refactor: replace session tabs with sectioned list

src/App.tsx

@@ -5,7 +5,7 @@ import FolderSelectionView from "./components/folder-selection-view"
 import InstanceWelcomeView from "./components/instance-welcome-view"
 import CommandPalette from "./components/command-palette"
 import InstanceTabs from "./components/instance-tabs"
-import SessionTabs from "./components/session-tabs"
+import SessionList from "./components/session-list"
 import MessageStream from "./components/message-stream"
 import PromptInput from "./components/prompt-input"
 import InfoView from "./components/info-view"
@@ -813,42 +813,46 @@ const App: Component = () => {
               {(instance) => (
                 <>
                   <Show when={activeSessions().size > 0} fallback={<InstanceWelcomeView instance={instance()} />}>
-                    <SessionTabs
-                      instanceId={instance().id}
-                      sessions={activeSessions()}
-                      activeSessionId={activeSessionIdForInstance()}
-                      onSelect={(id) => setActiveSession(instance().id, id)}
-                      onClose={(id) => handleCloseSession(instance().id, id)}
-                      onNew={() => handleNewSession(instance().id)}
-                    />
+                    <div class="flex h-full">
+                      {/* Session List Sidebar */}
+                      <SessionList
+                        instanceId={instance().id}
+                        sessions={activeSessions()}
+                        activeSessionId={activeSessionIdForInstance()}
+                        onSelect={(id) => setActiveSession(instance().id, id)}
+                        onClose={(id) => handleCloseSession(instance().id, id)}
+                        onNew={() => handleNewSession(instance().id)}
+                      />
 
-                    <div class="content-area flex-1 overflow-hidden flex flex-col">
-                      <Show
-                        when={activeSessionIdForInstance() === "info"}
-                        fallback={
-                          <Show
-                            when={activeSessionIdForInstance()}
-                            fallback={
-                              <div class="flex items-center justify-center h-full">
-                                <div class="text-center text-gray-500 dark:text-gray-400">
-                                  <p class="mb-2">No session selected</p>
-                                  <p class="text-sm">Select a session to view messages</p>
+                      {/* Main Content Area */}
+                      <div class="content-area flex-1 overflow-hidden flex flex-col">
+                        <Show
+                          when={activeSessionIdForInstance() === "info"}
+                          fallback={
+                            <Show
+                              when={activeSessionIdForInstance()}
+                              fallback={
+                                <div class="flex items-center justify-center h-full">
+                                  <div class="text-center text-gray-500 dark:text-gray-400">
+                                    <p class="mb-2">No session selected</p>
+                                    <p class="text-sm">Select a session to view messages</p>
+                                  </div>
                                 </div>
-                              </div>
-                            }
-                          >
-                            <SessionView
-                              sessionId={activeSessionIdForInstance()!}
-                              activeSessions={activeSessions()}
-                              instanceId={activeInstance()!.id}
-                              instanceFolder={activeInstance()!.folder}
-                              escapeInDebounce={escapeInDebounce()}
-                            />
-                          </Show>
-                        }
-                      >
-                        <InfoView instanceId={instance().id} />
-                      </Show>
+                              }
+                            >
+                              <SessionView
+                                sessionId={activeSessionIdForInstance()!}
+                                activeSessions={activeSessions()}
+                                instanceId={activeInstance()!.id}
+                                instanceFolder={activeInstance()!.folder}
+                                escapeInDebounce={escapeInDebounce()}
+                              />
+                            </Show>
+                          }
+                        >
+                          <InfoView instanceId={instance().id} />
+                        </Show>
+                      </div>
                     </div>
                   </Show>
                 </>

