fix(ui): remember splitter positions in the Git and other tool windows

SplitGroup only remembers sizes with a storageKey, and none of the Git views
passed one, so the Commit, Local Changes, Log, Stash/Shelf and revision
splitters went back to their defaults whenever the view was recreated. Give
them, the Commit dialog, and the Todo, Find, Problems, Usages, Build, HTTP
Client and Dependency Analyzer splits a key, with stable panel ids.

A view whose preview pane comes and goes keys its sizes per panel set;
SplitGroup now applies that set's saved sizes when the key changes, once the
panels have registered, so toggling a preview restores its size without
remounting the view.

src/features/build-tools/DependencyAnalyzer.tsx

@@ -440,7 +440,11 @@ export function DependencyAnalyzer(_props: { input: EditorInput }) {
 
   const treeView = (
     <div className={styles.body}>
-      <SplitGroup orientation="horizontal" id="maven-dependency-analyzer-split">
+      <SplitGroup
+        orientation="horizontal"
+        id="maven-dependency-analyzer-split"
+        storageKey="openidea.dependencyAnalyzer.split"
+      >
         <SplitPanel id="dependencies" minSize={200} className={styles.panel}>
           <Tree<Node>
             aria-label="Dependencies"

src/features/build/BuildView.tsx

@@ -339,7 +339,12 @@ export function BuildView() {
   }
   return (
     <div className={styles.view}>
-      <SplitGroup orientation="horizontal" className={styles.split} id="build-view-split">
+      <SplitGroup
+        orientation="horizontal"
+        className={styles.split}
+        id="build-view-split"
+        storageKey="openidea.build.split"
+      >
         <SplitPanel id="build-tree" defaultSize="38%" minSize="120px" className={styles.pane}>
           <BuildTree />
         </SplitPanel>

src/features/code-insight/ProblemsView.tsx

@@ -410,7 +410,7 @@ export function ProblemsView() {
     <div className={styles.view}>
       <div className={styles.body} onKeyDownCapture={onKeyDownCapture}>
         {options.preview ? (
-          <SplitGroup orientation="horizontal" id="problems-preview-split">
+          <SplitGroup orientation="horizontal" id="problems-preview-split" storageKey="openidea.problems.previewSplit">
             <SplitPanel id="problems" minSize={120} className={styles.panel}>
               {list}
             </SplitPanel>

src/features/code-insight/UsagesView.tsx

@@ -401,7 +401,7 @@ function UsagesSplit({ preview, children }: { preview: ReactNode; children: Reac
   const show = useUsagesOptions((s) => s.preview);
   if (!show) return children;
   return (
-    <SplitGroup orientation="horizontal" id="usages-preview-split">
+    <SplitGroup orientation="horizontal" id="usages-preview-split" storageKey="openidea.usages.previewSplit">
       <SplitPanel id="usages" minSize={160} className={styles.panel}>
         {children}
       </SplitPanel>

src/features/http-client/HttpClientView.tsx

@@ -261,7 +261,7 @@ export function HttpClientView() {
     void refreshHistory();
   }, []);
   return (
-    <SplitGroup orientation="horizontal" className={styles.root}>
+    <SplitGroup orientation="horizontal" className={styles.root} storageKey="openidea.httpClient.split">
       <SplitPanel id="http-history" defaultSize="32%" minSize="160px">
         <div className={styles.list} role="list" aria-label={tx("Response history")}>
           {running && (

src/features/search/find/FindToolWindow.tsx

@@ -422,7 +422,12 @@ function FindTabView({ tab }: { tab: FindTab }) {
           </>
         )}
       </div>
-      <SplitGroup orientation="horizontal" className={styles.split} id="find-results-split">
+      <SplitGroup
+        orientation="horizontal"
+        className={styles.split}
+        id="find-results-split"
+        storageKey={showPreview ? "openidea.find.previewSplit" : undefined}
+      >
         <SplitPanel id="results" minSize={120} className={styles.splitPanel}>
           <Tree<Node>
             className={styles.tree}

src/features/todo/TodoView.tsx

@@ -478,7 +478,11 @@ export function TodoView() {
       {tab === "scope" && <ScopeBar />}
       {tab === "changes" && <ChangelistBar />}
       <div className={styles.body}>
-        <SplitGroup orientation="horizontal" id="todo-preview-split">
+        <SplitGroup
+          orientation="horizontal"
+          id="todo-preview-split"
+          storageKey={showPreview ? "openidea.todo.previewSplit" : undefined}
+        >
           <SplitPanel id="items" minSize={160} className={styles.panel}>
             <Tree<Node>
               handleRef={tree}

