Panels jerk instead of smoothly resizing, when adjusted from their minSize state

[Chevindu]

Hi, first of all, thanks for all that you do! I first noticed this on my app, then later noted the same in your demo as well.
I can reproduce it on both desktop and mobile Firefox. So I'm not sure if this is a bug, hence creating a discussion instead.

Steps

1. Go to Collapsible panels demo
2. Resize a smaller panel so that it hits the minimum size (in this case, 100px in width)
3. Try to increase the size of that panel from its minimum size.

Expected result

Panel increases the size smoothly from its minimum size.

Actual result

Panel snaps from the minimum size to a larger size.
In the first example of the above linked page, it jumps to 200px. In the second one, it first jumps to 165px, then to 200px.

Is this the expected behavior? If yes, I'm confused about the values they snap to when increasing the size. Thanks in advance.

[bvaughn]

This is version 4.5.2:

firefox-4-5-2.mov

And this is the latest version:

firefox-latest.mov

It's a bit subtle but I agree, the resize behavior does look jumpier than expected.

[bvaughn]

Versions 4.5.3 and 4.5.4 exhibit the same behavior.

I assume this is related to the change in #635 + #642

[bvaughn]

Can confirm that disabling that recent behavior change fixes the Firefox jerkiness.

[bvaughn]

Thanks for the report, @Chevindu.

I believe this issue has been fixed in #644 and released in react-resizable-panels@4.5.6

Let me know if you see anything else

---

❤️ → ☕ givebrian.coffee

[bvaughn]

Update to this issue: The following unit test (added to adjustLayoutByDelta.test captures the regression reported above:

test("edge case discussions/643", () => {
  (
    [
      [4, l([10, 90])],
      // This step will fail without the collapsible change that caused this regression
      [6, l([20, 80])],
      // These steps will fail with the previous collapsible change (this is the regression/bug)
      [10, l([20, 80])],
      [15, l([25, 75])],
      [25, l([35, 65])],
      [40, l([50, 50])],
      [50, l([50, 50])]
    ] satisfies [number, Layout][]
  ).forEach(([delta, expectedLayout]) => {
    expect(
      adjustLayoutByDelta({
        delta,
        initialLayout: l([10, 90]),
        panelConstraints: c([
          {
            collapsedSize: 10,
            collapsible: true,
            defaultSize: 10,
            maxSize: 50,
            minSize: 20
          },
          {}
        ]),
        prevLayout: l([10, 90]),
        trigger: "mouse-or-touch"
      })
    ).toEqual(expectedLayout);
  });
});

[bvaughn]

Potential fix in #646

[bvaughn]

The original collapse behavior has been re-enabled, but with a fix for this issue, in version 4.5.7

Please let me know if you see anything else unexpected, @Chevindu

---

❤️ → ☕ givebrian.coffee

[Chevindu]

Hi, I tried version 4.5.8 this morning and can confirm the jumpy behavior I observed is fixed. The demos also work smoothly on Firefox now.
I'm sorry about the delayed response, and thanks for looking into this @bvaughn!

[bvaughn]

No worries! Thanks for letting me know 🙂

…

On Mon, Feb 2, 2026 at 5:22 AM Chevindu Wickramathilaka < ***@***.***> wrote: Hi, I tried version 4.5.8 this morning and can confirm the jumpy behavior I observed is fixed. The demos also work smoothly on Firefox now. I'm sorry about the delayed response, and thanks for looking into this @bvaughn <https://github.com/bvaughn>! — Reply to this email directly, view it on GitHub <#643 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAHHHJEBA6Z5NYZSQHZXS34J3NINAVCNFSM6AAAAACTNAWXXOVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTKNRWHA3TONY> . You are receiving this because you were mentioned.Message ID: <bvaughn/react-resizable-panels/repo-discussions/643/comments/15668777@ github.com>