diff --git a/.gitignore b/.gitignore
index 16f234a37..8ed8c0e1b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,3 +59,5 @@ plugins/posthog/local-skills/
 
 # Symlinked copies of posthog, to make developing against those APIs easier
 posthog-sym
+.pi-lens/
+Progress.md
diff --git a/apps/code/src/renderer/features/code-review/components/ReviewShell.test.tsx b/apps/code/src/renderer/features/code-review/components/ReviewShell.test.tsx
new file mode 100644
index 000000000..bcec2fb11
--- /dev/null
+++ b/apps/code/src/renderer/features/code-review/components/ReviewShell.test.tsx
@@ -0,0 +1,159 @@
+import { render } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+
+// Mock heavy dependencies that ReviewShell.tsx transitively imports
+vi.mock("@renderer/features/code-review/stores/reviewNavigationStore", () => ({
+  useReviewNavigationStore: vi.fn(),
+}));
+
+vi.mock("@features/code-editor/stores/diffViewerStore", () => ({
+  useDiffViewerStore: vi.fn(),
+}));
+
+vi.mock("@features/task-detail/components/ChangesPanel", () => ({
+  ChangesPanel: () => null,
+}));
+
+vi.mock("@features/git-interaction/utils/diffStats", () => ({
+  computeDiffStats: () => ({ linesAdded: 0, linesRemoved: 0 }),
+}));
+
+vi.mock("@stores/themeStore", () => ({
+  useThemeStore: vi.fn(() => ({ isDarkMode: false })),
+}));
+
+vi.mock("@pierre/diffs/react", () => ({
+  WorkerPoolContextProvider: ({ children }: { children: React.ReactNode }) =>
+    children,
+}));
+
+vi.mock("@pierre/diffs/worker/worker.js?worker&url", () => ({
+  default: "",
+}));
+
+vi.mock("@components/ui/FileIcon", () => ({
+  FileIcon: () => <span data-testid="file-icon" />,
+}));
+
+import { DeferredDiffPlaceholder, DiffFileHeader } from "./ReviewShell";
+
+// Minimal FileDiffMetadata shape for the test
+function makeFileDiff(name: string) {
+  return {
+    name,
+    prevName: null,
+    hunks: [{ additionLines: 3, deletionLines: 1 }],
+  } as unknown as import("@pierre/diffs/react").FileDiffMetadata;
+}
+
+/**
+ * Helper: find the filepath wrapper element in a rendered FileHeaderRow.
+ * The filepath is split into two spans: a gray directory span and a bold filename span.
+ * Their parent container must prevent wrapping between them.
+ */
+function getFilePathWrapper(container: HTMLElement): HTMLElement {
+  const button = container.querySelector("button");
+  expect(button).toBeTruthy();
+
+  const spans = button?.querySelectorAll<HTMLSpanElement>("span");
+  // Find the span that contains the directory path (has gray color, no fontWeight)
+  const dirSpan = Array.from(spans).find(
+    (s) => s.style.color === "var(--gray-9)" && !s.style.fontWeight,
+  );
+  expect(dirSpan).toBeTruthy();
+
+  // Find the bold filename span
+  const fileNameSpan = Array.from(spans).find(
+    (s) => s.style.fontWeight === "600",
+  );
+  expect(fileNameSpan).toBeTruthy();
+
+  // Both spans should share the same parent wrapper
+  expect(dirSpan?.parentElement).toBe(fileNameSpan?.parentElement);
+
+  return dirSpan?.parentElement!;
+}
+
+function hasNoWrapOrTruncation(el: HTMLElement): boolean {
+  const inline = el.style.whiteSpace === "nowrap";
+  const computed = getComputedStyle(el).whiteSpace === "nowrap";
+  const overflow = el.style.overflow === "hidden";
+  const textOverflow =
+    el.style.textOverflow === "ellipsis" ||
+    getComputedStyle(el).textOverflow === "ellipsis";
+  return inline || computed || overflow || textOverflow;
+}
+
+describe("DiffFileHeader", () => {
+  it("renders the directory path and filename", () => {
+    const { container } = render(
+      <DiffFileHeader
+        fileDiff={makeFileDiff(
+          "src/renderer/features/code-review/components/ReviewShell.tsx",
+        )}
+        collapsed={false}
+        onToggle={() => {}}
+      />,
+    );
+
+    const button = container.querySelector("button");
+    expect(button?.textContent).toContain(
+      "src/renderer/features/code-review/components/",
+    );
+    expect(button?.textContent).toContain("ReviewShell.tsx");
+  });
+
+  it("keeps the filepath on a single line (no wrapping between dir and filename)", () => {
+    const longPath =
+      "src/renderer/features/code-review/components/very-deeply-nested-directory/structure/ReviewShell.tsx";
+
+    const { container } = render(
+      <DiffFileHeader
+        fileDiff={makeFileDiff(longPath)}
+        collapsed={false}
+        onToggle={() => {}}
+      />,
+    );
+
+    const wrapper = getFilePathWrapper(container);
+    expect(hasNoWrapOrTruncation(wrapper)).toBe(true);
+  });
+});
+
+describe("DeferredDiffPlaceholder", () => {
+  it("renders the directory path and filename", () => {
+    const { container } = render(
+      <DeferredDiffPlaceholder
+        filePath="packages/core/src/utils/diff.ts"
+        linesAdded={10}
+        linesRemoved={2}
+        reason="generated"
+        collapsed={false}
+        onToggle={() => {}}
+      />,
+    );
+
+    const button = container.querySelector("button");
+    expect(button?.textContent).toContain("packages/core/src/utils/");
+    expect(button?.textContent).toContain("diff.ts");
+  });
+
+  it("keeps the filepath on a single line", () => {
+    const longPath =
+      "packages/core/src/utils/very/deeply/nested/structure/with/many/segments/helper.ts";
+
+    const { container } = render(
+      <DeferredDiffPlaceholder
+        filePath={longPath}
+        linesAdded={10}
+        linesRemoved={2}
+        reason="generated"
+        collapsed={false}
+        onToggle={() => {}}
+      />,
+    );
+
+    const wrapper = getFilePathWrapper(container);
+    expect(hasNoWrapOrTruncation(wrapper)).toBe(true);
+  });
+});
diff --git a/apps/code/src/renderer/features/code-review/components/ReviewShell.tsx b/apps/code/src/renderer/features/code-review/components/ReviewShell.tsx
index 060d20a72..24ccf328d 100644
--- a/apps/code/src/renderer/features/code-review/components/ReviewShell.tsx
+++ b/apps/code/src/renderer/features/code-review/components/ReviewShell.tsx
@@ -508,9 +508,19 @@ function FileHeaderRow({
         }}
       />
       <FileIcon filename={fileName} size={14} />
-      <span style={{ color: "var(--gray-9)" }}>{dirPath}</span>
-      <span style={{ fontWeight: 600, marginLeft: dirPath ? "-6px" : 0 }}>
-        {fileName}
+      <span
+        style={{
+          overflow: "hidden",
+          textOverflow: "ellipsis",
+          whiteSpace: "nowrap",
+          minWidth: 0,
+        }}
+        title={dirPath + fileName}
+      >
+        <span style={{ color: "var(--gray-9)" }}>{dirPath}</span>
+        <span style={{ fontWeight: 600, marginLeft: dirPath ? "-6px" : 0 }}>
+          {fileName}
+        </span>
       </span>
       <span style={{ fontFamily: "monospace", fontSize: "10px" }}>
         {additions > 0 && (