src/features/vcs/CommitDialog.tsx

@@ -69,14 +69,18 @@ function CommitDialog({ onClose }: { onClose: () => void }) {
       ]}
     >
       <div className={styles.body}>
-        <SplitGroup orientation="vertical" className={styles.split}>
-          <SplitPanel defaultSize="58%" minSize="25%">
-            <SplitGroup orientation="horizontal" className={styles.split}>
-              <SplitPanel defaultSize="64%" minSize="35%">
+        <SplitGroup orientation="vertical" className={styles.split} storageKey="openidea.vcs.commitDialogSplit">
+          <SplitPanel id="top" defaultSize="58%" minSize="25%">
+            <SplitGroup
+              orientation="horizontal"
+              className={styles.split}
+              storageKey="openidea.vcs.commitDialogOptionsSplit"
+            >
+              <SplitPanel id="changes" defaultSize="64%" minSize="35%">
                 <ChangesTree mode="dialog" />
               </SplitPanel>
               <SplitHandle />
-              <SplitPanel defaultSize="36%" minSize="200px">
+              <SplitPanel id="options" defaultSize="36%" minSize="200px">
                 <div className={styles.options} role="group" aria-label={tx("Commit Options")}>
                   <CommitOptionsBody />
                 </div>
@@ -84,7 +88,7 @@ function CommitDialog({ onClose }: { onClose: () => void }) {
             </SplitGroup>
           </SplitPanel>
           <SplitHandle />
-          <SplitPanel defaultSize="42%" minSize="120px">
+          <SplitPanel id="message" defaultSize="42%" minSize="120px">
             <div className={viewStyles.commit}>
               <CommitMessageField included={included} runner={runner} autoFocus />
             </div>

src/features/vcs/CommitView.tsx

@@ -184,12 +184,12 @@ export function StashContent({ tab }: { tab: CommitTab }) {
   const combine = useWorkflowSettings((s) => s.vcs.git.combineStashAndShelf);
   if (combine)
     return (
-      <SplitGroup orientation="vertical" className={styles.split}>
-        <SplitPanel defaultSize="50%" minSize="80px">
+      <SplitGroup orientation="vertical" className={styles.split} storageKey="openidea.vcs.stashShelfSplit">
+        <SplitPanel id="stashes" defaultSize="50%" minSize="80px">
           <StashesPanel />
         </SplitPanel>
         <SplitHandle />
-        <SplitPanel defaultSize="50%" minSize="80px">
+        <SplitPanel id="shelf" defaultSize="50%" minSize="80px">
           <ShelfPanel />
         </SplitPanel>
       </SplitGroup>
@@ -486,14 +486,18 @@ function ChangesPanel() {
   const path = useCommit((s) => (s.selection.length === 1 ? s.selection[0] : null));
   const hasChanges = useVcs((s) => s.status.length > 0);
   return (
-    <SplitGroup orientation="horizontal" className={styles.split}>
-      <SplitPanel defaultSize="62%" minSize="20%">
-        <SplitGroup orientation="vertical" className={styles.split}>
-          <SplitPanel defaultSize="62%" minSize="20%">
+    <SplitGroup
+      orientation="horizontal"
+      className={styles.split}
+      storageKey={preview ? "openidea.vcs.commitPreviewSplit" : undefined}
+    >
+      <SplitPanel id="commit" defaultSize="62%" minSize="20%">
+        <SplitGroup orientation="vertical" className={styles.split} storageKey="openidea.vcs.commitMessageSplit">
+          <SplitPanel id="changes" defaultSize="62%" minSize="20%">
             <ChangesTree mode="commit" />
           </SplitPanel>
           <SplitHandle />
-          <SplitPanel defaultSize="38%" minSize="120px">
+          <SplitPanel id="message" defaultSize="38%" minSize="120px">
             <CommitPanel included={included} />
           </SplitPanel>
         </SplitGroup>
@@ -501,7 +505,7 @@ function ChangesPanel() {
       {preview && (
         <>
           <SplitHandle />
-          <SplitPanel defaultSize="38%" minSize="120px">
+          <SplitPanel id="preview" defaultSize="38%" minSize="120px">
             {path ? (
               <DiffEditor input={diffInput(workingDiffData(path))} />
             ) : (
@@ -525,14 +529,20 @@ export function LocalChangesView() {
   const path = useCommit((s) => (s.selection.length === 1 ? s.selection[0] : null));
   const anchor = useToolWindowLayout((s) => s.placements.git?.anchor ?? "bottom");
   return (
-    <SplitGroup orientation={anchor === "bottom" ? "horizontal" : "vertical"} className={styles.split}>
-      <SplitPanel defaultSize="50%" minSize="20%">
+    <SplitGroup
+      orientation={anchor === "bottom" ? "horizontal" : "vertical"}
+      className={styles.split}
+      storageKey={
+        preview ? `openidea.vcs.localChangesSplit.${anchor === "bottom" ? "horizontal" : "vertical"}` : undefined
+      }
+    >
+      <SplitPanel id="changes" defaultSize="50%" minSize="20%">
         <ChangesTree mode="local" />
       </SplitPanel>
       {preview && (
         <>
           <SplitHandle />
-          <SplitPanel defaultSize="50%" minSize="120px">
+          <SplitPanel id="preview" defaultSize="50%" minSize="120px">
             {path ? (
               <DiffEditor input={diffInput(workingDiffData(path))} />
             ) : (

