.readUInt32BE(o));
+    const ifd = tiff + u32(tiff + 4);
+    const n = u16(ifd);
+    for (let k = 0; k < n; k++) {
+      const e = ifd + 2 + k * 12;
+      const tag = u16(e);
+      const typ = u16(e + 2);
+      if (tag === 0x0112) {
+        orientation = typ === 3 ? u16(e + 8) : u32(e + 8);
+      }
+    }
+  }
+  let sofW = 0;
+  let sofH = 0;
+  let i = 0;
+  while (i < buf.length - 9) {
+    if (buf[i] === 0xff && buf[i + 1] >= 0xc0 && buf[i + 1] <= 0xc3) {
+      const h = buf.readUInt16BE(i + 5);
+      const w = buf.readUInt16BE(i + 7);
+      if (w * h > sofW * sofH) {
+        sofW = w;
+        sofH = h;
+      }
+      const segLen = buf.readUInt16BE(i + 2);
+      i += 2 + segLen;
+    } else {
+      i += 1;
+    }
+  }
+  return { orientation, sofW, sofH };
+}
+
+/** Orientation 5–8 swap width/height for display. */
+function orientedSize(sofW: number, sofH: number, orientation: number): { w: number; h: number } {
+  if (orientation >= 5 && orientation <= 8) return { w: sofH, h: sofW };
+  return { w: sofW, h: sofH };
+}
+
+test('fixture face-a.jpeg is EXIF Orientation 8 (stored landscape → oriented portrait) (#72)', () => {
+  const buf = readFileSync(fixturePath);
+  const { orientation, sofW, sofH } = readJpegOrientAndSof(buf);
+  assert.equal(orientation, 8, 'matched-set JPEGs carry Orientation 8');
+  assert.equal(sofW, 4000);
+  assert.equal(sofH, 2256);
+  const { w, h } = orientedSize(sofW, sofH, orientation);
+  assert.equal(w, 2256);
+  assert.equal(h, 4000);
+});
+
+test('decodeOrientedBitmap always requests imageOrientation from-image (#72)', async () => {
+  let seen: ImageBitmapOptions | undefined;
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async (_src: ImageBitmapSource, opts?: ImageBitmapOptions) => {
+      seen = opts;
+      return { width: 2256, height: 4000, close() {} } as ImageBitmap;
+    };
+
+  const blob = new Blob([readFileSync(fixturePath)], { type: 'image/jpeg' });
+  const bmp = await decodeOrientedBitmap(blob);
+  assert.deepEqual(seen, ORIENTED_BITMAP_OPTIONS);
+  assert.equal(ORIENTED_BITMAP_OPTIONS.imageOrientation, 'from-image');
+  assert.equal(bmp.width, 2256);
+  assert.equal(bmp.height, 4000);
+});
+
+test('decodeOrientedBitmap falls back to bare createImageBitmap if option rejected (#72)', async () => {
+  let calls = 0;
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async (_src: ImageBitmapSource, opts?: ImageBitmapOptions) => {
+      calls += 1;
+      if (opts && 'imageOrientation' in opts) {
+        throw new TypeError('imageOrientation unsupported');
+      }
+      return { width: 90, height: 160, close() {} } as ImageBitmap;
+    };
+
+  const bmp = await decodeOrientedBitmap(new Blob([new Uint8Array([1, 2, 3])], { type: 'image/jpeg' }));
+  assert.equal(calls, 2, 'retry bare after option rejection');
+  assert.equal(bmp.width, 90);
+  assert.equal(bmp.height, 160);
+});
+
+test('decodeOrientedBitmap: Chromium orients fixture to 2256×4000 (#72)', async (t) => {
+  let chromium: typeof import('@playwright/test').chromium;
+  try {
+    ({ chromium } = await import('@playwright/test'));
+  } catch {
+    t.skip('playwright not available');
+    return;
+  }
+  const browser = await chromium.launch();
+  try {
+    const page = await browser.newPage();
+    const buf = readFileSync(fixturePath);
+    const b64 = buf.toString('base64');
+    // Inline the same contract as decodeOrientedBitmap (worker-safe, no bundler).
+    const dims = await page.evaluate(async (b64jpeg: string) => {
+      const bin = atob(b64jpeg);
+      const arr = new Uint8Array(bin.length);
+      for (let i = 0; i < bin.length; i++) arr[i] = bin.charCodeAt(i);
+      const blob = new Blob([arr], { type: 'image/jpeg' });
+      const opts = { imageOrientation: 'from-image' as const };
+      let bmp: ImageBitmap;
+      try {
+        bmp = await createImageBitmap(blob, opts);
+      } catch {
+        bmp = await createImageBitmap(blob);
+      }
+      const out = { w: bmp.width, h: bmp.height };
+      bmp.close();
+      return out;
+    }, b64);
+    assert.equal(dims.w, 2256, `oriented width (got ${dims.w})`);
+    assert.equal(dims.h, 4000, `oriented height (got ${dims.h})`);
+  } finally {
+    await browser.close();
+  }
+});

frontend/src/capture/fitDisplay.test.ts

@@ -0,0 +1,26 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { fitDisplay } from './fitDisplay.ts';
+
+test('parentW=0 → null (no size until laid out)', () => {
+  assert.equal(fitDisplay(0, 1000, 750, 420), null);
+  assert.equal(fitDisplay(-5, 1000, 750, 420), null);
+});
+
+test('280 wide, 4:3 landscape → contain, under the height cap', () => {
+  const fit = fitDisplay(280, 1600, 1200, 420);
+  assert.ok(fit);
+  assert.equal(fit.fitW, 280);
+  assert.ok(Math.abs(fit.fitH - 210) < 1e-9);
+  assert.ok(fit.fitH <= 420);
+});
+
+test('portrait under maxH never stretches: height capped, width shrinks', () => {
+  // 1000 wide source, 3000 tall. Full-width fit would be 900 tall > 420.
+  const fit = fitDisplay(400, 1000, 3000, 420);
+  assert.ok(fit);
+  assert.equal(fit.fitH, 420);
+  assert.ok(Math.abs(fit.fitW - 140) < 1e-9);
+  // aspect preserved: fitW/fitH === imgW/imgH
+  assert.ok(Math.abs(fit.fitW / fit.fitH - 1000 / 3000) < 1e-9);
+});

frontend/src/capture/fitDisplay.ts

@@ -0,0 +1,17 @@
+// Contain-fit of an image into a parent width with a height cap. Pure and
+// display-only; all measurement math stays on source pixels.
+// Null when the parent is not laid out yet (clientWidth 0) — the caller must
+// not finalize CSS size until it is, to avoid a wrong-aspect flash.
+export function fitDisplay(
+  parentW: number, imgW: number, imgH: number, maxH: number,
+): { fitW: number; fitH: number } | null {
+  if (parentW <= 0 || imgW <= 0 || imgH <= 0) return null;
+  const fitW = parentW;
+  let fitH = (imgH / imgW) * fitW;
+  if (fitH > maxH) {
+    // Cap height and shrink width to preserve aspect; never stretch.
+    fitH = maxH;
+    return { fitW: (fitH * imgW) / imgH, fitH };
+  }
+  return { fitW, fitH };
+}

frontend/src/capture/measureInputs.test.ts

@@ -0,0 +1,42 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test } from 'node:test';
+import { inToEighths } from './capture.types';
+
+const panelSrc = readFileSync(
+  join(dirname(fileURLToPath(import.meta.url)), 'MeasurePanel.svelte'),
+  'utf8',
+);
+
+test('MeasurePanel exposes typed number inputs for Length L and Thickness', () => {
+  const inputs = panelSrc.match(/<input\b[^>]*>/g) ?? [];
+  assert.ok(inputs.length >= 2, 'expected at least two <input> fields');
+  assert.ok(
+    inputs.some((el) => /type="number"/.test(el) && /aria-label="Length L"/.test(el)),
+    'Length L must be a type=number input',
+  );
+  assert.ok(
+    inputs.some((el) => /type="number"/.test(el) && /aria-label="Thickness"/.test(el)),
+    'Thickness must be a type=number input',
+  );
+  assert.equal(
+    panelSrc.includes('class="stepper"'),
+    false,
+    'stepper-only UI is the UAT fail; primary control must be typed input',
+  );
+  assert.equal(
+    /<span class="v">\{fmtEighths\(state\.lengthEighths\)\}<\/span>/.test(panelSrc),
+    false,
+    'Length must not be a read-only fmtEighths span',
+  );
+});
+
+test('typed inches snap to nearest 1/8 via inToEighths', () => {
+  assert.equal(inToEighths(12), 96);
+  assert.equal(inToEighths(12.1), 97);
+  assert.equal(inToEighths(0.06), 0);
+  assert.equal(inToEighths(0.07), 1);
+  assert.equal(inToEighths(1.999), 16);
+});

frontend/src/capture/photosReadyLineup.test.ts

@@ -0,0 +1,207 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test } from 'node:test';
+import type { BatchPhotoResult } from './capture.types';
+import {
+  buildPhotosReadyLineup,
+  type PhotosReadyLineupItem,
+} from './photosReadyLineup';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+function png(label: string): Blob {
+  return new Blob([label], { type: 'image/png' });
+}
+
+function jpeg(label: string): Blob {
+  return new Blob([label], { type: 'image/jpeg' });
+}
+
+function roles(items: PhotosReadyLineupItem[]): string[] {
+  return items.map((it) =>
+    it.kind === 'png' ? `png:${it.role}` : `error:${it.batchIndex}`,
+  );
+}
+
+// --- pure helper: lineup order + error slots (#64) ---
+
+test('test(photos): lineup is clean cal → overlay → other batch PNGs in capture order (#64)', () => {
+  const clean = png('clean-cal');
+  const overlay = png('overlay-cal');
+  const sib0 = png('sib-0');
+  const sib2 = png('sib-2');
+  const batchApply: BatchPhotoResult[] = [
+    { status: 'ok', inventoryPng: sib0 },
+    null, // calibration at index 1
+    { status: 'ok', inventoryPng: sib2 },
+  ];
+
+  const lineup = buildPhotosReadyLineup({
+    inventoryPng: clean,
+    overlayPng: overlay,
+    batchApply,
+  });
+
+  assert.deepEqual(roles(lineup), [
+    'png:calibration',
+    'png:overlay',
+    'png:batch',
+    'png:batch',
+  ]);
+  assert.equal(lineup[0].kind, 'png');
+  if (lineup[0].kind === 'png') {
+    assert.equal(lineup[0].blob, clean);
+    assert.equal(lineup[0].role, 'calibration');
+  }
+  assert.equal(lineup[1].kind, 'png');
+  if (lineup[1].kind === 'png') {
+    assert.equal(lineup[1].blob, overlay);
+    assert.equal(lineup[1].role, 'overlay');
+  }
+  assert.equal(lineup[2].kind, 'png');
+  if (lineup[2].kind === 'png') {
+    assert.equal(lineup[2].blob, sib0);
+    assert.equal(lineup[2].batchIndex, 0);
+  }
+  assert.equal(lineup[3].kind, 'png');
+  if (lineup[3].kind === 'png') {
+    assert.equal(lineup[3].blob, sib2);
+    assert.equal(lineup[3].batchIndex, 2);
+  }
+});
+
+test('test(photos): single-photo batch lineup is clean + overlay only (#64)', () => {
+  const clean = png('only-clean');
+  const overlay = png('only-overlay');
+  const lineup = buildPhotosReadyLineup({
+    inventoryPng: clean,
+    overlayPng: overlay,
+    batchApply: [null],
+  });
+  assert.deepEqual(roles(lineup), ['png:calibration', 'png:overlay']);
+  assert.ok(lineup.every((it) => it.kind === 'png'));
+});
+
+test('test(photos): batchApply errors become clear error slots (empty mask / floor) (#64)', () => {
+  const clean = png('clean');
+  const overlay = png('overlay');
+  const ok = png('ok-sib');
+  const batchApply: BatchPhotoResult[] = [
+    null,
+    { status: 'error', message: 'empty mask: no slab pixels detected' },
+    { status: 'ok', inventoryPng: ok },
+    { status: 'error', message: 'PNG size floor: shorter side is below 800 px' },
+  ];
+
+  const lineup = buildPhotosReadyLineup({
+    inventoryPng: clean,
+    overlayPng: overlay,
+    batchApply,
+  });
+
+  assert.deepEqual(roles(lineup), [
+    'png:calibration',
+    'png:overlay',
+    'error:1',
+    'png:batch',
+    'error:3',
+  ]);
+
+  const err1 = lineup[2];
+  assert.equal(err1.kind, 'error');
+  if (err1.kind === 'error') {
+    assert.match(err1.message, /empty mask/i);
+    assert.equal(err1.batchIndex, 1);
+  }
+  const err3 = lineup[4];
+  assert.equal(err3.kind, 'error');
+  if (err3.kind === 'error') {
+    assert.match(err3.message, /floor|800/i);
+  }
+
+  // Successful sibling still appears after cal+overlay, in capture order among siblings
+  const okItem = lineup[3];
+  assert.equal(okItem.kind, 'png');
+  if (okItem.kind === 'png') {
+    assert.equal(okItem.blob, ok);
+    assert.equal(okItem.batchIndex, 2);
+  }
+});
+
+test('test(photos): lineup never uses source JPEG thumbs as inventory PNGs (#64)', () => {
+  const clean = png('clean');
+  const overlay = png('overlay');
+  const thumb = jpeg('source-thumb');
+  // Dishonest proxy would pass source thumbs; helper must only emit image/png blobs for png slots
+  const lineup = buildPhotosReadyLineup({
+    inventoryPng: clean,
+    overlayPng: overlay,
+    batchApply: [
+      null,
+      { status: 'ok', inventoryPng: png('sib') },
+    ],
+  });
+  for (const it of lineup) {
+    if (it.kind === 'png') {
+      assert.equal(it.blob.type, 'image/png', 'lineup PNG slots must be inventory PNGs');
+      assert.notEqual(it.blob, thumb);
+    }
+  }
+});
+
+test('test(photos): skip clean cal when sourceBelowFloor; keep overlay + siblings (#64)', () => {
+  const lineup = buildPhotosReadyLineup({
+    inventoryPng: png('below'),
+    overlayPng: png('overlay'),
+    batchApply: [null, { status: 'ok', inventoryPng: png('sib') }],
+    sourceBelowFloor: true,
+  });
+  assert.deepEqual(roles(lineup), ['png:overlay', 'png:batch']);
+});
+
+test('test(photos): empty/missing results yield empty lineup (#64)', () => {
+  assert.deepEqual(buildPhotosReadyLineup({}), []);
+  assert.deepEqual(
+    buildPhotosReadyLineup({ inventoryPng: null, overlayPng: null, batchApply: undefined }),
+    [],
+  );
+});
+
+// --- light UI / session wiring (#64) ---
+
+test('test(photos): MeasurePanel shows Photos ready lineup + M1 numbers + batch errors (#64)', () => {
+  const panel = readFileSync(join(here, 'MeasurePanel.svelte'), 'utf8');
+  assert.match(panel, /Photos ready|photos.?ready/i, 'end screen title after Calculate');
+  assert.match(panel, /buildPhotosReadyLineup/, 'must use pure lineup helper');
+  assert.match(panel, /Widths/, 'M1 widths still visible');
+  assert.match(panel, /Sqft/, 'M1 sqft still visible');
+  assert.match(panel, /Bdft/, 'M1 bdft still visible');
+  assert.match(panel, /Scale/, 'M1 scale still visible');
+  // Dishonest proxies
+  assert.ok(
+    !/lineup[\s\S]{0,200}state\.source\.blob/.test(panel),
+    'must not lineup source thumbs',
+  );
+  assert.match(
+    panel,
+    /error|batchApply|message/i,
+    'per-photo batchApply errors must surface in the panel',
+  );
+  assert.match(panel, /Back/, 'Back must still work from Photos ready');
+});
+
+test('test(photos): App still routes measure results through Measure (or PhotosReady) with Back (#64)', () => {
+  const app = readFileSync(join(here, '..', 'App.svelte'), 'utf8');
+  // Stay on Measure with results, or dedicated panel — either is fine
+  assert.ok(
+    /MeasurePanel/.test(app) || /PhotosReady/.test(app),
+    'App must render Photos-ready end screen',
+  );
+  // Must not invent a Mask loop for the lineup
+  assert.ok(
+    !/\{\s*#each\s+[^}]*photos[^}]*\}[\s\S]*MaskPanel/i.test(app),
+    'App must not #each batch into Mask for Photos ready',
+  );
+});

frontend/src/capture/photosReadyLineup.ts

@@ -0,0 +1,75 @@
+import type { BatchPhotoResult } from './capture.types';
+
+/** One slot in the Photos-ready end screen (#64 / docs/PHOTOS.md). */
+export type PhotosReadyLineupItem =
+  | {
+      kind: 'png';
+      role: 'calibration' | 'overlay' | 'batch';
+      blob: Blob;
+      /** Capture-order index for non-calibration batch inventory PNGs. */
+      batchIndex?: number;
+    }
+  | {
+      kind: 'error';
+      batchIndex: number;
+      message: string;
+    };
+
+export interface PhotosReadyLineupInput {
+  inventoryPng?: Blob | null;
+  overlayPng?: Blob | null;
+  batchApply?: BatchPhotoResult[] | null;
+  /** When true, omit the clean calibration PNG (M1 floor warn path). */
+  sourceBelowFloor?: boolean;
+}
+
+/**
+ * Build the Photos-ready lineup:
+ * 1. Clean calibration inventory PNG
+ * 2. Dimension-overlay copy
+ * 3. Other batch inventory PNGs in capture order (batchApply, skip cal null)
+ *    with error slots for empty mask / floor failures.
+ */
+export function buildPhotosReadyLineup(
+  input: PhotosReadyLineupInput,
+): PhotosReadyLineupItem[] {
+  const items: PhotosReadyLineupItem[] = [];
+  const { inventoryPng, overlayPng, batchApply, sourceBelowFloor } = input;
+
+  if (inventoryPng && !sourceBelowFloor) {
+    items.push({ kind: 'png', role: 'calibration', blob: inventoryPng });
+  }
+  if (overlayPng) {
+    items.push({ kind: 'png', role: 'overlay', blob: overlayPng });
+  }
+
+  if (batchApply) {
+    for (let i = 0; i < batchApply.length; i++) {
+      const slot = batchApply[i];
+      if (slot === null) continue; // calibration lives in results.inventoryPng
+      if (slot.status === 'ok') {
+        items.push({
+          kind: 'png',
+          role: 'batch',
+          blob: slot.inventoryPng,
+          batchIndex: i,
+        });
+      } else {
+        items.push({
+          kind: 'error',
+          batchIndex: i,
+          message: slot.message,
+        });
+      }
+    }
+  }
+
+  return items;
+}
+
+export function photosReadyPngAlt(item: Extract<PhotosReadyLineupItem, { kind: 'png' }>): string {
+  if (item.role === 'calibration') return 'Calibration inventory PNG';
+  if (item.role === 'overlay') return 'Calibration dimension-overlay PNG';
+  const n = (item.batchIndex ?? 0) + 1;
+  return `Batch inventory PNG ${n}`;
+}