src/components/session-list.tsx

@@ -0,0 +1,307 @@
+import { Component, For, Show, createSignal, createEffect, onCleanup, onMount, createMemo } from "solid-js"
+import type { Session } from "../types/session"
+import { MessageSquare, Info, Plus, X } from "lucide-solid"
+import KeyboardHint from "./keyboard-hint"
+import { keyboardRegistry } from "../lib/keyboard-registry"
+
+interface SessionListItem {
+  id: string
+  title: string
+  isSpecial?: boolean
+  isActive: boolean
+  isParent?: boolean
+  onSelect: () => void
+  onClose?: () => void
+}
+
+interface SessionListProps {
+  instanceId: string
+  sessions: Map<string, Session>
+  activeSessionId: string | null
+  onSelect: (sessionId: string) => void
+  onClose: (sessionId: string) => void
+  onNew: () => void
+}
+
+const MIN_WIDTH = 200
+const MAX_WIDTH = 500
+const DEFAULT_WIDTH = 280
+const STORAGE_KEY = "opencode-session-sidebar-width"
+
+const SessionList: Component<SessionListProps> = (props) => {
+  const [sidebarWidth, setSidebarWidth] = createSignal(DEFAULT_WIDTH)
+  const [isResizing, setIsResizing] = createSignal(false)
+  const [startX, setStartX] = createSignal(0)
+  const [startWidth, setStartWidth] = createSignal(DEFAULT_WIDTH)
+
+  let mouseMoveHandler: ((event: MouseEvent) => void) | null = null
+  let mouseUpHandler: (() => void) | null = null
+  let touchMoveHandler: ((event: TouchEvent) => void) | null = null
+  let touchEndHandler: (() => void) | null = null
+
+  onMount(() => {
+    if (typeof window === "undefined") return
+    const saved = window.localStorage.getItem(STORAGE_KEY)
+    if (!saved) return
+
+    const width = Number.parseInt(saved, 10)
+    if (Number.isFinite(width) && width >= MIN_WIDTH && width <= MAX_WIDTH) {
+      setSidebarWidth(width)
+      setStartWidth(width)
+    }
+  })
+
+  createEffect(() => {
+    if (typeof window === "undefined") return
+    const width = sidebarWidth()
+    window.localStorage.setItem(STORAGE_KEY, width.toString())
+  })
+
+  const clampWidth = (width: number) => Math.max(MIN_WIDTH, Math.min(MAX_WIDTH, width))
+
+  const removeMouseListeners = () => {
+    if (mouseMoveHandler) {
+      document.removeEventListener("mousemove", mouseMoveHandler)
+      mouseMoveHandler = null
+    }
+    if (mouseUpHandler) {
+      document.removeEventListener("mouseup", mouseUpHandler)
+      mouseUpHandler = null
+    }
+  }
+
+  const removeTouchListeners = () => {
+    if (touchMoveHandler) {
+      document.removeEventListener("touchmove", touchMoveHandler)
+      touchMoveHandler = null
+    }
+    if (touchEndHandler) {
+      document.removeEventListener("touchend", touchEndHandler)
+      touchEndHandler = null
+    }
+  }
+
+  const stopResizing = () => {
+    setIsResizing(false)
+    removeMouseListeners()
+    removeTouchListeners()
+  }
+
+  const handleMouseMove = (event: MouseEvent) => {
+    if (!isResizing()) return
+    const diff = event.clientX - startX()
+    const newWidth = clampWidth(startWidth() + diff)
+    setSidebarWidth(newWidth)
+  }
+
+  const handleMouseUp = () => {
+    stopResizing()
+  }
+
+  const handleTouchMove = (event: TouchEvent) => {
+    if (!isResizing()) return
+    const touch = event.touches[0]
+    const diff = touch.clientX - startX()
+    const newWidth = clampWidth(startWidth() + diff)
+    setSidebarWidth(newWidth)
+  }
+
+  const handleTouchEnd = () => {
+    stopResizing()
+  }
+
+  const handleMouseDown = (event: MouseEvent) => {
+    event.preventDefault()
+    setIsResizing(true)
+    setStartX(event.clientX)
+    setStartWidth(sidebarWidth())
+
+    mouseMoveHandler = handleMouseMove
+    mouseUpHandler = handleMouseUp
+
+    document.addEventListener("mousemove", handleMouseMove)
+    document.addEventListener("mouseup", handleMouseUp)
+  }
+
+  const handleTouchStart = (event: TouchEvent) => {
+    event.preventDefault()
+    const touch = event.touches[0]
+    setIsResizing(true)
+    setStartX(touch.clientX)
+    setStartWidth(sidebarWidth())
+
+    touchMoveHandler = handleTouchMove
+    touchEndHandler = handleTouchEnd
+
+    document.addEventListener("touchmove", handleTouchMove)
+    document.addEventListener("touchend", handleTouchEnd)
+  }
+
+  onCleanup(() => {
+    removeMouseListeners()
+    removeTouchListeners()
+  })
+
+  const sessionSections = createMemo(() => {
+    const parentItems: SessionListItem[] = []
+    const childItems: SessionListItem[] = []
+
+    for (const [id, session] of props.sessions.entries()) {
+      const item: SessionListItem = {
+        id,
+        title: session.title || "Untitled",
+        isActive: id === props.activeSessionId,
+        isParent: session.parentId === null,
+        onSelect: () => props.onSelect(id),
+        onClose: session.parentId === null ? () => props.onClose(id) : undefined,
+      }
+
+      if (session.parentId === null) {
+        parentItems.push(item)
+      } else {
+        childItems.push(item)
+      }
+    }
+
+    childItems.sort((a, b) => {
+      const sessionA = props.sessions.get(a.id)
+      const sessionB = props.sessions.get(b.id)
+      if (!sessionA || !sessionB) return 0
+      return sessionB.time.updated - sessionA.time.updated
