feat: add simple git diff preview modal

2025-12-25 09:14:22 +01:00 · 2025-09-07 14:21:42 +09:00
parent 7fafb183f0
commit c5688310b6
20 changed files with 2085 additions and 0 deletions
--- a/package.json
+++ b/package.json
@@ -44,6 +44,7 @@
    "@radix-ui/react-collapsible": "^1.1.12",
    "@radix-ui/react-dialog": "^1.1.15",
    "@radix-ui/react-hover-card": "^1.1.15",
+    "@radix-ui/react-select": "^2.2.6",
    "@radix-ui/react-slot": "^1.2.3",
    "@radix-ui/react-tabs": "^1.1.13",
    "@tanstack/react-query": "^5.85.5",
@@ -53,6 +54,8 @@
    "jotai": "^2.13.1",
    "lucide-react": "^0.542.0",
    "next": "15.5.2",
+    "next-themes": "^0.4.6",
+    "parse-git-diff": "^0.0.19",
    "prexit": "^2.3.0",
    "react": "^19.1.1",
    "react-dom": "^19.1.1",
@@ -60,6 +63,7 @@
    "react-markdown": "^10.1.0",
    "react-syntax-highlighter": "^15.6.6",
    "remark-gfm": "^4.0.1",
+    "sonner": "^2.0.7",
    "tailwind-merge": "^3.3.1",
    "ulid": "^3.0.1",
    "zod": "^4.1.5"
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -29,6 +29,9 @@ importers:
      '@radix-ui/react-hover-card':
        specifier: ^1.1.15
        version: 1.1.15(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-select':
+        specifier: ^2.2.6
+        version: 2.2.6(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
      '@radix-ui/react-slot':
        specifier: ^1.2.3
        version: 1.2.3(@types/react@19.1.12)(react@19.1.1)
@@ -56,6 +59,12 @@ importers:
      next:
        specifier: 15.5.2
        version: 15.5.2(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      next-themes:
+        specifier: ^0.4.6
+        version: 0.4.6(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      parse-git-diff:
+        specifier: ^0.0.19
+        version: 0.0.19
      prexit:
        specifier: ^2.3.0
        version: 2.3.0
@@ -77,6 +86,9 @@ importers:
      remark-gfm:
        specifier: ^4.0.1
        version: 4.0.1
+      sonner:
+        specifier: ^2.0.7
+        version: 2.0.7(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
      tailwind-merge:
        specifier: ^3.3.1
        version: 3.3.1
@@ -842,6 +854,9 @@ packages:
    resolution: {integrity: sha512-7J6ca1tK0duM2BgVB+CuFMh3idlIVASOP2QvOCbNWDc6JnvjtKa9nufPoJQQ4xrwBonwgT1TIhRRcEtzdVgWsA==}
    engines: {node: ^20.9.0 || >=22.0.0, npm: '>=10.8.2'}

+  '@radix-ui/number@1.1.1':
+    resolution: {integrity: sha512-MkKCwxlXTgz6CFoJx3pCwn07GKp36+aZyu/u2Ln2VrA5DcdyCZkASEDBTd8x5whTQQL5CiYf4prXKLcgQdv29g==}
+
  '@radix-ui/primitive@1.1.3':
    resolution: {integrity: sha512-JTF99U/6XIjCBo0wqkU5sK10glYe27MRRsfwoiq5zzOEZLHU3A3KCMa5X/azekYRCJ0HlwI0crAXS/5dEHTzDg==}

@@ -1072,6 +1087,19 @@ packages:
      '@types/react-dom':
        optional: true