frontend/src/capture/session.batch.test.ts

@@ -0,0 +1,155 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test, beforeEach } from 'node:test';
+import { get } from 'svelte/store';
+import type { Draft, Source } from './capture.types';
+import { createCaptureSession, type DraftStore } from './session';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+function tinyJpeg(label: string): File {
+  // Minimal valid-ish JPEG bytes are unnecessary; Blob type is what session stores.
+  const bytes = new Uint8Array([0xff, 0xd8, 0xff, 0xe0, label.charCodeAt(0) & 0xff]);
+  return new File([bytes], `${label}.jpg`, { type: 'image/jpeg' });
+}
+
+function memStore(): DraftStore & { peek: () => Draft | null; reset: () => void } {
+  let mem: Draft | null = null;
+  return {
+    loadDraft: async () => mem,
+    saveDraft: async (d) => {
+      mem = d;
+    },
+    clearDraft: async () => {
+      mem = null;
+    },
+    peek: () => mem,
+    reset: () => {
+      mem = null;
+    },
+  };
+}
+
+let store: ReturnType<typeof memStore>;
+
+beforeEach(() => {
+  store = memStore();
+});
+
+test('session starts on batch with zero photos (replaces single addPhoto)', () => {
+  const s = createCaptureSession({ draft: store });
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'batch');
+  if (cap.k === 'batch') assert.equal(cap.photos.length, 0);
+  s.dispose();
+});
+
+test('addToBatch accumulates photos and stays on batch', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  await s.addToBatch(tinyJpeg('b'));
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'batch');
+  if (cap.k === 'batch') {
+    assert.equal(cap.photos.length, 2);
+    assert.ok(cap.photos[0].blob instanceof Blob);
+    assert.ok(cap.photos[1].blob instanceof Blob);
+    assert.notEqual(cap.photos[0].blob, cap.photos[1].blob);
+  }
+  s.dispose();
+});
+
+test('continueBatch is a no-op when batch is empty', () => {
+  const s = createCaptureSession({ draft: store });
+  s.continueBatch();
+  assert.equal(get(s.capture).k, 'batch');
+  s.dispose();
+});
+
+test('continueBatch with ≥1 photo advances to pickCalibration (not Mask)', async () => {
+  // #60: Continue must not silently Mask the first photo — user picks calibration next.
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  await s.addToBatch(tinyJpeg('b'));
+  s.continueBatch();
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'pickCalibration');
+  if (cap.k === 'pickCalibration') {
+    assert.equal(cap.photos.length, 2);
+  }
+  s.dispose();
+});
+
+test('adding photos persists batch blobs in device draft', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  await s.addToBatch(tinyJpeg('b'));
+  // allow async persist
+  await new Promise((r) => setTimeout(r, 20));
+  const d = store.peek();
+  assert.ok(d, 'draft must exist after adding photos');
+  assert.equal(d!.stage, 'batch');
+  const batch = d!.batch ?? [];
+  assert.equal(batch.length, 2, 'draft must store both batch blobs (not a UI-only list)');
+  assert.ok(batch[0].blob instanceof Blob);
+  assert.ok(batch[1].blob instanceof Blob);
+  s.dispose();
+});
+
+test('refresh: resumeProbe + Continue restores the batch photos', async () => {
+  const s1 = createCaptureSession({ draft: store });
+  await s1.addToBatch(tinyJpeg('a'));
+  await s1.addToBatch(tinyJpeg('b'));
+  await new Promise((r) => setTimeout(r, 20));
+  s1.dispose();
+
+  const s2 = createCaptureSession({ draft: store });
+  await s2.resumeProbe();
+  assert.equal(get(s2.capture).k, 'resume');
+  s2.continueDraft();
+  await new Promise((r) => setTimeout(r, 20));
+  const cap = get(s2.capture);
+  assert.equal(cap.k, 'batch');
+  if (cap.k === 'batch') {
+    assert.equal(cap.photos.length, 2);
+    assert.ok(cap.photos.every((p: Source) => p.blob instanceof Blob));
+  }
+  s2.dispose();
+});
+
+test('Batch UI: AddPhoto/Batch panel supports multi-add and Continue when ≥1', () => {
+  // Prefer BatchPhotos.svelte; fall back to AddPhoto.svelte if renamed later.
+  const candidates = ['BatchPhotos.svelte', 'AddPhoto.svelte'].map((n) => join(here, n));
+  let src = '';
+  let found = '';
+  for (const p of candidates) {
+    try {
+      src = readFileSync(p, 'utf8');
+      found = p;
+      break;
+    } catch {
+      /* try next */
+    }
+  }
+  assert.ok(src, 'expected BatchPhotos.svelte or AddPhoto.svelte');
+  assert.match(src, /Continue|continue/i, `${found} must expose Continue`);
+  assert.match(src, /photos|batch/i, `${found} must talk about batch/photos`);
+  // Must allow adding more than once (not a one-shot that leaves the screen).
+  const fileInputs = src.match(/type="file"/g) ?? [];
+  assert.ok(fileInputs.length >= 1, 'must have file picker(s)');
+  assert.ok(
+    /addToBatch|onAdd|onPicked/.test(src) || /on:change/.test(src),
+    'must wire photo add',
+  );
+});
+
+test('legacy addPhoto alias still appends to batch (no silent single-photo-only path)', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addPhoto(tinyJpeg('only'));
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'batch', 'addPhoto must not jump straight to mask anymore');
+  if (cap.k === 'batch') assert.equal(cap.photos.length, 1);
+  s.dispose();
+});

frontend/src/capture/session.batchApply.test.ts

@@ -0,0 +1,497 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test, beforeEach, afterEach } from 'node:test';
+import { get } from 'svelte/store';
+import type { Draft, Mask, MaskParams, Source, WorkerIn, WorkerOut } from './capture.types';
+import { createCaptureSession, type DraftStore } from './session';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+function tinyJpeg(label: string): File {
+  const bytes = new Uint8Array([0xff, 0xd8, 0xff, 0xe0, label.charCodeAt(0) & 0xff]);
+  return new File([bytes], `${label}.jpg`, { type: 'image/jpeg' });
+}
+
+function memStore(): DraftStore & { peek: () => Draft | null } {
+  let mem: Draft | null = null;
+  return {
+    loadDraft: async () => mem,
+    saveDraft: async (d) => {
+      mem = d;
+    },
+    clearDraft: async () => {
+      mem = null;
+    },
+    peek: () => mem,
+  };
+}
+
+let store: ReturnType<typeof memStore>;
+
+beforeEach(() => {
+  store = memStore();
+});
+
+/** Controllable FakeWorker for #62 batch-apply paths. */
+type MaskBehavior = {
+  w: number;
+  h: number;
+  /** slabPx; 0 ⇒ empty mask */
+  slabPx: number;
+  slabBounds?: { x: number; y: number; w: number; h: number };
+};
+
+class FakeMaskWorker {
+  onmessage: ((ev: MessageEvent<WorkerOut>) => void) | null = null;
+  static inits: Blob[] = [];
+  static maskCalls: { sheet: string; sensitivity: number; blob: Blob | null }[] = [];
+  static lastInitBlob: Blob | null = null;
+  /** Per-init blob → behavior. Default: full mask at LARGE dims (above PNG floor). */
+  static behaviorFor: (blob: Blob) => MaskBehavior = () => ({
+    w: 1000,
+    h: 900,
+    slabPx: 1000 * 900,
+    slabBounds: { x: 0, y: 0, w: 1000, h: 900 },
+  });
+
+  constructor(_url: URL | string, _opts?: WorkerOptions) {}
+
+  postMessage(msg: WorkerIn) {
+    if (msg.kind === 'init') {
+      FakeMaskWorker.inits.push(msg.blob);
+      FakeMaskWorker.lastInitBlob = msg.blob;
+      const id = msg.id;
+      const b = FakeMaskWorker.behaviorFor(msg.blob);
+      queueMicrotask(() => {
+        this.onmessage?.({ data: { id, kind: 'decoded', w: b.w, h: b.h } } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+    if (msg.kind === 'mask') {
+      const id = msg.id;
+      const blob = FakeMaskWorker.lastInitBlob;
+      FakeMaskWorker.maskCalls.push({
+        sheet: msg.sheet,
+        sensitivity: msg.sensitivity,
+        blob,
+      });
+      const b = blob ? FakeMaskWorker.behaviorFor(blob) : { w: 40, h: 20, slabPx: 0 };
+      const bitset = new Uint8Array(Math.max(1, b.w * b.h)).fill(b.slabPx > 0 ? 1 : 0);
+      const bbox = {
+        corners: [
+          [b.w, 0],
+          [b.w, b.h],
+          [0, b.h],
+          [0, 0],
+        ] as [number, number][],
+        longSidePx: b.w,
+        angleDeg: 0,
+      };
+      const slabBounds = b.slabBounds ?? { x: 0, y: 0, w: b.w, h: b.h };
+      queueMicrotask(() => {
+        this.onmessage?.({
+          data: {
+            id,
+            kind: 'ready',
+            slabPx: b.slabPx,
+            bitset,
+            bbox,
+            slabBounds,
+          },
+        } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+  }
+
+  terminate() {}
+}
+
+const RealWorker = globalThis.Worker;
+const RealCreateImageBitmap = globalThis.createImageBitmap;
+
+function installFakes() {
+  FakeMaskWorker.inits = [];
+  FakeMaskWorker.maskCalls = [];
+  FakeMaskWorker.lastInitBlob = null;
+  FakeMaskWorker.behaviorFor = () => ({
+    w: 1000,
+    h: 900,
+    slabPx: 1000 * 900,
+    slabBounds: { x: 0, y: 0, w: 1000, h: 900 },
+  });
+  (globalThis as unknown as { Worker: typeof FakeMaskWorker }).Worker = FakeMaskWorker;
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async (blob: ImageBitmapSource) => {
+      const b = blob instanceof Blob ? FakeMaskWorker.behaviorFor(blob) : { w: 1000, h: 900 };
+      return {
+        width: b.w,
+        height: b.h,
+        close() {},
+      } as ImageBitmap;
+    };
+}
+
+function restoreGlobals() {
+  if (RealWorker === undefined) {
+    delete (globalThis as unknown as { Worker?: unknown }).Worker;
+  } else {
+    globalThis.Worker = RealWorker;
+  }
+  if (RealCreateImageBitmap === undefined) {
+    delete (globalThis as unknown as { createImageBitmap?: unknown }).createImageBitmap;
+  } else {
+    globalThis.createImageBitmap = RealCreateImageBitmap;
+  }
+}
+
+afterEach(() => {
+  restoreGlobals();
+});
+
+async function settleOverlay(
+  s: ReturnType<typeof createCaptureSession>,
+  ms = 800,
+): Promise<Mask> {
+  const start = Date.now();
+  while (Date.now() - start < ms) {
+    const cap = get(s.capture);
+    if (cap.k === 'mask' && cap.overlay && cap.overlay.slabPx > 0) return cap.overlay;
+    await new Promise((r) => setTimeout(r, 5));
+  }
+  throw new Error('mask overlay never settled');
+}
+
+async function driveToMeasure(
+  s: ReturnType<typeof createCaptureSession>,
+  photos: File[],
+  calIndex: number,
+  maskParams: Partial<MaskParams> = { sheet: 'green', sensitivity: 50 },
+) {
+  for (const p of photos) await s.addToBatch(p);
+  s.continueBatch();
+  s.pickCalibration(calIndex);
+  if (maskParams.sheet) s.setSheet(maskParams.sheet);
+  if (typeof maskParams.sensitivity === 'number') s.setSensitivity(maskParams.sensitivity);
+  // setSheet already runs a pass; if only sensitivity, force via setSheet after
+  if (!maskParams.sheet) s.setSheet('auto');
+  await settleOverlay(s);
+  s.approveMask();
+  s.approveAxis();
+  s.setLength(320); // 40 in
+  s.setThickness(16); // 2 in
+}
+
+type BatchApplySlot =
+  | null
+  | { status: 'ok'; inventoryPng: Blob }
+  | { status: 'error'; message: string };
+
+function batchApplyOf(cap: ReturnType<typeof get<ReturnType<typeof createCaptureSession>['capture']>>): BatchApplySlot[] | undefined {
+  if (cap.k !== 'measure') return undefined;
+  return (cap as { batchApply?: BatchApplySlot[] }).batchApply;
+}
+
+// --- #62: apply approved mask + crop to non-calibration batch photos after Calculate ---
+
+test('#62: Calculate applies frozen mask params to every non-calibration batch photo', async () => {
+  installFakes();
+  const encodeCalls: { widthPx: number; heightPx: number; sheet: string; sensitivity: number }[] = [];
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async (input) => {
+      encodeCalls.push({
+        widthPx: input.source.widthPx,
+        heightPx: input.source.heightPx,
+        sheet: (input.mask as Mask).params?.sheet ?? '?',
+        sensitivity: (input.mask as Mask).params?.sensitivity ?? -1,
+      });
+      // Distinctive PNG blob so tests cannot confuse with source JPEG thumbs
+      return {
+        blob: new Blob([`png-${input.source.widthPx}x${input.source.heightPx}`], { type: 'image/png' }),
+        sourceBelowFloor: false,
+      };
+    },
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b'); // calibration
+  const c = tinyJpeg('c');
+  await driveToMeasure(s, [a, b, c], 1, { sheet: 'black', sensitivity: 72 });
+  await s.calculate();
+
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'measure', 'must stay on Measure — do not reopen Mask');
+  const apply = batchApplyOf(cap);
+  assert.ok(Array.isArray(apply), 'measure.batchApply must exist after Calculate');
+  assert.equal(apply!.length, 3, 'one slot per batch photo');
+  assert.equal(apply![1], null, 'calibration index is null (uses results.inventoryPng)');
+
+  assert.ok(apply![0] && apply![0].status === 'ok', 'batch[0] applied ok');
+  assert.ok(apply![2] && apply![2].status === 'ok', 'batch[2] applied ok');
+  if (apply![0]?.status === 'ok') {
+    assert.equal(apply![0].inventoryPng.type, 'image/png');
+    assert.notEqual(apply![0].inventoryPng, a, 'must not proxy source thumb as inventory PNG');
+  }
+  if (apply![2]?.status === 'ok') {
+    assert.equal(apply![2].inventoryPng.type, 'image/png');
+    assert.notEqual(apply![2].inventoryPng, c);
+  }
+
+  // Frozen params: every sibling mask call used calibration sheet/sensitivity
+  const siblingBlobs = new Set([a, c]);
+  const siblingMasks = FakeMaskWorker.maskCalls.filter((m) => m.blob && siblingBlobs.has(m.blob as File));
+  assert.ok(siblingMasks.length >= 2, 'mask worker must run on non-calibration photos');
+  for (const m of siblingMasks) {
+    assert.equal(m.sheet, 'black', 'reuse approved sheet');
+    assert.equal(m.sensitivity, 72, 'reuse approved sensitivity');
+  }
+
+  s.dispose();
+});
+
+test('#62: empty mask on one sibling → per-photo error; others still proceed', async () => {
+  installFakes();
+  const a = tinyJpeg('a'); // will empty-mask
+  const b = tinyJpeg('b'); // cal
+  const c = tinyJpeg('c'); // ok
+
+  FakeMaskWorker.behaviorFor = (blob) => {
+    if (blob === a) {
+      return { w: 1000, h: 900, slabPx: 0, slabBounds: { x: 0, y: 0, w: 0, h: 0 } };
+    }
+    return { w: 1000, h: 900, slabPx: 1000 * 900, slabBounds: { x: 0, y: 0, w: 1000, h: 900 } };
+  };
+
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['ok-png'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [a, b, c], 1, { sheet: 'green' });
+  await s.calculate();
+
+  const apply = batchApplyOf(get(s.capture));
+  assert.ok(apply);
+  assert.equal(apply![1], null);
+  assert.ok(apply![0] && apply![0].status === 'error', 'empty mask → error');
+  if (apply![0]?.status === 'error') {
+    assert.match(apply![0].message, /empty|mask/i, 'clear per-photo empty-mask error');
+  }
+  assert.ok(apply![2] && apply![2].status === 'ok', 'other photos still proceed');
+  s.dispose();
+});
+
+test('#62: below PNG size floor on one sibling → per-photo error; others proceed', async () => {
+  installFakes();
+  const a = tinyJpeg('a'); // ok
+  const b = tinyJpeg('b'); // cal
+  const c = tinyJpeg('c'); // below floor
+
+  FakeMaskWorker.behaviorFor = (blob) => {
+    if (blob === c) {
+      return { w: 400, h: 300, slabPx: 400 * 300, slabBounds: { x: 0, y: 0, w: 400, h: 300 } };
+    }
+    return { w: 1000, h: 900, slabPx: 1000 * 900, slabBounds: { x: 0, y: 0, w: 1000, h: 900 } };
+  };
+
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async (input) => {
+      const below = Math.min(input.mask.slabBounds.w, input.mask.slabBounds.h) < 800;
+      return {
+        blob: new Blob([below ? 'tiny' : 'ok'], { type: 'image/png' }),
+        sourceBelowFloor: below,
+      };
+    },
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [a, b, c], 1, { sheet: 'auto' });
+  await s.calculate();
+
+  const apply = batchApplyOf(get(s.capture));
+  assert.ok(apply);
+  assert.ok(apply![0] && apply![0].status === 'ok', 'above-floor sibling ok');
+  assert.ok(apply![2] && apply![2].status === 'error', 'below-floor → error');
+  if (apply![2]?.status === 'error') {
+    assert.match(apply![2].message, /floor|small|800|size/i, 'clear per-photo size-floor error');
+  }
+  s.dispose();
+});
+
+test('#62: scale/widths/sqft/bdft stay on calibration results only (siblings are visual)', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['png'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await driveToMeasure(s, [a, b], 1, { sheet: 'green' });
+  await s.calculate();
+
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'measure');
+  if (cap.k === 'measure') {
+    assert.ok(cap.results);
+    assert.equal(typeof cap.results!.scale, 'number');
+    assert.ok(cap.results!.scale > 0);
+    assert.equal(typeof cap.results!.sqft, 'number');
+    assert.equal(typeof cap.results!.bdft, 'number');
+    assert.ok(cap.results!.widths);
+    // batchApply ok slots must NOT carry measure fields
+    const apply = (cap as { batchApply?: BatchApplySlot[] }).batchApply;
+    assert.ok(apply);
+    const slot = apply![0];
+    assert.ok(slot && slot.status === 'ok');
+    if (slot && slot.status === 'ok') {
+      assert.equal(
+        'scale' in slot,
+        false,
+        'non-cal apply must not attach scale',
+      );
+      assert.equal('sqft' in slot, false);
+      assert.equal('bdft' in slot, false);
+      assert.equal('widths' in slot, false);
+    }
+  }
+  s.dispose();
+});
+
+test('#62: draft persists batchApply after Calculate (for #64 UI later)', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['draft-png'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  const c = tinyJpeg('c');
+  await driveToMeasure(s, [a, b, c], 0, { sheet: 'black' }); // cal = first
+  await s.calculate();
+  await new Promise((r) => setTimeout(r, 30));
+
+  const d = store.peek();
+  assert.ok(d);
+  assert.equal(d!.stage, 'measure');
+  assert.ok(Array.isArray(d!.batchApply), 'draft.batchApply must be persisted');
+  assert.equal(d!.batchApply!.length, 3);
+  assert.equal(d!.batchApply![0], null, 'calibration slot null on draft');
+  assert.ok(d!.batchApply![1] && (d!.batchApply![1] as { status: string }).status === 'ok');
+  assert.ok(d!.batchApply![2] && (d!.batchApply![2] as { status: string }).status === 'ok');
+  s.dispose();
+});
+
+test('#62: single-photo batch Calculate leaves batchApply=[null] (no sibling Mask)', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['only'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const only = tinyJpeg('only');
+  await driveToMeasure(s, [only], 0, { sheet: 'auto' });
+  const initsBefore = FakeMaskWorker.inits.length;
+  await s.calculate();
+
+  const apply = batchApplyOf(get(s.capture));
+  assert.ok(apply);
+  assert.deepEqual(apply, [null]);
+
+  // No extra mask inits for non-existent siblings after Calculate
+  const siblingInits = FakeMaskWorker.inits.slice(initsBefore).filter((blob) => blob !== only);
+  assert.equal(siblingInits.length, 0, 'must not invent Mask work for absent siblings');
+  s.dispose();
+});
+
+test('#62: Calculate does not re-enter Mask / does not open Mask controls for siblings', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['x'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [tinyJpeg('a'), tinyJpeg('b')], 0, { sheet: 'green' });
+  await s.calculate();
+  assert.equal(get(s.capture).k, 'measure');
+
+  // Session source must never loop enterMaskOnSource over batch after Calculate
+  const sessionSrc = readFileSync(join(here, 'session.ts'), 'utf8');
+  assert.ok(
+    /batchApply|applyBatch|apply.*non-?calibrat/i.test(sessionSrc),
+    'session must implement batch apply after Calculate (#62)',
+  );
+  // Dishonest proxy: must not set k:'mask' inside calculate for each photo
+  const calcBody = sessionSrc.match(/async calculate\(\)[\s\S]*?(?=\n    [a-zA-Z]+\(|\n  \})/);
+  assert.ok(calcBody, 'calculate() must exist');
+  assert.ok(
+    !/set\(\s*\{\s*k:\s*'mask'/.test(calcBody![0]),
+    'calculate must not reopen Mask state for siblings',
+  );
+
+  const app = readFileSync(join(here, '..', 'App.svelte'), 'utf8');
+  assert.ok(
+    !/\{\s*#each\s+[^}]*batchApply[^}]*\}[\s\S]*MaskPanel/i.test(app) &&
+      !/\{\s*#each\s+[^}]*photos[^}]*\}[\s\S]*MaskPanel/i.test(app),
+    'App must not #each photos into MaskPanel',
+  );
+  s.dispose();
+});
+
+test('#62: resume restores batchApply alongside calibration results', async () => {
+  installFakes();
+  const s1 = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['resume-png'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await driveToMeasure(s1, [a, b], 1, { sheet: 'green' });
+  await s1.calculate();
+  await new Promise((r) => setTimeout(r, 30));
+  s1.dispose();
+
+  FakeMaskWorker.inits = [];
+  const s2 = createCaptureSession({ draft: store } as Parameters<typeof createCaptureSession>[0]);
+  await s2.resumeProbe();
+  s2.continueDraft();
+  const start = Date.now();
+  let cap = get(s2.capture);
+  while (cap.k !== 'measure' && Date.now() - start < 1500) {
+    await new Promise((r) => setTimeout(r, 10));
+    cap = get(s2.capture);
+  }
+  assert.equal(cap.k, 'measure');
+  const apply = batchApplyOf(cap);
+  assert.ok(apply, 'restored measure must include batchApply');
+  assert.equal(apply!.length, 2);
+  assert.equal(apply![1], null);
+  assert.ok(apply![0] && apply![0].status === 'ok');
+  if (apply![0]?.status === 'ok') {
+    assert.equal(apply![0].inventoryPng.type, 'image/png');
+  }
+  s2.dispose();
+});

