diff --git a/src/app/(app)/collection-confirm/page.test.tsx b/src/app/(app)/collection-confirm/page.test.tsx
index 9e5a332..72faa0f 100644
--- a/src/app/(app)/collection-confirm/page.test.tsx
+++ b/src/app/(app)/collection-confirm/page.test.tsx
@@ -146,8 +146,7 @@ describe("CollectionConfirmPage", () => {
     );
   });
 
-  it("renders a photo strip chip per distinct filename; clicking opens the file via window.open", async () => {
-    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+  it("renders a photo strip chip per distinct filename; clicking opens the inline viewer (no tab switch)", async () => {
     const photoRows: ConfirmRow[] = [
       makeRow({
         id: "row-photo-1",
@@ -177,10 +176,170 @@ describe("CollectionConfirmPage", () => {
       screen.getByRole("button", { name: /Invoice 2 invoice-2\.pdf/i }),
     ).toBeInTheDocument();
 
-    // Clicking a chip opens the file-stream URL in a new tab.
+    // Clicking a chip opens the inline viewer — NOT a new tab. The
+    // window.open spy is asserted clean to catch a regression to the
+    // old behaviour.
+    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
     await user.click(
       screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
     );
+
+    const viewer = await screen.findByTestId("invoice-viewer");
+    expect(viewer).toBeInTheDocument();
+    const iframe = within(viewer).getByTestId("invoice-viewer-iframe");
+    expect(iframe).toHaveAttribute(
+      "src",
+      "/api/v1/files/order_items/row-photo-1/invoice-1.pdf",
+    );
+    // The chip is now marked active so the operator knows which
+    // invoice is being viewed.
+    expect(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "true");
+
+    // No tab opened — the operator stays on the page to compare the
+    // invoice against the items table.
+    expect(openSpy).not.toHaveBeenCalled();
+  });
+
+  it("toggles the inline invoice viewer: clicking the active chip closes it", async () => {
+    const photoRows: ConfirmRow[] = [
+      makeRow({
+        id: "row-photo-1",
+        order_item_attachements: ["invoice-1.pdf"],
+      }),
+    ];
+    buildFetchSpy(photoRows);
+
+    const user = userEvent.setup();
+    render(<Page />);
+
+    await waitFor(() =>
+      expect(screen.getByTestId("po-card-PO-1")).toBeInTheDocument(),
+    );
+
+    const chip = screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i });
+
+    // Open the viewer.
+    await user.click(chip);
+    expect(screen.getByTestId("invoice-viewer")).toBeInTheDocument();
+
+    // Click the same chip again → viewer closes (toggle).
+    await user.click(chip);
+    expect(screen.queryByTestId("invoice-viewer")).not.toBeInTheDocument();
+    expect(chip).toHaveAttribute("aria-pressed", "false");
+  });
+
+  it("swaps the invoice viewer content when a different chip is clicked", async () => {
+    const photoRows: ConfirmRow[] = [
+      makeRow({
+        id: "row-photo-1",
+        order_item_attachements: ["invoice-1.pdf"],
+      }),
+      makeRow({
+        id: "row-photo-2",
+        order_item_attachements: ["invoice-2.pdf"],
+      }),
+    ];
+    buildFetchSpy(photoRows);
+
+    const user = userEvent.setup();
+    render(<Page />);
+
+    await waitFor(() =>
+      expect(screen.getByTestId("po-card-PO-1")).toBeInTheDocument(),
+    );
+
+    await user.click(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    );
+    let viewer = await screen.findByTestId("invoice-viewer");
+    expect(
+      within(viewer).getByTestId("invoice-viewer-iframe"),
+    ).toHaveAttribute("src", "/api/v1/files/order_items/row-photo-1/invoice-1.pdf");
+
+    // Click the second chip — the viewer stays open and content swaps.
+    await user.click(
+      screen.getByRole("button", { name: /Invoice 2 invoice-2\.pdf/i }),
+    );
+    viewer = screen.getByTestId("invoice-viewer");
+    expect(
+      within(viewer).getByTestId("invoice-viewer-iframe"),
+    ).toHaveAttribute("src", "/api/v1/files/order_items/row-photo-2/invoice-2.pdf");
+
+    // Chip 2 is now the active one; chip 1 is no longer pressed.
+    expect(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "false");
+    expect(
+      screen.getByRole("button", { name: /Invoice 2 invoice-2\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "true");
+  });
+
+  it("closes the inline invoice viewer via the X button and via Esc", async () => {
+    const photoRows: ConfirmRow[] = [
+      makeRow({
+        id: "row-photo-1",
+        order_item_attachements: ["invoice-1.pdf"],
+      }),
+    ];
+    buildFetchSpy(photoRows);
+
+    const user = userEvent.setup();
+    render(<Page />);
+
+    await waitFor(() =>
+      expect(screen.getByTestId("po-card-PO-1")).toBeInTheDocument(),
+    );
+
+    // Open.
+    await user.click(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    );
+    const viewer = await screen.findByTestId("invoice-viewer");
+
+    // Close via X button.
+    await user.click(within(viewer).getByTestId("invoice-viewer-close"));
+    expect(screen.queryByTestId("invoice-viewer")).not.toBeInTheDocument();
+    expect(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "false");
+
+    // Re-open and close via Esc.
+    await user.click(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    );
+    expect(screen.getByTestId("invoice-viewer")).toBeInTheDocument();
+    await user.keyboard("{Escape}");
+    expect(screen.queryByTestId("invoice-viewer")).not.toBeInTheDocument();
+  });
+
+  it("still offers an in-viewer 'open in new tab' escape hatch", async () => {
+    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+    const photoRows: ConfirmRow[] = [
+      makeRow({
+        id: "row-photo-1",
+        order_item_attachements: ["invoice-1.pdf"],
+      }),
+    ];
+    buildFetchSpy(photoRows);
+
+    const user = userEvent.setup();
+    render(<Page />);
+
+    await waitFor(() =>
+      expect(screen.getByTestId("po-card-PO-1")).toBeInTheDocument(),
+    );
+
+    await user.click(
+      screen.getByRole("button", { name: /Invoice 1 invoice-1\.pdf/i }),
+    );
+    const viewer = await screen.findByTestId("invoice-viewer");
+    await user.click(within(viewer).getByTestId("invoice-viewer-open-new-tab"));
+
+    // The button explicitly opts into the historical new-tab flow,
+    // so window.open is invoked — but only because the operator
+    // asked for it via the viewer header, not from the chip itself.
     expect(openSpy).toHaveBeenCalledWith(
       "/api/v1/files/order_items/row-photo-1/invoice-1.pdf",
       "_blank",
diff --git a/src/app/(app)/collection-confirm/page.tsx b/src/app/(app)/collection-confirm/page.tsx
index ecabde9..a103e7c 100644
--- a/src/app/(app)/collection-confirm/page.tsx
+++ b/src/app/(app)/collection-confirm/page.tsx
@@ -6,7 +6,9 @@ import { toast } from "sonner";
 