+  '@radix-ui/react-select@2.2.6':
+    resolution: {integrity: sha512-I30RydO+bnn2PQztvo25tswPH+wFBjehVGtmagkU78yMdwTwVf12wnAOF+AeP8S2N8xD+5UPbGhkUfPyvT+mwQ==}
+    peerDependencies:
+      '@types/react': '*'
+      '@types/react-dom': '*'
+      react: ^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc
+      react-dom: ^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc
+    peerDependenciesMeta:
+      '@types/react':
+        optional: true
+      '@types/react-dom':
+        optional: true
+
  '@radix-ui/react-slot@1.2.3':
    resolution: {integrity: sha512-aeNmHnBxbi2St0au6VBVC7JXFlhLlOnvIIlePNniyUNAClzmtAUEY8/pBiK3iHjufOlwA+c20/8jngo7xcrg8A==}
    peerDependencies:
@@ -1175,6 +1203,19 @@ packages:
      '@types/react':
        optional: true

+  '@radix-ui/react-visually-hidden@1.2.3':
+    resolution: {integrity: sha512-pzJq12tEaaIhqjbzpCuv/OypJY/BPavOofm+dbab+MHLajy277+1lLm6JFcGgF5eskJ6mquGirhXY2GD/8u8Ug==}
+    peerDependencies:
+      '@types/react': '*'
+      '@types/react-dom': '*'
+      react: ^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc
+      react-dom: ^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc
+    peerDependenciesMeta:
+      '@types/react':
+        optional: true
+      '@types/react-dom':
+        optional: true
+
  '@radix-ui/rect@1.1.1':
    resolution: {integrity: sha512-HPwpGIzkl28mWyZqG52jiqDJ12waP11Pa1lGoiyUkIEuMLBP0oeK/C89esbXrxsky5we7dfd8U58nm0SgAWpVw==}

@@ -2517,6 +2558,12 @@ packages:
    resolution: {integrity: sha512-NHDDGYudnvRutt/VhKFlX26IotXe1w0cmkDm6JGquh5bz/bDTw0LufSmH/GxTjEdpHEO+bVKFTwdrcGa/9XlKQ==}
    engines: {node: ^12.20.0 || ^14.13.1 || >=16.0.0}

+  next-themes@0.4.6:
+    resolution: {integrity: sha512-pZvgD5L0IEvX5/9GWyHMf3m8BKiVQwsCMHfoFosXtXBMnaS0ZnIJ9ST4b4NqLVKDEm8QBxoNNGNaBv2JNF6XNA==}
+    peerDependencies:
+      react: ^16.8 || ^17 || ^18 || ^19 || ^19.0.0-rc
+      react-dom: ^16.8 || ^17 || ^18 || ^19 || ^19.0.0-rc
+
  next@15.5.2:
    resolution: {integrity: sha512-H8Otr7abj1glFhbGnvUt3gz++0AF1+QoCXEBmd/6aKbfdFwrn0LpA836Ed5+00va/7HQSDD+mOoVhn3tNy3e/Q==}
    engines: {node: ^18.18.0 || ^19.8.0 || >= 20.0.0}
@@ -2618,6 +2665,9 @@ packages:
  parse-entities@4.0.2:
    resolution: {integrity: sha512-GG2AQYWoLgL877gQIKeRPGO1xF9+eG1ujIb5soS5gPvLQ1y2o8FL90w2QWNdf9I361Mpp7726c+lj3U0qK1uGw==}

+  parse-git-diff@0.0.19:
+    resolution: {integrity: sha512-oh3giwKzsPlOhekiDDyd/pfFKn04IZoTjEThquhfKigwiUHymiP/Tp6AN5nGIwXQdWuBTQvz9AaRdN5TBsJ8MA==}
+
  parse-ms@4.0.0:
    resolution: {integrity: sha512-TXfryirbmq34y8QBwgqCVLi+8oA3oWx2eAnSn62ITyEhEYaWRlVZ2DvMM9eZbMs/RfxPu/PK/aBLyGj4IrqMHw==}
    engines: {node: '>=18'}
@@ -2883,6 +2933,12 @@ packages:
    resolution: {integrity: sha512-HLpt+uLy/pxB+bum/9DzAgiKS8CX1EvbWxI4zlmgGCExImLdiad2iCwXT5Z4c9c3Eq8rP2318mPW2c+QbtjK8A==}
    engines: {node: '>= 10.0.0', npm: '>= 3.0.0'}

