diff --git a/frontend/src/capture/session.batchApply.test.ts b/frontend/src/capture/session.batchApply.test.ts
index 131cbe8..1906e90 100644
--- a/frontend/src/capture/session.batchApply.test.ts
+++ b/frontend/src/capture/session.batchApply.test.ts
@@ -252,6 +252,35 @@ test('#62: Calculate applies frozen mask params to every non-calibration batch p
   s.dispose();
 });
 
+test('#62: calibration tape tilt is not copied to sibling photos (#99)', async () => {
+  installFakes();
+  const rotations: (number | undefined)[] = [];
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async (input) => {
+      rotations.push(input.rotationDeg);
+      return { blob: new Blob(['ok-png'], { type: 'image/png' }), sourceBelowFloor: false };
+    },
+  } as Parameters<typeof createCaptureSession>[0]);
+
+  await driveToMeasure(s, [tinyJpeg('sibling-a'), tinyJpeg('calibration'), tinyJpeg('sibling-b')], 1, { sheet: 'black' });
+  s.back();
+  s.setTapePose({
+    transform: { tiltDeg: 20, zoom: 1, panX: 0, panY: 0 },
+    tickStartY: 32,
+    tickEndY: 608,
+    sourceW: 1000,
+    sourceH: 900,
+  });
+  await s.calculateFromAxis(320, 16);
+
+  assert.equal(rotations.length, 3, 'one encoder call for calibration and each sibling');
+  assert.equal(rotations[0], 20, 'calibration receives the selected tape tilt');
+  assert.equal(rotations[1], undefined, 'sibling photos remain unrotated');
+  assert.equal(rotations[2], undefined, 'sibling photos remain unrotated');
+  s.dispose();
+});
+
 test('#62: empty mask on one sibling → per-photo error; others still proceed', async () => {
   installFakes();
   const a = tinyJpeg('a'); // will empty-mask
diff --git a/frontend/src/capture/session.calibrate.test.ts b/frontend/src/capture/session.calibrate.test.ts
index 34c77ee..a387b98 100644
--- a/frontend/src/capture/session.calibrate.test.ts
+++ b/frontend/src/capture/session.calibrate.test.ts
@@ -403,6 +403,44 @@ test('calculateFromAxis stays on the tape page until the calibrated result exist
   s.dispose();
 });
 