 import { Button } from "@/components/ui/button";
 import { ConfirmInvoiceDialog } from "@/components/collection-confirm/confirm-invoice-dialog";
+import { InvoiceViewer } from "@/components/collection-confirm/invoice-viewer";
 import { PoCard } from "@/components/collection-confirm/po-card";
+import type { Attachment } from "@/components/collection-confirm/photo-strip";
 import { getClientIdentity } from "@/lib/dev-identity";
 import type { ConfirmRow } from "@/lib/server/collection-confirm-service";
 
@@ -60,6 +62,25 @@ export default function CollectionConfirmPage() {
     rowIds: string[];
   } | null>(null);
   const [busy, setBusy] = useState<boolean>(false);
+  // Floating in-app invoice viewer. The operator clicks an invoice
+  // chip on a PoCard to open the PDF inline (instead of getting
+  // bounced to a new tab and losing the side-by-side comparison
+  // with the items table). `null` means the viewer is closed.
+  //
+  // Toggle behaviour: clicking the chip for the currently-active
+  // invoice closes the viewer; clicking a different invoice swaps
+  // content. The handler below encapsulates that logic so the
+  // PhotoStrip stays unaware of the toggle semantics.
+  const [viewer, setViewer] = useState<{ filename: string; url: string } | null>(null);
+
+  const handleInvoiceOpen = useCallback((attachment: Attachment) => {
+    setViewer((current) =>
+      current?.filename === attachment.filename ? null : {
+        filename: attachment.filename,
+        url: attachment.url,
+      },
+    );
+  }, []);
 
