diff --git a/src/render/mouse-hit.test.ts b/src/render/mouse-hit.test.ts
new file mode 100644
index 0000000..3f5eff5
--- /dev/null
+++ b/src/render/mouse-hit.test.ts
@@ -0,0 +1,115 @@
+import { describe, it, expect } from "bun:test";
+import { hitTestClick } from "./mouse-hit.ts";
+import type { RepoGroup, Row } from "../types.ts";
+
+function createTestGroup(name: string, repoSelected = true): RepoGroup {
+  return {
+    repoFullName: name,
+    repoSelected,
+    folded: false,
+    matches: [
+      {
+        filePath: "src/test.ts",
+        textMatches: [],
+        extractSelected: false,
+      },
+    ],
+    extractSelected: [false],
+    pickedFrom: undefined,
+    sectionLabel: undefined,
+  };
+}
+
+describe("hitTestClick", () => {
+  it("returns null for click out of bounds (y below rows)", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "repo", repoIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 0, 100);
+    expect(result).toBeNull();
+  });
+
+  it("returns null for click out of bounds (y at 0)", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "repo", repoIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 0, 0);
+    expect(result).toBeNull();
+  });
+
+  it("detects fold action on repo row arrow column", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "repo", repoIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 0, 1); // column 0, row 1
+    expect(result).toEqual({
+      row: rows[0],
+      column: 0,
+      action: "fold",
+    });
+  });
+
+  it("detects select action on repo row checkbox column", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "repo", repoIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 2, 1); // column 2, row 1
+    expect(result).toEqual({
+      row: rows[0],
+      column: 2,
+      action: "select",
+    });
+  });
+
+  it("detects navigate action on repo row elsewhere", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "repo", repoIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 10, 1); // column 10, row 1
+    expect(result).toEqual({
+      row: rows[0],
+      column: 10,
+      action: "navigate",
+    });
+  });
+
+  it("detects select action on extract row checkbox", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "extract", repoIndex: 0, extractIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 2, 1); // column 2, row 1
+    expect(result).toEqual({
+      row: rows[0],
+      column: 2,
+      action: "select",
+    });
+  });
+
+  it("detects navigate action on extract row elsewhere", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [{ type: "extract", repoIndex: 0, extractIndex: 0 }];
+    const result = hitTestClick(groups, rows, 0, 10, 1); // column 10, row 1
+    expect(result).toEqual({
+      row: rows[0],
+      column: 10,
+      action: "navigate",
+    });
+  });
+
+  it("handles multiple rows and identifies the correct row", () => {
+    const groups = [createTestGroup("org/repoA"), createTestGroup("org/repoB")];
+    const rows: Row[] = [
+      { type: "repo", repoIndex: 0 },
+      { type: "repo", repoIndex: 1 },
+    ];
+    // Row 1 is repoA, row 2 is repoB
+    const result = hitTestClick(groups, rows, 0, 2, 2); // column 2, row 2
+    expect(result?.row.repoIndex).toBe(1);
+    expect(result?.action).toBe("select");
+  });
+
+  it("handles section rows (no special action)", () => {
+    const groups = [createTestGroup("org/repo")];
+    const rows: Row[] = [
+      { type: "section", repoIndex: -1, sectionLabel: "section-a" },
+      { type: "repo", repoIndex: 0 },
+    ];
+    const result = hitTestClick(groups, rows, 0, 0, 1); // section row
+    expect(result?.row.type).toBe("section");
+    expect(result?.action).toBe("navigate");
+  });
+});
diff --git a/src/render/mouse-hit.ts b/src/render/mouse-hit.ts
new file mode 100644
index 0000000..97c6579
--- /dev/null
+++ b/src/render/mouse-hit.ts
@@ -0,0 +1,74 @@
+// Hit-testing for mouse clicks in the TUI viewport.
+// Maps clicked (x, y) coordinates to logical Row and action type.
+
+import type { RepoGroup, Row } from "../types.ts";
+import { rowTerminalLines } from "./rows.ts";
+
+export interface ClickTarget {
+  row: Row;
+  column: number; // Column index within the row (0-based terminal position)
+  action: "fold" | "select" | "navigate";
+}
+
+/**
+ * Hit-test a mouse click against the rendered rows.