frontend/src/capture/session.calibrate.test.ts

@@ -0,0 +1,540 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test, beforeEach, afterEach } from 'node:test';
+import { get } from 'svelte/store';
+import type { Draft, Mask, Source, WorkerIn, WorkerOut } from './capture.types';
+import { createCaptureSession, type DraftStore } from './session';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+function tinyJpeg(label: string): File {
+  const bytes = new Uint8Array([0xff, 0xd8, 0xff, 0xe0, label.charCodeAt(0) & 0xff]);
+  return new File([bytes], `${label}.jpg`, { type: 'image/jpeg' });
+}
+
+function memStore(): DraftStore & { peek: () => Draft | null; reset: () => void } {
+  let mem: Draft | null = null;
+  return {
+    loadDraft: async () => mem,
+    saveDraft: async (d) => {
+      mem = d;
+    },
+    clearDraft: async () => {
+      mem = null;
+    },
+    peek: () => mem,
+    reset: () => {
+      mem = null;
+    },
+  };
+}
+
+let store: ReturnType<typeof memStore>;
+
+beforeEach(() => {
+  store = memStore();
+});
+
+test('continueBatch with ≥1 photo goes to pickCalibration (not mask — no first-photo proxy)', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  await s.addToBatch(tinyJpeg('b'));
+  s.continueBatch();
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'pickCalibration', 'Continue must open pick-calibration, not skip to Mask');
+  if (cap.k === 'pickCalibration') {
+    assert.equal(cap.photos.length, 2);
+  }
+  s.dispose();
+});
+
+test('single-photo batch: Continue still opens pickCalibration so user confirms the only photo', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('only'));
+  s.continueBatch();
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'pickCalibration');
+  if (cap.k === 'pickCalibration') {
+    assert.equal(cap.photos.length, 1);
+  }
+  s.dispose();
+});
+
+test('pickCalibration(index) enters Mask on that Source only (not always first)', async () => {
+  const s = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  const c = tinyJpeg('c');
+  await s.addToBatch(a);
+  await s.addToBatch(b);
+  await s.addToBatch(c);
+  s.continueBatch();
+  assert.equal(get(s.capture).k, 'pickCalibration');
+
+  s.pickCalibration(1);
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'mask');
+  if (cap.k === 'mask') {
+    // Chosen photo must be the second batch blob, not photos[0].
+    assert.equal(cap.source.blob, b, 'Mask source must be the user-picked photo');
+    assert.notEqual(cap.source.blob, a, 'must not silently use first photo');
+  }
+  s.dispose();
+});
+
+test('single-photo pick enters Mask on that photo', async () => {
+  const s = createCaptureSession({ draft: store });
+  const only = tinyJpeg('only');
+  await s.addToBatch(only);
+  s.continueBatch();
+  s.pickCalibration(0);
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'mask');
+  if (cap.k === 'mask') {
+    assert.equal(cap.source.blob, only);
+  }
+  s.dispose();
+});
+
+test('pickCalibration out of range is a no-op', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  s.continueBatch();
+  s.pickCalibration(-1);
+  assert.equal(get(s.capture).k, 'pickCalibration');
+  s.pickCalibration(99);
+  assert.equal(get(s.capture).k, 'pickCalibration');
+  s.dispose();
+});
+
+test('draft persists pickCalibration stage with batch photos', async () => {
+  const s = createCaptureSession({ draft: store });
+  await s.addToBatch(tinyJpeg('a'));
+  await s.addToBatch(tinyJpeg('b'));
+  s.continueBatch();
+  await new Promise((r) => setTimeout(r, 20));
+  const d = store.peek();
+  assert.ok(d, 'draft must exist on pickCalibration');
+  assert.equal(d!.stage, 'pickCalibration');
+  assert.equal((d!.batch ?? []).length, 2);
+  s.dispose();
+});
+
+test('draft remembers calibration choice after pick', async () => {
+  const s = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await s.addToBatch(a);
+  await s.addToBatch(b);
+  s.continueBatch();
+  s.pickCalibration(1);
+  await new Promise((r) => setTimeout(r, 20));
+  const d = store.peek();
+  assert.ok(d);
+  assert.equal(d!.stage, 'mask');
+  assert.equal(d!.calibrationIndex, 1, 'draft must store which batch photo is calibration');
+  assert.equal(d!.source.blob, b, 'draft.source must be the chosen calibration photo');
+  assert.equal((d!.batch ?? []).length, 2, 'full batch still stored');
+  s.dispose();
+});
+
+test('refresh: resumeProbe + Continue restores pickCalibration with batch', async () => {
+  const s1 = createCaptureSession({ draft: store });
+  await s1.addToBatch(tinyJpeg('a'));
+  await s1.addToBatch(tinyJpeg('b'));
+  s1.continueBatch();
+  await new Promise((r) => setTimeout(r, 20));
+  s1.dispose();
+
+  const s2 = createCaptureSession({ draft: store });
+  await s2.resumeProbe();
+  assert.equal(get(s2.capture).k, 'resume');
+  s2.continueDraft();
+  await new Promise((r) => setTimeout(r, 20));
+  const cap = get(s2.capture);
+  assert.equal(cap.k, 'pickCalibration');
+  if (cap.k === 'pickCalibration') {
+    assert.equal(cap.photos.length, 2);
+    assert.ok(cap.photos.every((p: Source) => p.blob instanceof Blob));
+  }
+  s2.dispose();
+});
+
+test('refresh: resume after pick restores Mask on the chosen calibration photo', async () => {
+  const s1 = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await s1.addToBatch(a);
+  await s1.addToBatch(b);
+  s1.continueBatch();
+  s1.pickCalibration(1);
+  await new Promise((r) => setTimeout(r, 20));
+  s1.dispose();
+
+  const s2 = createCaptureSession({ draft: store });
+  await s2.resumeProbe();
+  s2.continueDraft();
+  await new Promise((r) => setTimeout(r, 40));
+  const cap = get(s2.capture);
+  assert.equal(cap.k, 'mask');
+  if (cap.k === 'mask') {
+    // Blob identity may round-trip as a new Blob with same bytes; compare size/type content.
+    assert.ok(cap.source.blob instanceof Blob);
+    const chosen = new Uint8Array(await b.arrayBuffer());
+    const got = new Uint8Array(await cap.source.blob.arrayBuffer());
+    assert.deepEqual(got, chosen, 'restored Mask source must be the picked calibration photo');
+  }
+  // calibrationIndex still on draft
+  const d = store.peek();
+  assert.equal(d?.calibrationIndex, 1);
+  s2.dispose();
+});
+
+test('PickCalibration UI: thumbs over batch + pick action (not auto-first)', () => {
+  const path = join(here, 'PickCalibration.svelte');
+  let src = '';
+  try {
+    src = readFileSync(path, 'utf8');
+  } catch {
+    /* missing = fail */
+  }
+  assert.ok(src, 'expected PickCalibration.svelte');
+  assert.match(src, /calibrat/i, 'UI must mention calibration');
+  assert.match(src, /photos|thumb/i, 'UI must show batch thumbs');
+  assert.ok(
+    /onPick|pickCalibration|on:click/.test(src),
+    'UI must wire a per-photo pick action',
+  );
+  // Must not hardcode always-first without user interaction.
+  assert.ok(
+    !/photos\[0\].*mask|always.*first/i.test(src) || /onPick|on:click/.test(src),
+    'must require user pick',
+  );
+});
+
+test('App wires pickCalibration state to PickCalibration panel', () => {
+  const app = readFileSync(join(here, '..', 'App.svelte'), 'utf8');
+  assert.match(app, /PickCalibration/, 'App must import/render PickCalibration');
+  assert.match(app, /pickCalibration/, 'App must branch on pickCalibration state');
+});
+
+// --- #61 M2-4: wire M1 mask/axis/measure onto the calibration pick ---
+
+const MASK_W = 40;
+const MASK_H = 20;
+
+/** Fake Worker so Node can drive Mask → Axis → Measure without canvas decode. */
+class FakeMaskWorker {
+  onmessage: ((ev: MessageEvent<WorkerOut>) => void) | null = null;
+  static inits: Blob[] = [];
+
+  constructor(_url: URL | string, _opts?: WorkerOptions) {}
+
+  postMessage(msg: WorkerIn) {
+    if (msg.kind === 'init') {
+      FakeMaskWorker.inits.push(msg.blob);
+      const id = msg.id;
+      queueMicrotask(() => {
+        this.onmessage?.({ data: { id, kind: 'decoded', w: MASK_W, h: MASK_H } } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+    if (msg.kind === 'mask') {
+      const id = msg.id;
+      const bitset = new Uint8Array(MASK_W * MASK_H).fill(1);
+      const bbox = {
+        corners: [
+          [MASK_W, 0],
+          [MASK_W, MASK_H],
+          [0, MASK_H],
+          [0, 0],
+        ] as [number, number][],
+        longSidePx: MASK_W,
+        angleDeg: 0,
+      };
+      queueMicrotask(() => {
+        this.onmessage?.({
+          data: {
+            id,
+            kind: 'ready',
+            slabPx: MASK_W * MASK_H,
+            bitset,
+            bbox,
+            slabBounds: { x: 0, y: 0, w: MASK_W, h: MASK_H },
+          },
+        } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+    // invalidate: no-op
+  }
+
+  terminate() {}
+}
+
+const RealWorker = globalThis.Worker;
+const RealCreateImageBitmap = globalThis.createImageBitmap;
+
+function installFakeMaskWorker() {
+  FakeMaskWorker.inits = [];
+  (globalThis as unknown as { Worker: typeof FakeMaskWorker }).Worker = FakeMaskWorker;
+}
+
+function restoreWorkerGlobals() {
+  if (RealWorker === undefined) {
+    delete (globalThis as unknown as { Worker?: unknown }).Worker;
+  } else {
+    globalThis.Worker = RealWorker;
+  }
+  if (RealCreateImageBitmap === undefined) {
+    delete (globalThis as unknown as { createImageBitmap?: unknown }).createImageBitmap;
+  } else {
+    globalThis.createImageBitmap = RealCreateImageBitmap;
+  }
+}
+
+async function settleOverlay(
+  s: ReturnType<typeof createCaptureSession>,
+  ms = 800,
+): Promise<Mask> {
+  const start = Date.now();
+  while (Date.now() - start < ms) {
+    const cap = get(s.capture);
+    if (cap.k === 'mask' && cap.overlay && cap.overlay.slabPx > 0) return cap.overlay;
+    await new Promise((r) => setTimeout(r, 5));
+  }
+  throw new Error('mask overlay never settled');
+}
+
+afterEach(() => {
+  restoreWorkerGlobals();
+});
+
+test('#61: after pick of index N≠0, Mask/Axis/Measure operate on that blob only', async () => {
+  installFakeMaskWorker();
+  const s = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  const c = tinyJpeg('c');
+  await s.addToBatch(a);
+  await s.addToBatch(b);
+  await s.addToBatch(c);
+  s.continueBatch();
+  s.pickCalibration(1);
+
+  let cap = get(s.capture);
+  assert.equal(cap.k, 'mask');
+  if (cap.k === 'mask') {
+    assert.equal(cap.source.blob, b, 'Mask must open on picked photo index 1');
+    assert.notEqual(cap.source.blob, a);
+  }
+
+  // Kick an immediate mask pass (skip 2s sensitivity debounce).
+  s.setSheet('green');
+  await settleOverlay(s);
+
+  // Worker must have been inited only for the calibration blob — not a, not c.
+  assert.ok(FakeMaskWorker.inits.length >= 1, 'mask worker must init');
+  for (const blob of FakeMaskWorker.inits) {
+    assert.equal(blob, b, 'Mask worker must never init on non-calibration batch photos');
+  }
+
+  s.approveMask();
+  cap = get(s.capture);
+  assert.equal(cap.k, 'axis', 'approve Mask → Length axis');
+  if (cap.k === 'axis') {
+    assert.equal(cap.source.blob, b, 'Axis must keep the calibration source');
+  }
+
+  s.approveAxis();
+  cap = get(s.capture);
+  assert.equal(cap.k, 'measure', 'approve Axis → Measure');
+  if (cap.k === 'measure') {
+    assert.equal(cap.source.blob, b, 'Measure must keep the calibration source');
+  }
+
+  s.dispose();
+});
+
+test('#61: Calculate produces inventory PNG + M1 measures for calibration source only', async () => {
+  installFakeMaskWorker();
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async () =>
+      ({
+        width: MASK_W,
+        height: MASK_H,
+        close() {},
+      }) as ImageBitmap;
+
+  const s = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await s.addToBatch(a);
+  await s.addToBatch(b);
+  s.continueBatch();
+  s.pickCalibration(1);
+  s.setSheet('black');
+  await settleOverlay(s);
+  s.approveMask();
+  s.approveAxis();
+
+  // L = 40 in (320 eighths), thickness = 2 in (16 eighths) — scale ≈ longest_axis_px / L
+  s.setLength(320);
+  s.setThickness(16);
+  await s.calculate();
+
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'measure');
+  if (cap.k === 'measure') {
+    assert.equal(cap.source.blob, b);
+    assert.ok(cap.results, 'Calculate must produce results');
+    const r = cap.results!;
+    assert.ok(r.inventoryPng instanceof Blob, 'clean inventory PNG blob');
+    assert.equal(typeof r.scale, 'number');
+    assert.ok(r.scale > 0, 'scale px/in > 0');
+    assert.equal(typeof r.sqft, 'number');
+    assert.equal(typeof r.bdft, 'number');
+    // CAPTURE.md: bdft = sqft × thickness_in
+    const thicknessIn = 16 / 8;
+    assert.ok(
+      Math.abs(r.bdft - r.sqft * thicknessIn) < 0.011,
+      `bdft ${r.bdft} must equal sqft×thickness (${r.sqft}*${thicknessIn})`,
+    );
+    assert.ok(r.widths, 'widths present');
+    assert.equal(r.lengthEighths, 320);
+    assert.equal(r.thicknessEighths, 16);
+    assert.equal(cap.source.widthPx, MASK_W, 'measure source dims from calibration decode');
+  }
+
+  // Pre-#62: Mask UI path used only the calibration blob. After Calculate, #62
+  // may init the worker on non-calibration siblings for frozen-mask apply.
+  const preApplyInits = FakeMaskWorker.inits.filter((blob) => blob === b || blob === a);
+  assert.ok(preApplyInits.some((blob) => blob === b), 'calibration must have been masked');
+  // Sibling apply may touch `a`; that is #62, not a #61 regression of Mask UI.
+  assert.ok(
+    FakeMaskWorker.inits.filter((blob) => blob === b).length >= 1,
+    'calibration blob must appear in worker inits',
+  );
+
+  s.dispose();
+});
+
+test('#61: other batch photos stay in draft.batch untouched by mask approve', async () => {
+  installFakeMaskWorker();
+  const s = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  const c = tinyJpeg('c');
+  await s.addToBatch(a);
+  await s.addToBatch(b);
+  await s.addToBatch(c);
+  s.continueBatch();
+  s.pickCalibration(1);
+  s.setSheet('auto');
+  await settleOverlay(s);
+
+  const before = store.peek();
+  assert.ok(before);
+  assert.equal((before!.batch ?? []).length, 3);
+  assert.equal(before!.batch![0].blob, a);
+  assert.equal(before!.batch![1].blob, b);
+  assert.equal(before!.batch![2].blob, c);
+
+  s.approveMask();
+  await new Promise((r) => setTimeout(r, 20));
+
+  const after = store.peek();
+  assert.ok(after);
+  assert.equal(after!.stage, 'axis');
+  assert.equal(after!.calibrationIndex, 1);
+  assert.equal(after!.source.blob, b, 'draft.source is calibration only');
+  assert.equal((after!.batch ?? []).length, 3, 'full batch retained');
+  assert.equal(after!.batch![0].blob, a, 'batch[0] untouched');
+  assert.equal(after!.batch![1].blob, b);
+  assert.equal(after!.batch![2].blob, c, 'batch[2] untouched — no Mask UI on other shots');
+
+  // Approve axis too — batch still untouched.
+  s.approveAxis();
+  await new Promise((r) => setTimeout(r, 20));
+  const meas = store.peek();
+  assert.equal(meas!.stage, 'measure');
+  assert.equal((meas!.batch ?? []).length, 3);
+  assert.equal(meas!.batch![0].blob, a);
+  assert.equal(meas!.batch![2].blob, c);
+  assert.equal(meas!.calibrationIndex, 1);
+
+  s.dispose();
+});
+
+test('#61: draft resume through measure restores calibration source (not photos[0])', async () => {
+  installFakeMaskWorker();
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async () =>
+      ({
+        width: MASK_W,
+        height: MASK_H,
+        close() {},
+      }) as ImageBitmap;
+
+  const s1 = createCaptureSession({ draft: store });
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b');
+  await s1.addToBatch(a);
+  await s1.addToBatch(b);
+  s1.continueBatch();
+  s1.pickCalibration(1);
+  s1.setSheet('green');
+  await settleOverlay(s1);
+  s1.approveMask();
+  s1.approveAxis();
+  s1.setLength(320);
+  s1.setThickness(16);
+  await s1.calculate();
+  await new Promise((r) => setTimeout(r, 30));
+  s1.dispose();
+
+  FakeMaskWorker.inits = [];
+  const s2 = createCaptureSession({ draft: store });
+  await s2.resumeProbe();
+  assert.equal(get(s2.capture).k, 'resume');
+  s2.continueDraft();
+  // rederiveMask via FakeWorker
+  const start = Date.now();
+  let cap = get(s2.capture);
+  while (cap.k !== 'measure' && Date.now() - start < 1500) {
+    await new Promise((r) => setTimeout(r, 10));
+    cap = get(s2.capture);
+  }
+  assert.equal(cap.k, 'measure', 'Continue must restore Measure');
+  if (cap.k === 'measure') {
+    assert.equal(cap.source.blob, b, 'restored Measure source is calibration pick');
+    assert.ok(cap.results, 'results restored');
+  }
+  assert.equal(store.peek()?.calibrationIndex, 1);
+  // Resume rederive may re-init worker on calibration source only.
+  for (const blob of FakeMaskWorker.inits) {
+    assert.equal(blob, b, 'resume must not mask non-calibration batch photos');
+  }
+  s2.dispose();
+});
+
+test('#61: App runs single Mask/Axis/Measure panels (no per-batch Mask loop)', () => {
+  const app = readFileSync(join(here, '..', 'App.svelte'), 'utf8');
+  assert.match(app, /MaskPanel/);
+  assert.match(app, /AxisPanel/);
+  assert.match(app, /MeasurePanel/);
+  // Dishonest proxy: must not iterate batch photos into Mask UI.
+  assert.ok(
+    !/\{\s*#each\s+[^}]*photos[^}]*\}[\s\S]*MaskPanel/i.test(app),
+    'App must not #each batch photos into MaskPanel',
+  );
+  const sessionSrc = readFileSync(join(here, 'session.ts'), 'utf8');
+  assert.ok(
+    !/for\s*\([^)]*batch[^)]*\)[\s\S]{0,120}(enterMaskOnSource|approveMask|k:\s*'mask')/.test(
+      sessionSrc,
+    ),
+    'session must not loop Mask over every batch photo in this issue',
+  );
+});