   const load = useCallback(async () => {
     setRows(null);
@@ -369,6 +390,8 @@ export default function CollectionConfirmPage() {
                       ? () => void handleBookStock(stockRowIds)
                       : undefined
                   }
+                  onInvoiceOpen={handleInvoiceOpen}
+                  activeInvoiceFilename={viewer?.filename ?? null}
                 />
               );
             })}
@@ -387,6 +410,13 @@ export default function CollectionConfirmPage() {
         }}
         onSubmit={(args) => void handleConfirmSubmit(args)}
       />
+
+      <InvoiceViewer
+        open={!!viewer}
+        filename={viewer?.filename ?? ""}
+        url={viewer?.url ?? ""}
+        onClose={() => setViewer(null)}
+      />
     </div>
   );
 }
diff --git a/src/components/collection-confirm/invoice-viewer.test.tsx b/src/components/collection-confirm/invoice-viewer.test.tsx
new file mode 100644
index 0000000..9f51b6b
--- /dev/null
+++ b/src/components/collection-confirm/invoice-viewer.test.tsx
@@ -0,0 +1,347 @@
+import { act, fireEvent, render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { InvoiceViewer } from "./invoice-viewer";
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+const URL = "/api/v1/files/order_items/row-1/invoice.pdf";
+const FILENAME = "invoice.pdf";
+
+/**
+ * Helper: jsdom doesn't implement matchMedia or layout, so for the
+ * mobile-detection tests we stub `window.matchMedia` to return the
+ * desired match state. Tests that need desktop behaviour don't
+ * stub it — the default jsdom implementation reports no match,
+ * which means `useMediaQuery` returns `false` (desktop mode).
+ */
+function mockMatchMedia(matches: boolean) {
+  const listeners: Array<(event: MediaQueryListEvent) => void> = [];
+  Object.defineProperty(window, "matchMedia", {
+    writable: true,
+    value: vi.fn().mockImplementation((query: string) => ({
+      matches,
+      media: query,
+      onchange: null,
+      addEventListener: (_: string, listener: (event: MediaQueryListEvent) => void) => {
+        listeners.push(listener);
+      },
+      removeEventListener: vi.fn(),
+      dispatchEvent: vi.fn(),
+    })),
+  });
+  return listeners;
+}
+
+describe("InvoiceViewer", () => {
+  it("renders nothing when closed", () => {
+    const { container } = render(
+      <InvoiceViewer open={false} filename={FILENAME} url={URL} onClose={vi.fn()} />,
+    );
+    expect(container).toBeEmptyDOMElement();
+  });
+
+  it("renders an iframe with the file URL when open", () => {
+    render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+    const iframe = screen.getByTestId("invoice-viewer-iframe");
+    expect(iframe).toHaveAttribute("src", URL);
+    expect(iframe).toHaveAttribute("title", FILENAME);
+  });
+
+  it("shows the filename in the header", () => {
+    render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+    expect(screen.getByText(FILENAME)).toBeInTheDocument();
+  });
+
+  it("invokes onClose when the X button is clicked", async () => {
+    const onClose = vi.fn();
+    const user = userEvent.setup();
+    render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={onClose} />);
+    await user.click(screen.getByTestId("invoice-viewer-close"));
+    expect(onClose).toHaveBeenCalledTimes(1);
+  });
+
+  it("invokes onClose when Esc is pressed", async () => {
+    const onClose = vi.fn();
+    const user = userEvent.setup();
+    render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={onClose} />);
+    await user.keyboard("{Escape}");
+    expect(onClose).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not listen for Esc when closed", async () => {
+    const onClose = vi.fn();
+    const user = userEvent.setup();
+    render(<InvoiceViewer open={false} filename={FILENAME} url={URL} onClose={onClose} />);
+    await user.keyboard("{Escape}");
+    expect(onClose).not.toHaveBeenCalled();
+  });
+
+  it("opens the file in a new tab via the explicit button (opt-in escape hatch)", async () => {
+    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+    const user = userEvent.setup();
+    render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+    await user.click(screen.getByTestId("invoice-viewer-open-new-tab"));
+    expect(openSpy).toHaveBeenCalledWith(URL, "_blank", "noopener,noreferrer");
+  });
+
+  it("moves the panel when the header is dragged", () => {
+    // jsdom doesn't lay out real boxes, so seed the header's
+    // bounding rect with a known origin (top-left = 100,100) and
+    // width 200. A mousedown at (120,110) creates an offset of
+    // (20,10); dragging to (300,400) must place the panel at
+    // (280, 390).
+    const header = (() => {
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      return screen.getByTestId("invoice-viewer-header");
+    })();
+
+    vi.spyOn(header, "getBoundingClientRect").mockReturnValue({
+      x: 100,
+      y: 100,
+      left: 100,
+      top: 100,
+      right: 300,
+      bottom: 140,
+      width: 200,
+      height: 40,
+      toJSON: () => ({}),
+    });
+
+    fireEvent.mouseDown(header, { clientX: 120, clientY: 110 });
+    fireEvent.mouseMove(window, { clientX: 300, clientY: 400 });
+    fireEvent.mouseUp(window);
+
+    const panel = screen.getByTestId("invoice-viewer");
+    expect(panel.style.left).toBe("280px");
+    expect(panel.style.top).toBe("390px");
+  });
+
+  it("does not start a drag when mousedown lands on a button in the header", async () => {
+    const closeBtn = (() => {
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      return screen.getByTestId("invoice-viewer-close");
+    })();
+    const header = screen.getByTestId("invoice-viewer-header");
+
+    vi.spyOn(header, "getBoundingClientRect").mockReturnValue({
+      x: 100,
+      y: 100,
+      left: 100,
+      top: 100,
+      right: 300,
+      bottom: 140,
+      width: 200,
+      height: 40,
+      toJSON: () => ({}),
+    });
+
+    // mousedown on the close button — the handler must NOT begin a drag.
+    fireEvent.mouseDown(closeBtn, { clientX: 280, clientY: 110 });
+    fireEvent.mouseMove(window, { clientX: 999, clientY: 999 });
+
+    const panel = screen.getByTestId("invoice-viewer");
+    // Position unchanged from the default (jsdom default viewport is
+    // 1024x768 → defaultPosition() = { x: 280, y: 184 }).
+    expect(panel.style.left).toBe("280px");
+    expect(panel.style.top).toBe("184px");
+  });
+
+  describe("zoom controls", () => {
+    it("starts at 100% zoom", () => {
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("100%");
+    });
+
+    it("zooms in by one step on + and out by one step on −", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+
+      const level = screen.getByTestId("invoice-viewer-zoom-level");
+      const zoomIn = screen.getByTestId("invoice-viewer-zoom-in");
+      const zoomOut = screen.getByTestId("invoice-viewer-zoom-out");
+
+      expect(level).toHaveTextContent("100%");
+
+      await user.click(zoomIn);
+      expect(level).toHaveTextContent("125%");
+      await user.click(zoomIn);
+      expect(level).toHaveTextContent("150%");
+
+      await user.click(zoomOut);
+      expect(level).toHaveTextContent("125%");
+      await user.click(zoomOut);
+      expect(level).toHaveTextContent("100%");
+      await user.click(zoomOut);
+      expect(level).toHaveTextContent("75%");
+    });
+
+    it("clamps zoom in at 300% and disables the + button there", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      const zoomIn = screen.getByTestId("invoice-viewer-zoom-in");
+      // 100 → 125 → 150 → 200 → 300 → clamped
+      for (let i = 0; i < 10; i++) await user.click(zoomIn);
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("300%");
+      expect(zoomIn).toBeDisabled();
+    });
+
