diff --git a/src/app/projects/[projectId]/components/ProjectPage.tsx b/src/app/projects/[projectId]/components/ProjectPage.tsx
index 796f1cc..3cfa5ac 100644
--- a/src/app/projects/[projectId]/components/ProjectPage.tsx
+++ b/src/app/projects/[projectId]/components/ProjectPage.tsx
@@ -3,12 +3,14 @@
 import { useQueryClient } from "@tanstack/react-query";
 import {
   ArrowLeftIcon,
+  ChevronDownIcon,
   FolderIcon,
   MessageSquareIcon,
   PlusIcon,
+  SettingsIcon,
 } from "lucide-react";
 import Link from "next/link";
-import { useEffect } from "react";
+import { useEffect, useState } from "react";
 import { SettingsControls } from "@/components/SettingsControls";
 import { Button } from "@/components/ui/button";
 import {
@@ -18,6 +20,11 @@ import {
   CardHeader,
   CardTitle,
 } from "@/components/ui/card";
+import {
+  Collapsible,
+  CollapsibleContent,
+  CollapsibleTrigger,
+} from "@/components/ui/collapsible";
 import { useConfig } from "../../../hooks/useConfig";
 import { projectQueryConfig, useProject } from "../hooks/useProject";
 import { firstCommandToTitle } from "../services/firstCommandToTitle";
@@ -29,6 +36,7 @@ export const ProjectPageContent = ({ projectId }: { projectId: string }) => {
   } = useProject(projectId);
   const { config } = useConfig();
   const queryClient = useQueryClient();
+  const [isSettingsOpen, setIsSettingsOpen] = useState(false);
 
   // biome-ignore lint/correctness/useExhaustiveDependencies: invalidate when config changed
   useEffect(() => {
@@ -44,48 +52,77 @@ export const ProjectPageContent = ({ projectId }: { projectId: string }) => {
   };
 
   return (
-    <div className="container mx-auto px-4 py-8">
-      <header className="mb-8">
+    <div className="container mx-auto px-2 sm:px-4 py-4 sm:py-8 max-w-6xl">
+      <header className="mb-6 sm:mb-8">
         <Button asChild variant="ghost" className="mb-4">
           <Link href="/projects" className="flex items-center gap-2">
             <ArrowLeftIcon className="w-4 h-4" />
-            Back to Projects
+            <span className="hidden sm:inline">Back to Projects</span>
+            <span className="sm:hidden">Back</span>
           </Link>
         </Button>
 
-        <div className="flex items-center justify-between mb-2">
-          <div className="flex items-center gap-3">
-            <FolderIcon className="w-6 h-6" />
-            <h1 className="text-3xl font-bold">
+        <div className="flex flex-col gap-4 sm:flex-row sm:items-center sm:justify-between mb-2">
+          <div className="flex items-center gap-2 sm:gap-3 min-w-0 flex-1">
+            <FolderIcon className="w-5 h-5 sm:w-6 sm:h-6 flex-shrink-0" />
+            <h1 className="text-xl sm:text-2xl md:text-3xl font-bold break-words overflow-hidden">
               {project.meta.projectPath ?? project.claudeProjectPath}
             </h1>
           </div>
-          <NewChatModal
-            projectId={projectId}
-            trigger={
-              <Button size="lg" className="gap-2">
-                <PlusIcon className="w-5 h-5" />
-                Start New Chat
-              </Button>
-            }
-          />
+          <div className="flex-shrink-0">
+            <NewChatModal
+              projectId={projectId}
+              trigger={
+                <Button size="lg" className="gap-2 w-full sm:w-auto">
+                  <PlusIcon className="w-4 h-4 sm:w-5 sm:h-5" />
+                  <span className="hidden sm:inline">Start New Chat</span>
+                  <span className="sm:hidden">New Chat</span>
+                </Button>
+              }
+            />
+          </div>
         </div>
-        <p className="text-muted-foreground font-mono text-sm">
+        <p className="text-muted-foreground font-mono text-xs sm:text-sm break-all">
           History File: {project.claudeProjectPath ?? "unknown"}
         </p>
       </header>
 
       <main>
         <section>
-          <h2 className="text-xl font-semibold mb-4">
+          <h2 className="text-lg sm:text-xl font-semibold mb-4">
             Conversation Sessions{" "}
             {sessions.length > 0 ? `(${sessions.length})` : ""}
           </h2>
 