+test('calculateFromAxis passes the tape tilt to the calibration PNG and overlay only', async () => {
+  installFakeMaskWorker();
+  (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
+    async () => ({ width: MASK_W, height: MASK_H, close() {} }) as ImageBitmap;
+
+  const inventoryTilts: (number | undefined)[] = [];
+  const overlayTilts: (number | undefined)[] = [];
+  const s = createCaptureSession({
+    draft: store,
+    encodeInventory: async (input) => {
+      inventoryTilts.push((input as typeof input & { rotationDeg?: number }).rotationDeg);
+      return { blob: new Blob(['clean'], { type: 'image/png' }), sourceBelowFloor: false };
+    },
+    encodeOverlay: async (input) => {
+      overlayTilts.push((input as typeof input & { rotationDeg?: number }).rotationDeg);
+      return new Blob(['overlay'], { type: 'image/png' });
+    },
+  });
+  await s.addToBatch(tinyJpeg('cal'));
+  s.continueBatch();
+  s.pickCalibration(0);
+  s.setSheet('black');
+  await settleOverlay(s);
+  s.approveMask();
+  s.setTapePose({
+    transform: { tiltDeg: 20, zoom: 1, panX: 0, panY: 0 },
+    tickStartY: 32,
+    tickEndY: 608,
+    sourceW: MASK_W,
+    sourceH: MASK_H,
+  });
+  await s.calculateFromAxis(320, 16);
+
+  assert.deepEqual(inventoryTilts, [20], 'calibration inventory must receive tape tilt');
+  assert.deepEqual(overlayTilts, [20], 'dimension overlay must receive tape tilt');
+  s.dispose();
+});
+
 test('#61: Calculate produces inventory PNG + M1 measures for calibration source only', async () => {
   installFakeMaskWorker();
   (globalThis as unknown as { createImageBitmap: typeof createImageBitmap }).createImageBitmap =
diff --git a/frontend/src/capture/session.ts b/frontend/src/capture/session.ts
index 501a2d8..0d21e21 100644
--- a/frontend/src/capture/session.ts
+++ b/frontend/src/capture/session.ts
@@ -370,7 +370,7 @@ export function createCaptureSession(opts: SessionOpts = {}): CaptureSession {
         { start: axis.tapeStart, end: axis.tapeEnd },
       );
       try {
-        const encoded = await encodeInventory({ bitmap, mask: approvedMask, source, cropFill });
+        const encoded = await encodeInventory({ bitmap, mask: approvedMask, source, cropFill, rotationDeg: axis.photoTransform.tiltDeg });
         pngBlob = encoded.blob;
         belowFloor = encoded.sourceBelowFloor;
       } catch {
@@ -390,6 +390,7 @@ export function createCaptureSession(opts: SessionOpts = {}): CaptureSession {
             slabBounds: approvedMask.slabBounds,
             source,
             cropFill,
+            rotationDeg: axis.photoTransform.tiltDeg,
           });
         } catch {
           return new Blob(['overlay'], { type: 'image/png' });
diff --git a/frontend/src/png/inventory.test.ts b/frontend/src/png/inventory.test.ts
index 669c042..1fd1449 100644
--- a/frontend/src/png/inventory.test.ts
+++ b/frontend/src/png/inventory.test.ts
@@ -107,6 +107,37 @@ test('90% fill: limiting dimension maps to 0.9 × frame side (#68)', () => {
   assert.ok(Math.abs(hExtent - 648) <= 2, `height extent ${hExtent} ≈ 648 (1800×0.36)`);
 });
 
+test('calibration rotation turns a landscape slab into an upright crop extent (#99)', () => {
+  const width = 6;
+  const height = 4;
+  const bitset = new Uint8Array(width * height);
+  for (let y = 1; y <= 2; y++) {
+    for (let x = 1; x <= 4; x++) bitset[y * width + x] = 1;
+  }
+  const source: Pick<Source, 'widthPx' | 'heightPx'> = { widthPx: width, heightPx: height };
+  const mask = maskFor(bitset, { x: 1, y: 1, w: 4, h: 2 });
+  const photo = makePhoto(width, height, (x, y) =>
+    bitset[y * width + x] ? [200, 40, 20, 255] : [0, 255, 0, 255],
+  );
+  const extent = (rgba: Uint8Array, outW: number, outH: number) => {
+    let minX = outW, maxX = -1, minY = outH, maxY = -1;
+    for (let y = 0; y < outH; y++) {
+      for (let x = 0; x < outW; x++) {
+        if (rgba[(y * outW + x) * 4 + 3] === 0) continue;
+        minX = Math.min(minX, x); maxX = Math.max(maxX, x);
+        minY = Math.min(minY, y); maxY = Math.max(maxY, y);
+      }
+    }
+    return { width: maxX - minX + 1, height: maxY - minY + 1 };
+  };
+  const unrotated = composeInventoryFrame(photo, mask, source, 1, 0);
+  const rotated = composeInventoryFrame(photo, mask, source, 1, 90);
+  assert.ok(extent(unrotated.rgba, unrotated.width, unrotated.height).width >
+    extent(unrotated.rgba, unrotated.width, unrotated.height).height);
+  assert.ok(extent(rotated.rgba, rotated.width, rotated.height).height >
+    extent(rotated.rgba, rotated.width, rotated.height).width);
+});
+
 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);
diff --git a/frontend/src/png/inventory.ts b/frontend/src/png/inventory.ts
index 3ce49e9..b4fcf32 100644
--- a/frontend/src/png/inventory.ts
+++ b/frontend/src/png/inventory.ts
@@ -13,6 +13,8 @@ export interface InventoryInput {
   source: SourcePick;
   /** Global crop fill percent. Default 90. */
   cropFill?: number;
+  /** Calibration-photo rotation in degrees; batch siblings remain unrotated. */
+  rotationDeg?: number;
 }
 