+    it("clamps zoom out at 50% and disables the − button there", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      const zoomOut = screen.getByTestId("invoice-viewer-zoom-out");
+      for (let i = 0; i < 10; i++) await user.click(zoomOut);
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("50%");
+      expect(zoomOut).toBeDisabled();
+    });
+
+    it("Reset snaps back to 100% from any zoom level", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("200%");
+      await user.click(screen.getByTestId("invoice-viewer-zoom-reset"));
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("100%");
+    });
+
+    it("Reset is disabled at the default 100% zoom (no-op to invoke)", () => {
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      expect(screen.getByTestId("invoice-viewer-zoom-reset")).toBeDisabled();
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toBeDisabled();
+    });
+
+    it("clicking the zoom level label also resets (it's a button)", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      await user.click(screen.getByTestId("invoice-viewer-zoom-level"));
+      expect(screen.getByTestId("invoice-viewer-zoom-level")).toHaveTextContent("100%");
+    });
+
+    it("scales the PDF wrapper element width with the zoom level", async () => {
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      const wrapper = screen.getByTestId("invoice-viewer-pdf-wrapper");
+      const iframe = screen.getByTestId("invoice-viewer-iframe");
+      // 100% → wrapper is 100% × 100%, iframe CSS box is 100% × 100%,
+      // transform: scale(1) (no visual change).
+      expect(wrapper.style.width).toBe("100%");
+      expect(wrapper.style.height).toBe("100%");
+      expect(iframe.style.width).toBe("100%");
+      expect(iframe.style.height).toBe("100%");
+      expect(iframe.style.transform).toBe("scale(1)");
+
+      // 200% → wrapper is 200% × 200% (scrollbars appear so the
+      // operator can pan around the zoomed PDF). iframe CSS box
+      // shrinks to 50% × 50% and transform scales it back up.
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      expect(wrapper.style.width).toBe("200%");
+      expect(wrapper.style.height).toBe("200%");
+      expect(iframe.style.width).toBe("50%");
+      expect(iframe.style.height).toBe("50%");
+      expect(iframe.style.transform).toBe("scale(2)");
+
+      // 50% → wrapper collapses to 50% × 50% (but min 100% keeps
+      // the scrollable area usable), iframe CSS grows to 200% ×
+      // 200% and transform shrinks it back.
+      await user.click(screen.getByTestId("invoice-viewer-zoom-reset"));
+      for (let i = 0; i < 10; i++) await user.click(screen.getByTestId("invoice-viewer-zoom-out"));
+      expect(wrapper.style.width).toBe("50%");
+      expect(wrapper.style.height).toBe("50%");
+      expect(iframe.style.width).toBe("200%");
+      expect(iframe.style.height).toBe("200%");
+      expect(iframe.style.transform).toBe("scale(0.5)");
+    });
+  });
+
+  describe("mobile layout", () => {
+    it("renders full-screen and hides the drag affordances when the viewport is narrow", () => {
+      mockMatchMedia(true); // simulate ≤ 640px viewport
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+
+      const panel = screen.getByTestId("invoice-viewer");
+      expect(panel.getAttribute("data-mobile")).toBe("true");
+      expect(panel.style.width).toBe("100vw");
+      expect(panel.style.height).toBe("100dvh");
+      expect(panel.style.left).toBe("0px");
+      expect(panel.style.top).toBe("0px");
+
+      // The grip icon is hidden on mobile (nothing to drag).
+      expect(screen.queryByTestId("invoice-viewer-grip")).not.toBeInTheDocument();
+      // The "Viewing" badge is also hidden on mobile (the panel
+      // fills the screen, so it's obvious what's being viewed).
+      expect(screen.queryByText(/Viewing/i)).not.toBeInTheDocument();
+      // The header still has a grab cursor style on desktop but
+      // not on mobile — checked via the absence of cursor-grab.
+      const header = screen.getByTestId("invoice-viewer-header");
+      expect(header.className).not.toContain("cursor-grab");
+    });
+
+    it("still exposes zoom controls on mobile", async () => {
+      mockMatchMedia(true);
+      const user = userEvent.setup();
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+
+      const level = screen.getByTestId("invoice-viewer-zoom-level");
+      expect(level).toHaveTextContent("100%");
+      await user.click(screen.getByTestId("invoice-viewer-zoom-in"));
+      expect(level).toHaveTextContent("125%");
+      await user.click(screen.getByTestId("invoice-viewer-zoom-out"));
+      expect(level).toHaveTextContent("100%");
+    });
+
+    it("does not start a drag from a header mousedown on mobile", () => {
+      mockMatchMedia(true);
+      const header = (() => {
+        render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+        return screen.getByTestId("invoice-viewer-header");
+      })();
+
+      vi.spyOn(header, "getBoundingClientRect").mockReturnValue({
+        x: 100,
+        y: 100,
+        left: 100,
+        top: 100,
+        right: 300,
+        bottom: 140,
+        width: 200,
+        height: 40,
+        toJSON: () => ({}),
+      });
+
+      fireEvent.mouseDown(header, { clientX: 120, clientY: 110 });
+      fireEvent.mouseMove(window, { clientX: 9999, clientY: 9999 });
+
+      // Position unchanged — no drag occurred on mobile.
+      const panel = screen.getByTestId("invoice-viewer");
+      expect(panel.style.left).toBe("0px");
+      expect(panel.style.top).toBe("0px");
+    });
+
+    it("flips from mobile to desktop layout when the viewport widens", () => {
+      const listeners = mockMatchMedia(false); // start desktop
+      render(<InvoiceViewer open={true} filename={FILENAME} url={URL} onClose={vi.fn()} />);
+      // Desktop: floating box, has the grip icon + Viewing badge.
+      expect(screen.getByTestId("invoice-viewer").getAttribute("data-mobile")).toBe("false");
+      expect(screen.getByTestId("invoice-viewer-grip")).toBeInTheDocument();
+      expect(screen.getByText(/Viewing/i)).toBeInTheDocument();
+
+      // Simulate the media query flipping to mobile (e.g. operator
+      // rotates their phone, or resizes a desktop browser window).
+      // Wrap the synchronous listener dispatch in `act` so React
+      // commits the resulting re-render before we assert on it.
+      act(() => {
+        listeners.forEach((listener) => listener({ matches: true } as MediaQueryListEvent));
+      });
+      expect(screen.getByTestId("invoice-viewer").getAttribute("data-mobile")).toBe("true");
+      expect(screen.queryByText(/Viewing/i)).not.toBeInTheDocument();
+    });
+  });
+});
diff --git a/src/components/collection-confirm/invoice-viewer.tsx b/src/components/collection-confirm/invoice-viewer.tsx
new file mode 100644
index 0000000..11f02d9
--- /dev/null
+++ b/src/components/collection-confirm/invoice-viewer.tsx
@@ -0,0 +1,419 @@
+"use client";
+
+import { useCallback, useEffect, useRef, useState } from "react";
+import { ExternalLink, GripVertical, Minus, Plus, RotateCcw, X } from "lucide-react";
+
+import { Button } from "@/components/ui/button";
+
+/**
+ * Floating, draggable invoice PDF viewer for the collection-confirm
+ * page.
+ *
+ * Why this exists: the original flow was `window.open(url, "_blank")`
+ * on the photo-strip chip, which kicks the operator out to a new
+ * tab to verify the invoice against the items table. The tab switch
+ * breaks the side-by-side comparison the operator actually wants to
+ * do (look at a line on the invoice, look at the same line in the
+ * table, look back).
+ *
+ * This panel keeps the operator in the page:
+ *
+ *   - Renders the PDF inside an `<iframe>` against
+ *     `/api/v1/files/order_items/<id>/`. That route already
+ *     returns `Content-Type: application/pdf` and
+ *     `Content-Disposition: inline`, so the browser's built-in PDF