+    })
+
+    parentItems.push({
+      id: "info",
+      title: "Info",
+      isSpecial: true,
+      isActive: props.activeSessionId === "info",
+      onSelect: () => props.onSelect("info"),
+    })
+
+    return { parentItems, childItems }
+  })
+
+  return (
+    <div
+      class="session-list-container bg-surface-secondary border-r border-base flex flex-col"
+      style={{ width: `${sidebarWidth()}px` }}
+    >
+      <div
+        class="session-resize-handle"
+        onMouseDown={handleMouseDown}
+        onTouchStart={handleTouchStart}
+        role="presentation"
+        aria-hidden="true"
+      />
+
+      <div class="session-list-header p-3 border-b border-base">
+        <div class="flex items-center justify-between gap-3">
+          <h3 class="text-sm font-semibold text-primary">Sessions</h3>
+          <KeyboardHint
+            shortcuts={[keyboardRegistry.get("session-prev")!, keyboardRegistry.get("session-next")!].filter(Boolean)}
+          />
+        </div>
+      </div>
+
+      <div class="session-list flex-1 overflow-y-auto">
+        <div class="session-section">
+          <div class="session-section-header px-3 py-2 text-xs font-semibold text-primary/70 uppercase tracking-wide">
+            Parent & Info
+          </div>
+          <For each={sessionSections().parentItems}>
+            {(item) => (
+              <div class="session-list-item group">
+                <button
+                  class={`session-item-base ${
+                    item.isActive ? "session-item-active" : "session-item-inactive"
+                  } ${item.isSpecial ? "session-item-special" : ""}`}
+                  onClick={item.onSelect}
+                  title={item.title}
+                  role="button"
+                  aria-selected={item.isActive}
+                >
+                  <Show when={item.isSpecial} fallback={<MessageSquare class="w-4 h-4 flex-shrink-0" />}>
+                    <Info class="w-4 h-4 flex-shrink-0" />
+                  </Show>
+
+                  <span class="session-item-title truncate">{item.title}</span>
+
+                  <Show when={!item.isSpecial && item.onClose}>
+                    <span
+                      class="session-item-close opacity-0 group-hover:opacity-100 hover:bg-status-error hover:text-white rounded p-0.5 transition-all"
+                      onClick={(event) => {
+                        event.stopPropagation()
+                        item.onClose?.()
+                      }}
+                      role="button"
+                      tabIndex={0}
+                      aria-label="Close session"
+                    >
+                      <X class="w-3 h-3" />
+                    </span>
+                  </Show>
+                </button>
+              </div>
+            )}
+          </For>
+        </div>
+
+        <Show when={sessionSections().childItems.length > 0}>
+          <div class="session-section">
+            <div class="session-section-header px-3 py-2 text-xs font-semibold text-primary/70 uppercase tracking-wide">
+              Child Sessions
+            </div>
+            <For each={sessionSections().childItems}>
+              {(item) => (
+                <div class="session-list-item group">
+                  <button
+                    class={`session-item-base ${
+                      item.isActive ? "session-item-active" : "session-item-inactive"
+                    } ${item.isSpecial ? "session-item-special" : ""}`}
+                    onClick={item.onSelect}
+                    title={item.title}
+                    role="button"
+                    aria-selected={item.isActive}
+                  >
+                    <MessageSquare class="w-4 h-4 flex-shrink-0" />
+
+                    <span class="session-item-title truncate">{item.title}</span>
+
+                    <Show when={!item.isSpecial && item.onClose}>
+                      <span
+                        class="session-item-close opacity-0 group-hover:opacity-100 hover:bg-status-error hover:text-white rounded p-0.5 transition-all"
+                        onClick={(event) => {
+                          event.stopPropagation()
+                          item.onClose?.()
+                        }}
+                        role="button"
+                        tabIndex={0}
+                        aria-label="Close session"
+                      >
+                        <X class="w-3 h-3" />
+                      </span>
+                    </Show>
+                  </button>
+                </div>
+              )}
+            </For>
+          </div>
+        </Show>
+      </div>
+
+      <div class="session-list-footer p-3 border-t border-base">
+        <button
+          class="session-new-button w-full flex items-center gap-2 px-3 py-2 rounded-md transition-colors text-sm font-medium"
+          onClick={props.onNew}
+          title="New session (Cmd/Ctrl+T)"
+          aria-label="New session"
+        >
+          <Plus class="w-4 h-4" />
+          <span>New Session</span>
+        </button>
+      </div>
+    </div>
+  )
+}
+
+export default SessionList