 export interface Frame {
@@ -27,7 +29,11 @@ export function composeInventoryFrame(
   mask: MaskPick,
   source: SourcePick,
   fill = 0.9,
+  rotationDeg = 0,
 ): Frame {
+  if (Number.isFinite(rotationDeg) && Math.abs(rotationDeg % 360) > 1e-8) {
+    return composeRotatedInventoryFrame(src, mask, source, fill, rotationDeg);
+  }
   const b = mask.slabBounds;
   const x0 = Math.max(0, Math.round(b.x));
   const y0 = Math.max(0, Math.round(b.y));
@@ -64,10 +70,130 @@ export function composeInventoryFrame(
   return { width: outW, height: outH, rgba, sourceBelowFloor: belowFloor };
 }
 
+interface PixelBounds {
+  minX: number;
+  minY: number;
+  maxX: number;
+  maxY: number;
+}
+
+function maskPixelBounds(bitset: Uint8Array, w: number, h: number): PixelBounds | null {
+  let minX = w, minY = h, maxX = -1, maxY = -1;
+  for (let y = 0; y < h; y++) {
+    for (let x = 0; x < w; x++) {
+      if (!bitset[y * w + x]) continue;
+      minX = Math.min(minX, x); minY = Math.min(minY, y);
+      maxX = Math.max(maxX, x); maxY = Math.max(maxY, y);
+    }
+  }
+  return maxX < 0 ? null : { minX, minY, maxX, maxY };
+}
+
+function rotatePoint(
+  x: number, y: number, bounds: PixelBounds, radians: number,
+): [number, number] {
+  const cx = (bounds.minX + bounds.maxX) / 2;
+  const cy = (bounds.minY + bounds.maxY) / 2;
+  const dx = x - cx, dy = y - cy;
+  const cos = Math.cos(radians), sin = Math.sin(radians);
+  return [cx + dx * cos - dy * sin, cy + dx * sin + dy * cos];
+}
+
+export interface MaskRotation {
+  bounds: { x: number; y: number; w: number; h: number };
+  toRotated: (x: number, y: number) => [number, number];
+  toSource: (x: number, y: number) => [number, number];
+}
+
+export function createMaskRotation(
+  bitset: Uint8Array,
+  w: number,
+  h: number,
+  rotationDeg: number,
+): MaskRotation {
+  const pixels = maskPixelBounds(bitset, w, h);
+  if (!pixels) {
+    return {
+      bounds: { x: 0, y: 0, w: 0, h: 0 },
+      toRotated: (x, y) => [x, y],
+      toSource: (x, y) => [x, y],
+    };
+  }
+  const radians = (rotationDeg * Math.PI) / 180;
+  const toRotated = (x: number, y: number) => rotatePoint(x, y, pixels, radians);
+  const toSource = (x: number, y: number) => rotatePoint(x, y, pixels, -radians);
+  let minX = Infinity, minY = Infinity, maxX = -Infinity, maxY = -Infinity;
+  for (let y = 0; y < h; y++) {
+    for (let x = 0; x < w; x++) {
+      if (!bitset[y * w + x]) continue;
+      const [rx, ry] = toRotated(x, y);
+      minX = Math.min(minX, rx); minY = Math.min(minY, ry);
+      maxX = Math.max(maxX, rx); maxY = Math.max(maxY, ry);
+    }
+  }
+  return {
+    bounds: { x: minX - 0.5, y: minY - 0.5, w: maxX - minX + 1, h: maxY - minY + 1 },