+ *     viewer takes over inside the panel.
+ *
+ *   - Desktop: the panel is a floating box anchored to the
+ *     bottom-right. The header bar is draggable — mousedown on the
+ *     bar captures the cursor offset, mousemove (attached to
+ *     `window` so dragging keeps working when the cursor leaves the
+ *     header) translates the panel. The drop releases.
+ *
+ *   - Mobile (viewport ≤ 640px): the panel becomes a full-screen
+ *     modal. The drag affordance is dropped because there's
+ *     nowhere to drag to, and the close / zoom controls remain
+ *     reachable at the top.
+ *
+ *   - Zoom: discrete levels (50% / 75% / 100% / 125% / 150% / 200%
+ *     / 300%) via + / − buttons and a Reset button. Implemented
+ *     as a CSS `transform: scale()` on the iframe (with the
+ *     iframe's CSS box pre-shrunk to `${100 / zoom}%` so the
+ *     scale lands it back at the panel's natural size). A
+ *     wrapper sized to `${zoom * 100}%` provides the scrollable
+ *     area so scrollbars appear at the right zoom levels. CSS
+ *     resize-only does NOT work for PDF iframes — Chrome / Safari
+ *     / Firefox's built-in PDF viewers cache the initial render
+ *     size and ignore post-load iframe resizes, so the page
+ *     content visually stays the same. Transform scales the
+ *     already-rendered output and works reliably across browsers.
+ *
+ *   - Esc closes the panel. The page-level `onClose` callback is
+ *     also invoked so the parent can clear its `viewer` state and
+ *     un-highlight the chip.
+ *
+ *   - "Open in new tab" is preserved as an opt-in header button
+ *     for full-screen viewing (e.g. landscape invoices). The chip
+ *     itself no longer opens a new tab by default.
+ *
+ * Note on accessibility: the panel is a `role="dialog"` with
+ * `aria-label`. Zoom buttons expose `aria-label` describing the
+ * action. Focus is left on the triggering chip — we don't trap
+ * focus inside the iframe (it's the operator's main interaction
+ * target).
+ */
+export type InvoiceViewerProps = {
+  open: boolean;
+  filename: string;
+  url: string;
+  onClose: () => void;
+};
+
+type Position = { x: number; y: number };
+
+const DEFAULT_WIDTH = 720;
+const DEFAULT_HEIGHT = 560;
+const MOBILE_BREAKPOINT = 640;
+
+/**
+ * Discrete zoom levels, in CSS scale units (1 = 100%).
+ * Clamped at the low end so the operator can see the whole page
+ * even on very small viewports; clamped at the high end so a
+ * runaway click doesn't push the PDF past 8× pixel-density where
+ * the browser PDF viewer renders blank pages.
+ */
+const ZOOM_LEVELS = [0.5, 0.75, 1, 1.25, 1.5, 2, 3] as const;
+const DEFAULT_ZOOM = 1;
+
+/**
+ * Cheap inline media-query hook. Re-evaluates on resize so the
+ * panel can flip between desktop (draggable, floating) and mobile
+ * (full-screen) layouts when the operator rotates their device.
+ *
+ * Initial value is computed lazily on first render via the
+ * matchMedia API — a window resize listener is attached after
+ * mount, and the SSR guard returns `false` on the server.
+ */
+function useMediaQuery(query: string): boolean {
+  const [matches, setMatches] = useState<boolean>(() => {
+    if (typeof window === "undefined") return false;
+    // jsdom (used by the test suite) doesn't implement matchMedia.
+    // Guard so the hook defaults to "no match" (desktop) instead
+    // of throwing — the mobile-specific tests stub matchMedia
+    // themselves.
+    if (typeof window.matchMedia !== "function") return false;
+    try {
+      return window.matchMedia(query).matches;
+    } catch {
+      return false;
+    }
+  });
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+    if (typeof window.matchMedia !== "function") return;
+    const mql = window.matchMedia(query);
+    const handler = (event: MediaQueryListEvent) => setMatches(event.matches);
+    mql.addEventListener("change", handler);
+    return () => mql.removeEventListener("change", handler);
+  }, [query]);
+  return matches;
+}
+
+function defaultPosition(): Position {
+  // Bottom-right with a 24px gutter. Computed at mount-time so a
+  // small viewport doesn't push the panel off-screen.
+  if (typeof window === "undefined") return { x: 0, y: 0 };
+  const x = Math.max(16, window.innerWidth - DEFAULT_WIDTH - 24);
+  const y = Math.max(16, window.innerHeight - DEFAULT_HEIGHT - 24);
+  return { x, y };
+}
+
+export function InvoiceViewer({ open, filename, url, onClose }: InvoiceViewerProps) {
+  const [position, setPosition] = useState<Position>(() => defaultPosition());
+  const [dragging, setDragging] = useState<boolean>(false);
+  // Latest offset between cursor and panel top-left, captured at
+  // mousedown so a fast drag doesn't snap the panel under the cursor.
+  const dragOffsetRef = useRef<{ dx: number; dy: number }>({ dx: 0, dy: 0 });
+  // Discrete zoom level. Steps through ZOOM_LEVELS via + / −; the
+  // Reset button snaps back to 100%. State stays inside the
+  // viewer so closing + reopening starts fresh at 100% (matches
+  // the principle that the viewer is a fresh context per open).
+  const [zoom, setZoom] = useState<number>(DEFAULT_ZOOM);
+
+  const isMobile = useMediaQuery(`(max-width: ${MOBILE_BREAKPOINT}px)`);
+
+  // Esc closes — matches the modal-shell convention used elsewhere.
+  useEffect(() => {
+    if (!open) return;
+    const handler = (event: KeyboardEvent) => {
+      if (event.key === "Escape") onClose();
+    };
+    window.addEventListener("keydown", handler);
+    return () => window.removeEventListener("keydown", handler);
+  }, [open, onClose]);
+
+  // Window-level mousemove / mouseup so the drag survives the
+  // cursor leaving the header. Cleanup releases the listeners on
+  // mouseup or unmount. Disabled on mobile where the panel
+  // fills the screen and dragging is meaningless.
+  useEffect(() => {
+    if (!dragging || isMobile) return;
+    const handleMove = (event: MouseEvent) => {
+      const nextX = event.clientX - dragOffsetRef.current.dx;
+      const nextY = event.clientY - dragOffsetRef.current.dy;
+      // Clamp to viewport so the header can't be dragged off-screen
+      // (the operator would lose the close button entirely).
+      const minX = -DEFAULT_WIDTH + 80;
+      const maxX = window.innerWidth - 80;
+      const minY = 0;
+      const maxY = window.innerHeight - 40;
+      setPosition({
+        x: Math.min(Math.max(nextX, minX), maxX),
+        y: Math.min(Math.max(nextY, minY), maxY),
+      });
+    };
+    const handleUp = () => setDragging(false);
+    window.addEventListener("mousemove", handleMove);
+    window.addEventListener("mouseup", handleUp);
+    return () => {
+      window.removeEventListener("mousemove", handleMove);
+      window.removeEventListener("mouseup", handleUp);
+    };
+  }, [dragging, isMobile]);
+
+  const handleHeaderMouseDown = useCallback(
+    (event: React.MouseEvent<HTMLDivElement>) => {
+      // No drag on mobile — the panel fills the screen anyway.
+      if (isMobile) return;
+      // Ignore drags that started on the buttons inside the header —
+      // those should still click, not initiate a drag.
+      const target = event.target as HTMLElement;
+      if (target.closest("button")) return;
+      const rect = event.currentTarget.getBoundingClientRect();
+      dragOffsetRef.current = {
+        dx: event.clientX - rect.left,
+        dy: event.clientY - rect.top,
+      };
+      setDragging(true);
+      event.preventDefault();
+    },
+    [isMobile],
+  );
+
+  const handleOpenInNewTab = useCallback(() => {
+    window.open(url, "_blank", "noopener,noreferrer");
+  }, [url]);
+
+  /**
+   * Zoom controls — step to the next / previous discrete level
+   * in ZOOM_LEVELS. Clamped via array bounds, so the operator
+   * can't zoom past the limit by spamming the button.
+   */