src/components/session-tab.tsx

@@ -1,56 +0,0 @@
-import { Component, Show } from "solid-js"
-import type { Session } from "../types/session"
-import { MessageSquare, Info, X } from "lucide-solid"
-
-interface SessionTabProps {
-  session?: Session
-  special?: "info"
-  active: boolean
-  isParent?: boolean
-  onSelect: () => void
-  onClose?: () => void
-}
-
-const SessionTab: Component<SessionTabProps> = (props) => {
-  const label = () => {
-    if (props.special === "info") return "Info"
-    return props.session?.title || "Untitled"
-  }
-
-  return (
-    <div class="group">
-      <button
-        class={`session-tab-base ${
-          props.active
-            ? "session-tab-active"
-            : "session-tab-inactive"
-        } ${props.special === "info" ? "session-tab-special" : ""} ${props.isParent && !props.active ? "font-semibold" : ""}`}
-        onClick={props.onSelect}
-        title={label()}
-        role="tab"
-        aria-selected={props.active}
-      >
-        <Show when={props.special === "info"} fallback={<MessageSquare class="w-3.5 h-3.5 flex-shrink-0" />}>
-          <Info class="w-3.5 h-3.5 flex-shrink-0" />
-        </Show>
-        <span class="tab-label">{label()}</span>
-        <Show when={!props.special && props.onClose}>
-          <span
-            class="tab-close"
-            onClick={(e) => {
-              e.stopPropagation()
-              props.onClose?.()
-            }}
-            role="button"
-            tabIndex={0}
-            aria-label="Close session"
-          >
-            <X class="w-3 h-3" />
-          </span>
-        </Show>
-      </button>
-    </div>
-  )
-}
-
-export default SessionTab