+    toRotated,
+    toSource,
+  };
+}
+
+export function rotatedMaskBounds(
+  bitset: Uint8Array,
+  w: number,
+  h: number,
+  rotationDeg: number,
+) {
+  return createMaskRotation(bitset, w, h, rotationDeg).bounds;
+}
+
+function composeRotatedInventoryFrame(
+  src: { width: number; height: number; rgba: Uint8Array | Uint8ClampedArray },
+  mask: MaskPick,
+  source: SourcePick,
+  fill: number,
+  rotationDeg: number,
+): Frame {
+  const rotation = createMaskRotation(mask.bitset, source.widthPx, source.heightPx, rotationDeg);
+  if (!(rotation.bounds.w > 0 && rotation.bounds.h > 0)) {
+    throw new RangeError('Cannot rotate an empty approved mask');
+  }
+  const rotated = rotation.bounds;
+  const belowFloor = Math.min(rotated.w, rotated.h) < FLOOR;
+  const outW = belowFloor ? Math.max(1, Math.min(rotated.w, FLOOR)) : FLOOR;
+  const outH = Math.round((outW * ASPECT_H) / ASPECT_W);
+  const scale = Math.min((outW * fill) / Math.max(rotated.w, 1), (outH * fill) / Math.max(rotated.h, 1));
+  const dw = rotated.w * scale;
+  const dh = rotated.h * scale;
+  const ox = (outW - dw) / 2;
+  const oy = (outH - dh) / 2;
+  const rgba = new Uint8Array(outW * outH * 4);
+  for (let y = 0; y < outH; y++) {
+    for (let x = 0; x < outW; x++) {
+      if (x + 0.5 < ox || x + 0.5 >= ox + dw || y + 0.5 < oy || y + 0.5 >= oy + dh) continue;
+      const rx = rotated.x + (x + 0.5 - ox) / scale;
+      const ry = rotated.y + (y + 0.5 - oy) / scale;
+      const [sourceX, sourceY] = rotation.toSource(rx, ry);
+      const sx = Math.round(sourceX);
+      const sy = Math.round(sourceY);
+      if (sx < 0 || sy < 0 || sx >= source.widthPx || sy >= source.heightPx) continue;
+      const siPixel = sy * source.widthPx + sx;
+      if (mask.bitset[siPixel] !== 1) continue;
+      const si = siPixel * 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, cropFill } = input;
+  const { bitmap, mask, source, cropFill, rotationDeg } = input;
   const fill = Math.max(1, Math.min(100, cropFill ?? 90)) / 100;
   const srcCanvas = new OffscreenCanvas(source.widthPx, source.heightPx);
   const srcCtx = srcCanvas.getContext('2d')!;
@@ -78,6 +204,7 @@ export async function encodeInventoryPng(
     mask,
     source,
     fill,
+    rotationDeg,
   );
   const out = new OffscreenCanvas(frame.width, frame.height);
   const ctx = out.getContext('2d')!;
diff --git a/frontend/src/png/overlay.test.ts b/frontend/src/png/overlay.test.ts
index d3940d9..d3950ec 100644
--- a/frontend/src/png/overlay.test.ts
+++ b/frontend/src/png/overlay.test.ts
@@ -299,7 +299,37 @@ test('buildOverlayPlan: font smaller than prior 28/scale*1.2 and 22/scale*1.0 (#
 });
 