+  const zoomIn = useCallback(() => {
+    setZoom((current) => {
+      const idx = ZOOM_LEVELS.indexOf(current as (typeof ZOOM_LEVELS)[number]);
+      // If current is somehow not in the list (shouldn't happen,
+      // but be defensive), fall back to the default.
+      const nextIdx = idx === -1
+        ? ZOOM_LEVELS.indexOf(DEFAULT_ZOOM as (typeof ZOOM_LEVELS)[number]) + 1
+        : Math.min(idx + 1, ZOOM_LEVELS.length - 1);
+      return ZOOM_LEVELS[nextIdx];
+    });
+  }, []);
+
+  const zoomOut = useCallback(() => {
+    setZoom((current) => {
+      const idx = ZOOM_LEVELS.indexOf(current as (typeof ZOOM_LEVELS)[number]);
+      const nextIdx = idx === -1
+        ? ZOOM_LEVELS.indexOf(DEFAULT_ZOOM as (typeof ZOOM_LEVELS)[number]) - 1
+        : Math.max(idx - 1, 0);
+      return ZOOM_LEVELS[nextIdx];
+    });
+  }, []);
+
+  const zoomReset = useCallback(() => {
+    setZoom(DEFAULT_ZOOM);
+  }, []);
+
+  if (!open) return null;
+
+  // Mobile: full-screen, no drag, no grip, no "Viewing" badge —
+  // the panel *is* the screen so context is obvious.
+  // Desktop: floating box, draggable, with all the affordances.
+  const panelStyle = isMobile
+    ? {
+        left: 0,
+        top: 0,
+        width: "100vw",
+        height: "100dvh",
+        maxWidth: "100vw",
+        maxHeight: "100dvh",
+        borderRadius: 0,
+      }
+    : {
+        left: position.x,
+        top: position.y,
+        width: DEFAULT_WIDTH,
+        height: DEFAULT_HEIGHT,
+        maxWidth: "calc(100vw - 32px)",
+        maxHeight: "calc(100vh - 32px)",
+      };
+
+  const zoomPercent = Math.round(zoom * 100);
+  const canZoomIn = zoom < ZOOM_LEVELS[ZOOM_LEVELS.length - 1];
+  const canZoomOut = zoom > ZOOM_LEVELS[0];
+
+  return (
+    <div
+      role="dialog"
+      aria-label={`Invoice viewer — ${filename}`}
+      data-testid="invoice-viewer"
+      data-mobile={isMobile ? "true" : "false"}
+      className={`fixed z-50 flex flex-col bg-background shadow-2xl ${
+        isMobile ? "rounded-none border-0" : "rounded-lg border"
+      }`}
+      style={panelStyle}
+    >
+      <div
+        onMouseDown={handleHeaderMouseDown}
+        className={`flex shrink-0 items-center justify-between gap-2 border-b bg-muted/50 px-3 py-2 ${
+          !isMobile && dragging ? "cursor-grabbing select-none" : ""
+        } ${!isMobile ? "cursor-grab" : ""}`}
+        data-testid="invoice-viewer-header"
+      >
+        <div className="flex min-w-0 flex-1 items-center gap-2">
+          {!isMobile ? (
+            <GripVertical
+              className="h-4 w-4 shrink-0 text-muted-foreground"
+              aria-hidden="true"
+              data-testid="invoice-viewer-grip"
+            />
+          ) : null}
+          <span className="truncate text-sm font-medium" title={filename}>
+            {filename}
+          </span>
+          {!isMobile ? (
+            <span className="shrink-0 rounded-full bg-primary/10 px-2 py-0.5 text-[10px] font-medium uppercase tracking-wide text-primary">
+              Viewing
+            </span>
+          ) : null}
+        </div>
+        <div className="flex shrink-0 items-center gap-1">
+          {/* Zoom controls — grouped so the visual unit is
+              obvious. `icon-sm` is 32px (a comfortable touch
+              target on mobile) and the surrounding gap of 0.5
+              keeps the cluster compact enough to fit on a
+              360px-wide phone header. */}
+          <div
+            className="flex items-center gap-0.5 rounded-md border bg-background px-1 py-0.5"
+            role="group"
+            aria-label="Zoom controls"
+            data-testid="invoice-viewer-zoom"
+          >
+            <Button
+              type="button"
+              variant="ghost"
+              size="icon-sm"
+              onClick={zoomOut}
+              disabled={!canZoomOut}
+              aria-label="Zoom out"
+              data-testid="invoice-viewer-zoom-out"
+            >
+              <Minus className="h-3.5 w-3.5" />
+            </Button>
+            <button
+              type="button"
+              onClick={zoomReset}
+              disabled={zoom === DEFAULT_ZOOM}
+              aria-label={`Reset zoom (currently ${zoomPercent}%)`}
+              data-testid="invoice-viewer-zoom-level"
+              className="min-w-[3rem] rounded px-1.5 py-0.5 text-center font-mono text-xs tabular-nums text-foreground transition-colors hover:bg-accent disabled:cursor-default disabled:hover:bg-transparent disabled:opacity-70"
+            >
+              {zoomPercent}%
+            </button>
+            <Button
+              type="button"
+              variant="ghost"
+              size="icon-sm"
+              onClick={zoomIn}
+              disabled={!canZoomIn}
+              aria-label="Zoom in"
+              data-testid="invoice-viewer-zoom-in"
+            >
+              <Plus className="h-3.5 w-3.5" />
+            </Button>
+            <Button
+              type="button"
+              variant="ghost"
+              size="icon-sm"
+              onClick={zoomReset}
+              disabled={zoom === DEFAULT_ZOOM}
+              aria-label="Reset zoom to 100%"
+              data-testid="invoice-viewer-zoom-reset"
+            >
+              <RotateCcw className="h-3.5 w-3.5" />
+            </Button>
+          </div>
+          <Button
+            type="button"
+            variant="ghost"
+            size="sm"
+            onClick={handleOpenInNewTab}
+            aria-label={`Open ${filename} in a new tab`}
+            data-testid="invoice-viewer-open-new-tab"
+          >
+            <ExternalLink className="mr-1 h-3.5 w-3.5" />
+            New tab
+          </Button>
+          <Button
+            type="button"
+            variant="ghost"
+            size="icon"
+            onClick={onClose}
+            className="h-8 w-8"
+            aria-label="Close invoice viewer"
+            data-testid="invoice-viewer-close"
+          >
+            <X className="h-4 w-4" />
+          </Button>
+        </div>
+      </div>
+      {/* PDF area. The wrapper is sized to `${zoom * 100}% × zoom
+          * 100%` so scrollbars appear at the right zoom levels.
+          The iframe's CSS box is pre-shrunk to `${100 / zoom}%`
+          (so its layout footprint matches the wrapper) and
+          scaled back via `transform: scale(zoom)`. This is the
+          only reliable way to zoom a PDF iframe — resizing the
+          iframe's CSS dimensions alone doesn't work because the
+          browser's PDF viewer caches the initial render size. */}
+      <div className="relative flex-1 overflow-auto bg-zinc-100 dark:bg-zinc-900">
+        <div
+          data-testid="invoice-viewer-pdf-wrapper"
+          style={{
+            width: `${zoom * 100}%`,
+            height: `${zoom * 100}%`,
+            minWidth: "100%",
+            minHeight: "100%",
+          }}
+        >
+          <iframe
+            key={url}
+            src={url}
+            title={filename}
+            data-testid="invoice-viewer-iframe"
+            className="border-0 bg-white"
+            style={{
+              width: `${100 / zoom}%`,
+              height: `${100 / zoom}%`,
+              transform: `scale(${zoom})`,
+              transformOrigin: "top left",
+              display: "block",
+            }}
+          />
+        </div>
+      </div>
+    </div>
+  );
+}
+
+export default InvoiceViewer;
diff --git a/src/components/collection-confirm/photo-strip.test.tsx b/src/components/collection-confirm/photo-strip.test.tsx
index 4330930..804bbe3 100644
--- a/src/components/collection-confirm/photo-strip.test.tsx
+++ b/src/components/collection-confirm/photo-strip.test.tsx
@@ -46,19 +46,56 @@ describe("PhotoStrip", () => {
     expect(screen.getByText(/Attach dialog/i)).toBeInTheDocument();
   });
 
