diff --git a/packages/electron-app/electron/main/storage.ts b/packages/electron-app/electron/main/storage.ts
index e137fc61..a93cc19e 100644
--- a/packages/electron-app/electron/main/storage.ts
+++ b/packages/electron-app/electron/main/storage.ts
@@ -59,7 +59,7 @@ export function setupStorageIPC() {
       return await readConfigWithCache()
     } catch (error) {
       // Return empty config if file doesn't exist
-      return JSON.stringify({ preferences: { showThinkingBlocks: false }, recentFolders: [] }, null, 2)
+      return JSON.stringify({ preferences: { showThinkingBlocks: false, thinkingBlocksExpansion: "expanded" }, recentFolders: [] }, null, 2)
     }
   })
 
diff --git a/packages/server/src/config/schema.ts b/packages/server/src/config/schema.ts
index 517534c6..a2c88f02 100644
--- a/packages/server/src/config/schema.ts
+++ b/packages/server/src/config/schema.ts
@@ -10,6 +10,7 @@ const AgentModelSelectionsSchema = z.record(z.string(), AgentModelSelectionSchem
 
 const PreferencesSchema = z.object({
   showThinkingBlocks: z.boolean().default(false),
+  thinkingBlocksExpansion: z.enum(["expanded", "collapsed"]).default("expanded"),
   lastUsedBinary: z.string().optional(),
   environmentVariables: z.record(z.string()).default({}),
   modelRecents: z.array(ModelPreferenceSchema).default([]),
diff --git a/packages/ui/src/App.tsx b/packages/ui/src/App.tsx
index 1dd3cb13..d811b498 100644
--- a/packages/ui/src/App.tsx
+++ b/packages/ui/src/App.tsx
@@ -51,6 +51,7 @@ const App: Component = () => {
     setDiffViewMode,
     setToolOutputExpansion,
     setDiagnosticsExpansion,
+    setThinkingBlocksExpansion,
   } = useConfig()
   const [escapeInDebounce, setEscapeInDebounce] = createSignal(false)
   const [launchErrorBinary, setLaunchErrorBinary] = createSignal<string | null>(null)
@@ -210,6 +211,7 @@ const App: Component = () => {
     setDiffViewMode,
     setToolOutputExpansion,
     setDiagnosticsExpansion,
+    setThinkingBlocksExpansion,
     handleNewInstanceRequest,
     handleCloseInstance,
     handleNewSession,
diff --git a/packages/ui/src/components/message-stream-v2.tsx b/packages/ui/src/components/message-stream-v2.tsx
index 4d76edb8..3fa1fe16 100644
--- a/packages/ui/src/components/message-stream-v2.tsx
+++ b/packages/ui/src/components/message-stream-v2.tsx
@@ -23,6 +23,10 @@ const codeNomadLogo = new URL("../images/CodeNomad-Icon.png", import.meta.url).h
 const messageItemCache = new Map<string, ContentDisplayItem>()
 const toolItemCache = new Map<string, ToolDisplayItem>()
 
+const USER_BORDER_COLOR = "var(--message-user-border)"
+const ASSISTANT_BORDER_COLOR = "var(--message-assistant-border)"
+const TOOL_BORDER_COLOR = "var(--message-tool-border)"
+
 type ToolCallPart = Extract<ClientPart, { type: "tool" }>
 
 type ToolState = import("@opencode-ai/sdk").ToolState
@@ -139,6 +143,7 @@ interface StepDisplayItem {
   key: string
   part: ClientPart
   messageInfo?: MessageInfo
+  accentColor?: string
 }
 
 type ReasoningDisplayItem = {
@@ -147,6 +152,7 @@ type ReasoningDisplayItem = {
   part: ClientPart
   messageInfo?: MessageInfo
   showAgentMeta?: boolean
+  defaultExpanded: boolean
 }
 
 type MessageBlockItem = ContentDisplayItem | ToolDisplayItem | StepDisplayItem | ReasoningDisplayItem
@@ -261,6 +267,7 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
     const infoMap = messageInfoMap()
     const showThinking = preferences().showThinkingBlocks
     const showUsageMetrics = showUsagePreference()
+    const thinkingDefaultExpanded = (preferences().thinkingBlocksExpansion ?? "expanded") === "expanded"
     const revert = revertTarget()
     const instanceId = props.instanceId
     const blocks: MessageDisplayBlock[] = []
@@ -284,6 +291,8 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
       let segmentIndex = 0
       let pendingParts: ClientPart[] = []
       let agentMetaAttached = record.role !== "assistant"
+      const defaultAccentColor = record.role === "user" ? USER_BORDER_COLOR : ASSISTANT_BORDER_COLOR
+      let lastAccentColor = defaultAccentColor
 
       const flushContent = () => {
         if (pendingParts.length === 0) return
@@ -317,6 +326,7 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
         }
         items.push(cached)
         usedMessageKeys.add(segmentKey)
+        lastAccentColor = defaultAccentColor
         pendingParts = []
       }
 
