From cd3b12c579ffc668c28f30f1acbbb17ec3ab7033 Mon Sep 17 00:00:00 2001
From: James Long <longster@gmail.com>
Date: Fri, 28 Aug 2026 13:47:50 -0400
Subject: [PATCH] feat(tui): resize terminal panes (#45979)

---
 packages/tui/src/component/session-frame.tsx | 59 +++++++++++++++++---
 packages/tui/src/component/terminal-pane.tsx |  5 ++
 packages/tui/src/ui/layout.ts                |  6 ++
 packages/tui/src/ui/pane-resize-handle.tsx   |  7 ++-
 4 files changed, 67 insertions(+), 10 deletions(-)

diff --git a/packages/tui/src/component/session-frame.tsx b/packages/tui/src/component/session-frame.tsx
index 12391d8f81a..d62275ee60a 100644
--- a/packages/tui/src/component/session-frame.tsx
+++ b/packages/tui/src/component/session-frame.tsx
@@ -1,4 +1,4 @@
-import { RGBA } from "@opentui/core"
+import { RGBA, type MouseEvent } from "@opentui/core"
 import { useRenderer, useTerminalDimensions } from "@opentui/solid"
 import { batch, createEffect, createMemo, createResource, createSignal, on, Show } from "solid-js"
 import { useConfig } from "../config"
@@ -6,9 +6,12 @@ import { useData } from "../context/data"
 import { Keymap } from "../context/keymap"
 import { useSessionTerminals } from "../context/session-terminals"
 import { usePromptRef } from "../context/prompt"
+import { useStorage } from "../context/storage"
 import { Session } from "../routes/session"
 import { Sidebar } from "../routes/session/sidebar"
-import { SESSION_SIDEBAR_WIDTH } from "../ui/layout"
+import { clampTerminalPaneWidth, SESSION_SIDEBAR_WIDTH } from "../ui/layout"
+import { createPaneResize } from "../ui/pane-resize"
+import { PaneResizeHandle } from "../ui/pane-resize-handle"
 import { useToast } from "../ui/toast"
 import { TerminalPane } from "./terminal-pane"
 
@@ -20,6 +23,32 @@ export function SessionFrame(props: { sessionID: string; verticalTabsWidth: numb
   const toast = useToast()
   const renderer = useRenderer()
   const dimensions = useTerminalDimensions()
+  const availableWidth = () => Math.max(0, dimensions().width - props.verticalTabsWidth)
+  const defaultTerminalWidth = () => Math.max(1, Math.floor(dimensions().width / 2))
+  const [layout, updateLayout] = useStorage().store<{ terminalWidth?: number }>("layout", { initial: {} })
+  const terminalResize = createPaneResize({
+    value: () => layout.terminalWidth ?? defaultTerminalWidth(),
+    defaultValue: defaultTerminalWidth,
+    clamp: (width) => clampTerminalPaneWidth(width, availableWidth()),
+    fromMouse: (event) => dimensions().width - event.x - 1,
+    contains: (event, width) => event.x >= dimensions().width - width - 1 && event.x <= dimensions().width - width,
+    onCommit: (width) => {
+      void updateLayout((draft) => {
+        draft.terminalWidth = width
+      }).catch((error) => console.error("Failed to persist TUI layout", error))
+    },
+  })
+  let resizeRelease = false
+  const finishTerminalResize = (event: MouseEvent) => {
+    if (terminalResize.resizing()) {
+      // A captured drag-end can be followed by mouse-up on the focus overlay.
+      resizeRelease = true
+      queueMicrotask(() => {
+        resizeRelease = false
+      })
+    }
+    terminalResize.onMouseUp(event)
+  }
   const [sidebarOpen, setSidebarOpen] = createSignal(false)
   const [sessionWidth, setSessionWidth] = createSignal<number>()
   const [terminalFocused, setTerminalFocused] = createSignal(false)
@@ -96,7 +125,16 @@ export function SessionFrame(props: { sessionID: string; verticalTabsWidth: numb
   }))
 