-  it("opens the file from its first row in a new tab", async () => {
-    const user = userEvent.setup();
-    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+  it("calls onOpen with the attachment when a chip is clicked (page-level toggle path)", async () => {
+    const onOpen = vi.fn();
     const rows: ConfirmRow[] = [
       { id: "row/one", order_item_attachements: ["invoice copy.pdf"] },
       { id: "row-2", order_item_attachements: ["invoice copy.pdf"] },
     ];
 
-    render(<PhotoStrip rows={rows} />);
+    const user = userEvent.setup();
+    render(<PhotoStrip rows={rows} onOpen={onOpen} />);
     await user.click(screen.getByRole("button", { name: /Invoice 1 invoice copy\.pdf/i }));
 
+    expect(onOpen).toHaveBeenCalledTimes(1);
+    expect(onOpen).toHaveBeenCalledWith({
+      filename: "invoice copy.pdf",
+      url: "/api/v1/files/order_items/row%2Fone/invoice%20copy.pdf",
+      itemId: "row/one",
+    });
+  });
+
+  it("marks the activeFilename chip with aria-pressed=true", () => {
+    const rows: ConfirmRow[] = [
+      { id: "row-1", order_item_attachements: ["a.pdf"] },
+      { id: "row-2", order_item_attachements: ["b.pdf"] },
+    ];
+
+    render(<PhotoStrip rows={rows} activeFilename="b.pdf" />);
+
+    expect(
+      screen.getByRole("button", { name: /Invoice 1 a\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "false");
+    expect(
+      screen.getByRole("button", { name: /Invoice 2 b\.pdf/i }),
+    ).toHaveAttribute("aria-pressed", "true");
+  });
+
+  it("falls back to window.open when no onOpen handler is provided", async () => {
+    // The strip is still useful in isolation (e.g. embedded in a
+    // future read-only context) — without an onOpen the chip keeps
+    // the historical "open in new tab" behaviour.
+    const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+    const rows: ConfirmRow[] = [
+      { id: "row-1", order_item_attachements: ["invoice.pdf"] },
+    ];
+
+    const user = userEvent.setup();
+    render(<PhotoStrip rows={rows} />);
+    await user.click(screen.getByRole("button", { name: /Invoice 1 invoice\.pdf/i }));
+
     expect(openSpy).toHaveBeenCalledWith(
-      "/api/v1/files/order_items/row%2Fone/invoice%20copy.pdf",
+      "/api/v1/files/order_items/row-1/invoice.pdf",
       "_blank",
       "noopener,noreferrer",
     );
diff --git a/src/components/collection-confirm/photo-strip.tsx b/src/components/collection-confirm/photo-strip.tsx
index dc3f01d..5d9ebdb 100644
--- a/src/components/collection-confirm/photo-strip.tsx
+++ b/src/components/collection-confirm/photo-strip.tsx
@@ -4,11 +4,52 @@ import { dedupeAttachments } from "@/app/(app)/collection-confirm/view-model";
 import { Button } from "@/components/ui/button";
 import type { ConfirmRow } from "@/lib/server/collection-confirm-service";
 
