fix: prevent infinite height growth in time picker

CLAUDE.md

@@ -155,6 +155,18 @@ The repo uses Husky with lint-staged. On commit:
 - **Formatting**: Prettier 3.4.2
 - **CSS**: Sass 1.93.2
 
+## Bug Fix Workflow (TDD)
+
+When fixing bugs, always follow Test-Driven Development:
+
+1. **Write the test first** - Create a failing test that reproduces the bug
+2. **Confirm it fails** - Run the test to verify it captures the broken behavior
+3. **Implement the fix** - Make the minimal code change to fix the issue
+4. **Verify the test passes** - Run the test again to confirm the fix works
+5. **Run full test suite** - Ensure no regressions with `yarn test:ci`
+
+This ensures every bug fix has regression coverage and documents the expected behavior.
+
 ## Code Conventions
 
 - **Prettier handles all code formatting** - don't worry about tabs vs spaces

src/test/timepicker_test.test.tsx

@@ -80,6 +80,44 @@ describe("TimePicker", () => {
         expect(resizeObserverCallback).toBe(null);
       });
     });
+
+    it("should not cause infinite loop when resize callback is called multiple times", async () => {
+      const { container } = render(
+        <DatePicker
+          inline
+          selected={new Date()}
+          showTimeSelect
+          timeIntervals={15}
+        />,
+      );
+
+      await waitFor(() => {
+        expect(mockObserve).toHaveBeenCalledTimes(1);
+      });
+
+      const resizeObserverCallback = getResizeObserverCallback();
+      const mockObserveElement = mockObserve.mock.calls[0][0];
+      expect(typeof resizeObserverCallback).toBe("function");
+
+      const timeList = container.querySelector(
+        ".react-datepicker__time-list",
+      ) as HTMLElement;
+      expect(timeList).not.toBeNull();
+
+      // Get initial height
+      const initialHeight = timeList.style.height;
+
+      // Call resize callback multiple times (simulating what would happen in an infinite loop)
+      if (resizeObserverCallback) {
+        resizeObserverCallback([], mockObserveElement);
+        resizeObserverCallback([], mockObserveElement);
+        resizeObserverCallback([], mockObserveElement);
+      }
+
+      // Height should remain stable (not grow infinitely)
+      // The fix ensures setState is only called when height actually changes
+      expect(timeList.style.height).toBe(initialHeight);
+    });
   });
 
   it("should update on input time change", () => {

src/time.tsx

@@ -97,9 +97,14 @@ export default class Time extends Component<TimeProps, TimeState> {
 
   private updateContainerHeight(): void {
     if (this.props.monthRef && this.header) {
-      this.setState({
-        height: this.props.monthRef.clientHeight - this.header.clientHeight,
-      });
+      const newHeight =
+        this.props.monthRef.clientHeight - this.header.clientHeight;
+      // Only update state if height actually changed to prevent infinite resize loops
+      if (this.state.height !== newHeight) {
+        this.setState({
+          height: newHeight,
+        });
+      }
     }
   }