   return (
-    <box flexGrow={1} minWidth={0} minHeight={0} flexDirection="row" position="relative">
+    <box
+      flexGrow={1}
+      minWidth={0}
+      minHeight={0}
+      flexDirection="row"
+      position="relative"
+      onMouseDrag={terminalResize.onMouseDrag}
+      onMouseDragEnd={finishTerminalResize}
+      onMouseUp={finishTerminalResize}
+    >
       <box
         flexGrow={1}
         flexBasis={0}
@@ -124,18 +162,17 @@ export function SessionFrame(props: { sessionID: string; verticalTabsWidth: numb
             height="100%"
             zIndex={1}
             // Consume the release before revealing permission buttons underneath.
-            onMouseUp={focusSession}
+            onMouseUp={() => {
+              if (terminalResize.resizing() || resizeRelease) return
+              focusSession()
+            }}
           />
         </Show>
       </box>
       <Show when={rightPane() === "terminal" || (rightPane() === "sidebar" && wide())}>
         <box
           flexShrink={0}
-          width={
-            rightPane() === "terminal"
-              ? Math.max(1, Math.floor((dimensions().width - props.verticalTabsWidth) / 2))
-              : SESSION_SIDEBAR_WIDTH
-          }
+          width={rightPane() === "terminal" ? terminalResize.size() : SESSION_SIDEBAR_WIDTH}
           minWidth={0}
           minHeight={0}
         >
@@ -146,6 +183,7 @@ export function SessionFrame(props: { sessionID: string; verticalTabsWidth: numb
                 {(ptyID) => (
                   <TerminalPane
                     ptyID={ptyID}
+                    resizing={terminalResize.resizing()}
                     autoFocus={restoreTerminalFocus() || sessions.shouldFocus(ptyID)}
                     onAutoFocus={() => {
                       sessions.clearFocus(ptyID)
@@ -163,6 +201,9 @@ export function SessionFrame(props: { sessionID: string; verticalTabsWidth: numb
           </Show>
         </box>
       </Show>
+      <Show when={rightPane() === "terminal" && availableWidth() >= 3}>
+        <PaneResizeHandle resize={terminalResize} left={availableWidth() - terminalResize.size() - 1} highlight="right" />
+      </Show>
       <Show when={rightPane() === "sidebar" && !wide()}>
         <box
           position="absolute"
diff --git a/packages/tui/src/component/terminal-pane.tsx b/packages/tui/src/component/terminal-pane.tsx
index 6d4ebf09c5c..ea600d06b4d 100644
--- a/packages/tui/src/component/terminal-pane.tsx
+++ b/packages/tui/src/component/terminal-pane.tsx
@@ -23,6 +23,7 @@ type StreamItem =
 
 export function TerminalPane(props: {
   ptyID: string
+  resizing?: boolean
   autoFocus?: boolean
   onAutoFocus?: () => void
   onFocusRequest?: (focus: (() => void) | undefined) => void
@@ -77,6 +78,10 @@ export function TerminalPane(props: {
     send(interactionFrame(size))
   }
 
+  createEffect(() => {
+    if (props.resizing) interact()
+  })
+
   const sendInput = (data: Uint8Array) => {
     if (!restored) {
       pendingInput.push(data)
diff --git a/packages/tui/src/ui/layout.ts b/packages/tui/src/ui/layout.ts
index e1dad76fe7f..85aa92ca5e8 100644
--- a/packages/tui/src/ui/layout.ts
+++ b/packages/tui/src/ui/layout.ts
@@ -13,3 +13,9 @@ export function clampSessionTabsWidth(width: number, total: number) {
     Math.min(width, SESSION_SIDEBAR_MAX_WIDTH, total - SESSION_CONTENT_MIN_WIDTH),
   )
 }
+
+export function clampTerminalPaneWidth(width: number, total: number) {
+  const half = Math.max(1, Math.floor(total / 2))
+  // Preserve the equal split when there is not enough room for both pane minima.
+  return Math.max(Math.min(24, half), Math.min(width, Math.max(half, total - SESSION_CONTENT_MIN_WIDTH)))
+}
diff --git a/packages/tui/src/ui/pane-resize-handle.tsx b/packages/tui/src/ui/pane-resize-handle.tsx
index 180ac92f226..edd1e04b75e 100644
--- a/packages/tui/src/ui/pane-resize-handle.tsx
+++ b/packages/tui/src/ui/pane-resize-handle.tsx
@@ -1,7 +1,11 @@
 import { useTheme } from "../context/theme"
 import type { createPaneResize } from "./pane-resize"
 
-export function PaneResizeHandle(props: { resize: ReturnType<typeof createPaneResize>; left: number }) {
+export function PaneResizeHandle(props: {
+  resize: ReturnType<typeof createPaneResize>
+  left: number
+  highlight?: "left" | "right"
+}) {
   const theme = useTheme("elevated")
 
   return (
@@ -19,6 +23,7 @@ export function PaneResizeHandle(props: { resize: ReturnType<typeof createPaneRe
       <box
         width={1}
         height="100%"
+        marginLeft={props.highlight === "right" ? 1 : 0}
         backgroundColor={
           props.resize.hovered() || props.resize.resizing() ? theme.background.action.primary.hovered : undefined
         }