src/components/session-tabs.tsx

@@ -1,62 +0,0 @@
-import { Component, For, Show } from "solid-js"
-import type { Session } from "../types/session"
-import SessionTab from "./session-tab"
-import KeyboardHint from "./keyboard-hint"
-import { Plus } from "lucide-solid"
-import { keyboardRegistry } from "../lib/keyboard-registry"
-
-interface SessionTabsProps {
-  instanceId: string
-  sessions: Map<string, Session>
-  activeSessionId: string | null
-  onSelect: (sessionId: string) => void
-  onClose: (sessionId: string) => void
-  onNew: () => void
-}
-
-const SessionTabs: Component<SessionTabsProps> = (props) => {
-  const sessionsList = () => Array.from(props.sessions.entries())
-  const totalTabs = () => sessionsList().length + 1
-
-  return (
-    <div class="tab-bar tab-bar-session">
-      <div class="tab-container" role="tablist">
-        <div class="flex items-center gap-1 overflow-x-auto">
-          <For each={sessionsList()}>
-            {([id, session]) => (
-              <SessionTab
-                session={session}
-                active={id === props.activeSessionId}
-                isParent={session.parentId === null}
-                onSelect={() => props.onSelect(id)}
-                onClose={session.parentId === null ? () => props.onClose(id) : undefined}
-              />
-            )}
-          </For>
-          <SessionTab
-            special="info"
-            active={props.activeSessionId === "info"}
-            onSelect={() => props.onSelect("info")}
-          />
-          <button
-            class="new-tab-button"
-            onClick={props.onNew}
-            title="New parent session (Cmd/Ctrl+T)"
-            aria-label="New parent session"
-          >
-            <Plus class="w-4 h-4" />
-          </button>
-        </div>
-        <Show when={totalTabs() > 1}>
-          <div class="flex-shrink-0 ml-4">
-            <KeyboardHint
-              shortcuts={[keyboardRegistry.get("session-prev")!, keyboardRegistry.get("session-next")!].filter(Boolean)}
-            />
-          </div>
-        </Show>
-      </div>
-    </div>
-  )
-}
-
-export default SessionTabs

src/lib/shortcuts/navigation.ts

@@ -5,6 +5,21 @@ import { getSessionFamily, activeSessionId, setActiveSession, activeParentSessio
 export function registerNavigationShortcuts() {
   const isMac = () => navigator.platform.toLowerCase().includes("mac")
 
+  const buildNavigationOrder = (instanceId: string): string[] => {
+    const parentId = activeParentSessionId().get(instanceId)
+    if (!parentId) return []
+
+    const familySessions = getSessionFamily(instanceId, parentId)
+    if (familySessions.length === 0) return []
+
+    const [parentSession, ...childSessions] = familySessions
+    if (!parentSession) return []
+
+    const sortedChildren = childSessions.slice().sort((a, b) => b.time.updated - a.time.updated)
+
+    return [parentSession.id, "info", ...sortedChildren.map((session) => session.id)]
+  }
+
   keyboardRegistry.register({
     id: "instance-prev",
     key: "[",
@@ -43,16 +58,20 @@ export function registerNavigationShortcuts() {
       const instanceId = activeInstanceId()
       if (!instanceId) return
 
-      const parentId = activeParentSessionId().get(instanceId)
-      if (!parentId) return
+      const navigationIds = buildNavigationOrder(instanceId)
+      if (navigationIds.length === 0) return
 
-      const familySessions = getSessionFamily(instanceId, parentId)
-      const ids = familySessions.map((s) => s.id).concat(["info"])
-      if (ids.length <= 1) return
+      const currentActiveId = activeSessionId().get(instanceId)
+      let currentIndex = navigationIds.indexOf(currentActiveId || "")
 
-      const current = ids.indexOf(activeSessionId().get(instanceId) || "")
-      const prev = current <= 0 ? ids.length - 1 : current - 1
-      if (ids[prev]) setActiveSession(instanceId, ids[prev])
+      if (currentIndex === -1) {
+        currentIndex = navigationIds.length - 1
+      }
+
+      const targetIndex = currentIndex <= 0 ? navigationIds.length - 1 : currentIndex - 1
+      const targetSessionId = navigationIds[targetIndex]
+
+      setActiveSession(instanceId, targetSessionId)
     },
     description: "previous session",
     context: "global",
@@ -66,16 +85,20 @@ export function registerNavigationShortcuts() {
       const instanceId = activeInstanceId()
       if (!instanceId) return
 
-      const parentId = activeParentSessionId().get(instanceId)
-      if (!parentId) return
+      const navigationIds = buildNavigationOrder(instanceId)
+      if (navigationIds.length === 0) return
 
-      const familySessions = getSessionFamily(instanceId, parentId)
-      const ids = familySessions.map((s) => s.id).concat(["info"])
-      if (ids.length <= 1) return
+      const currentActiveId = activeSessionId().get(instanceId)
+      let currentIndex = navigationIds.indexOf(currentActiveId || "")
 