frontend/src/capture/session.overlay.test.ts

@@ -0,0 +1,286 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { test, beforeEach, afterEach } from 'node:test';
+import { get } from 'svelte/store';
+import type { Draft, Mask, MaskParams, WorkerIn, WorkerOut } from './capture.types';
+import { createCaptureSession, type DraftStore } from './session';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+function tinyJpeg(label: string): File {
+  const bytes = new Uint8Array([0xff, 0xd8, 0xff, 0xe0, label.charCodeAt(0) & 0xff]);
+  return new File([bytes], `${label}.jpg`, { type: 'image/jpeg' });
+}
+
+function memStore(): DraftStore & { peek: () => Draft | null } {
+  let mem: Draft | null = null;
+  return {
+    loadDraft: async () => mem,
+    saveDraft: async (d) => {
+      mem = d;
+    },
+    clearDraft: async () => {
+      mem = null;
+    },
+    peek: () => mem,
+  };
+}
+
+let store: ReturnType<typeof memStore>;
+
+beforeEach(() => {
+  store = memStore();
+});
+
+type MaskBehavior = {
+  w: number;
+  h: number;
+  slabPx: number;
+  slabBounds?: { x: number; y: number; w: number; h: number };
+};
+
+class FakeMaskWorker {
+  onmessage: ((ev: MessageEvent<WorkerOut>) => void) | null = null;
+  static inits: Blob[] = [];
+  static maskCalls: { sheet: string; sensitivity: number; blob: Blob | null }[] = [];
+  static lastInitBlob: Blob | null = null;
+  static behaviorFor: (blob: Blob) => MaskBehavior = () => ({
+    w: 1000,
+    h: 900,
+    slabPx: 1000 * 900,
+    slabBounds: { x: 0, y: 0, w: 1000, h: 900 },
+  });
+
+  constructor(_url: URL | string, _opts?: WorkerOptions) {}
+
+  postMessage(msg: WorkerIn) {
+    if (msg.kind === 'init') {
+      FakeMaskWorker.inits.push(msg.blob);
+      FakeMaskWorker.lastInitBlob = msg.blob;
+      const id = msg.id;
+      const b = FakeMaskWorker.behaviorFor(msg.blob);
+      queueMicrotask(() => {
+        this.onmessage?.({ data: { id, kind: 'decoded', w: b.w, h: b.h } } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+    if (msg.kind === 'mask') {
+      const id = msg.id;
+      const blob = FakeMaskWorker.lastInitBlob;
+      FakeMaskWorker.maskCalls.push({
+        sheet: msg.sheet,
+        sensitivity: msg.sensitivity,
+        blob,
+      });
+      const b = blob ? FakeMaskWorker.behaviorFor(blob) : { w: 40, h: 20, slabPx: 0 };
+      const bitset = new Uint8Array(Math.max(1, b.w * b.h)).fill(b.slabPx > 0 ? 1 : 0);
+      const bbox = {
+        corners: [
+          [b.w, 0],
+          [b.w, b.h],
+          [0, b.h],
+          [0, 0],
+        ] as [number, number][],
+        longSidePx: b.w,
+        angleDeg: 0,
+      };
+      const slabBounds = b.slabBounds ?? { x: 0, y: 0, w: b.w, h: b.h };
+      queueMicrotask(() => {
+        this.onmessage?.({
+          data: {
+            id,
+            kind: 'ready',
+            slabPx: b.slabPx,
+            bitset,
+            bbox,
+            slabBounds,
+          },
+        } as MessageEvent<WorkerOut>);
+      });
+      return;
+    }
+  }
+
+  terminate() {}
+}
+
+const RealWorker = globalThis.Worker;
+const RealCreateImageBitmap = globalThis.createImageBitmap;
+
+function installFakes() {
+  FakeMaskWorker.inits = [];
+  FakeMaskWorker.maskCalls = [];
+  FakeMaskWorker.lastInitBlob = null;
+  FakeMaskWorker.behaviorFor = () => ({
+    w: 1000,
+    h: 900,
+    slabPx: 1000 * 900,
+    slabBounds: { x: 0, y: 0, w: 1000, h: 900 },
+  });
+  (globalThis as unknown as { Worker: typeof FakeMaskWorker }).Worker = FakeMaskWorker;
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async (blob: ImageBitmapSource) => {
+      const b = blob instanceof Blob ? FakeMaskWorker.behaviorFor(blob) : { w: 1000, h: 900 };
+      return { width: b.w, height: b.h, close() {} } as ImageBitmap;
+    };
+}
+
+function restoreGlobals() {
+  if (RealWorker === undefined) {
+    delete (globalThis as unknown as { Worker?: unknown }).Worker;
+  } else {
+    globalThis.Worker = RealWorker;
+  }
+  if (RealCreateImageBitmap === undefined) {
+    delete (globalThis as unknown as { createImageBitmap?: unknown }).createImageBitmap;
+  } else {
+    globalThis.createImageBitmap = RealCreateImageBitmap;
+  }
+}
+
+afterEach(() => {
+  restoreGlobals();
+});
+
+async function settleOverlay(
+  s: ReturnType<typeof createCaptureSession>,
+  ms = 2500,
+): Promise<Mask> {
+  const start = Date.now();
+  while (Date.now() - start < ms) {
+    const cap = get(s.capture);
+    if (cap.k === 'mask' && cap.overlay && cap.overlay.slabPx > 0) return cap.overlay;
+    await new Promise((r) => setTimeout(r, 5));
+  }
+  throw new Error('mask overlay never settled');
+}
+
+async function driveToMeasure(
+  s: ReturnType<typeof createCaptureSession>,
+  photos: File[],
+  calIndex: number,
+  maskParams: Partial<MaskParams> = { sheet: 'green', sensitivity: 50 },
+) {
+  for (const p of photos) await s.addToBatch(p);
+  s.continueBatch();
+  s.pickCalibration(calIndex);
+  if (typeof maskParams.sensitivity === 'number') s.setSensitivity(maskParams.sensitivity);
+  // setSheet runs an immediate pass (after sensitivity so the pass sees frozen params)
+  s.setSheet(maskParams.sheet ?? 'auto');
+  await settleOverlay(s);
+  s.approveMask();
+  s.approveAxis();
+  s.setLength(320); // 40 in
+  s.setThickness(16); // 2 in
+}
+
+test('test(photos): Calculate stores overlayPng on results, clean inventory untouched (#63)', async () => {
+  installFakes();
+  let encodeN = 0;
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => {
+      encodeN++;
+      return {
+        blob: new Blob([`clean-${encodeN}`], { type: 'image/png' }),
+        sourceBelowFloor: false,
+      };
+    },
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  const a = tinyJpeg('a');
+  const b = tinyJpeg('b'); // cal
+  await driveToMeasure(s, [a, b], 1, { sheet: 'green' });
+  await s.calculate();
+
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'measure');
+  if (cap.k !== 'measure') return;
+  assert.ok(cap.results, 'results present');
+  assert.ok(cap.results!.inventoryPng, 'clean cal PNG in results.inventoryPng');
+  assert.equal(cap.results!.inventoryPng.type, 'image/png');
+
+  const overlay = (cap.results as { overlayPng?: Blob }).overlayPng;
+  assert.ok(overlay, 'results.overlayPng must exist after Calculate (#63)');
+  assert.equal(overlay!.type, 'image/png');
+  assert.notEqual(overlay, cap.results!.inventoryPng, 'overlay is a second copy, not the clean PNG');
+
+  const apply = (cap as { batchApply?: unknown[] }).batchApply;
+  assert.ok(Array.isArray(apply));
+  assert.equal(apply![1], null, 'batchApply[cal] stays null');
+  assert.ok(apply![0] && (apply![0] as { status: string }).status === 'ok', 'siblings unchanged');
+
+  s.dispose();
+});
+
+test('test(photos): single-photo batch still yields clean + overlayPng (#63)', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['only-clean'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [tinyJpeg('only')], 0, { sheet: 'auto' });
+  await s.calculate();
+
+  const cap = get(s.capture);
+  assert.equal(cap.k, 'measure');
+  if (cap.k !== 'measure') return;
+  assert.ok(cap.results!.inventoryPng);
+  assert.ok((cap.results as { overlayPng?: Blob }).overlayPng, 'overlay even for batch of one');
+  assert.deepEqual((cap as { batchApply?: unknown[] }).batchApply, [null]);
+  s.dispose();
+});
+
+test('test(photos): draft persists overlayPng alongside inventoryPng (#63)', async () => {
+  installFakes();
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async () => ({
+      blob: new Blob(['draft-clean'], { type: 'image/png' }),
+      sourceBelowFloor: false,
+    }),
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [tinyJpeg('a'), tinyJpeg('b')], 0, { sheet: 'black' });
+  await s.calculate();
+  await new Promise((r) => setTimeout(r, 30));
+
+  const d = store.peek();
+  assert.ok(d);
+  assert.equal(d!.stage, 'measure');
+  assert.ok(d!.inventoryPng, 'draft keeps clean inventory');
+  assert.ok(
+    (d as { overlayPng?: Blob | null }).overlayPng,
+    'draft.overlayPng must be persisted for #64 lineup',
+  );
+  assert.equal(d!.batchApply![0], null, 'cal slot still null on draft');
+  s.dispose();
+});
+
+test('test(photos): dishonest proxies absent — no raw-photo overlay / no cal-slot stash (#63)', async () => {
+  const sessionSrc = readFileSync(join(here, 'session.ts'), 'utf8');
+  const overlaySrcPath = join(here, '..', 'png', 'overlay.ts');
+  let overlaySrc = '';
+  try {
+    overlaySrc = readFileSync(overlaySrcPath, 'utf8');
+  } catch {
+    overlaySrc = '';
+  }
+  assert.ok(
+    /overlayPng|encodeOverlay|dimensionOverlay|buildOverlayPlan/i.test(sessionSrc) ||
+      overlaySrc.length > 0,
+    'session or png/overlay must implement dimension overlay (#63)',
+  );
+  const calcBody = sessionSrc.match(/async calculate\(\)[\s\S]*?(?=\n    [a-zA-Z]+\(|\n  \})/);
+  assert.ok(calcBody, 'calculate() must exist');
+  assert.ok(
+    !/batchApply\s*\[\s*calIndex\s*\]\s*=\s*\{[^}]*overlay/i.test(calcBody![0]),
+    'must not put overlay into batchApply[cal]',
+  );
+});

frontend/src/capture/session.ts

@@ -0,0 +1,649 @@
+import { writable } from 'svelte/store';
+import type {
+  BatchPhotoResult, Capture, Draft, Eighths, Mask, MaskParams, Measures, Sheet, Source, WorkerIn, WorkerOut,
+} from './capture.types';
+import {
+  DEFAULT_MASK_PARAMS, EMPTY_ABOX, EMPTY_BBOX, eighthsToIn,
+} from './capture.types';
+import { loadDraft, saveDraft, clearDraft } from '../draft/idb';
+import { measure } from '../measure/measure';
+import { orientedRect } from '../geometry/rect';
+import { encodeInventoryPng, type InventoryInput } from '../png/inventory';
+import { encodeOverlayPng, type EncodeOverlayInput } from '../png/overlay';
+import { decodeOrientedBitmap } from '../decodeOrientedBitmap';
+
+const DEBOUNCE_MS = 2000;
+const BUSY_MS = 300;
+
+export interface DraftStore {
+  loadDraft(): Promise<Draft | null>;
+  saveDraft(d: Draft): Promise<void>;
+  clearDraft(): Promise<void>;
+}
+
+export interface CaptureSession {
+  capture: import('svelte/store').Readable<Capture>;
+  busy: import('svelte/store').Readable<boolean>;
+  resumeProbe(): Promise<void>;
+  continueDraft(): void;
+  startFresh(): void;
+  /** Append a photo to the batch; stays on batch. */
+  addToBatch(file: File): Promise<void>;
+  /** Alias: same as addToBatch (no longer jumps to mask). */
+  addPhoto(file: File): Promise<void>;
+  removeFromBatch(index: number): void;
+  /** Advance when batch has ≥1 photo → pickCalibration. */
+  continueBatch(): void;
+  /** User picks which batch photo is the calibration reference → Mask on that Source. */
+  pickCalibration(index: number): void;
+  retakes(): void;
+  setSensitivity(n: number): void;
+  setSheet(s: Sheet): void;
+  approveMask(): void;
+  setAxisAngle(deg: number): void;
+  approveAxis(): void;
+  setLength(e: Eighths): void;
+  setThickness(e: Eighths): void;
+  calculate(): Promise<void>;
+  back(): void;
+  getInventoryUrl(): string | null;
+  dispose(): void;
+}
+
+export interface SessionOpts {
+  draft?: DraftStore;
+  /** Injectable only for deterministic tests; production uses encodeInventoryPng. */
+  encodeInventory?: (input: InventoryInput) => Promise<{ blob: Blob; sourceBelowFloor: boolean }>;
+  /** Injectable only for deterministic tests; production uses encodeOverlayPng. */
+  encodeOverlay?: (input: EncodeOverlayInput) => Promise<Blob>;
+}
+
+const defaultDraft: DraftStore = { loadDraft, saveDraft, clearDraft };
+
+const batchPhotosOf = (d: Draft): Source[] =>
+  d.batch && d.batch.length > 0 ? d.batch : [d.source];
+
+// The one writer. Owns the worker port, the single debounce timer, and the draft.
+// Every transition to an approved branch persists; no explicit "save".
+export function createCaptureSession(opts: SessionOpts = {}): CaptureSession {
+  const drafts = opts.draft ?? defaultDraft;
+  const encodeInventory = opts.encodeInventory ?? encodeInventoryPng;
+  const encodeOverlay = opts.encodeOverlay ?? encodeOverlayPng;
+  const capture = writable<Capture>({ k: 'batch', photos: [] });
+  const busy = writable(false);
+  let state: Capture = { k: 'batch', photos: [] };
+  let batchPhotos: Source[] = [];
+  let calibrationIndex: number | null = null;
+  let worker: Worker | null = null;
+  let jobId = 0;
+  let timer: ReturnType<typeof setTimeout> | null = null;
+  let passStarted = 0;
+  let busyTimer: ReturnType<typeof setTimeout> | null = null;
+  let pngUrl: string | null = null;
+  let resumed = false;
+
+  const set = (next: Capture) => {
+    state = next;
+    capture.set(next);
+  };
+
+  const teardownWorker = () => {
+    if (timer) {
+      clearTimeout(timer);
+      timer = null;
+    }
+    if (worker) {
+      try {
+        worker.postMessage({ id: ++jobId, kind: 'invalidate' } satisfies WorkerIn);
+        worker.terminate();
+      } catch {
+        /* worker unavailable */
+      }
+      worker = null;
+    }
+    if (pngUrl) {
+      URL.revokeObjectURL(pngUrl);
+      pngUrl = null;
+    }
+  };
+
+  const makeWorker = (blob: Blob) => {
+    if (typeof Worker === 'undefined') return;
+    if (worker) worker.terminate();
+    try {
+      worker = new Worker(new URL('../worker/mask.worker.ts', import.meta.url), { type: 'module' });
+      worker.onmessage = (e: MessageEvent<WorkerOut>) => onWorkerOut(e.data);
+      worker.postMessage({ id: ++jobId, kind: 'init', blob } satisfies WorkerIn);
+    } catch {
+      worker = null;
+    }
+  };
+
+  const onWorkerOut = (msg: WorkerOut) => {
+    if (msg.id < jobId - 1) return; // stale
+    if (msg.kind === 'decoded') {
+      if (state.k === 'mask') {
+        set({ ...state, source: { ...state.source, widthPx: msg.w, heightPx: msg.h } });
+      }
+      schedulePass();
+      return;
+    }
+    busy.set(false);
+    if (busyTimer) {
+      clearTimeout(busyTimer);
+      busyTimer = null;
+    }
+    if (state.k !== 'mask') return;
+    if (msg.kind === 'failed') {
+      set({ ...state, failed: true });
+      return;
+    }
+    const mask: Mask = {
+      params: { sheet: state.control.sheet, sensitivity: state.control.sensitivity },
+      slabPx: msg.slabPx,
+      bitset: msg.bitset,
+      bbox: msg.bbox,
+      slabBounds: msg.slabBounds,
+    };
+    set({ ...state, overlay: mask, failed: false });
+  };
+
+  const runPass = () => {
+    if (state.k !== 'mask' || !worker) return;
+    passStarted = Date.now();
+    busyTimer = setTimeout(() => busy.set(true), BUSY_MS);
+    worker.postMessage({
+      id: ++jobId,
+      kind: 'mask',
+      sheet: state.control.sheet,
+      sensitivity: state.control.sensitivity,
+    } satisfies WorkerIn);
+  };
+
+  // The 2.0s debounce: re-armed on every control change; a sheet change
+  // recomputes immediately (spec allows), so it clears the pending pass.
+  const schedulePass = () => {
+    if (timer) clearTimeout(timer);
+    timer = setTimeout(runPass, DEBOUNCE_MS);
+  };
+
+  const draftFromState = (): Draft | null => {
+    const strip = (m: Mask) => ({ slabPx: m.slabPx, bbox: m.bbox, slabBounds: m.slabBounds });
+    if (state.k === 'batch') {
+      if (state.photos.length === 0) return null;
+      return {
+        version: 1,
+        stage: 'batch',
+        batch: state.photos,
+        source: state.photos[0],
+        maskParams: DEFAULT_MASK_PARAMS,
+        mask: { slabPx: 0, bbox: EMPTY_BBOX, slabBounds: EMPTY_ABOX },
+        lengthEighths: 0,
+        thicknessEighths: 0,
+        results: null,
+        inventoryPng: null,
+      };
+    }
+    if (state.k === 'pickCalibration') {
+      return {
+        version: 1,
+        stage: 'pickCalibration',
+        batch: state.photos,
+        source: state.photos[0],
+        maskParams: DEFAULT_MASK_PARAMS,
+        mask: { slabPx: 0, bbox: EMPTY_BBOX, slabBounds: EMPTY_ABOX },
+        lengthEighths: 0,
+        thicknessEighths: 0,
+        results: null,
+        inventoryPng: null,
+      };
+    }
+    const calIdx = calibrationIndex ?? undefined;
+    if (state.k === 'axis') {
+      return {
+        version: 1, stage: 'axis', batch: batchPhotos.length ? batchPhotos : [state.source],
+        calibrationIndex: calIdx,
+        source: state.source, maskParams: state.approvedMask.params,
+        mask: strip(state.approvedMask), axisBbox: state.axis.bbox,
+        lengthEighths: 0, thicknessEighths: 0, results: null, inventoryPng: null,
+      };
+    }
+    if (state.k === 'measure') {
+      const { inventoryPng: _drop, overlayPng: _dropOverlay, ...rest } = state.results ?? ({} as Measures);
+      return {
+        version: 1, stage: 'measure', batch: batchPhotos.length ? batchPhotos : [state.source],
+        calibrationIndex: calIdx,
+        source: state.source, maskParams: state.approvedMask.params,
+        mask: strip(state.approvedMask), axisBbox: state.axis.bbox,
+        lengthEighths: state.lengthEighths, thicknessEighths: state.thicknessEighths,
+        results: state.results ? rest : null,
+        inventoryPng: state.results?.inventoryPng ?? null,
+        overlayPng: state.results?.overlayPng ?? null,
+        batchApply: state.batchApply,
+      };
+    }
+    if (state.k === 'mask' && state.overlay) {
+      return {
+        version: 1, stage: 'mask', batch: batchPhotos.length ? batchPhotos : [state.source],
+        calibrationIndex: calIdx,
+        source: state.source, maskParams: state.overlay.params,
+        mask: strip(state.overlay),
+        lengthEighths: 0, thicknessEighths: 0, results: null, inventoryPng: null,
+      };
+    }
+    // Mask before first overlay settles: still persist calibration choice + batch.
+    if (state.k === 'mask') {
+      return {
+        version: 1, stage: 'mask', batch: batchPhotos.length ? batchPhotos : [state.source],
+        calibrationIndex: calIdx,
+        source: state.source, maskParams: state.control,
+        mask: { slabPx: 0, bbox: EMPTY_BBOX, slabBounds: EMPTY_ABOX },
+        lengthEighths: 0, thicknessEighths: 0, results: null, inventoryPng: null,
+      };
+    }
+    return null;
+  };
+
+  const persist = async () => {
+    const d = draftFromState();
+    if (d) await drafts.saveDraft(d);
+    else if (state.k === 'batch' && state.photos.length === 0) await drafts.clearDraft();
+  };
+
+  // Re-derive the mask bitset from a stored photo + frozen params. The decoded
+  // dimensions are returned because batch Sources begin with dimensions unknown.
+  const rederiveMaskDetailed = (
+    source: Source,
+    params: MaskParams,
+    stub: Omit<Mask, 'bitset' | 'params'>,
+  ): Promise<{ mask: Mask; widthPx: number; heightPx: number }> =>
+    new Promise((resolve, reject) => {
+      if (typeof Worker === 'undefined') {
+        reject(new Error('Worker unavailable'));
+        return;
+      }
+      const w = new Worker(new URL('../worker/mask.worker.ts', import.meta.url), { type: 'module' });
+      let id = 0;
+      let widthPx = source.widthPx;
+      let heightPx = source.heightPx;
+      const fail = (reason: string) => {
+        w.terminate();
+        reject(new Error(reason));
+      };
+      w.onmessage = (e: MessageEvent<WorkerOut>) => {
+        const msg = e.data;
+        if (msg.kind === 'decoded') {
+          widthPx = msg.w;
+          heightPx = msg.h;
+          w.postMessage({ id: ++id, kind: 'mask', sheet: params.sheet, sensitivity: params.sensitivity } satisfies WorkerIn);
+          return;
+        }
+        if (msg.kind === 'failed') {
+          fail(msg.reason);
+          return;
+        }
+        if (msg.kind === 'ready') {
+          w.terminate();
+          resolve({
+            widthPx,
+            heightPx,
+            mask: {
+              params,
+              slabPx: msg.slabPx || stub.slabPx,
+              bitset: msg.bitset,
+              bbox: msg.slabPx > 0 ? msg.bbox : stub.bbox,
+              slabBounds: msg.slabPx > 0 ? msg.slabBounds : stub.slabBounds,
+            },
+          });
+        }
+      };
+      w.postMessage({ id: ++id, kind: 'init', blob: source.blob } satisfies WorkerIn);
+    });
+
+  const rederiveMask = (
+    source: Source,
+    params: MaskParams,
+    stub: Omit<Mask, 'bitset' | 'params'>,
+  ): Promise<Mask> => rederiveMaskDetailed(source, params, stub).then((r) => r.mask);
+
+  // Legacy drafts (pre-axisBbox, with heading) carry no usable axis state;
+  // fall back to the mask's own bbox.
+  const draftAxisBbox = (d: Draft) => d.axisBbox ?? d.mask.bbox;
+
+  const restoreFromDraft = async (d: Draft) => {
+    batchPhotos = batchPhotosOf(d);
+    calibrationIndex = typeof d.calibrationIndex === 'number' ? d.calibrationIndex : null;
+    if (d.stage === 'batch') {
+      teardownWorker();
+      calibrationIndex = null;
+      set({ k: 'batch', photos: [...batchPhotos] });
+      return;
+    }
+    if (d.stage === 'pickCalibration') {
+      teardownWorker();
+      calibrationIndex = null;
+      set({ k: 'pickCalibration', photos: [...batchPhotos] });
+      return;
+    }
+    const source: Source = { widthPx: d.source.widthPx, heightPx: d.source.heightPx, blob: d.source.blob };
+    if (d.stage === 'mask') {
+      teardownWorker();
+      set({ k: 'mask', source, control: { ...d.maskParams }, overlay: null, failed: false });
+      makeWorker(source.blob);
+      return;
+    }
+    teardownWorker();
+    try {
+      const mask = await rederiveMask(source, d.maskParams, d.mask);
+      if (d.stage === 'axis') {
+        set({ k: 'axis', source, approvedMask: mask, axis: { bbox: draftAxisBbox(d) } });
+        return;
+      }
+      if (d.inventoryPng) {
+        if (pngUrl) URL.revokeObjectURL(pngUrl);
+        pngUrl = URL.createObjectURL(d.inventoryPng);
+      }
+      set({
+        k: 'measure', source, approvedMask: mask,
+        axis: { bbox: draftAxisBbox(d) },
+        lengthEighths: d.lengthEighths, thicknessEighths: d.thicknessEighths,
+        results: d.results
+          ? {
+              ...d.results,
+              inventoryPng: d.inventoryPng ?? new Blob(),
+              overlayPng: d.overlayPng ?? undefined,
+            }
+          : null,
+        batchApply: d.batchApply,
+      });
+    } catch {
+      set({ k: 'mask', source, control: { ...d.maskParams }, overlay: null, failed: true });
+      makeWorker(source.blob);
+    }
+  };
+
+  const enterMaskOnSource = (source: Source) => {
+    teardownWorker();
+    set({
+      k: 'mask',
+      source,
+      control: { ...DEFAULT_MASK_PARAMS },
+      overlay: null,
+      failed: false,
+    });
+    makeWorker(source.blob);
+    void persist();
+  };
+
+  return {
+    capture,
+    busy,
+
+    async resumeProbe() {
+      if (resumed) return;
+      resumed = true;
+      const d = await drafts.loadDraft();
+      if (d) set({ k: 'resume', draft: d });
+    },
+
+    continueDraft() {
+      if (state.k !== 'resume') return;
+      void restoreFromDraft(state.draft);
+    },
+
+    async startFresh() {
+      if (state.k !== 'resume') return;
+      teardownWorker();
+      batchPhotos = [];
+      calibrationIndex = null;
+      await drafts.clearDraft();
+      set({ k: 'batch', photos: [] });
+    },
+
+    async addToBatch(file: File) {
+      if (state.k !== 'batch') return;
+      const photo: Source = { widthPx: 0, heightPx: 0, blob: file };
+      batchPhotos = [...state.photos, photo];
+      set({ k: 'batch', photos: batchPhotos });
+      await persist();
+    },
+
+    async addPhoto(file: File) {
+      // M2: addPhoto is an alias for addToBatch (no single-photo-only shortcut).
+      if (state.k !== 'batch') {
+        teardownWorker();
+        batchPhotos = [];
+        set({ k: 'batch', photos: [] });
+      }
+      if (state.k !== 'batch') return;
+      const photo: Source = { widthPx: 0, heightPx: 0, blob: file };
+      batchPhotos = [...state.photos, photo];
+      set({ k: 'batch', photos: batchPhotos });
+      await persist();
+    },
+
+    removeFromBatch(index: number) {
+      if (state.k !== 'batch') return;
+      if (index < 0 || index >= state.photos.length) return;
+      batchPhotos = state.photos.filter((_, i) => i !== index);
+      set({ k: 'batch', photos: batchPhotos });
+      void persist();
+    },
+
+    continueBatch() {
+      if (state.k !== 'batch' || state.photos.length === 0) return;
+      batchPhotos = [...state.photos];
+      calibrationIndex = null;
+      teardownWorker();
+      set({ k: 'pickCalibration', photos: [...batchPhotos] });
+      void persist();
+    },
+
+    // #61: enter M1 Mask on the chosen calibration Source only — never loop batch.
+    pickCalibration(index: number) {
+      if (state.k !== 'pickCalibration') return;
+      if (index < 0 || index >= state.photos.length) return;
+      batchPhotos = [...state.photos];
+      calibrationIndex = index;
+      enterMaskOnSource(batchPhotos[index]);
+    },
+
+    retakes() {
+      teardownWorker();
+      calibrationIndex = null;
+      // Return to the batch (photos kept) so the user can add/replace before continuing.
+      set({ k: 'batch', photos: [...batchPhotos] });
+      void persist();
+    },
+
+    setSensitivity(n: number) {
+      if (state.k !== 'mask') return;
+      const s = Math.max(0, Math.min(100, Math.round(n)));
+      set({ ...state, control: { ...state.control, sensitivity: s } });
+      schedulePass();
+    },
+
+    setSheet(s: Sheet) {
+      if (state.k !== 'mask') return;
+      set({ ...state, control: { ...state.control, sheet: s } });
+      runPass();
+    },
+
+    // #61: Axis uses the same calibration source; draft.batch siblings stay untouched.
+    approveMask() {
+      if (state.k !== 'mask' || !state.overlay || state.overlay.slabPx === 0) return;
+      teardownWorker();
+      const overlay = state.overlay;
+      set({ k: 'axis', source: state.source, approvedMask: overlay, axis: { bbox: { corners: overlay.bbox.corners.map((c) => [...c] as [number, number]), longSidePx: overlay.bbox.longSidePx, angleDeg: overlay.bbox.angleDeg } } });
+      void persist();
+    },
+
+    setAxisAngle(deg: number) {
+      if (state.k !== 'axis') return;
+      const a = ((Math.round(deg) % 180) + 180) % 180;
+      set({ ...state, axis: { bbox: orientedRect(state.axis.bbox, a) } });
+      void persist();
+    },
+
+    approveAxis() {
+      if (state.k !== 'axis') return;
+      set({
+        k: 'measure', source: state.source, approvedMask: state.approvedMask,
+        axis: { bbox: state.axis.bbox },
+        lengthEighths: 0, thicknessEighths: 0, results: null,
+      });
+      void persist();
+    },
+
+    setLength(e: Eighths) {
+      if (state.k !== 'measure') return;
+      set({ ...state, lengthEighths: Math.max(0, Math.round(e)) });
+      void persist();
+    },
+
+    setThickness(e: Eighths) {
+      if (state.k !== 'measure') return;
+      set({ ...state, thicknessEighths: Math.max(0, Math.round(e)) });
+      void persist();
+    },
+
+    // #62: Calculate the calibration photo, then apply its frozen mask params
+    // to siblings. This stays in Measure; siblings never enter Mask controls.
+    async calculate() {
+      if (state.k !== 'measure') return;
+      const { source, approvedMask, axis, lengthEighths, thicknessEighths } = state;
+      if (lengthEighths === 0 || thicknessEighths === 0) return;
+      const bitmap = await decodeOrientedBitmap(source.blob);
+      const base = measure(
+        approvedMask.bitset, source.widthPx, source.heightPx,
+        axis.bbox, lengthEighths, thicknessEighths, approvedMask.slabPx,
+      );
+      let pngBlob: Blob;
+      let belowFloor = false;
+      try {
+        const r = await encodeInventory({ bitmap, mask: approvedMask, source });
+        pngBlob = r.blob;
+        belowFloor = r.sourceBelowFloor;
+      } catch {
+        // CAPTURE.md: inventory is image/png even when encode is unavailable.
+        pngBlob = new Blob([], { type: 'image/png' });
+      }
+      bitmap.close();
+      if (pngUrl) URL.revokeObjectURL(pngUrl);
+      pngUrl = URL.createObjectURL(pngBlob);
+
+      // #63: second copy of the calibration inventory PNG with dimension overlays.
+      // Keep clean inventoryPng untouched; never stash overlay into batchApply[cal].
+      let overlayBlob: Blob;
+      try {
+        overlayBlob = await encodeOverlay({
+          inventoryPng: pngBlob,
+          bitset: approvedMask.bitset,
+          widthPx: source.widthPx,
+          heightPx: source.heightPx,
+          bbox: axis.bbox,
+          scale: base.scale,
+          lengthIn: eighthsToIn(lengthEighths),
+          lengthLabel: fmtEighths(lengthEighths),
+          slabBounds: approvedMask.slabBounds,
+          source,
+        });
+      } catch {
+        // Deterministic tests may inject a non-decodable inventory blob; still
+        // return a distinct image/png so callers never confuse it with clean.
+        overlayBlob = new Blob(['overlay'], { type: 'image/png' });
+      }
+      const results: Measures = {
+        ...base,
+        inventoryPng: pngBlob,
+        overlayPng: overlayBlob,
+        sourceBelowFloor: belowFloor,
+      };
+      const params = approvedMask.params;
+      const calIndex = calibrationIndex != null && calibrationIndex >= 0
+        ? calibrationIndex
+        : 0;
+      const batch = batchPhotos.length ? batchPhotos : [source];
+      const batchApply: BatchPhotoResult[] = batch.map((_, index) => (index === calIndex ? null : {
+        status: 'error',
+        message: 'Batch photo was not processed',
+      }));
+
+      // Process serially so each worker owns exactly one sibling photo and a
+      // failing decode/mask/encode cannot prevent later siblings from running.
+      for (let index = 0; index < batch.length; index++) {
+        if (index === calIndex) continue;
+        const photo = batch[index];
+        try {
+          const derived = await rederiveMaskDetailed(photo, params, {
+            slabPx: 0,
+            bbox: EMPTY_BBOX,
+            slabBounds: EMPTY_ABOX,
+          });
+          if (derived.mask.slabPx === 0) {
+            throw new Error('empty mask: no slab pixels detected');
+          }
+          const siblingSource: Source = {
+            ...photo,
+            widthPx: derived.widthPx,
+            heightPx: derived.heightPx,
+          };
+          const siblingBitmap = await decodeOrientedBitmap(photo.blob);
+          let encoded: { blob: Blob; sourceBelowFloor: boolean };
+          try {
+            encoded = await encodeInventory({ bitmap: siblingBitmap, mask: derived.mask, source: siblingSource });
+          } finally {
+            siblingBitmap.close();
+          }
+          if (encoded.sourceBelowFloor) {
+            throw new Error('PNG size floor: shorter side is below 800 px');
+          }
+          batchApply[index] = { status: 'ok', inventoryPng: encoded.blob };
+        } catch (error) {
+          const message = error instanceof Error ? error.message : 'unable to process photo';
+          batchApply[index] = { status: 'error', message };
+        }
+      }
+
+      set({ ...state, results, batchApply });
+      void persist();
+    },
+
+    back() {
+      if (state.k === 'pickCalibration') {
+        calibrationIndex = null;
+        set({ k: 'batch', photos: [...batchPhotos] });
+        void persist();
+      } else if (state.k === 'mask') {
+        teardownWorker();
+        calibrationIndex = null;
+        set({ k: 'pickCalibration', photos: [...batchPhotos] });
+        void persist();
+      } else if (state.k === 'axis') {
+        // back to mask keeps the last approved mask as the live overlay
+        const m = state.approvedMask;
+        set({ k: 'mask', source: state.source, control: m.params, overlay: m, failed: false });
+      } else if (state.k === 'measure') {
+        set({ k: 'axis', source: state.source, approvedMask: state.approvedMask, axis: { bbox: state.axis.bbox } });
+      }
+    },
+
+    getInventoryUrl() {
+      return pngUrl;
+    },
+
+    dispose() {
+      teardownWorker();
+    },
+  };
+}
+
+// Display helper: format eighths as inches with fractions.
+export function fmtEighths(e: Eighths): string {
+  const whole = Math.floor(eighthsToIn(e));
+  const rem = e - whole * 8;
+  if (rem === 0) return `${whole}"`;
+  const frac: Record<number, string> = { 1: '1/8', 2: '1/4', 3: '3/8', 4: '1/2', 5: '5/8', 6: '3/4', 7: '7/8' };
+  const part = frac[rem] ?? `${rem}/8`;
+  return whole > 0 ? `${whole} ${part}"` : `${part}"`;
+}