+  sonner@2.0.7:
+    resolution: {integrity: sha512-W6ZN4p58k8aDKA4XPcx2hpIQXBRAgyiWVkYhT7CvK6D3iAu7xjvVyhQHg2/iaKJZ1XVJ4r7XuwGL+WGEK37i9w==}
+    peerDependencies:
+      react: ^18.0.0 || ^19.0.0 || ^19.0.0-rc
+      react-dom: ^18.0.0 || ^19.0.0 || ^19.0.0-rc
+
  source-map-js@1.2.1:
    resolution: {integrity: sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==}
    engines: {node: '>=0.10.0'}
@@ -3800,6 +3856,8 @@ snapshots:

  '@phun-ky/typeof@1.2.8': {}

+  '@radix-ui/number@1.1.1': {}
+
  '@radix-ui/primitive@1.1.3': {}

  '@radix-ui/react-arrow@1.1.7(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)':
@@ -4026,6 +4084,35 @@ snapshots:
      '@types/react': 19.1.12
      '@types/react-dom': 19.1.9(@types/react@19.1.12)

+  '@radix-ui/react-select@2.2.6(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)':
+    dependencies:
+      '@radix-ui/number': 1.1.1
+      '@radix-ui/primitive': 1.1.3
+      '@radix-ui/react-collection': 1.1.7(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-compose-refs': 1.1.2(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-context': 1.1.2(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-direction': 1.1.1(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-dismissable-layer': 1.1.11(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-focus-guards': 1.1.3(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-focus-scope': 1.1.7(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-id': 1.1.1(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-popper': 1.2.8(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-portal': 1.1.9(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-primitive': 2.1.3(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      '@radix-ui/react-slot': 1.2.3(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-use-callback-ref': 1.1.1(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-use-controllable-state': 1.2.2(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-use-layout-effect': 1.1.1(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-use-previous': 1.1.1(@types/react@19.1.12)(react@19.1.1)
+      '@radix-ui/react-visually-hidden': 1.2.3(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      aria-hidden: 1.2.6
+      react: 19.1.1
+      react-dom: 19.1.1(react@19.1.1)
+      react-remove-scroll: 2.7.1(@types/react@19.1.12)(react@19.1.1)
+    optionalDependencies:
+      '@types/react': 19.1.12
+      '@types/react-dom': 19.1.9(@types/react@19.1.12)
+
  '@radix-ui/react-slot@1.2.3(@types/react@19.1.12)(react@19.1.1)':
    dependencies:
      '@radix-ui/react-compose-refs': 1.1.2(@types/react@19.1.12)(react@19.1.1)
@@ -4110,6 +4197,15 @@ snapshots:
    optionalDependencies:
      '@types/react': 19.1.12

+  '@radix-ui/react-visually-hidden@1.2.3(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)':
+    dependencies:
+      '@radix-ui/react-primitive': 2.1.3(@types/react-dom@19.1.9(@types/react@19.1.12))(@types/react@19.1.12)(react-dom@19.1.1(react@19.1.1))(react@19.1.1)
+      react: 19.1.1
+      react-dom: 19.1.1(react@19.1.1)
+    optionalDependencies:
+      '@types/react': 19.1.12
+      '@types/react-dom': 19.1.9(@types/react@19.1.12)
+
  '@radix-ui/rect@1.1.1': {}

  '@rollup/rollup-android-arm-eabi@4.49.0':
@@ -5567,6 +5663,11 @@ snapshots:
    dependencies:
      type-fest: 2.19.0

+  next-themes@0.4.6(react-dom@19.1.1(react@19.1.1))(react@19.1.1):
+    dependencies:
+      react: 19.1.1
+      react-dom: 19.1.1(react@19.1.1)
+
  next@15.5.2(react-dom@19.1.1(react@19.1.1))(react@19.1.1):
    dependencies:
      '@next/env': 15.5.2
@@ -5714,6 +5815,8 @@ snapshots:
      is-decimal: 2.0.1
      is-hexadecimal: 2.0.1