@@ -349,6 +359,7 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
           }
           items.push(toolItem)
           usedToolKeys.add(cacheKey)
+          lastAccentColor = TOOL_BORDER_COLOR
           return
         }
 
@@ -361,7 +372,9 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
           flushContent()
           if (showUsageMetrics) {
             const key = makeInstanceCacheKey(instanceId, `${record.id}:${part.id ?? partIndex}:${part.type}`)
-            items.push({ type: part.type, key, part, messageInfo })
+            const accentColor = lastAccentColor || defaultAccentColor
+            items.push({ type: part.type, key, part, messageInfo, accentColor })
+            lastAccentColor = accentColor
           }
           return
         }
@@ -374,7 +387,15 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
             if (showAgentMeta) {
               agentMetaAttached = true
             }
-            items.push({ type: "reasoning", key, part, messageInfo, showAgentMeta })
+            items.push({
+              type: "reasoning",
+              key,
+              part,
+              messageInfo,
+              showAgentMeta,
+              defaultExpanded: thinkingDefaultExpanded,
+            })
+            lastAccentColor = ASSISTANT_BORDER_COLOR
           }
           return
         }
@@ -707,6 +728,7 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
                         part={(item as StepDisplayItem).part}
                         messageInfo={(item as StepDisplayItem).messageInfo}
                         showUsage={showUsagePreference()}
+                        borderColor={(item as StepDisplayItem).accentColor}
                       />
                     </Match>
                     <Match when={item.type === "reasoning"}>
@@ -716,6 +738,7 @@ export default function MessageStreamV2(props: MessageStreamV2Props) {
                         instanceId={props.instanceId}
                         sessionId={props.sessionId}
                         showAgentMeta={(item as ReasoningDisplayItem).showAgentMeta}
+                        defaultExpanded={(item as ReasoningDisplayItem).defaultExpanded}
                       />
                     </Match>
                   </Switch>
@@ -764,6 +787,7 @@ interface StepCardProps {
   messageInfo?: MessageInfo
   showAgentMeta?: boolean
   showUsage?: boolean
+  borderColor?: string
 }
 
 function StepCard(props: StepCardProps) {
@@ -815,6 +839,8 @@ function StepCard(props: StepCardProps) {
     }
   }
 
+  const finishStyle = () => (props.borderColor ? { "border-left-color": props.borderColor } : undefined)
+
   const renderUsageChips = (usage: NonNullable<ReturnType<typeof usageStats>>) => (
     <div class="message-step-usage">
       <div class="inline-flex items-center gap-1 rounded-full border border-[var(--border-base)] px-2 py-0.5 text-[10px]">
@@ -850,7 +876,7 @@ function StepCard(props: StepCardProps) {
       return null
     }
     return (
-      <div class={`message-step-card message-step-finish`}>
+      <div class={`message-step-card message-step-finish message-step-finish-flush`} style={finishStyle()}>
         {renderUsageChips(usage)}
       </div>
     )
@@ -886,10 +912,15 @@ interface ReasoningCardProps {
   instanceId: string
   sessionId: string
   showAgentMeta?: boolean
+  defaultExpanded?: boolean
 }
 
 function ReasoningCard(props: ReasoningCardProps) {
-  const [expanded, setExpanded] = createSignal(false)
+  const [expanded, setExpanded] = createSignal(Boolean(props.defaultExpanded))
+
+  createEffect(() => {
+    setExpanded(Boolean(props.defaultExpanded))
+  })
 
   const timestamp = () => {
     const value = props.messageInfo?.time?.created ?? (props.part as any)?.time?.start ?? Date.now()
diff --git a/packages/ui/src/lib/hooks/use-commands.ts b/packages/ui/src/lib/hooks/use-commands.ts
index f2127072..0bc52575 100644
--- a/packages/ui/src/lib/hooks/use-commands.ts
+++ b/packages/ui/src/lib/hooks/use-commands.ts
@@ -24,6 +24,7 @@ export interface UseCommandsOptions {
   setDiffViewMode: (mode: "split" | "unified") => void
   setToolOutputExpansion: (mode: ExpansionPreference) => void
   setDiagnosticsExpansion: (mode: ExpansionPreference) => void
+  setThinkingBlocksExpansion: (mode: ExpansionPreference) => void
   handleNewInstanceRequest: () => void
   handleCloseInstance: (instanceId: string) => Promise<void>
   handleNewSession: (instanceId: string) => Promise<void>
@@ -385,10 +386,26 @@ export function useCommands(options: UseCommandsOptions) {
       label: () => `${options.preferences().showThinkingBlocks ? "Hide" : "Show"} Thinking Blocks`,
       description: "Show/hide AI thinking process",
       category: "System",
-      keywords: ["/thinking", "toggle", "show", "hide"],
+      keywords: ["/thinking", "thinking", "reasoning", "toggle", "show", "hide"],
       action: options.toggleShowThinkingBlocks,
     })
 