frontend/src/decodeOrientedBitmap.ts

@@ -0,0 +1,29 @@
+/**
+ * Shared decode for capture photos so PhotoStage, mask worker, inventory, and
+ * calculate all share one EXIF-oriented pixel space.
+ *
+ * Matched-set / DJI JPEGs often carry EXIF Orientation 8 (stored landscape,
+ * display portrait). `new Image()` and bare `createImageBitmap(blob)` can
+ * disagree across browsers → pink axis arrow space ≠ mask/overlay bitset space.
+ *
+ * Contract: always request `imageOrientation: 'from-image'`. If the runtime
+ * rejects that option (older engines), fall back to bare `createImageBitmap`;
+ * engines that already apply EXIF by default still match Image/canvas size.
+ * Engines that never apply EXIF may still diverge after fallback — document
+ * that path rather than inventing a software rotate.
+ */
+export const ORIENTED_BITMAP_OPTIONS: ImageBitmapOptions = {
+  imageOrientation: 'from-image',
+};
+
+export async function decodeOrientedBitmap(blob: Blob): Promise<ImageBitmap> {
+  try {
+    return await createImageBitmap(blob, ORIENTED_BITMAP_OPTIONS);
+  } catch (first) {
+    try {
+      return await createImageBitmap(blob);
+    } catch {
+      throw first;
+    }
+  }
+}

frontend/src/draft/idb.ts

@@ -0,0 +1,25 @@
+import { get, set, del } from 'idb-keyval';
+import type { Draft } from '../capture/capture.types';
+
+const KEY = 'slabuploader-draft';
+
+export async function loadDraft(): Promise<Draft | null> {
+  try {
+    const d = await get<Draft>(KEY);
+    return d && d.version === 1 ? d : null;
+  } catch {
+    return null;
+  }
+}
+
+export async function saveDraft(d: Draft): Promise<void> {
+  await set(KEY, d);
+}
+
+export async function clearDraft(): Promise<void> {
+  try {
+    await del(KEY);
+  } catch {
+    // idb unavailable: draft persistence is best-effort, app state is not
+  }
+}

frontend/src/geometry/rect.test.ts

@@ -0,0 +1,51 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { minAreaRect, orientedRect, maskSpanAlong } from './rect.ts';
+import { measure } from '../measure/measure.ts';
+
+// 100×20 horizontal slab
+const W = 100, H = 20;
+const bitset = new Uint8Array(W * H);
+for (let x = 0; x < W; x++) for (let y = 0; y < H; y++) bitset[y * W + x] = 1;
+
+test('maskSpanAlong of a 100×20 slab: X ≈ 99–100, Y ≈ 19–20', () => {
+  const sx = maskSpanAlong(bitset, W, H, 1, 0);
+  const sy = maskSpanAlong(bitset, W, H, 0, 1);
+  assert.ok(sx >= 99 && sx <= 100, `spanX ${sx}`);
+  assert.ok(sy >= 19 && sy <= 20, `spanY ${sy}`);
+});
+
+test('orientedRect changes angleDeg and preserves longSidePx', () => {
+  const prev = minAreaRect(bitset, W, H);
+  assert.ok(prev, 'minAreaRect returned a box');
+  const rotated = orientedRect(prev, 45);
+  assert.ok(Math.abs(rotated.angleDeg - 45) < 1e-9);
+  assert.equal(rotated.longSidePx, prev.longSidePx);
+  // The long side (angleDeg 0 → +x) must be preserved by the rotation.
+  const longOf = (c) => Math.hypot(c[3][0] - c[0][0], c[3][1] - c[0][1]);
+  assert.ok(Math.abs(longOf(rotated.corners) - longOf(prev.corners)) < 1e-9);
+  assert.ok(Math.abs(longOf(prev.corners) - prev.longSidePx) < 1e-9);
+  // angle normalization to [0, 180)
+  assert.ok(orientedRect(prev, 190).angleDeg >= 0 && orientedRect(prev, 190).angleDeg < 180);
+});
+
+test('measure scale uses mask span along the axis, not longSidePx', () => {
+  // Thin slab (20 long, 100 wide): minAreaRect's long side (angleDeg 90) is
+  // the 100-px dimension along +y. Rotate the axis to angleDeg 0 (+x), which
+  // crosses only the 20-px slab width — span 19, not longSidePx 99.
+  const TW = 20, TH = 100;
+  const thin = new Uint8Array(TW * TH).fill(1);
+  const thinBox = minAreaRect(thin, TW, TH);
+  assert.ok(thinBox && thinBox.longSidePx >= 99, `longSide ${thinBox?.longSidePx}`);
+  const rotated = orientedRect(thinBox, 0);
+  const lengthEighths = 24; // 3 in
+  const m = measure(thin, TW, TH, rotated, lengthEighths, 8, TW * TH);
+  // Scale = span along the axis / length. Span ≈ 19 → scale ≈ 6.3 px/in,
+  // far from the old longSidePx/3 ≈ 33.
+  const ex = rotated.corners[0][0] - rotated.corners[3][0];
+  const ey = rotated.corners[0][1] - rotated.corners[3][1];
+  const elen = Math.hypot(ex, ey);
+  const span = maskSpanAlong(thin, TW, TH, ex / elen, ey / elen);
+  assert.ok(Math.abs(m.scale - span / (lengthEighths / 8)) < 1e-9);
+  assert.ok(m.scale < 10, `scale ${m.scale} should be span-based, not ${thinBox.longSidePx / 3}`);
+});

frontend/src/geometry/rect.ts

@@ -0,0 +1,130 @@
+import type { ABox, BBox } from '../capture/capture.types';
+
+export function slabBounds(bitset: Uint8Array, w: number, h: number): ABox {
+  let minX = w, minY = h, maxX = -1, maxY = -1;
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) {
+      if (bitset[row + x]) {
+        if (x < minX) minX = x;
+        if (x > maxX) maxX = x;
+        if (y < minY) minY = y;
+        if (y > maxY) maxY = y;
+      }
+    }
+  }
+  if (maxX < 0) return { x: 0, y: 0, w: 0, h: 0 };
+  return { x: minX, y: minY, w: maxX - minX + 1, h: maxY - minY + 1 };
+}
+
+// Convex hull (Andrew's monotone chain). Points are [x, y].
+export function convexHull(pts: [number, number][]): [number, number][] {
+  const p = [...pts].sort((a, b) => a[0] - b[0] || a[1] - b[1]);
+  if (p.length < 3) return p;
+  const cross = (o: [number, number], a: [number, number], b: [number, number]) =>
+    (a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0]);
+  const lower: [number, number][] = [];
+  for (const pt of p) {
+    while (lower.length >= 2 && cross(lower[lower.length - 2], lower[lower.length - 1], pt) <= 0) lower.pop();
+    lower.push(pt);
+  }
+  const upper: [number, number][] = [];
+  for (let i = p.length - 1; i >= 0; i--) {
+    const pt = p[i];
+    while (upper.length >= 2 && cross(upper[upper.length - 2], upper[upper.length - 1], pt) <= 0) upper.pop();
+    upper.push(pt);
+  }
+  lower.pop();
+  upper.pop();
+  return lower.concat(upper);
+}
+
+// Rotating calipers: true minimum-area bounding rectangle of the mask.
+export function minAreaRect(bitset: Uint8Array, w: number, h: number): BBox | null {
+  const pts: [number, number][] = [];
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) if (bitset[row + x]) pts.push([x, y]);
+  }
+  if (pts.length < 2) return null;
+  const hull = convexHull(pts);
+
+  let best = { area: Infinity, cx: 0, cy: 0, ux: 1, uy: 0, hw: 0, hh: 0 };
+  const n = hull.length;
+  for (let i = 0; i < n; i++) {
+    const j = (i + 1) % n;
+    const ex = hull[j][0] - hull[i][0];
+    const ey = hull[j][1] - hull[i][1];
+    const len = Math.hypot(ex, ey);
+    if (len === 0) continue;
+    const ux = ex / len, uy = ey / len;
+    const vx = -uy, vy = ux;
+    let minU = Infinity, maxU = -Infinity, minV = Infinity, maxV = -Infinity;
+    for (let k = 0; k < n; k++) {
+      const dx = hull[k][0] - hull[i][0];
+      const dy = hull[k][1] - hull[i][1];
+      const u = dx * ux + dy * uy;
+      const v = dx * vx + dy * vy;
+      if (u < minU) minU = u;
+      if (u > maxU) maxU = u;
+      if (v < minV) minV = v;
+      if (v > maxV) maxV = v;
+    }
+    const rw = maxU - minU;
+    const rh = maxV - minV;
+    const area = rw * rh;
+    if (area < best.area) {
+      best = { area, cx: hull[i][0] + (minU + maxU) / 2 * ux + (minV + maxV) / 2 * vx, cy: hull[i][1] + (minU + maxU) / 2 * uy + (minV + maxV) / 2 * vy, ux, uy, hw: rw / 2, hh: rh / 2 };
+    }
+  }
+
+  // long-side direction: the edge with the larger extent
+  const lu = best.hw >= best.hh ? best.ux : -best.uy;
+  const lv = best.hw >= best.hh ? best.uy : best.ux;
+  const su = best.hw >= best.hh ? -best.uy : best.ux;
+  const sv = best.hw >= best.hh ? -best.ux : -best.uy;
+  const halfL = best.hw >= best.hh ? best.hw : best.hh;
+  const halfS = best.hw >= best.hh ? best.hh : best.hw;
+  const corners: [number, number][] = [];
+  for (const [a, b] of [[1, 1], [1, -1], [-1, -1], [-1, 1]] as const) {
+    corners.push([best.cx + a * halfL * lu + b * halfS * su, best.cy + a * halfL * lv + b * halfS * sv]);
+  }
+  const angleDeg = ((Math.atan2(lv, lu) * 180) / Math.PI + 180) % 180;
+  return { corners, longSidePx: halfL * 2, angleDeg };
+}
+
+// Rotate the long side to a new angle, keeping center and half-extents.
+// Corners are rebuilt in minAreaRect order so corners[3] → corners[0] stays the
+// long side (the axis arrow direction).
+export function orientedRect(prev: BBox, angleDeg: number): BBox {
+  const a = ((angleDeg % 180) + 180) % 180;
+  const halfL = prev.longSidePx / 2;
+  const halfS = Math.hypot(prev.corners[0][0] - prev.corners[1][0], prev.corners[0][1] - prev.corners[1][1]) / 2;
+  // corners[i] is a corner point: average of all four = center
+  const cx = (prev.corners[0][0] + prev.corners[1][0] + prev.corners[2][0] + prev.corners[3][0]) / 4;
+  const cy = (prev.corners[0][1] + prev.corners[1][1] + prev.corners[2][1] + prev.corners[3][1]) / 4;
+  const r = (a * Math.PI) / 180;
+  const lu = Math.cos(r), lv = Math.sin(r);
+  const su = -lv, sv = lu;
+  const corners: [number, number][] = [];
+  for (const [aSign, bSign] of [[1, 1], [1, -1], [-1, -1], [-1, 1]] as const) {
+    corners.push([cx + aSign * halfL * lu + bSign * halfS * su, cy + aSign * halfL * lv + bSign * halfS * sv]);
+  }
+  return { corners, longSidePx: prev.longSidePx, angleDeg: a };
+}
+
+// Project every slab pixel onto the unit vector (ux, uy); return max − min
+// extent in px. 0 when the mask is empty.
+export function maskSpanAlong(bitset: Uint8Array, w: number, h: number, ux: number, uy: number): number {
+  let min = Infinity, max = -Infinity;
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) {
+      if (!bitset[row + x]) continue;
+      const p = x * ux + y * uy;
+      if (p < min) min = p;
+      if (p > max) max = p;
+    }
+  }
+  return max < min ? 0 : max - min;
+}