 
-// --- Length dim must not overshoot wood footprint (#69) ---
+test('inventorySourceMap follows calibration rotation for overlay geometry (#99)', () => {
+  const W = 400, H = 400;
+  const bitset = new Uint8Array(W * H).fill(1);
+  const slabBounds = { x: 0, y: 0, w: W, h: H };
+  const unrotated = inventorySourceMap(
+    slabBounds,
+    { widthPx: W, heightPx: H },
+    800,
+    1067,
+    0.9,
+  );
+  const rotated = inventorySourceMap(
+    slabBounds,
+    { widthPx: W, heightPx: H },
+    800,
+    1067,
+    0.9,
+    bitset,
+    90,
+  );
+  const horizontal = (map: ReturnType<typeof inventorySourceMap>) => {
+    const a = map.mapToInventory(100, 200);
+    const b = map.mapToInventory(300, 200);
+    return [b[0] - a[0], b[1] - a[1]] as const;
+  };
+  const [unrotatedDx, unrotatedDy] = horizontal(unrotated);
+  const [rotatedDx, rotatedDy] = horizontal(rotated);
+  assert.ok(Math.abs(unrotatedDx) > Math.abs(unrotatedDy), 'unrotated source axis stays horizontal');
+  assert.ok(Math.abs(rotatedDy) > Math.abs(rotatedDx), '90° calibration rotation maps it vertically');
+});
+
 
 /** Tilted-axis slab: irregular mask + approved bbox long side ~10° from vertical. */
 function tiltedSlabFixture() {
diff --git a/frontend/src/png/overlay.ts b/frontend/src/png/overlay.ts
index f731be3..5eb8955 100644
--- a/frontend/src/png/overlay.ts
+++ b/frontend/src/png/overlay.ts
@@ -1,5 +1,6 @@
 import type { BBox } from '../capture/capture.types';
 import { axisEndpoints } from '../measure/measure';
+import { createMaskRotation } from './inventory';
 
 /** Width overlay stations: 6, 18, 30, … while ≤ L − 6 (tip-exclusive). */
 export function overlayWidthStations(lengthIn: number): number[] {
@@ -486,15 +487,30 @@ export function inventorySourceMap(
   outW: number,
   outH: number,
   fill = 0.9,
+  bitset?: Uint8Array,
+  rotationDeg = 0,
 ): InventoryMap {
-  const fillRatio = fill;
+  if (bitset && Math.abs(rotationDeg % 360) > 1e-8) {
+    const rotation = createMaskRotation(bitset, source.widthPx, source.heightPx, rotationDeg);
+    const scale = Math.min((outW * fill) / Math.max(rotation.bounds.w, 1), (outH * fill) / Math.max(rotation.bounds.h, 1));
+    const ox = (outW - rotation.bounds.w * scale) / 2;
+    const oy = (outH - rotation.bounds.h * scale) / 2;
+    return {
+      outW,
+      outH,
+      mapToInventory: (sx, sy) => {
+        const [rx, ry] = rotation.toRotated(sx, sy);
+        return [ox + (rx - rotation.bounds.x) * scale, oy + (ry - rotation.bounds.y) * scale];
+      },
+    };
+  }
   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 * fillRatio) / Math.max(sw, 1), (outH * fillRatio) / Math.max(sh, 1));
+  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;
@@ -519,6 +535,7 @@ export interface EncodeOverlayInput {
   slabBounds: { x: number; y: number; w: number; h: number };
   source: { widthPx: number; heightPx: number };
   cropFill?: number;
+  rotationDeg?: number;
 }
 
 /**
@@ -534,7 +551,15 @@ export async function encodeOverlayPng(input: EncodeOverlayInput): Promise<Blob>
     const ctx = canvas.getContext('2d')!;
     ctx.drawImage(bmp, 0, 0);
     const fill = Math.max(1, Math.min(100, input.cropFill ?? 90)) / 100;
-    const { mapToInventory } = inventorySourceMap(input.slabBounds, input.source, outW, outH, fill);
+    const { mapToInventory } = inventorySourceMap(
+      input.slabBounds,
+      input.source,
+      outW,
+      outH,
+      fill,
+      input.bitset,
+      input.rotationDeg,
+    );
     const plan = buildOverlayPlan({
       bitset: input.bitset,
       widthPx: input.widthPx,