+    commandRegistry.register({
+      id: "thinking-default-visibility",
+      label: () => {
+        const mode = options.preferences().thinkingBlocksExpansion ?? "expanded"
+        return `Thinking Blocks Default · ${mode === "expanded" ? "Expanded" : "Collapsed"}`
+      },
+      description: "Toggle whether thinking blocks start expanded",
+      category: "System",
+      keywords: ["/thinking", "thinking", "reasoning", "expand", "collapse", "default"],
+      action: () => {
+        const mode = options.preferences().thinkingBlocksExpansion ?? "expanded"
+        const next: ExpansionPreference = mode === "expanded" ? "collapsed" : "expanded"
+        options.setThinkingBlocksExpansion(next)
+      },
+    })
+
     commandRegistry.register({
       id: "diff-view-split",
       label: () => `${(options.preferences().diffViewMode || "split") === "split" ? "✓ " : ""}Use Split Diff View`,
diff --git a/packages/ui/src/stores/preferences.tsx b/packages/ui/src/stores/preferences.tsx
index a1847f3b..59611498 100644
--- a/packages/ui/src/stores/preferences.tsx
+++ b/packages/ui/src/stores/preferences.tsx
@@ -29,6 +29,7 @@ export type ExpansionPreference = "expanded" | "collapsed"
 
 export interface Preferences {
   showThinkingBlocks: boolean
+  thinkingBlocksExpansion: ExpansionPreference
   lastUsedBinary?: string
   environmentVariables: Record<string, string>
   modelRecents: ModelPreference[]
@@ -56,6 +57,7 @@ const MAX_RECENT_MODELS = 5
 
 const defaultPreferences: Preferences = {
   showThinkingBlocks: false,
+  thinkingBlocksExpansion: "expanded",
   environmentVariables: {},
   modelRecents: [],
   diffViewMode: "split",
@@ -88,6 +90,7 @@ function normalizePreferences(pref?: Partial<Preferences> & { agentModelSelectio
 
   return {
     showThinkingBlocks: sanitized.showThinkingBlocks ?? defaultPreferences.showThinkingBlocks,
+    thinkingBlocksExpansion: sanitized.thinkingBlocksExpansion ?? defaultPreferences.thinkingBlocksExpansion,
     lastUsedBinary: sanitized.lastUsedBinary ?? defaultPreferences.lastUsedBinary,
     environmentVariables,
     modelRecents,
@@ -269,6 +272,11 @@ function setDiagnosticsExpansion(mode: ExpansionPreference): void {
   updatePreferences({ diagnosticsExpansion: mode })
 }
 
+function setThinkingBlocksExpansion(mode: ExpansionPreference): void {
+  if (preferences().thinkingBlocksExpansion === mode) return
+  updatePreferences({ thinkingBlocksExpansion: mode })
+}
+
 function toggleShowThinkingBlocks(): void {
   updatePreferences({ showThinkingBlocks: !preferences().showThinkingBlocks })
 }
@@ -381,6 +389,7 @@ interface ConfigContextValue {
   setDiffViewMode: typeof setDiffViewMode
   setToolOutputExpansion: typeof setToolOutputExpansion
   setDiagnosticsExpansion: typeof setDiagnosticsExpansion
+  setThinkingBlocksExpansion: typeof setThinkingBlocksExpansion
   addRecentFolder: typeof addRecentFolder
   removeRecentFolder: typeof removeRecentFolder
   addOpenCodeBinary: typeof addOpenCodeBinary
@@ -412,6 +421,7 @@ const configContextValue: ConfigContextValue = {
   setDiffViewMode,
   setToolOutputExpansion,
   setDiagnosticsExpansion,
+  setThinkingBlocksExpansion,
   addRecentFolder,
   removeRecentFolder,
   addOpenCodeBinary,
@@ -480,7 +490,9 @@ export {
   setDiffViewMode,
   setToolOutputExpansion,
   setDiagnosticsExpansion,
+  setThinkingBlocksExpansion,
   themePreference,
   setThemePreference,
   recordWorkspaceLaunch,
-}
+ }
+
diff --git a/packages/ui/src/styles/messaging/message-base.css b/packages/ui/src/styles/messaging/message-base.css
index 7a1ec9e4..c0c9461a 100644
--- a/packages/ui/src/styles/messaging/message-base.css
+++ b/packages/ui/src/styles/messaging/message-base.css
@@ -27,6 +27,10 @@
   margin-bottom: 0.125rem;
 }
 
+.message-step-finish-flush {
+  margin-top: -0.125rem;
+}
+
 .message-step-usage {
   @apply flex flex-wrap items-center gap-1 text-[10px] text-[var(--text-muted)];
 }