-      const current = ids.indexOf(activeSessionId().get(instanceId) || "")
-      const next = (current + 1) % ids.length
-      if (ids[next]) setActiveSession(instanceId, ids[next])
+      if (currentIndex === -1) {
+        currentIndex = 0
+      }
+
+      const targetIndex = (currentIndex + 1) % navigationIds.length
+      const targetSessionId = navigationIds[targetIndex]
+
+      setActiveSession(instanceId, targetSessionId)
     },
     description: "next session",
     context: "global",

src/styles/components.css

@@ -1599,4 +1599,142 @@ button.button-primary {
   @apply flex flex-col h-full;
   background-color: var(--surface-base);
   color: inherit;
+}
+
+/* Session list component */
+.session-list-container {
+  @apply flex flex-col h-full relative;
+  background-color: var(--surface-secondary);
+  min-width: 200px;
+  max-width: 500px;
+}
+
+.session-resize-handle {
+  @apply absolute top-0 right-0 w-1 h-full cursor-col-resize bg-transparent transition-colors;
+  z-index: 10;
+}
+
+.session-resize-handle:hover {
+  background-color: var(--accent-primary);
+}
+
+.session-resize-handle::before {
+  content: "";
+  @apply absolute top-0 left-0 w-2 h-full -translate-x-1/2;
+}
+
+.session-list-header {
+  @apply border-b relative;
+  border-color: var(--border-base);
+}
+
+.session-list-header h3 {
+  color: var(--text-primary);
+  font-size: var(--font-size-sm);
+  font-weight: var(--font-weight-semibold);
+}
+
+.session-header-hints {
+  @apply flex-shrink-0;
+}
+
+.session-list {
+  @apply flex-1;
+}
+
+.session-list-item {
+  @apply border-b last:border-b-0;
+  border-color: var(--border-base);
+}
+
+.session-item-base {
+  @apply w-full flex items-center gap-3 px-3 py-2.5 text-left transition-colors outline-none;
+  font-family: var(--font-family-sans);
+  font-size: var(--font-size-sm);
+}
+
+.session-item-base:focus-visible {
+  @apply ring-2 ring-offset-1;
+  ring-color: var(--accent-primary);
+  ring-offset-color: var(--surface-secondary);
+}
+
+.session-item-active {
+  background-color: var(--accent-primary);
+  color: var(--text-inverted);
+  font-weight: var(--font-weight-medium);
+}
+
+.session-item-inactive {
+  color: var(--text-secondary);
+}
+
+.session-item-inactive:hover {
+  background-color: var(--surface-hover);
+  color: var(--text-primary);
+}
+
+.session-item-special {
+  color: var(--text-muted);
+  font-style: italic;
+}
+
+.session-item-active .session-item-close:hover {
+  background-color: rgba(255, 255, 255, 0.2);
+}
+
+.session-item-title {
+  @apply flex-1 min-w-0;
+  font-weight: inherit;
+}
+
+.session-item-close {
+  @apply flex-shrink-0 p-0.5 rounded transition-all;
+}
+
+.session-item-close:focus-visible {
+  @apply ring-2 ring-offset-1;
+  ring-color: var(--accent-primary);
+  ring-offset-color: inherit;
+}
+
+.session-list-footer {
+  @apply border-t;
+  border-color: var(--border-base);
+}
+
+.session-new-button {
+  background-color: var(--surface-base);
+  color: var(--text-primary);
+  border: 1px solid var(--border-base);
+}
+
+.session-new-button:hover {
+  background-color: var(--surface-hover);
+}
+
+.session-new-button:focus-visible {
+  @apply ring-2 ring-offset-1;
+  ring-color: var(--accent-primary);
+  ring-offset-color: var(--surface-secondary);
+}
+
+[data-theme="dark"] .session-new-button {
+  background-color: var(--surface-base);
+  color: var(--text-primary);
+}
+
+[data-theme="dark"] .session-new-button:hover {
+  background-color: var(--surface-hover);
+}
+
+/* Responsive behavior for session list */
+@media (max-width: 768px) {
+  .session-list-container {
+    min-width: 200px;
+  }
+  
+  .session-item-base {
+    @apply px-2 py-2;
+  }
 }