           {/* Filter Controls */}
-          <div className="mb-6 p-4 bg-muted/50 rounded-lg">
-            <SettingsControls onConfigChange={handleConfigChange} />
-          </div>
+          <Collapsible open={isSettingsOpen} onOpenChange={setIsSettingsOpen}>
+            <div className="mb-6">
+              <CollapsibleTrigger asChild>
+                <Button
+                  variant="outline"
+                  className="w-full justify-between mb-2 h-auto py-3"
+                >
+                  <div className="flex items-center gap-2">
+                    <SettingsIcon className="w-4 h-4" />
+                    <span className="font-medium">Filter Settings</span>
+                    <span className="text-xs text-muted-foreground">
+                      ({sessions.length} sessions)
+                    </span>
+                  </div>
+                  <ChevronDownIcon
+                    className={`w-4 h-4 transition-transform ${
+                      isSettingsOpen ? "rotate-180" : ""
+                    }`}
+                  />
+                </Button>
+              </CollapsibleTrigger>
+              <CollapsibleContent>
+                <div className="p-4 bg-muted/50 rounded-lg border">
+                  <SettingsControls onConfigChange={handleConfigChange} />
+                </div>
+              </CollapsibleContent>
+            </div>
+          </Collapsible>
 
           {sessions.length === 0 ? (
             <Card>
@@ -117,7 +154,7 @@ export const ProjectPageContent = ({ projectId }: { projectId: string }) => {
                 >
                   <CardHeader>
                     <CardTitle className="flex items-center gap-2">
-                      <span className="break-all overflow-ellipsis line-clamp-2 text-xl">
+                      <span className="break-words overflow-ellipsis line-clamp-2 text-lg sm:text-xl">
                         {session.meta.firstCommand !== null
                           ? firstCommandToTitle(session.meta.firstCommand)
                           : session.id}
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx
index 8fd7b59..dae14d0 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx
@@ -1,7 +1,13 @@
 "use client";
 
 import { useMutation } from "@tanstack/react-query";
-import { ArrowLeftIcon, LoaderIcon, PauseIcon, XIcon } from "lucide-react";
+import {
+  ArrowLeftIcon,
+  LoaderIcon,
+  MenuIcon,
+  PauseIcon,
+  XIcon,
+} from "lucide-react";
 import Link from "next/link";
 import type { FC } from "react";
 import { useEffect, useRef, useState } from "react";
@@ -41,6 +47,7 @@ export const SessionPageContent: FC<{
 
   const [previousConversationLength, setPreviousConversationLength] =
     useState(0);
+  const [isMobileSidebarOpen, setIsMobileSidebarOpen] = useState(false);
   const scrollContainerRef = useRef<HTMLDivElement>(null);
 
   // 自動スクロール処理
@@ -62,27 +69,44 @@ export const SessionPageContent: FC<{
 
   return (
     <div className="flex h-screen">
-      <SessionSidebar currentSessionId={sessionId} projectId={projectId} />
+      <SessionSidebar
+        currentSessionId={sessionId}
+        projectId={projectId}
+        isMobileOpen={isMobileSidebarOpen}
+        onMobileOpenChange={setIsMobileSidebarOpen}
+      />
 
       <div className="flex-1 flex flex-col overflow-hidden">
         <div
           ref={scrollContainerRef}
           className="max-w-none flex-1 overflow-y-auto"
         >
-          <header className="px-3 py-3 sticky top-0 z-10 bg-background w-full">
-            <Button asChild variant="ghost">
-              <Link
-                href={`/projects/${projectId}`}
-                className="flex items-center gap-2"
+          <header className="px-2 sm:px-3 py-3 sticky top-0 z-10 bg-background w-full">
+            <div className="flex items-center gap-2 mb-2">
+              <Button
+                variant="ghost"
+                size="sm"
+                className="md:hidden"
+                onClick={() => setIsMobileSidebarOpen(true)}
               >
-                <ArrowLeftIcon className="w-4 h-4" />
-                Back to Session List
-              </Link>
-            </Button>
+                <MenuIcon className="w-4 h-4" />
+              </Button>
+
+              <Button asChild variant="ghost">
+                <Link
+                  href={`/projects/${projectId}`}
+                  className="flex items-center gap-2"
+                >
+                  <ArrowLeftIcon className="w-4 h-4" />
+                  <span className="hidden sm:inline">Back to Session List</span>
+                  <span className="sm:hidden">Back</span>
+                </Link>
+              </Button>
+            </div>
 