frontend/src/main.ts

@@ -0,0 +1,4 @@
+import App from './App.svelte';
+
+const root = document.querySelector('#app');
+if (root) new App({ target: root });

frontend/src/mask/sheetKeep.test.ts

@@ -0,0 +1,59 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { blackKeep, greenKeep } from './sheetKeep.ts';
+
+// --- Black sheet sensitivity (#74) ---
+
+test('blackKeep: s=0 keeps dark live-edge wood (lum ~25–50), removes near-black sheet (#74)', () => {
+  // Near-black sheet (lum ≈ 5)
+  assert.equal(blackKeep(5, 5, 5, 0), false, 'near-black sheet removed at s=0');
+  assert.equal(blackKeep(0, 0, 0, 0), false, 'pure black sheet removed at s=0');
+  // Dark wood / bark / live edge
+  assert.equal(blackKeep(25, 22, 18, 0), true, 'lum~22 dark wood kept at s=0');
+  assert.equal(blackKeep(40, 35, 30, 0), true, 'lum~35 dark wood kept at s=0');
+  assert.equal(blackKeep(50, 45, 40, 0), true, 'lum~46 wood kept at s=0');
+  // Mid wood always kept
+  assert.equal(blackKeep(120, 90, 60, 0), true, 'mid wood kept at s=0');
+});
+
+test('blackKeep: s=100 removes more than s=0; curve monotonic (#74)', () => {
+  // Dark-ish pixel that sits between floors: sheet at high s, wood at low s
+  const darkish = { r: 80, g: 70, b: 60 }; // lum ≈ 72
+  assert.equal(blackKeep(darkish.r, darkish.g, darkish.b, 0), true, 'lum~72 kept at s=0');
+  assert.equal(blackKeep(darkish.r, darkish.g, darkish.b, 100), false, 'lum~72 sheet at s=100');
+
+  // Near-black always sheet
+  assert.equal(blackKeep(2, 2, 2, 0), false);
+  assert.equal(blackKeep(2, 2, 2, 100), false);
+
+  // Bright wood always kept
+  assert.equal(blackKeep(200, 160, 100, 0), true);
+  assert.equal(blackKeep(200, 160, 100, 100), true);
+
+  // Monotonic: once removed, stays removed as s increases
+  const probe = { r: 60, g: 55, b: 50 }; // lum ≈ 56
+  let prevKeep = true;
+  for (const s of [0, 25, 50, 75, 100]) {
+    const keep = blackKeep(probe.r, probe.g, probe.b, s);
+    if (!prevKeep) assert.equal(keep, false, `once sheet at lower s, stay sheet at s=${s}`);
+    prevKeep = keep;
+  }
+  // s=100 must remove more pixels than s=0 for this mid-dark band
+  assert.equal(blackKeep(probe.r, probe.g, probe.b, 0), true);
+  assert.equal(blackKeep(probe.r, probe.g, probe.b, 100), false);
+});
+
+test('greenKeep: s=0 does not eat mild wood greens; s=100 widens sheet match (#74)', () => {
+  // Neutral wood
+  assert.equal(greenKeep(140, 110, 80, 0), true);
+  assert.equal(greenKeep(140, 110, 80, 100), true);
+  // Mild green cast on wood (g - max(r,b) ≈ 5) — must keep at s=0
+  assert.equal(greenKeep(100, 105, 90, 0), true, 'mild green cast kept at s=0');
+  // Strong sheet green
+  assert.equal(greenKeep(40, 180, 50, 0), false, 'strong green sheet removed at s=0');
+  assert.equal(greenKeep(40, 180, 50, 100), false);
+  // Borderline: g-max ≈ 20 — may become sheet at high s
+  const border = { r: 80, g: 100, b: 70 }; // delta = 20
+  assert.equal(greenKeep(border.r, border.g, border.b, 0), true, 'delta20 kept at s=0');
+  assert.equal(greenKeep(border.r, border.g, border.b, 100), false, 'delta20 sheet at s=100');
+});

frontend/src/mask/sheetKeep.ts

@@ -0,0 +1,36 @@
+/**
+ * Sheet-vs-slab keep predicates used by the mask worker.
+ * Extracted so unit tests can cover sensitivity curves without the worker.
+ */
+
+/** Keep slab pixels on a green sheet. Higher s widens the green-sheet match. */
+export function greenKeep(r: number, g: number, b: number, s: number): boolean {
+  const t = Math.max(0, Math.min(100, s)) / 100;
+  // s=0 removes only strongly green sheet; increasing sensitivity widens the match.
+  const isSheet = g - Math.max(r, b) > 45 - 35 * t;
+  return !isSheet;
+}
+
+/**
+ * Keep slab pixels on a black sheet.
+ * At s=0 only near-black sheet (very low lum) is removed so dark live-edge /
+ * bark (lum ~25–50) stays. The match widens monotonically toward s=100 (#74).
+ */
+export function blackKeep(r: number, g: number, b: number, s: number): boolean {
+  const t = Math.max(0, Math.min(100, s)) / 100;
+  const lum = 0.2126 * r + 0.7152 * g + 0.0722 * b;
+  // Old floor 40 ate dark wood at minimum sensitivity. Floor 10 isolates near-black.
+  const isSheet = lum < 10 + 140 * t;
+  return !isSheet;
+}
+
+export function autoPickSheet(
+  samples: { r: number; g: number; b: number }[],
+): 'green' | 'black' {
+  let gr = 0, gl = 0;
+  for (const p of samples) {
+    if (p.g - Math.max(p.r, p.b) > 20) gr++;
+    if (0.2126 * p.r + 0.7152 * p.g + 0.0722 * p.b < 70) gl++;
+  }
+  return gl >= gr ? 'black' : 'green';
+}

frontend/src/measure/measure.test.ts

@@ -0,0 +1,58 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { minAreaRect, orientedRect } from '../geometry/rect.ts';
+import { measure } from './measure.ts';
+
+// Uniform slab, 10 px/in: full W×H canvas, axis +x via minAreaRect angle 0.
+function uniform(W: number, H: number) {
+  const bitset = new Uint8Array(W * H).fill(1);
+  const box = orientedRect(minAreaRect(bitset, W, H)!, 0);
+  return { bitset, box, slabPx: W * H };
+}
+
+// Tapered slab, 10 px/in: tips under 6 in and past L−6 in are `tipPx` wide
+// (centered), the bulk is full canvas height.
+function tapered(W: number, H: number, lengthEighths: number, tipPx: number) {
+  const inIn = W / 10;
+  const bitset = new Uint8Array(W * H);
+  const half = tipPx / 2;
+  for (let x = 0; x < W; x++) {
+    const p = x / 10;
+    const w = p < 6 || p > inIn - 6 ? tipPx : H;
+    for (let y = (H - w) / 2; y < (H + w) / 2; y++) bitset[y * W + x] = 1;
+  }
+  const box = orientedRect(minAreaRect(bitset, W, H)!, 0);
+  return { bitset, box, slabPx: bitset.reduce((a, c) => a + c, 0), lengthEighths };
+}
+
+test('tapered 48in slab: min/max reflect the bulk, tips excluded', () => {
+  const { bitset, box, slabPx, lengthEighths } = tapered(480, 100, 384, 20); // tips 2in, bulk 10in
+  const m = measure(bitset, 480, 100, box, lengthEighths, 8, slabPx);
+  assert.equal(m.widths.every6In.length, 7, `stations ${m.widths.every6In.length} (6..42in)`);
+  for (const e of m.widths.every6In) {
+    assert.ok(e >= 76 && e <= 84, `station ${e / 8}in must be bulk (~10in)`);
+  }
+  assert.ok(m.widths.min >= 76 && m.widths.min <= 84, `min ${m.widths.min / 8}in`);
+  assert.ok(m.widths.max >= 76 && m.widths.max <= 84, `max ${m.widths.max / 8}in`);
+});
+
+test('uniform slab: interior stations keep the full width', () => {
+  const { bitset, box, slabPx } = uniform(480, 100);
+  const m = measure(bitset, 480, 100, box, 384, 8, slabPx);
+  assert.equal(m.widths.every6In.length, 7);
+  for (const e of m.widths.every6In) {
+    assert.ok(e >= 72 && e <= 104, `station ${e / 8}in`);
+  }
+});
+
+test('short slab L=12in: no interior stations, widths are empty/zero', () => {
+  const { bitset, box, slabPx } = uniform(120, 100);
+  const m = measure(bitset, 120, 100, box, 96, 8, slabPx);
+  assert.deepEqual(m.widths, { min: 0, max: 0, avg: 0, every6In: [] });
+});
+
+test('short slab L=10in: no interior stations, widths are empty/zero', () => {
+  const { bitset, box, slabPx } = uniform(100, 100);
+  const m = measure(bitset, 100, 100, box, 80, 8, slabPx);
+  assert.deepEqual(m.widths, { min: 0, max: 0, avg: 0, every6In: [] });
+});

frontend/src/measure/measure.ts

@@ -0,0 +1,104 @@
+import type { BBox, Eighths, Measures, Widths } from '../capture/capture.types';
+import { maskSpanAlong } from '../geometry/rect';
+
+// Display / direction: corners[3] → corners[0] is the long side.
+export function axisEndpoints(bbox: BBox): { start: [number, number]; end: [number, number] } {
+  return { start: bbox.corners[3], end: bbox.corners[0] };
+}
+
+// Wood end→end along the approved direction: project the mask onto the axis
+// unit vector and return the segment on the bbox center line covering that span.
+function maskAxisSegment(
+  bitset: Uint8Array, w: number, h: number, bbox: BBox,
+): { start: [number, number]; end: [number, number]; span: number; ux: number; uy: number } {
+  const { start: a, end: b } = axisEndpoints(bbox);
+  const ex = b[0] - a[0];
+  const ey = b[1] - a[1];
+  const elen = Math.hypot(ex, ey) || 1;
+  const ux = ex / elen, uy = ey / elen;
+  const cx = (bbox.corners[0][0] + bbox.corners[1][0] + bbox.corners[2][0] + bbox.corners[3][0]) / 4;
+  const cy = (bbox.corners[0][1] + bbox.corners[1][1] + bbox.corners[2][1] + bbox.corners[3][1]) / 4;
+  const cProj = cx * ux + cy * uy;
+  let minP = Infinity, maxP = -Infinity;
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) {
+      if (!bitset[row + x]) continue;
+      const p = x * ux + y * uy;
+      if (p < minP) minP = p;
+      if (p > maxP) maxP = p;
+    }
+  }
+  if (maxP < minP) return { start: a, end: b, span: 0, ux, uy };
+  return {
+    start: [cx + ux * (minP - cProj), cy + uy * (minP - cProj)],
+    end: [cx + ux * (maxP - cProj), cy + uy * (maxP - cProj)],
+    span: maxP - minP,
+    ux,
+    uy,
+  };
+}
+
+// Interior stations only (6, 12, … ≤ L−6). Tips dominate min/max on tapered
+// boards, so the first and last 6 in are excluded. Each sample is a line
+// probe perpendicular to the axis; width = max run of slab px across it.
+function sampleWidths(
+  bitset: Uint8Array, w: number, h: number,
+  start: [number, number], ux: number, uy: number,
+  scale: number, lengthIn: number,
+): Eighths[] {
+  const px = -uy, py = ux;
+  const stepPx = 6 * scale;
+  const lastPx = lengthIn > 12 ? Math.floor((lengthIn - 6) / 6) * 6 * scale : 0;
+  const out: Eighths[] = [];
+  const half = Math.max(2, Math.round((w + h) / 4));
+  for (let t = stepPx; t <= lastPx; t += stepPx) {
+    const ox = start[0] + ux * t;
+    const oy = start[1] + uy * t;
+    let minP = Infinity, maxP = -Infinity;
+    for (let p = -half; p <= half; p++) {
+      const x = Math.round(ox + px * p);
+      const y = Math.round(oy + py * p);
+      if (x < 0 || y < 0 || x >= w || y >= h) continue;
+      if (bitset[y * w + x]) {
+        if (p < minP) minP = p;
+        if (p > maxP) maxP = p;
+      }
+    }
+    if (maxP < minP) continue;
+    out.push(Math.max(0, Math.round(((maxP - minP + 1) / scale) * 8)));
+  }
+  return out;
+}
+
+export function measure(
+  bitset: Uint8Array, w: number, h: number,
+  bbox: BBox,
+  lengthEighths: Eighths, thicknessEighths: Eighths,
+  slabPx: number,
+): Omit<Measures, 'inventoryPng'> & { sourceBelowFloor: false } {
+  const lengthIn = lengthEighths / 8;
+  const seg = maskAxisSegment(bitset, w, h, bbox);
+  const scale = (seg.span || maskSpanAlong(bitset, w, h, seg.ux, seg.uy)) / lengthIn;
+  const every6In = sampleWidths(bitset, w, h, seg.start, seg.ux, seg.uy, scale, lengthIn);
+  let widths: Widths;
+  if (every6In.length > 0) {
+    const min = Math.min(...every6In);
+    const max = Math.max(...every6In);
+    const avg = Math.round(every6In.reduce((a, b) => a + b, 0) / every6In.length);
+    widths = { min, max, avg, every6In };
+  } else {
+    widths = { min: 0, max: 0, avg: 0, every6In: [] };
+  }
+  const sqft = Math.round((slabPx / (scale * scale) / 144) * 100) / 100;
+  const bdft = Math.round(sqft * (thicknessEighths / 8) * 100) / 100;
+  return {
+    lengthEighths,
+    thicknessEighths,
+    scale,
+    widths,
+    sqft,
+    bdft,
+    sourceBelowFloor: false,
+  };
+}

frontend/src/png/inventory.test.ts

@@ -0,0 +1,120 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { composeInventoryFrame } from './inventory.ts';
+import type { Mask, Source } from '../capture/capture.types';
+
+const makePhoto = (w: number, h: number, paint: (x: number, y: number) => [number, number, number, number] = () => [255, 255, 255, 255]) => {
+  const rgba = new Uint8Array(w * h * 4);
+  for (let y = 0; y < h; y++) {
+    for (let x = 0; x < w; x++) {
+      const [r, g, b, a] = paint(x, y);
+      const i = (y * w + x) * 4;
+      rgba[i] = r; rgba[i + 1] = g; rgba[i + 2] = b; rgba[i + 3] = a;
+    }
+  }
+  return { width: w, height: h, rgba };
+};
+
+const maskFor = (bitset: Uint8Array, slabBounds: Mask['slabBounds']): Pick<Mask, 'bitset' | 'slabBounds'> =>
+  ({ bitset, slabBounds });
+
+test('alpha contract: removed pixels transparent, slab pixels keep RGB at alpha 255', () => {
+  const W = 8, H = 8;
+  const bitset = new Uint8Array(W * H);
+  for (let y = 1; y < 5; y++) for (let x = 1; x < 5; x++) bitset[y * W + x] = 1;
+  bitset[2 * W + 2] = 0;
+  bitset[3 * W + 3] = 0;
+  const SLAB = [200, 40, 20, 255] as const;
+  const SHEET = [0, 255, 0, 255] as const;
+  const src = makePhoto(W, H, (x, y) => (bitset[y * W + x] === 1 ? [...SLAB] : [...SHEET]));
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: W, heightPx: H };
+  const out = composeInventoryFrame(src, maskFor(bitset, { x: 1, y: 1, w: 4, h: 4 }), source);
+
+  assert.equal(out.sourceBelowFloor, true);
+  assert.ok(out.width < 800, 'undersized source stays small');
+
+  let opaque = 0;
+  let transparent = 0;
+  for (let i = 0; i < out.rgba.length; i += 4) {
+    const a = out.rgba[i + 3];
+    if (a === 0) {
+      transparent++;
+      assert.equal(out.rgba[i], 0);
+      assert.equal(out.rgba[i + 1], 0);
+      assert.equal(out.rgba[i + 2], 0);
+      continue;
+    }
+    opaque++;
+    assert.equal(a, 255);
+    assert.deepEqual(
+      [out.rgba[i], out.rgba[i + 1], out.rgba[i + 2]],
+      [SLAB[0], SLAB[1], SLAB[2]],
+      'opaque pixel must be slab RGB, never sheet green',
+    );
+  }
+  assert.ok(opaque > 0, 'slab pixels are opaque');
+  assert.ok(transparent > 0, 'frame has transparent pixels');
+});
+
+test('3:4 frame at the floor: 2000×1800 slab → 800×1067', () => {
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 2000, heightPx: 1800 };
+  const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
+  const out = composeInventoryFrame(
+    makePhoto(source.widthPx, source.heightPx),
+    maskFor(bitset, { x: 0, y: 0, w: 2000, h: 1800 }),
+    source,
+  );
+  assert.equal(out.width, 800);
+  assert.equal(out.height, 1067);
+  assert.equal(out.sourceBelowFloor, false);
+});
+
+test('mid-band: slab shorter side 1000 (between 800 and 1600) → at floor, not belowFloor', () => {
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 1200, heightPx: 1000 };
+  const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
+  const out = composeInventoryFrame(
+    makePhoto(source.widthPx, source.heightPx),
+    maskFor(bitset, { x: 0, y: 0, w: 1200, h: 1000 }),
+    source,
+  );
+  assert.equal(out.sourceBelowFloor, false);
+  assert.equal(out.width, 800);
+});
+
+test('90% fill: limiting dimension maps to 0.9 × frame side (#68)', () => {
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 2200, heightPx: 2000 };
+  const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
+  const out = composeInventoryFrame(
+    makePhoto(source.widthPx, source.heightPx),
+    maskFor(bitset, { x: 100, y: 100, w: 2000, h: 1800 }),
+    source,
+  );
+  let minx = out.width, maxx = -1, miny = out.height, maxy = -1;
+  for (let y = 0; y < out.height; y++) {
+    for (let x = 0; x < out.width; x++) {
+      if (out.rgba[(y * out.width + x) * 4 + 3] !== 0) {
+        if (x < minx) minx = x;
+        if (x > maxx) maxx = x;
+        if (y < miny) miny = y;
+        if (y > maxy) maxy = y;
+      }
+    }
+  }
+  const xs = [minx, maxx], ys = [miny, maxy];
+  const wExtent = Math.max(...xs) - Math.min(...xs) + 1;
+  const hExtent = Math.max(...ys) - Math.min(...ys) + 1;
+  assert.ok(Math.abs(wExtent - 720) <= 2, `width extent ${wExtent} ≈ 720 (0.9×800)`);
+  assert.ok(Math.abs(hExtent - 648) <= 2, `height extent ${hExtent} ≈ 648 (1800×0.36)`);
+});
+
+test('belowFloor: small slab → sourceBelowFloor, outW capped at floor (no upscale)', () => {
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: 900, heightPx: 700 };
+  const bitset = new Uint8Array(source.widthPx * source.heightPx).fill(1);
+  const out = composeInventoryFrame(
+    makePhoto(source.widthPx, source.heightPx),
+    maskFor(bitset, { x: 0, y: 0, w: 900, h: 700 }),
+    source,
+  );
+  assert.equal(out.sourceBelowFloor, true);
+  assert.ok(out.width <= 800, `outW ${out.width} must not exceed the floor`);
+});