-type PhotoStripProps = {
-  rows: ConfirmRow[];
+export type Attachment = {
+  filename: string;
+  url: string;
+  /**
+   * First item id that carries this attachment. Used by the
+   * `/api/v1/files/...` URL pattern (collection/recordId/filename)
+   * so the same item still resolves the file even if the operator
+   * uploaded the same filename to multiple rows.
+   */
+  itemId: string;
 };
 
-export function PhotoStrip({ rows }: PhotoStripProps) {
+type PhotoStripProps = {
+  rows: ConfirmRow[];
+  /**
+   * Called when the operator clicks a chip. The page-level handler
+   * decides whether to open the floating viewer, swap content, or
+   * close (toggle) based on whether the clicked attachment matches
+   * the currently-active one.
+   *
+   * If not provided, the chip falls back to opening the file in a
+   * new tab (the historical behaviour) so the strip still works in
+   * isolation — useful for tests and any future caller that doesn't
+   * need the in-app viewer.
+   */
+  onOpen?: (attachment: Attachment) => void;
+  /**
+   * Filename currently being viewed in the floating panel, if any.
+   * When set, the matching chip renders an "active" visual state
+   * (border + ring) so the operator can tell which invoice is open.
+   * Clicking that chip again closes the viewer (handled by the
+   * page-level `onOpen` toggle).
+   */
+  activeFilename?: string | null;
+};
+
+/**
+ * One chip per distinct attachment filename. Clicking a chip
+ * forwards the attachment to the parent's `onOpen` handler; the
+ * parent decides whether to render the inline viewer or fall back
+ * to a new-tab open.
+ *
+ * The historical "open in new tab" behaviour is preserved when no
+ * `onOpen` is supplied (see the prop doc above).
+ */
+export function PhotoStrip({ rows, onOpen, activeFilename }: PhotoStripProps) {
   const attachments = dedupeAttachments(rows);
 
   if (attachments.length === 0) {
@@ -30,16 +71,29 @@ export function PhotoStrip({ rows }: PhotoStripProps) {
         if (!firstItemId) return null;
 
         const url = `/api/v1/files/order_items/${encodeURIComponent(firstItemId)}/${encodeURIComponent(filename)}`;
+        const isActive = activeFilename === filename;
 
         return (
           <Button
             key={filename}
             type="button"
-            variant="outline"
+            variant={isActive ? "default" : "outline"}
             size="sm"
-            className="h-auto max-w-full py-2"
             aria-label={`Invoice ${index + 1} ${filename}`}
-            onClick={() => window.open(url, "_blank", "noopener,noreferrer")}          >
+            aria-pressed={isActive}
+            className={`h-auto max-w-full py-2 ${
+              isActive ? "ring-2 ring-primary ring-offset-1" : ""
+            }`}
+            data-testid={`photo-strip-chip-${index + 1}`}
+            data-active={isActive ? "true" : "false"}
+            onClick={() => {
+              if (onOpen) {
+                onOpen({ filename, url, itemId: firstItemId });
+              } else {
+                window.open(url, "_blank", "noopener,noreferrer");
+              }
+            }}
+          >
             <span className="font-medium">Invoice {index + 1}</span>
             <span className="truncate text-muted-foreground">{filename}</span>
           </Button>
diff --git a/src/components/collection-confirm/po-card.tsx b/src/components/collection-confirm/po-card.tsx
index 2681151..b1a15c2 100644
--- a/src/components/collection-confirm/po-card.tsx
+++ b/src/components/collection-confirm/po-card.tsx
@@ -3,7 +3,7 @@
 import { Button } from "@/components/ui/button";
 import type { ConfirmRow } from "@/lib/server/collection-confirm-service";
 import { ItemsTable } from "./items-table";
-import { PhotoStrip } from "./photo-strip";
+import { PhotoStrip, type Attachment } from "./photo-strip";
 
 type Props = {
   rows: ConfirmRow[];
@@ -19,6 +19,20 @@ type Props = {
    * both render.
    */
   onBookStock?: () => void;
+  /**
+   * Optional handler invoked when an invoice chip is clicked. The
+   * page-level handler typically toggles the floating in-app viewer
+   * (open / swap / close) so the operator doesn't have to tab out
+   * to verify the invoice against the items table. When omitted,
+   * the chip falls back to opening the file in a new tab.
+   */
+  onInvoiceOpen?: (attachment: Attachment) => void;
+  /**
+   * Filename currently being viewed in the page's floating viewer,
+   * if any. The matching chip on this card renders an active
+   * visual state so the operator can see which invoice is open.
+   */
+  activeInvoiceFilename?: string | null;
 };
 
 /**
@@ -47,6 +61,8 @@ export function PoCard({
   onCostChange,
   onConfirm,
   onBookStock,
+  onInvoiceOpen,
+  activeInvoiceFilename,
 }: Props) {
   const itemCount = rows.length;
   const hasStockRows = rows.some((r) => r.source === "stock");
@@ -68,7 +84,11 @@ export function PoCard({
       </header>
 
       <div className="mb-4">
-        <PhotoStrip rows={rows} />
+        <PhotoStrip
+          rows={rows}
+          onOpen={onInvoiceOpen}
+          activeFilename={activeInvoiceFilename}
+        />
       </div>
 
       <div className="mb-4">