             <div className="space-y-3">
               <div className="flex items-center gap-3">
-                <h1 className="text-3xl font-bold break-all overflow-ellipsis line-clamp-2 px-5">
+                <h1 className="text-xl sm:text-2xl md:text-3xl font-bold break-words overflow-ellipsis line-clamp-2 px-2 sm:px-5">
                   {session.meta.firstCommand !== null
                     ? firstCommandToTitle(session.meta.firstCommand)
                     : sessionId}
@@ -137,7 +161,7 @@ export const SessionPageContent: FC<{
             </div>
           </header>
 
-          <main className="w-full px-20 pb-10 relative z-5">
+          <main className="w-full px-4 sm:px-8 md:px-12 lg:px-16 xl:px-20 pb-10 relative z-5">
             <ConversationList
               conversations={conversations}
               getToolResult={getToolResult}
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/AssistantConversationContent.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/AssistantConversationContent.tsx
index 65d1d28..9aa6f4c 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/AssistantConversationContent.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/AssistantConversationContent.tsx
@@ -26,7 +26,7 @@ export const AssistantConversationContent: FC<{
 }> = ({ content, getToolResult }) => {
   if (content.type === "text") {
     return (
-      <div className="w-full mx-2 my-6">
+      <div className="w-full mx-1 sm:mx-2 my-4 sm:my-6">
         <MarkdownContent content={content.text} />
       </div>
     );
@@ -111,7 +111,7 @@ export const AssistantConversationContent: FC<{
               <CollapsibleContent>
                 <div className="bg-background rounded border p-2 mt-1">
                   {typeof toolResult.content === "string" ? (
-                    <pre className="text-xs overflow-x-auto whitespace-pre-line">
+                    <pre className="text-xs overflow-x-auto whitespace-pre-wrap break-words">
                       {toolResult.content}
                     </pre>
                   ) : (
@@ -129,7 +129,7 @@ export const AssistantConversationContent: FC<{
                         return (
                           <pre
                             key={item.text}
-                            className="text-xs overflow-x-auto whitespace-pre-line"
+                            className="text-xs overflow-x-auto whitespace-pre-wrap break-words"
                           >
                             {item.text}
                           </pre>
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/ConversationList.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/ConversationList.tsx
index c45ff53..5b870ac 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/ConversationList.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/ConversationList.tsx
@@ -66,7 +66,7 @@ export const ConversationList: FC<ConversationListProps> = ({
             }`}
             key={getConversationKey(conversation)}
           >
-            <div className="w-[85%]">{elm}</div>
+            <div className="w-full max-w-4xl sm:w-[90%] md:w-[85%]">{elm}</div>
           </li>,
         ];
       })}
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/UserTextContent.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/UserTextContent.tsx
index 1396322..2364330 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/UserTextContent.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationList/UserTextContent.tsx
@@ -78,7 +78,9 @@ export const UserTextContent: FC<{ text: string; id?: string }> = ({
           </div>
         </CardHeader>
         <CardContent className="py-0 px-4">
-          <pre className="text-xs overflow-x-auto">{parsed.stdout}</pre>
+          <pre className="text-xs overflow-x-auto whitespace-pre-wrap break-words">
+            {parsed.stdout}
+          </pre>
         </CardContent>
       </Card>
     );
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/sessionSidebar/SessionSidebar.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/sessionSidebar/SessionSidebar.tsx
index 35e6c7c..f6e63e7 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/sessionSidebar/SessionSidebar.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/sessionSidebar/SessionSidebar.tsx
@@ -2,6 +2,7 @@
 
 import { ListTodoIcon, MessageSquareIcon, SettingsIcon } from "lucide-react";
 import { type FC, useState } from "react";
+import { Dialog, DialogContent } from "@/components/ui/dialog";
 import { cn } from "@/lib/utils";
 import { useProject } from "../../../../hooks/useProject";
 import { SessionsTab } from "./SessionsTab";
@@ -12,7 +13,15 @@ export const SessionSidebar: FC<{
   currentSessionId: string;
   projectId: string;
   className?: string;
-}> = ({ currentSessionId, projectId, className }) => {
+  isMobileOpen?: boolean;
+  onMobileOpenChange?: (open: boolean) => void;
+}> = ({
+  currentSessionId,
+  projectId,
+  className,
+  isMobileOpen = false,
+  onMobileOpenChange,
+}) => {
   const {
     data: { sessions },
   } = useProject(projectId);
@@ -51,71 +60,87 @@ export const SessionSidebar: FC<{
     }
   };
 