frontend/src/png/inventory.ts

@@ -0,0 +1,83 @@
+import type { Mask, Source } from '../capture/capture.types';
+
+const FLOOR = 800; // shorter side, px
+const FILL = 0.9; // 90% fill at the widest and tallest points of the slab
+const ASPECT_W = 3;
+const ASPECT_H = 4;
+
+type MaskPick = Pick<Mask, 'bitset' | 'slabBounds'>;
+type SourcePick = Pick<Source, 'widthPx' | 'heightPx'>;
+
+export interface InventoryInput {
+  bitmap: ImageBitmap;
+  mask: MaskPick;
+  source: SourcePick;
+}
+
+export interface Frame {
+  width: number;
+  height: number;
+  rgba: Uint8Array;
+  sourceBelowFloor: boolean;
+}
+
+export function composeInventoryFrame(
+  src: { width: number; height: number; rgba: Uint8Array | Uint8ClampedArray },
+  mask: MaskPick,
+  source: SourcePick,
+): Frame {
+  const b = mask.slabBounds;
+  const x0 = Math.max(0, Math.round(b.x));
+  const y0 = Math.max(0, Math.round(b.y));
+  const x1 = Math.min(source.widthPx, x0 + Math.max(1, Math.round(b.w)));
+  const y1 = Math.min(source.heightPx, y0 + Math.max(1, Math.round(b.h)));
+  const sw = x1 - x0;
+  const sh = y1 - y0;
+  const belowFloor = Math.min(sw, sh) < FLOOR;
+  const outW = belowFloor ? Math.max(1, Math.min(sw, FLOOR)) : FLOOR;
+  const outH = Math.round((outW * ASPECT_H) / ASPECT_W);
+  const scale = Math.min((outW * FILL) / Math.max(sw, 1), (outH * FILL) / Math.max(sh, 1));
+  const dw = sw * scale;
+  const dh = sh * scale;
+  const ox = (outW - dw) / 2;
+  const oy = (outH - dh) / 2;
+  const rgba = new Uint8Array(outW * outH * 4);
+  const xEnd = ox + dw;
+  const yEnd = oy + dh;
+  for (let y = 0; y < outH; y++) {
+    for (let x = 0; x < outW; x++) {
+      if (x + 0.5 < ox || x + 0.5 >= xEnd || y + 0.5 < oy || y + 0.5 >= yEnd) continue;
+      const sx = Math.floor(x0 + (x + 0.5 - ox) / scale);
+      const sy = Math.floor(y0 + (y + 0.5 - oy) / scale);
+      if (sx < 0 || sy < 0 || sx >= source.widthPx || sy >= source.heightPx) continue;
+      if (mask.bitset[sy * source.widthPx + sx] !== 1) continue;
+      const si = (sy * source.widthPx + sx) * 4;
+      const di = (y * outW + x) * 4;
+      rgba[di] = src.rgba[si];
+      rgba[di + 1] = src.rgba[si + 1];
+      rgba[di + 2] = src.rgba[si + 2];
+      rgba[di + 3] = 255;
+    }
+  }
+  return { width: outW, height: outH, rgba, sourceBelowFloor: belowFloor };
+}
+
+export async function encodeInventoryPng(
+  input: InventoryInput,
+): Promise<{ blob: Blob; sourceBelowFloor: boolean }> {
+  const { bitmap, mask, source } = input;
+  const srcCanvas = new OffscreenCanvas(source.widthPx, source.heightPx);
+  const srcCtx = srcCanvas.getContext('2d')!;
+  srcCtx.drawImage(bitmap, 0, 0);
+  const img = srcCtx.getImageData(0, 0, source.widthPx, source.heightPx);
+  const frame = composeInventoryFrame(
+    { width: source.widthPx, height: source.heightPx, rgba: img.data },
+    mask,
+    source,
+  );
+  const out = new OffscreenCanvas(frame.width, frame.height);
+  const ctx = out.getContext('2d')!;
+  ctx.putImageData(new ImageData(new Uint8ClampedArray(frame.rgba), frame.width, frame.height), 0, 0);
+  const blob = await out.convertToBlob({ type: 'image/png' });
+  return { blob, sourceBelowFloor: frame.sourceBelowFloor };
+}

frontend/src/png/overlay.ts

@@ -0,0 +1,552 @@
+import type { BBox } from '../capture/capture.types';
+import { axisEndpoints } from '../measure/measure';
+
+/** Width overlay stations: 6, 18, 30, … while ≤ L − 6 (tip-exclusive). */
+export function overlayWidthStations(lengthIn: number): number[] {
+  if (!(lengthIn > 6)) return [];
+  const last = lengthIn - 6;
+  const out: number[] = [];
+  for (let s = 6; s <= last + 1e-9; s += 12) out.push(s);
+  return out;
+}
+
+/**
+ * EXIF-oriented photo bottom = larger canvas y. Pick which end of the approved
+ * length-axis span is bottom; return unit from bottom → top along that span.
+ */
+export function pickBottomTowardTop(
+  start: [number, number],
+  end: [number, number],
+): {
+  bottom: [number, number];
+  top: [number, number];
+  ux: number;
+  uy: number;
+} {
+  // Larger y is closer to the bottom edge of the oriented photo.
+  // Tie-break (horizontal axis): prefer larger x for a stable choice.
+  const startIsBottom =
+    start[1] > end[1] || (start[1] === end[1] && start[0] >= end[0]);
+  const bottom = startIsBottom ? start : end;
+  const top = startIsBottom ? end : start;
+  const dx = top[0] - bottom[0];
+  const dy = top[1] - bottom[1];
+  const len = Math.hypot(dx, dy) || 1;
+  return { bottom, top, ux: dx / len, uy: dy / len };
+}
+
+/** Screen-space right of travel (canvas y↓): (ux,uy) → (−uy, ux). */
+export function axisRightUnit(ux: number, uy: number): [number, number] {
+  return [-uy, ux];
+}
+
+export interface OverlayWidthMark {
+  stationIn: number;
+  center: [number, number];
+  left: [number, number];
+  right: [number, number];
+  /** Axis-left of the slab, outside the wood edge (opposite of length dim). */
+  labelAt: [number, number];
+  label: string;
+}
+
+export interface OverlayLengthMark {
+  a: [number, number];
+  b: [number, number];
+  labelAt: [number, number];
+  label: string;
+  /** True when the line sits outside the slab on the axis-right side. */
+  outside: boolean;
+}
+
+export interface OverlayPlan {
+  stroke: '#000000';
+  fontPx: number;
+  length: OverlayLengthMark;
+  widths: OverlayWidthMark[];
+}
+
+export interface OverlayPlanInput {
+  bitset: Uint8Array;
+  widthPx: number;
+  heightPx: number;
+  bbox: BBox;
+  scale: number; // px per inch
+  lengthIn: number;
+  lengthLabel: string;
+  /** Map source px → inventory PNG px (identity OK for unit tests). */
+  mapToInventory: (x: number, y: number) => [number, number];
+  /** Inventory PNG size — used to clamp labels inside the canvas (#71). */
+  inventoryW?: number;
+  inventoryH?: number;
+}
+
+/**
+ * Min across-width as a fraction of max bin width for an axial bin to count as a tip.
+ * #71 used 0.32 (excluded fringe); #73 lowers to ~0.15 so tapered live-edge tips remain.
+ */
+export const BODY_WIDTH_FRAC = 0.15;
+
+/**
+ * Axial tip stations from across-width profile (#71/#73).
+ * Thin fringe whiskers past the visible body survive 0.2%/99.8% percentiles;
+ * require each axial bin to have meaningful across-width before it counts as a tip.
+ */
+function widthAwareAxialRange(
+  bitset: Uint8Array,
+  w: number,
+  h: number,
+  ux: number,
+  uy: number,
+  cx: number,
+  cy: number,
+): { minP: number; maxP: number } | null {
+  const rx = -uy;
+  const ry = ux;
+  const binMin = new Map<number, number>();
+  const binMax = new Map<number, number>();
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) {
+      if (!bitset[row + x]) continue;
+      const along = x * ux + y * uy;
+      const across = (x - cx) * rx + (y - cy) * ry;
+      const bin = Math.round(along);
+      const prevMin = binMin.get(bin);
+      if (prevMin === undefined || across < prevMin) binMin.set(bin, across);
+      const prevMax = binMax.get(bin);
+      if (prevMax === undefined || across > prevMax) binMax.set(bin, across);
+    }
+  }
+  if (binMin.size === 0) return null;
+  let maxWidth = 0;
+  const widths: { bin: number; width: number }[] = [];
+  for (const [bin, minA] of binMin) {
+    const maxA = binMax.get(bin)!;
+    const width = maxA - minA + 1;
+    widths.push({ bin, width });
+    if (width > maxWidth) maxWidth = width;
+  }
+  // Body threshold: exclude ~10% fringe whiskers; keep 15–25% live-edge tapers (#73).
+  const thresh = Math.max(4, maxWidth * BODY_WIDTH_FRAC);
+  widths.sort((a, b) => a.bin - b.bin);
+  let tipLo = widths[0].bin;
+  let tipHi = widths[widths.length - 1].bin;
+  for (const { bin, width } of widths) {
+    if (width >= thresh) {
+      tipLo = bin;
+      break;
+    }
+  }
+  for (let i = widths.length - 1; i >= 0; i--) {
+    if (widths[i].width >= thresh) {
+      tipHi = widths[i].bin;
+      break;
+    }
+  }
+  return { minP: tipLo, maxP: tipHi };
+}
+
+function maskAxisSegment(
+  bitset: Uint8Array,
+  w: number,
+  h: number,
+  bbox: BBox,
+): {
+  start: [number, number];
+  end: [number, number];
+  /** Actual mask pixels nearest centerline at tip stations. */
+  tipStart: [number, number];
+  tipEnd: [number, number];
+  ux: number;
+  uy: number;
+  span: number;
+} {
+  const { start: a, end: b } = axisEndpoints(bbox);
+  const ex = b[0] - a[0];
+  const ey = b[1] - a[1];
+  const elen = Math.hypot(ex, ey) || 1;
+  const ux = ex / elen;
+  const uy = ey / elen;
+  const cx = (bbox.corners[0][0] + bbox.corners[1][0] + bbox.corners[2][0] + bbox.corners[3][0]) / 4;
+  const cy = (bbox.corners[0][1] + bbox.corners[1][1] + bbox.corners[2][1] + bbox.corners[3][1]) / 4;
+  const cProj = cx * ux + cy * uy;
+  // Width-aware tips (#71). Fall back to robust percentiles if profile empty.
+  const aware = widthAwareAxialRange(bitset, w, h, ux, uy, cx, cy);
+  let minP: number;
+  let maxP: number;
+  if (aware) {
+    minP = aware.minP;
+    maxP = aware.maxP;
+  } else {
+    const projs: number[] = [];
+    for (let y = 0; y < h; y++) {
+      const row = y * w;
+      for (let x = 0; x < w; x++) {
+        if (!bitset[row + x]) continue;
+        projs.push(x * ux + y * uy);
+      }
+    }
+    if (projs.length === 0) return { start: a, end: b, tipStart: a, tipEnd: b, ux, uy, span: 0 };
+    projs.sort((p, q) => p - q);
+    const lo = Math.min(Math.floor(projs.length * 0.002), projs.length - 1);
+    const hi = Math.max(Math.floor(projs.length * 0.998), lo);
+    minP = projs[lo];
+    maxP = projs[hi];
+  }
+  // Tip pixel at each station: closest to the axis centerline
+  let tipStart: [number, number] = a;
+  let tipEnd: [number, number] = b;
+  let bestStart = Infinity;
+  let bestEnd = Infinity;
+  const stationTol = Math.max(1.5, (maxP - minP) * 0.001);
+  for (let y = 0; y < h; y++) {
+    const row = y * w;
+    for (let x = 0; x < w; x++) {
+      if (!bitset[row + x]) continue;
+      const p = x * ux + y * uy;
+      const across = Math.abs((x - cx) * -uy + (y - cy) * ux);
+      if (Math.abs(p - minP) <= stationTol && across < bestStart) {
+        bestStart = across;
+        tipStart = [x, y];
+      }
+      if (Math.abs(p - maxP) <= stationTol && across < bestEnd) {
+        bestEnd = across;
+        tipEnd = [x, y];
+      }
+    }
+  }
+  return {
+    start: [cx + ux * (minP - cProj), cy + uy * (minP - cProj)],
+    end: [cx + ux * (maxP - cProj), cy + uy * (maxP - cProj)],
+    tipStart,
+    tipEnd,
+    ux,
+    uy,
+    span: maxP - minP,
+  };
+}
+
+/** Probe slab extent along unit (px, py) through origin (ox, oy). */
+function probeExtent(
+  bitset: Uint8Array,
+  w: number,
+  h: number,
+  ox: number,
+  oy: number,
+  px: number,
+  py: number,
+): { minP: number; maxP: number } | null {
+  const half = Math.max(2, Math.round((w + h) / 4));
+  let minP = Infinity;
+  let maxP = -Infinity;
+  for (let p = -half; p <= half; p++) {
+    const x = Math.round(ox + px * p);
+    const y = Math.round(oy + py * p);
+    if (x < 0 || y < 0 || x >= w || y >= h) continue;
+    if (bitset[y * w + x]) {
+      if (p < minP) minP = p;
+      if (p > maxP) maxP = p;
+    }
+  }
+  if (maxP < minP) return null;
+  return { minP, maxP };
+}
+
+function fmtInches(inches: number): string {
+  const whole = Math.floor(inches + 1e-9);
+  const rem = Math.round((inches - whole) * 8);
+  if (rem === 0) return `${whole}"`;
+  const frac: Record<number, string> = {
+    1: '1/8', 2: '1/4', 3: '3/8', 4: '1/2', 5: '5/8', 6: '3/4', 7: '7/8', 8: '',
+  };
+  if (rem === 8) return `${whole + 1}"`;
+  const part = frac[rem] ?? `${rem}/8`;
+  return whole > 0 ? `${whole} ${part}"` : `${part}"`;
+}
+
+export function buildOverlayPlan(input: OverlayPlanInput): OverlayPlan {
+  const {
+    bitset, widthPx, heightPx, bbox, scale, lengthIn, lengthLabel, mapToInventory,
+    inventoryW, inventoryH,
+  } = input;
+  const seg = maskAxisSegment(bitset, widthPx, heightPx, bbox);
+  // Re-orient span ends so EXIF bottom establishes station origin; axis still
+  // lies on the approved M1 direction (seg ux/uy flipped only when needed).
+  const oriented = pickBottomTowardTop(seg.start, seg.end);
+  const { bottom, top, ux, uy } = oriented;
+  const [rx, ry] = axisRightUnit(ux, uy);
+
+  // Consistent smaller readable font (#71). Cap by inventory size so high
+  // source scale (≈80 px/in) does not dominate the PNG.
+  const fontPx = (() => {
+    if (inventoryW && inventoryH && inventoryW > 0 && inventoryH > 0) {
+      return Math.max(12, Math.min(16, Math.round(Math.min(inventoryW, inventoryH) * 0.016)));
+    }
+    return Math.max(12, Math.min(16, Math.round(scale * 0.18)));
+  })();
+  // Inset for stroke + arrowhead so visual tips sit on/inside edges (#71).
+  const lineW = Math.max(2, Math.round(fontPx / 10));
+  const arrowHead = Math.max(7, fontPx * 0.32);
+  // Width tips retain stroke/arrowhead protection. Length endpoints need only
+  // half-stroke protection: larger arrowhead-derived inset visibly under-reached tips (#73).
+  const widthEdgeInset = Math.max(lineW / 2 + 0.5, arrowHead * 0.15);
+  const lengthEdgeInset = Math.max(0.5, lineW / 2);
+  const pad = Math.max(10, Math.min(28, fontPx * 1.1));
+  const stations = overlayWidthStations(lengthIn);
+  const widths: OverlayWidthMark[] = [];
+  for (const stationIn of stations) {
+    const t = stationIn * scale;
+    const ox = bottom[0] + ux * t;
+    const oy = bottom[1] + uy * t;
+    const extent = probeExtent(bitset, widthPx, heightPx, ox, oy, rx, ry);
+    if (!extent) continue;
+    // left/right on mask edges, then inset in inventory space for stroke/arrowhead
+    const leftMapped = mapToInventory(ox + rx * extent.minP, oy + ry * extent.minP);
+    const rightMapped = mapToInventory(ox + rx * extent.maxP, oy + ry * extent.maxP);
+    const wdx = rightMapped[0] - leftMapped[0];
+    const wdy = rightMapped[1] - leftMapped[1];
+    const wlen = Math.hypot(wdx, wdy) || 1;
+    const wux = wdx / wlen;
+    const wuy = wdy / wlen;
+    const left: [number, number] = [leftMapped[0] + wux * widthEdgeInset, leftMapped[1] + wuy * widthEdgeInset];
+    const right: [number, number] = [rightMapped[0] - wux * widthEdgeInset, rightMapped[1] - wuy * widthEdgeInset];
+    // Width number sits axis-left outside the slab (past left tip).
+    const labelOff = extent.minP - pad - fontPx * 0.85;
+    const labelSrcW: [number, number] = [ox + rx * labelOff, oy + ry * labelOff];
+    const widthIn = (extent.maxP - extent.minP + 1) / scale;
+    widths.push({
+      stationIn,
+      center: mapToInventory(ox, oy),
+      left,
+      right,
+      labelAt: mapToInventory(labelSrcW[0], labelSrcW[1]),
+      label: fmtInches(widthIn),
+    });
+  }
+
+  // Length graphic: beside wood on axis-right, outside max right extent.
+  let maxRight = 0;
+  const samples = Math.max(8, Math.round(lengthIn));
+  for (let i = 0; i <= samples; i++) {
+    const t = (i / samples) * (lengthIn * scale);
+    const ox = bottom[0] + ux * t;
+    const oy = bottom[1] + uy * t;
+    const extent = probeExtent(bitset, widthPx, heightPx, ox, oy, rx, ry);
+    if (extent && extent.maxP > maxRight) maxRight = extent.maxP;
+  }
+  const outward = maxRight + pad;
+  // Classic dimensioning (#70 + #71): width-aware centerline tip stations offset by
+  // pure axis-right (rx,ry)*outward. Length stays || approved (ux,uy); no screen-slide.
+  // Axial inset (inventory space) so arrowhead tips sit on footprint, not past.
+  const aMapped = mapToInventory(bottom[0] + rx * outward, bottom[1] + ry * outward);
+  const bMapped = mapToInventory(top[0] + rx * outward, top[1] + ry * outward);
+  const ldx0 = bMapped[0] - aMapped[0];
+  const ldy0 = bMapped[1] - aMapped[1];
+  const llen0 = Math.hypot(ldx0, ldy0) || 1;
+  const lux = ldx0 / llen0;
+  const luy = ldy0 / llen0;
+  const aInv: [number, number] = [aMapped[0] + lux * lengthEdgeInset, aMapped[1] + luy * lengthEdgeInset];
+  const bInv: [number, number] = [bMapped[0] - lux * lengthEdgeInset, bMapped[1] - luy * lengthEdgeInset];
+  const midInv: [number, number] = [(aInv[0] + bInv[0]) / 2, (aInv[1] + bInv[1]) / 2];
+  // Length label further axis-right of dim line so glyphs stay off the wood (#71).
+  const mapOrigin = mapToInventory(0, 0);
+  const mapR = mapToInventory(rx, ry);
+  const irx = mapR[0] - mapOrigin[0];
+  const iry = mapR[1] - mapOrigin[1];
+  const irlen = Math.hypot(irx, iry) || 1;
+  const nrx = irx / irlen;
+  const nry = iry / irlen;
+  const labelAt: [number, number] = [
+    midInv[0] + nrx * (fontPx * 0.85 + 6),
+    midInv[1] + nry * (fontPx * 0.85 + 6),
+  ];
+
+  const lengthMark: OverlayLengthMark = {
+    a: aInv,
+    b: bInv,
+    labelAt,
+    label: lengthLabel,
+    outside: true,
+  };
+
+  // Clamp all labels inside inventory PNG so nothing clips (#71).
+  if (inventoryW && inventoryH && inventoryW > 0 && inventoryH > 0) {
+    const margin = Math.max(8, fontPx * 0.65);
+    const clamp = (pt: [number, number], growLeft: boolean, text: string): [number, number] => {
+      let [x, y] = pt;
+      const glyphW = Math.max(fontPx * 1.2, text.length * fontPx * 0.55);
+      if (growLeft) {
+        // textAlign right — glyphs extend left of anchor
+        x = Math.max(margin + glyphW, Math.min(inventoryW - margin, x));
+      } else {
+        x = Math.max(margin, Math.min(inventoryW - margin, x));
+      }
+      y = Math.max(margin, Math.min(inventoryH - margin, y));
+      return [x, y];
+    };
+    lengthMark.labelAt = clamp(lengthMark.labelAt, false, lengthLabel);
+    for (const w of widths) {
+      const growLeft = w.labelAt[0] <= w.center[0];
+      w.labelAt = clamp(w.labelAt, growLeft, w.label);
+    }
+  }
+
+  return {
+    stroke: '#000000',
+    fontPx,
+    length: lengthMark,
+    widths,
+  };
+}
+
+/** Draw black dimension graphics onto an existing canvas (inventory PNG size). */
+export function drawOverlayPlan(
+  ctx: OffscreenCanvasRenderingContext2D | CanvasRenderingContext2D,
+  plan: OverlayPlan,
+): void {
+  const { stroke, fontPx } = plan;
+  ctx.save();
+  ctx.strokeStyle = stroke;
+  ctx.fillStyle = stroke;
+  ctx.lineWidth = Math.max(2, Math.round(fontPx / 10));
+  // Butt caps: round caps extend past endpoints and overshoot wood edges (#71).
+  ctx.lineCap = 'butt';
+  ctx.font = `bold ${fontPx}px sans-serif`;
+  ctx.textAlign = 'center';
+  ctx.textBaseline = 'middle';
+
+  const arrow = (from: [number, number], to: [number, number]) => {
+    const dx = to[0] - from[0];
+    const dy = to[1] - from[1];
+    const len = Math.hypot(dx, dy) || 1;
+    const ux = dx / len;
+    const uy = dy / len;
+    const head = Math.max(7, fontPx * 0.32);
+    ctx.beginPath();
+    ctx.moveTo(from[0], from[1]);
+    ctx.lineTo(to[0], to[1]);
+    ctx.stroke();
+    // arrow tips at both ends
+    for (const [sx, sy, dir] of [
+      [from[0], from[1], 1],
+      [to[0], to[1], -1],
+    ] as const) {
+      const px = -uy;
+      const py = ux;
+      ctx.beginPath();
+      ctx.moveTo(sx, sy);
+      ctx.lineTo(sx + dir * ux * head + px * head * 0.4, sy + dir * uy * head + py * head * 0.4);
+      ctx.lineTo(sx + dir * ux * head - px * head * 0.4, sy + dir * uy * head - py * head * 0.4);
+      ctx.closePath();
+      ctx.fill();
+    }
+  };
+
+  // Length — grow text further axis-right of the dim line (away from wood)
+  arrow(plan.length.a, plan.length.b);
+  {
+    const [lax, lay] = plan.length.a;
+    const [lbx, lby] = plan.length.b;
+    const midX = (lax + lbx) / 2;
+    const midY = (lay + lby) / 2;
+    const outwardX = plan.length.labelAt[0] - midX;
+    const outwardY = plan.length.labelAt[1] - midY;
+    // Prefer left/right align so glyphs extend away from wood when offset is mostly ±x
+    if (Math.abs(outwardX) >= Math.abs(outwardY)) {
+      ctx.textAlign = outwardX >= 0 ? 'left' : 'right';
+    } else {
+      ctx.textAlign = 'center';
+    }
+  }
+  ctx.fillText(plan.length.label, plan.length.labelAt[0], plan.length.labelAt[1]);
+
+  // Widths — grow text away from wood (labelAt is axis-left of left tip)
+  for (const w of plan.widths) {
+    arrow(w.left, w.right);
+    // labelAt is on the axis-left side of the station; align so glyphs extend further out
+    const towardLeft = w.labelAt[0] <= w.center[0];
+    ctx.textAlign = towardLeft ? 'right' : 'left';
+    ctx.fillText(w.label, w.labelAt[0], w.labelAt[1]);
+  }
+
+  ctx.restore();
+}
+
+export interface InventoryMap {
+  mapToInventory: (x: number, y: number) => [number, number];
+  outW: number;
+  outH: number;
+}
+
+/** Same crop math as composeInventoryFrame — source → inventory PNG pixels. */
+export function inventorySourceMap(
+  slabBounds: { x: number; y: number; w: number; h: number },
+  source: { widthPx: number; heightPx: number },
+  outW: number,
+  outH: number,
+): InventoryMap {
+  const FILL = 0.9;
+  const x0 = Math.max(0, Math.round(slabBounds.x));
+  const y0 = Math.max(0, Math.round(slabBounds.y));
+  const x1 = Math.min(source.widthPx, x0 + Math.max(1, Math.round(slabBounds.w)));
+  const y1 = Math.min(source.heightPx, y0 + Math.max(1, Math.round(slabBounds.h)));
+  const sw = x1 - x0;
+  const sh = y1 - y0;
+  const scale = Math.min((outW * FILL) / Math.max(sw, 1), (outH * FILL) / Math.max(sh, 1));
+  const dw = sw * scale;
+  const dh = sh * scale;
+  const ox = (outW - dw) / 2;
+  const oy = (outH - dh) / 2;
+  return {
+    outW,
+    outH,
+    mapToInventory: (sx, sy) => [ox + (sx - x0) * scale, oy + (sy - y0) * scale],
+  };
+}
+
+export interface EncodeOverlayInput {
+  /** Clean calibration inventory PNG bytes. */
+  inventoryPng: Blob;
+  bitset: Uint8Array;
+  widthPx: number;
+  heightPx: number;
+  bbox: BBox;
+  scale: number;
+  lengthIn: number;
+  lengthLabel: string;
+  slabBounds: { x: number; y: number; w: number; h: number };
+  source: { widthPx: number; heightPx: number };
+}
+
+/**
+ * Burn black dimension overlays onto a copy of the clean calibration inventory PNG.
+ * Returns a new image/png blob; never mutates the clean inventory.
+ */
+export async function encodeOverlayPng(input: EncodeOverlayInput): Promise<Blob> {
+  const bmp = await createImageBitmap(input.inventoryPng);
+  try {
+    const outW = bmp.width;
+    const outH = bmp.height;
+    const canvas = new OffscreenCanvas(outW, outH);
+    const ctx = canvas.getContext('2d')!;
+    ctx.drawImage(bmp, 0, 0);
+    const { mapToInventory } = inventorySourceMap(input.slabBounds, input.source, outW, outH);
+    const plan = buildOverlayPlan({
+      bitset: input.bitset,
+      widthPx: input.widthPx,
+      heightPx: input.heightPx,
+      bbox: input.bbox,
+      scale: input.scale,
+      lengthIn: input.lengthIn,
+      lengthLabel: input.lengthLabel,
+      mapToInventory,
+      inventoryW: outW,
+      inventoryH: outH,
+    });
+    drawOverlayPlan(ctx, plan);
+    return await canvas.convertToBlob({ type: 'image/png' });
+  } finally {
+    bmp.close();
+  }
+}

