From 4875b64293906e053d5c8dd60be3657cd752343b Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Sat, 29 Aug 2026 02:36:26 -0700
Subject: [PATCH] Split pane tree equalization logic

---
 config/max-lines-baseline.txt                 |  1 -
 .../pane-manager/pane-tree-equalization.ts    | 59 ++++++++++++++++++
 .../src/lib/pane-manager/pane-tree-ops.ts     | 62 +------------------
 3 files changed, 60 insertions(+), 62 deletions(-)
 create mode 100644 src/renderer/src/lib/pane-manager/pane-tree-equalization.ts

diff --git a/config/max-lines-baseline.txt b/config/max-lines-baseline.txt
index 740626e9bae..db6c77afbd8 100644
--- a/config/max-lines-baseline.txt
+++ b/config/max-lines-baseline.txt
@@ -61,7 +61,6 @@ inline src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.ts
 inline src/renderer/src/components/terminal-pane/use-terminal-pane-lifecycle.ts
 inline src/renderer/src/hooks/useAutomationDispatchEvents.ts
 inline src/renderer/src/hooks/useSettingsNavigationMetadata.ts
-inline src/renderer/src/lib/pane-manager/pane-tree-ops.ts
 inline src/renderer/src/runtime/remote-runtime-terminal-multiplexer.ts
 inline src/renderer/src/runtime/runtime-file-client.ts
 inline src/renderer/src/runtime/sync-runtime-graph.ts
diff --git a/src/renderer/src/lib/pane-manager/pane-tree-equalization.ts b/src/renderer/src/lib/pane-manager/pane-tree-equalization.ts
new file mode 100644
index 00000000000..7e36064d9bc
--- /dev/null
+++ b/src/renderer/src/lib/pane-manager/pane-tree-equalization.ts
@@ -0,0 +1,59 @@
+/** Find non-divider children (panes and splits) of an element. */
+export function findPaneChildren(parent: HTMLElement): HTMLElement[] {
+  return Array.from(parent.children).filter(
+    (child): child is HTMLElement =>
+      child instanceof HTMLElement &&
+      (child.classList.contains('pane') || child.classList.contains('pane-split'))
+  )
+}
+
+function getSplitDirection(split: HTMLElement): 'vertical' | 'horizontal' {
+  return split.classList.contains('is-horizontal') ? 'horizontal' : 'vertical'
+}
+
+function getEqualizeWeight(el: HTMLElement, direction: 'vertical' | 'horizontal'): number {
+  if (!el.classList.contains('pane-split') || getSplitDirection(el) !== direction) {
+    return 1
+  }
+
+  const children = findPaneChildren(el)
+  return Math.max(
+    1,
+    children.reduce((sum, child) => sum + getEqualizeWeight(child, direction), 0)
+  )
+}
+
+export function equalizePaneSplitSizes(root: HTMLElement | null): boolean {
+  if (!root) {
+    return false
+  }
+
+  let changed = false
+  const visit = (el: HTMLElement): void => {
+    if (!el.classList.contains('pane-split')) {
+      return
+    }
+
+    const direction = getSplitDirection(el)
+    const children = findPaneChildren(el)
+    if (children.length >= 2) {
+      for (const child of children) {
+        // Why: same-axis nested splits need pane-count weighting so three
+        // side-by-side panes become thirds, not 50/25/25.
+        const weight = getEqualizeWeight(child, direction)
+        const nextFlex = `${weight} 1 0%`
+        if (child.style.flex !== nextFlex) {
+          child.style.flex = nextFlex
+          changed = true
+        }
+      }
+    }
+
+    for (const child of children) {
+      visit(child)
+    }
+  }
+
+  visit(root)
+  return changed
+}
diff --git a/src/renderer/src/lib/pane-manager/pane-tree-ops.ts b/src/renderer/src/lib/pane-manager/pane-tree-ops.ts
index 833eb1ff822..3549860183b 100644
--- a/src/renderer/src/lib/pane-manager/pane-tree-ops.ts
+++ b/src/renderer/src/lib/pane-manager/pane-tree-ops.ts
@@ -1,4 +1,3 @@
-/* eslint-disable max-lines -- Why: split-tree DOM reparent, promote, and equalize rules need one consistent owner. */
 import type {
   DropZone,
   ManagedPane,
@@ -16,6 +15,7 @@ export {
   type SafeFitContinuationHandle
 } from './pane-fit'
 export { captureScrollState, restoreScrollState } from './pane-scroll'
+export { equalizePaneSplitSizes, findPaneChildren } from './pane-tree-equalization'
 
 // ---------------------------------------------------------------------------
 // Split-tree manipulation: detach, insert, promote sibling
@@ -242,66 +242,6 @@ export function removeDividers(parent: HTMLElement): void {
   }
 }
 
-/** Find non-divider children (panes and splits) of an element. */
-export function findPaneChildren(parent: HTMLElement): HTMLElement[] {
-  return Array.from(parent.children).filter(
-    (child): child is HTMLElement =>
-      child instanceof HTMLElement &&
-      (child.classList.contains('pane') || child.classList.contains('pane-split'))
-  )
-}
-
-function getSplitDirection(split: HTMLElement): 'vertical' | 'horizontal' {
-  return split.classList.contains('is-horizontal') ? 'horizontal' : 'vertical'
-}
-
-function getEqualizeWeight(el: HTMLElement, direction: 'vertical' | 'horizontal'): number {
-  if (!el.classList.contains('pane-split') || getSplitDirection(el) !== direction) {
-    return 1
-  }
-
-  const children = findPaneChildren(el)
-  return Math.max(
-    1,
-    children.reduce((sum, child) => sum + getEqualizeWeight(child, direction), 0)
-  )
-}
-
-export function equalizePaneSplitSizes(root: HTMLElement | null): boolean {
-  if (!root) {
-    return false
-  }
-
-  let changed = false
-  const visit = (el: HTMLElement): void => {
-    if (!el.classList.contains('pane-split')) {
-      return
-    }
-
-    const direction = getSplitDirection(el)
-    const children = findPaneChildren(el)
-    if (children.length >= 2) {
-      for (const child of children) {
-        // Why: same-axis nested splits need pane-count weighting so three
-        // side-by-side panes become thirds, not 50/25/25.
-        const weight = getEqualizeWeight(child, direction)
-        const nextFlex = `${weight} 1 0%`
-        if (child.style.flex !== nextFlex) {
-          child.style.flex = nextFlex
-          changed = true
-        }
-      }
-    }
-
-    for (const child of children) {
-      visit(child)
-    }
-  }
-
-  visit(root)
-  return changed
-}
-
 /**
  * Create a flex split wrapper that replaces `existingContainer` in the DOM,
  * then places [existing] [divider] [new] inside it.