-  return (
-    <div className={cn("hidden md:flex h-full", className)}>
-      <div
-        className={cn(
-          "h-full border-r border-sidebar-border transition-all duration-300 ease-in-out flex bg-sidebar text-sidebar-foreground",
-          isExpanded ? "w-72 lg:w-80" : "w-12",
-        )}
-      >
-        {/* Vertical Icon Menu - Always Visible */}
-        <div className="w-12 flex flex-col border-r border-sidebar-border bg-sidebar/50">
-          <div className="flex flex-col p-2 space-y-1">
-            <button
-              type="button"
-              onClick={() => handleTabClick("sessions")}
-              className={cn(
-                "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
-                "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
-                activeTab === "sessions" && isExpanded
-                  ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
-                  : "text-sidebar-foreground/70",
-              )}
-              title="Sessions"
-            >
-              <MessageSquareIcon className="w-4 h-4" />
-            </button>
+  const sidebarContent = (
+    <div
+      className={cn(
+        "h-full border-r border-sidebar-border transition-all duration-300 ease-in-out flex bg-sidebar text-sidebar-foreground",
+        isExpanded ? "w-72 lg:w-80" : "w-12",
+      )}
+    >
+      {/* Vertical Icon Menu - Always Visible */}
+      <div className="w-12 flex flex-col border-r border-sidebar-border bg-sidebar/50">
+        <div className="flex flex-col p-2 space-y-1">
+          <button
+            type="button"
+            onClick={() => handleTabClick("sessions")}
+            className={cn(
+              "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
+              "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
+              activeTab === "sessions" && isExpanded
+                ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
+                : "text-sidebar-foreground/70",
+            )}
+            title="Sessions"
+          >
+            <MessageSquareIcon className="w-4 h-4" />
+          </button>
 
-            <button
-              type="button"
-              onClick={() => handleTabClick("tasks")}
-              className={cn(
-                "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
-                "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
-                activeTab === "tasks" && isExpanded
-                  ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
-                  : "text-sidebar-foreground/70",
-              )}
-              title="Tasks"
-            >
-              <ListTodoIcon className="w-4 h-4" />
-            </button>
+          <button
+            type="button"
+            onClick={() => handleTabClick("tasks")}
+            className={cn(
+              "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
+              "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
+              activeTab === "tasks" && isExpanded
+                ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
+                : "text-sidebar-foreground/70",
+            )}
+            title="Tasks"
+          >
+            <ListTodoIcon className="w-4 h-4" />
+          </button>
 
-            <button
-              type="button"
-              onClick={() => handleTabClick("settings")}
-              className={cn(
-                "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
-                "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
-                activeTab === "settings" && isExpanded
-                  ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
-                  : "text-sidebar-foreground/70",
-              )}
-              title="Settings"
-            >
-              <SettingsIcon className="w-4 h-4" />
-            </button>
-          </div>
+          <button
+            type="button"
+            onClick={() => handleTabClick("settings")}
+            className={cn(
+              "w-8 h-8 flex items-center justify-center rounded-md transition-colors",
+              "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
+              activeTab === "settings" && isExpanded
+                ? "bg-sidebar-accent text-sidebar-accent-foreground shadow-sm"
+                : "text-sidebar-foreground/70",
+            )}
+            title="Settings"
+          >
+            <SettingsIcon className="w-4 h-4" />
+          </button>
         </div>
-
-        {/* Content Area - Only shown when expanded */}
-        {isExpanded && (
-          <div className="flex-1 flex flex-col overflow-hidden">
-            {renderContent()}
-          </div>
-        )}
       </div>
+
+      {/* Content Area - Only shown when expanded */}
+      {isExpanded && (
+        <div className="flex-1 flex flex-col overflow-hidden">
+          {renderContent()}
+        </div>
+      )}
     </div>
   );
+
+  return (
+    <>
+      {/* Desktop sidebar */}
+      <div className={cn("hidden md:flex h-full", className)}>
+        {sidebarContent}
+      </div>
+
+      {/* Mobile sidebar - rendered in dialog */}
+      <div className="md:hidden">
+        <Dialog open={isMobileOpen} onOpenChange={onMobileOpenChange}>
+          <DialogContent className="p-0 max-w-sm w-full h-[90vh] max-h-[90vh] overflow-hidden flex flex-col">
+            <div className="flex-1 overflow-hidden">{sidebarContent}</div>
+          </DialogContent>
+        </Dialog>
+      </div>
+    </>
+  );
 };