+  parse-git-diff@0.0.19: {}
+
  parse-ms@4.0.0: {}

  parse-path@7.1.0:
@@ -6078,6 +6181,11 @@ snapshots:
      ip-address: 10.0.1
      smart-buffer: 4.2.0

+  sonner@2.0.7(react-dom@19.1.1(react@19.1.1))(react@19.1.1):
+    dependencies:
+      react: 19.1.1
+      react-dom: 19.1.1(react@19.1.1)
+
  source-map-js@1.2.1: {}

  source-map-support@0.5.21:
--- a/src/app/layout.tsx
+++ b/src/app/layout.tsx
@@ -1,5 +1,6 @@
 import type { Metadata } from "next";
 import { Geist, Geist_Mono } from "next/font/google";
+import { Toaster } from "../components/ui/sonner";
 import { QueryClientProviderWrapper } from "../lib/api/QueryClientProviderWrapper";
 import { RootErrorBoundary } from "./components/RootErrorBoundary";
 import { ServerEventsProvider } from "./components/ServerEventsProvider";
@@ -47,6 +48,7 @@ export default async function RootLayout({
            <ServerEventsProvider>{children}</ServerEventsProvider>
          </QueryClientProviderWrapper>
        </RootErrorBoundary>
+        <Toaster position="top-right" />
      </body>
    </html>
  );
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/SessionPageContent.tsx
@@ -3,6 +3,7 @@
 import { useMutation } from "@tanstack/react-query";
 import {
  ExternalLinkIcon,
+  GitCompareIcon,
  LoaderIcon,
  MenuIcon,
  PauseIcon,
@@ -19,6 +20,7 @@ import { firstCommandToTitle } from "../../../services/firstCommandToTitle";
 import { useAliveTask } from "../hooks/useAliveTask";
 import { useSession } from "../hooks/useSession";
 import { ConversationList } from "./conversationList/ConversationList";
+import { DiffModal } from "./diffModal";
 import { ResumeChat } from "./resumeChat/ResumeChat";
 import { SessionSidebar } from "./sessionSidebar/SessionSidebar";

@@ -51,6 +53,7 @@ export const SessionPageContent: FC<{
  const [previousConversationLength, setPreviousConversationLength] =
    useState(0);
  const [isMobileSidebarOpen, setIsMobileSidebarOpen] = useState(false);
+  const [isDiffModalOpen, setIsDiffModalOpen] = useState(false);
  const scrollContainerRef = useRef<HTMLDivElement>(null);

  // 自動スクロール処理
@@ -177,6 +180,23 @@ export const SessionPageContent: FC<{
              getToolResult={getToolResult}
            />