src/features/vcs/GitLog.tsx

@@ -327,6 +327,7 @@ export function LogView() {
       key={showBranches ? "branches" : "no-branches"}
       orientation="horizontal"
       id={showBranches ? "git-log" : "git-log-no-branches"}
+      storageKey={`openidea.vcs.logSplit.${showBranches ? "branches" : "noBranches"}.${showDetails ? "details" : "noDetails"}`}
       className={styles.split}
     >
       {showBranches && (
@@ -2681,7 +2682,7 @@ export function CommitDetails({ commits }: { commits: Commit[] }) {
   };
 
   const details = (
-    <SplitGroup orientation="vertical" id="git-log-details">
+    <SplitGroup orientation="vertical" id="git-log-details" storageKey="openidea.vcs.logDetailsSplit">
       <SplitPanel id="files" defaultSize="60%" minSize="60px">
         <div
           className={styles.filesPane}
@@ -2802,6 +2803,7 @@ export function CommitDetails({ commits }: { commits: Commit[] }) {
         <SplitGroup
           orientation={diffLocation === "right" ? "horizontal" : "vertical"}
           id={`git-log-preview-${diffLocation}`}
+          storageKey={`openidea.vcs.logPreviewSplit.${diffLocation}`}
         >
           <SplitPanel id="changes" defaultSize="55%" minSize="20%">
             {details}

src/features/vcs/RevisionBrowser.tsx

@@ -146,7 +146,7 @@ function RevisionBrowser({
         ) : !files ? (
           <Spinner />
         ) : (
-          <SplitGroup orientation="horizontal" id="git-revision-browser">
+          <SplitGroup orientation="horizontal" id="git-revision-browser" storageKey="openidea.vcs.revisionBrowserSplit">
             <SplitPanel id="files" defaultSize="30%" minSize="20%">
               <Tree
                 roots={tree}

src/ui/Splitter.test.tsx

@@ -0,0 +1,43 @@
+import { afterEach, expect, it } from "vitest";
+import { createRef } from "react";
+import { render } from "@testing-library/react";
+import type { GroupImperativeHandle } from "react-resizable-panels";
+import { SplitGroup, SplitHandle, SplitPanel } from "./Splitter";
+
+afterEach(() => localStorage.clear());
+
+function Split({ storageKey, preview }: { storageKey: string; preview: boolean }) {
+  return (
+    <SplitGroup orientation="horizontal" storageKey={storageKey} groupRef={ref}>
+      <SplitPanel id="tree" defaultSize="60%" />
+      {preview && (
+        <>
+          <SplitHandle />
+          <SplitPanel id="preview" defaultSize="40%" />
+        </>
+      )}
+    </SplitGroup>
+  );
+}
+const ref = createRef<GroupImperativeHandle>();
+
+it("starts from the sizes saved under its key", () => {
+  localStorage.setItem("split.preview", JSON.stringify({ tree: 30, preview: 70 }));
+  render(<Split storageKey="split.preview" preview />);
+  expect(ref.current!.getLayout()).toEqual({ tree: 30, preview: 70 });
+});
+
+it("applies the saved sizes of a panel set that appears later", () => {
+  localStorage.setItem("split.preview", JSON.stringify({ tree: 25, preview: 75 }));
+  const view = render(<Split storageKey="split.plain" preview={false} />);
+  view.rerender(<Split storageKey="split.preview" preview />);
+  expect(ref.current!.getLayout()).toEqual({ tree: 25, preview: 75 });
+});
+
+it("ignores saved sizes for other panels", () => {
+  localStorage.setItem("split.preview", JSON.stringify({ other: 25, preview: 75 }));
+  const view = render(<Split storageKey="split.plain" preview={false} />);
+  view.rerender(<Split storageKey="split.preview" preview />);
+  expect(Object.keys(ref.current!.getLayout()).sort()).toEqual(["preview", "tree"]);
+  expect(ref.current!.getLayout().tree).not.toBe(25);
+});