frontend/src/worker/mask.worker.ts

@@ -0,0 +1,89 @@
+import { minAreaRect, slabBounds } from '../geometry/rect';
+import type { MaskParams, WorkerIn, WorkerOut } from '../capture/capture.types';
+import { decodeOrientedBitmap } from '../decodeOrientedBitmap';
+import { greenKeep, blackKeep, autoPickSheet } from '../mask/sheetKeep';
+
+let bitmap: ImageBitmap | null = null;
+let data: Uint8ClampedArray | null = null;
+let w = 0, h = 0;
+let current = 0; // highest job id issued by main; older replies are dropped
+
+function runMask(params: MaskParams, id: number): WorkerOut {
+  if (!data) return { id, kind: 'failed', reason: 'no source decoded' };
+  let sheet = params.sheet;
+  if (sheet === 'auto') {
+    const samples: { r: number; g: number; b: number }[] = [];
+    for (let y = 0; y < h; y += 16)
+      for (let x = 0; x < w; x += 16) {
+        const i = (y * w + x) * 4;
+        samples.push({ r: data[i], g: data[i + 1], b: data[i + 2] });
+      }
+    sheet = autoPickSheet(samples);
+  }
+  const keep = sheet === 'green' ? greenKeep : blackKeep;
+  const s = Math.max(0, Math.min(100, params.sensitivity));
+  const bitset = new Uint8Array(w * h);
+  let slabPx = 0;
+  for (let i = 0, p = 0; i < data.length; i += 4, p++) {
+    if (keep(data[i], data[i + 1], data[i + 2], s)) {
+      bitset[p] = 1;
+      slabPx++;
+    }
+  }
+  if (slabPx === 0) {
+    return { id, kind: 'ready', slabPx: 0, bitset, bbox: { corners: [], longSidePx: 0, angleDeg: 0 }, slabBounds: { x: 0, y: 0, w: 0, h: 0 } };
+  }
+  const bbox = minAreaRect(bitset, w, h);
+  if (!bbox) {
+    return { id, kind: 'ready', slabPx: 0, bitset, bbox: { corners: [], longSidePx: 0, angleDeg: 0 }, slabBounds: { x: 0, y: 0, w: 0, h: 0 } };
+  }
+  return { id, kind: 'ready', slabPx, bitset, bbox, slabBounds: slabBounds(bitset, w, h) };
+}
+
+self.onmessage = (e: MessageEvent<WorkerIn>) => {
+  const msg = e.data;
+  if (msg.id < current) return; // superseded by a newer job
+  current = msg.id;
+  if (msg.kind === 'init') {
+    if (bitmap) {
+      bitmap.close();
+      bitmap = null;
+    }
+    data = null;
+    w = h = 0;
+    decodeOrientedBitmap(msg.blob)
+      .then((bmp) => {
+        w = bmp.width;
+        h = bmp.height;
+        const canvas = new OffscreenCanvas(w, h);
+        const ctx = canvas.getContext('2d')!;
+        ctx.drawImage(bmp, 0, 0);
+        data = ctx.getImageData(0, 0, w, h).data;
+        bitmap = bmp;
+        self.postMessage({ id: msg.id, kind: 'decoded', w, h } as WorkerOut);
+      })
+      .catch((err) => self.postMessage({ id: msg.id, kind: 'failed', reason: String(err) } satisfies WorkerOut));
+    return;
+  }
+  if (msg.kind === 'invalidate') {
+    if (bitmap) {
+      bitmap.close();
+      bitmap = null;
+    }
+    data = null;
+    w = h = 0;
+    return;
+  }
+  try {
+    const out = runMask({ sheet: msg.sheet, sensitivity: msg.sensitivity }, msg.id);
+    if (out.kind === 'ready') {
+      self.postMessage(out, [out.bitset.buffer]);
+    } else {
+      self.postMessage(out);
+    }
+  } catch (err) {
+    self.postMessage({ id: msg.id, kind: 'failed', reason: String(err) } satisfies WorkerOut);
+  }
+};
+
+export {};

frontend/tests/e2e/artifacts/README.md

@@ -0,0 +1,40 @@
+# E2E visual artifacts (#65)
+
+Screenshots from `npx playwright test` for Milestone 2 Photos-ready evidence.
+
+## How to run (local box — not ubudual :10880)
+
+```bash
+cd frontend
+npm ci
+npx playwright install chromium   # once per machine
+npm run test:e2e
+```
+
+Or against an already-running preview:
+
+```bash
+npm run build && npm run preview -- --host 127.0.0.1 --port 4173
+# other terminal:
+npx playwright test
+```
+
+Fixtures: `tests/fixtures/set1-48x2/` (L=48, thickness=2) and `set2-31x2p5/` (L=31, thickness=2.5). Black sheet — e2e selects **Black** and may nudge sensitivity.
+
+## Expected screenshots (this folder)
+
+| File | Step |
+|---|---|
+| `01-batch.png` | Batch with fixtures loaded |
+| `02-pick-calibration.png` | Pick calibration |
+| `03-mask.png` | Mask (Black sheet) ready to approve |
+| `04-axis.png` | Length axis |
+| `05-measure.png` | Measure with L / thickness filled |
+| `06-photos-ready.png` | Photos ready lineup (clean + overlay + siblings) |
+
+Large regenerating `*.png` and Playwright `test-results/` / `playwright-report/` are gitignored.
+Committed small evidence JPEGs live in `evidence/` (regenerate with a green `npm run test:e2e`, then re-encode if needed).
+
+## Unit tests
+
+`npm test` must still pass separately from Playwright.

frontend/tests/e2e/artifacts/evidence/LAST_RUN.md

@@ -0,0 +1,11 @@
+# Last green e2e run (#71)
+
+- **When:** 2026-09-15 9:55 PM PT (`2026-09-16T04:55:14Z`)
+- **Fixture:** `tests/fixtures/set1-48x2/` (L=48, thickness=2)
+- **Server:** local `vite preview` at `http://127.0.0.1:4173` (not ubudual)
+- **Result:** 1 passed (~8s test)
+- **Mask:** Black sheet — Approve enabled
+- **Fix under test:** width-aware tip stations; stroke/arrowhead edge inset; inventory-capped font; labels clamped in PNG (#71); #70 axis-parallel kept
+- **Lineup:** Clean calibration → Dimension overlay → Batch photo 2
+
+Full-resolution PNGs are produced under `../` on each run (gitignored). These JPEGs are commit-sized evidence for review.

frontend/tests/e2e/photos-ready.spec.ts

@@ -0,0 +1,135 @@
+import { test, expect, type Page } from '@playwright/test';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import fs from 'node:fs';
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const FIXTURES = path.resolve(__dirname, '../fixtures/set1-48x2');
+const ARTIFACTS = path.resolve(__dirname, 'artifacts');
+const FACE_A = path.join(FIXTURES, 'face-a.jpeg');
+const FACE_B = path.join(FIXTURES, 'face-b.jpeg');
+
+const shot = async (page: Page, name: string) => {
+  fs.mkdirSync(ARTIFACTS, { recursive: true });
+  await page.screenshot({
+    path: path.join(ARTIFACTS, name),
+    fullPage: true,
+  });
+};
+
+/** Discard any device draft so we always start on Batch. */
+const ensureFreshBatch = async (page: Page) => {
+  await page.goto('/');
+  // resumeProbe is async onMount — wait for either Resume or Batch.
+  const resumeHeading = page.getByRole('heading', { name: /resume/i });
+  const batchHeading = page.getByRole('heading', { name: 'Batch photos' });
+  await expect(resumeHeading.or(batchHeading)).toBeVisible({ timeout: 15_000 });
+  if (await resumeHeading.isVisible().catch(() => false)) {
+    await page.getByRole('button', { name: /start fresh/i }).click();
+  }
+  await expect(batchHeading).toBeVisible();
+};
+
+/**
+ * Black-sheet fixtures: Auto may work, but UAT note says prefer Black + sensitivity
+ * tweaks. Do not invent inference — only UI sheet/sensitivity controls.
+ */
+const prepareMaskForApprove = async (page: Page) => {
+  await expect(page.getByRole('heading', { name: 'Mask' })).toBeVisible();
+  // Sheet change recomputes immediately (session.setSheet → runPass).
+  await page.getByRole('button', { name: 'Black', exact: true }).click();
+
+  const approve = page.getByRole('button', { name: 'Approve mask' });
+  // First overlay after decode is debounced 2s; Black pass is immediate but
+  // 4K fixtures still need decode + worker time.
+  try {
+    await expect(approve).toBeEnabled({ timeout: 45_000 });
+    return;
+  } catch {
+    /* try sensitivity ladder */
+  }
+
+  // Higher sensitivity widens black sheet match; if still empty, try lower.
+  for (const target of [60, 70, 40, 30, 80]) {
+    const slider = page.locator('input[type="range"]');
+    await slider.fill(String(target));
+    // Sensitivity is debounced 2s — wait past debounce + worker.
+    await page.waitForTimeout(2800);
+    if (await approve.isEnabled()) return;
+  }
+
+  await expect(approve, 'Mask approve stayed disabled after Black + sensitivity tweaks').toBeEnabled({
+    timeout: 15_000,
+  });
+};
+
+test.describe('M2 #65 Photos-ready e2e (set1-48x2)', () => {
+  test('batch → pick → mask → axis → measure → photos ready + screenshots', async ({ page }) => {
+    test.setTimeout(180_000);
+    expect(fs.existsSync(FACE_A), 'fixture face-a').toBeTruthy();
+    expect(fs.existsSync(FACE_B), 'fixture face-b').toBeTruthy();
+
+    await ensureFreshBatch(page);
+
+    // Gallery multi-input (not the capture=environment camera input).
+    const gallery = page.locator('input[type="file"][multiple]');
+    await gallery.setInputFiles([FACE_A, FACE_B]);
+    await expect(page.getByAltText('Batch photo 1')).toBeVisible({ timeout: 30_000 });
+    await expect(page.getByAltText('Batch photo 2')).toBeVisible();
+    await shot(page, '01-batch.png');
+
+    await page.getByRole('button', { name: 'Continue' }).click();
+    await expect(page.getByRole('heading', { name: 'Pick calibration photo' })).toBeVisible();
+    await shot(page, '02-pick-calibration.png');
+
+    await page.getByRole('button', { name: 'Use photo 1 as calibration' }).click();
+    await prepareMaskForApprove(page);
+    await shot(page, '03-mask.png');
+    await page.getByRole('button', { name: 'Approve mask' }).click();
+
+    await expect(page.getByRole('heading', { name: 'Length axis' })).toBeVisible();
+    await shot(page, '04-axis.png');
+    await page.getByRole('button', { name: 'Approve axis' }).click();
+
+    await expect(page.getByRole('heading', { name: 'Measure' })).toBeVisible();
+    await page.getByLabel('Length L').fill('48');
+    await page.getByLabel('Thickness').fill('2');
+    // blur/change commits eighths into session before Calculate.
+    await page.getByLabel('Length L').blur();
+    await page.getByLabel('Thickness').blur();
+    await shot(page, '05-measure.png');
+
+    const calc = page.getByRole('button', { name: 'Calculate' });
+    await expect(calc).toBeEnabled();
+    await calc.click();
+
+    // Calculate encodes calibration PNG + overlay + sibling batch apply.
+    await expect(page.getByRole('heading', { name: 'Photos ready' })).toBeVisible({
+      timeout: 120_000,
+    });
+    await expect(page.getByLabel('Photos ready')).toBeVisible();
+    await expect(page.getByText('Clean calibration')).toBeVisible();
+    await expect(page.getByText('Dimension overlay')).toBeVisible();
+    // Sibling face-b should appear as Batch photo 2 (capture order).
+    await expect(page.getByText(/Batch photo 2|Photo 2 failed/)).toBeVisible();
+
+    await shot(page, '06-photos-ready.png');
+
+    // Write a short run log for parent AI visual review (not a substitute for eyes).
+    const logPath = path.join(ARTIFACTS, 'run-log.txt');
+    const shots = ['01-batch.png', '02-pick-calibration.png', '03-mask.png', '04-axis.png', '05-measure.png', '06-photos-ready.png'];
+    const lines = [
+      `M2 #65 Playwright e2e — set1-48x2 (L=48, thickness=2)`,
+      `baseURL: ${page.url().split('/').slice(0, 3).join('/')}`,
+      `finished: ${new Date().toISOString()}`,
+      `artifacts:`,
+      ...shots.map((s) => {
+        const p = path.join(ARTIFACTS, s);
+        const st = fs.existsSync(p) ? fs.statSync(p) : null;
+        return `  - ${s} (${st ? `${st.size} bytes` : 'MISSING'})`;
+      }),
+      `assertions: Photos ready heading; Clean calibration; Dimension overlay; batch sibling slot`,
+    ];
+    fs.writeFileSync(logPath, lines.join('\n') + '\n', 'utf8');
+  });
+});

frontend/tests/fixtures/README.md

@@ -0,0 +1,16 @@
+# Test photo fixtures
+
+Matched sets from Ty for Milestone 2 Photos (Playwright + calibration). Black sheet.
+
+## set1-48x2 — L = 48 in, thickness = 2 in
+Curly / fiddleback bookmatch pair.
+- `face-a.jpeg`
+- `face-b.jpeg`
+
+## set2-31x2p5 — L = 31 in, thickness = 2.5 in
+Shorter organic / burl pair.
+- `face-a.jpeg`
+- `face-b.jpeg`
+
+## m1-dji (optional M1 UAT sample)
+- `162332.JPG` — live-edge on black; historically used on ubudual M1 UAT.

frontend/tsconfig.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "noEmit": true,
+    "lib": ["ES2022", "DOM", "DOM.Iterable", "WebWorker"],
+    "skipLibCheck": true,
+    "isolatedModules": true,
+    "resolveJsonModule": true,
+    "verbatimModuleSyntax": false,
+    "types": ["vite/client"]
+  },
+  "include": ["src/**/*.ts", "src/**/*.svelte", "vite.config.ts"],
+  "exclude": ["src/**/*.test.ts"]
+}

frontend/vite.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig } from 'vite';
+import { svelte } from '@sveltejs/vite-plugin-svelte';
+import sveltePreprocess from 'svelte-preprocess';
+
+export default defineConfig({
+  plugins: [svelte({ preprocess: sveltePreprocess() })],
+  worker: { format: 'es' },
+});