+ *
+ * Returns a ClickTarget if the click lands on a valid row; null if out of bounds.
+ * Coordinates (x, y) are 1-indexed (terminal convention).
+ *
+ * Actions:
+ *   - "fold" on repo rows: click lands on the ▸/▾ column (column 0)
+ *   - "select" on any row: click lands on the ✓ checkbox column (column ~2-6 depending on line type)
+ *   - "navigate" on any row: click elsewhere (just move cursor to that row)
+ */
+export function hitTestClick(
+  groups: RepoGroup[],
+  rows: Row[],
+  scrollOffset: number,
+  x: number,
+  y: number,
+): ClickTarget | null {
+  // Convert 1-indexed terminal coordinates to 0-indexed row list
+  const clickedRowIndex = y - 1;
+  if (clickedRowIndex < 0 || clickedRowIndex >= rows.length) return null;
+
+  // Calculate cumulative line heights to find which row was clicked
+  let lineOffset = 0;
+  for (let i = 0; i < rows.length; i++) {
+    const row = rows[i];
+    const group = groups[row.repoIndex] ?? undefined;
+    const h = rowTerminalLines(group, row);
+
+    if (lineOffset <= clickedRowIndex && clickedRowIndex < lineOffset + h) {
+      // This row was clicked
+      // Column 0 is the fold arrow (for repo rows)
+      // Column ~2 is the checkbox (after "▸ " or "  ")
+      // For extract rows, the checkbox offset is slightly different based on line type
+
+      let action: "fold" | "select" | "navigate" = "navigate";
+
+      if (row.type === "repo") {
+        // Repo row layout: "▸ ✓ repo-name"
+        // Arrow at column 0, checkbox at column 2 (after "▸ ")
+        if (x === 0) {
+          action = "fold";
+        } else if (x === 2) {
+          action = "select";
+        }
+      } else if (row.type === "extract") {
+        // Extract row layout: "  ✓ path:line:col"
+        // Checkbox at column 2 (after "  ")
+        if (x === 2) {
+          action = "select";
+        }
+      }
+      // Section rows don't support any action (just navigate)
+
+      return { row, column: x, action };
+    }
+
+    lineOffset += h;
+  }
+
+  return null;
+}
diff --git a/src/tui.ts b/src/tui.ts
index b2bf801..9260513 100644
--- a/src/tui.ts
+++ b/src/tui.ts
@@ -20,6 +20,7 @@ import {
   rebuildTeamSections,
 } from "./group.ts";
 import { parseMouseEvent } from "./render/mouse.ts";
+import { hitTestClick } from "./render/mouse-hit.ts";
 import type { FilterTarget, OutputFormat, OutputType, RepoGroup, Row } from "./types.ts";
 
 // ─── Key binding constants ────────────────────────────────────────────────────
@@ -291,7 +292,36 @@ export async function runInteractive(
     // Try parsing as a mouse event; if it's not a mouse event, treat as keyboard input
     const mouseEvent = parseMouseEvent(key);
     if (mouseEvent !== null) {
-      // Mouse events are silently ignored for now; this hook is here for future #170 / #168
+      // Hit-test the click against visible rows
+      const target = hitTestClick(groups, rows, scrollOffset, mouseEvent.x, mouseEvent.y);
+      if (target !== null) {
+        const row = target.row;
+        if (target.action === "fold" && row.type === "repo") {
+          // Toggle fold for this repo
+          const group = groups[row.repoIndex];
+          group.folded = !group.folded;
+          redraw();
+        } else if (target.action === "select") {
+          if (row.type === "repo") {
+            // Toggle repo selection
+            const group = groups[row.repoIndex];
+            group.repoSelected = !group.repoSelected;
+          } else if (row.type === "extract" && row.extractIndex !== undefined) {
+            // Toggle extract selection
+            const group = groups[row.repoIndex];
+            group.extractSelected[row.extractIndex] = !group.extractSelected[row.extractIndex];
+          }
+          redraw();
+        } else if (target.action === "navigate") {
+          // Move cursor to this row
+          const rowIndex = rows.findIndex((r) => r === row);
+          if (rowIndex >= 0) {
+            cursor = rowIndex;
+            scrollOffset = Math.min(scrollOffset, cursor);
+            redraw();
+          }
+        }
+      }
       continue;
     }