src/ui/Splitter.tsx

@@ -2,36 +2,84 @@
  * Thin wrappers over react-resizable-panels with IDE styling: 1px hairline
  * separators with a wider invisible hit area and an accent hover state.
  */
-import { Group, Panel, Separator, type GroupProps, type PanelProps, type SeparatorProps } from "react-resizable-panels";
+import {
+  Group,
+  Panel,
+  Separator,
+  type GroupImperativeHandle,
+  type GroupProps,
+  type PanelProps,
+  type SeparatorProps,
+} from "react-resizable-panels";
 import clsx from "clsx";
-import { useState } from "react";
+import { useEffect, useImperativeHandle, useRef, useState } from "react";
 import styles from "./Splitter.module.css";
 
+function savedLayout(storageKey: string | undefined): Record<string, number> | undefined {
+  try {
+    const value: unknown = storageKey ? JSON.parse(localStorage.getItem(storageKey) ?? "null") : null;
+    return value &&
+      typeof value === "object" &&
+      !Array.isArray(value) &&
+      Object.values(value).every((n) => typeof n === "number" && Number.isFinite(n) && n >= 0 && n <= 100)
+      ? (value as Record<string, number>)
+      : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+/**
+ * `storageKey` remembers the sizes the user drags to. A group whose panels come and go (a
+ * preview pane) passes a key per panel set; when it changes, that set's sizes are applied.
+ */
 export function SplitGroup({
   className,
   storageKey,
   defaultLayout,
   onLayoutChanged,
+  groupRef,
   ...rest
 }: GroupProps & { storageKey?: string }) {
-  const [saved] = useState(() => {
-    try {
-      const value: unknown = storageKey ? JSON.parse(localStorage.getItem(storageKey) ?? "null") : null;
-      return value &&
-        typeof value === "object" &&
-        !Array.isArray(value) &&
-        Object.values(value).every((n) => typeof n === "number" && Number.isFinite(n) && n >= 0 && n <= 100)
-        ? (value as Record<string, number>)
-        : undefined;
-    } catch {
-      return undefined;
-    }
-  });
+  const [saved] = useState(() => savedLayout(storageKey));
+  const group = useRef<GroupImperativeHandle | null>(null);
+  const mountedKey = useRef(storageKey);
+  // Sizes to apply once the group's panels match them (a panel added with the new key registers later).
+  const pending = useRef<Record<string, number> | null>(null);
+  const applyPending = (current: Record<string, number>) => {
+    const layout = pending.current;
+    if (!layout) return;
+    const ids = Object.keys(current);
+    if (ids.length !== Object.keys(layout).length || !ids.every((id) => id in layout)) return;
+    pending.current = null;
+    group.current?.setLayout(layout);
+  };
+  useEffect(() => {
+    if (storageKey === mountedKey.current) return;
+    mountedKey.current = storageKey;
+    pending.current = savedLayout(storageKey) ?? null;
+    const current = group.current?.getLayout();
+    if (current) applyPending(current);
+  }, [storageKey]);
+  useImperativeHandle(
+    groupRef,
+    () => ({
+      getLayout: () => group.current?.getLayout() ?? {},
+      setLayout: (layout) => group.current?.setLayout(layout) ?? layout,
+    }),
+    [],
+  );
+  const onLayoutChange: GroupProps["onLayoutChange"] = (layout) => {
+    applyPending(layout);
+    rest.onLayoutChange?.(layout);
+  };
   if (!storageKey)
     return (
       <Group
         className={clsx(styles.group, className)}
         {...rest}
+        groupRef={group}
+        onLayoutChange={onLayoutChange}
         defaultLayout={defaultLayout}
         onLayoutChanged={onLayoutChanged}
       />
@@ -40,6 +88,8 @@ export function SplitGroup({
     <Group
       className={clsx(styles.group, className)}
       {...rest}
+      groupRef={group}
+      onLayoutChange={onLayoutChange}
       defaultLayout={saved ?? defaultLayout}
       onLayoutChanged={(layout, meta) => {
         if (storageKey && meta.isUserInteraction) {