+            {isRunningTask && (
+              <div className="flex justify-start items-center py-8">
+                <div className="flex flex-col items-center gap-4">
+                  <div className="flex items-center gap-2">
+                    <div className="flex gap-1">
+                      <div className="w-2 h-2 bg-primary rounded-full animate-bounce"></div>
+                      <div className="w-2 h-2 bg-primary rounded-full animate-bounce [animation-delay:0.1s]"></div>
+                      <div className="w-2 h-2 bg-primary rounded-full animate-bounce [animation-delay:0.2s]"></div>
+                    </div>
+                  </div>
+                  <p className="text-sm text-muted-foreground font-medium">
+                    Claude Code is processing...
+                  </p>
+                </div>
+              </div>
+            )}
+
            <ResumeChat
              projectId={projectId}
              sessionId={sessionId}
@@ -186,6 +206,22 @@ export const SessionPageContent: FC<{
          </main>
        </div>
      </div>
+
+      {/* Fixed Diff Button */}
+      <Button
+        onClick={() => setIsDiffModalOpen(true)}
+        className="fixed bottom-6 right-6 w-14 h-14 rounded-full shadow-lg hover:shadow-xl transition-all duration-200 z-50"
+        size="lg"
+      >
+        <GitCompareIcon className="w-6 h-6" />
+      </Button>
+
+      {/* Diff Modal */}
+      <DiffModal
+        projectId={projectId}
+        isOpen={isDiffModalOpen}
+        onOpenChange={setIsDiffModalOpen}
+      />
    </div>
  );
 };
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/DiffModal.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/DiffModal.tsx
@@ -0,0 +1,305 @@
+"use client";
+
+import { FileText, GitBranch, Loader2, RefreshCcwIcon } from "lucide-react";
+import type { FC } from "react";
+import { useCallback, useEffect, useId, useState } from "react";
+import { Button } from "@/components/ui/button";
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogHeader,
+  DialogTitle,
+} from "@/components/ui/dialog";
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from "@/components/ui/select";
+import { cn } from "@/lib/utils";
+import { useGitBranches, useGitCommits, useGitDiff } from "../../hooks/useGit";
+import { DiffViewer } from "./DiffViewer";
+import type { DiffModalProps, DiffSummary, GitRef } from "./types";
+
+interface DiffSummaryProps {
+  summary: DiffSummary;
+  className?: string;
+}
+
+const DiffSummaryComponent: FC<DiffSummaryProps> = ({ summary, className }) => {
+  return (
+    <div
+      className={cn(
+        "bg-gray-50 dark:bg-gray-800 rounded-lg p-4 border border-gray-200 dark:border-gray-700",
+        className,
+      )}
+    >
+      <div className="flex items-center justify-between text-sm">
+        <div className="flex items-center gap-1">
+          <FileText className="h-4 w-4 text-gray-600 dark:text-gray-400" />
+          <span className="font-medium">
+            <span className="hidden sm:inline">
+              {summary.filesChanged} files changed
+            </span>
+            <span className="sm:hidden">{summary.filesChanged} files</span>
+          </span>
+        </div>
+        <div className="flex items-center gap-3">
+          {summary.insertions > 0 && (
+            <span className="text-green-600 dark:text-green-400 font-medium">
+              +{summary.insertions}
+            </span>
+          )}
+          {summary.deletions > 0 && (
+            <span className="text-red-600 dark:text-red-400 font-medium">
+              -{summary.deletions}
+            </span>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+};
+
+interface RefSelectorProps {
+  label: string;
+  value: string;
+  onValueChange: (value: GitRef["name"]) => void;
+  refs: GitRef[];
+}
+
+const RefSelector: FC<RefSelectorProps> = ({
+  label,
+  value,
+  onValueChange,
+  refs,
+}) => {
+  const id = useId();
+  const getRefIcon = (type: GitRef["type"]) => {
+    switch (type) {
+      case "branch":
+        return <GitBranch className="h-4 w-4" />;
+      case "commit":
+        return <span className="text-xs">📝</span>;
+      case "working":
+        return <span className="text-xs">🚧</span>;
+      default:
+        return <GitBranch className="h-4 w-4" />;
+    }
+  };
+
+  return (
+    <div className="space-y-2">
+      <label
+        htmlFor={id}
+        className="text-sm font-medium text-gray-700 dark:text-gray-300"
+      >
+        {label}
+      </label>
+      <Select value={value} onValueChange={onValueChange}>
+        <SelectTrigger className="w-full sm:w-80">
+          <SelectValue placeholder={`Select ${label.toLowerCase()}`} />
+        </SelectTrigger>
+        <SelectContent id={id}>
+          {refs.map((ref) => (
+            <SelectItem key={ref.name} value={ref.name}>
+              <div className="flex items-center gap-2">
+                {getRefIcon(ref.type)}
+                <span>{ref.displayName}</span>
+                {ref.sha && (
+                  <span className="text-xs text-gray-500 dark:text-gray-400 font-mono">
+                    {ref.sha.substring(0, 7)}
+                  </span>
+                )}
+              </div>
+            </SelectItem>
+          ))}
+        </SelectContent>
+      </Select>
+    </div>
+  );
+};
+
+export const DiffModal: FC<DiffModalProps> = ({
+  isOpen,
+  onOpenChange,
+  projectId,
+  defaultCompareFrom = "HEAD",
+  defaultCompareTo = "working",
+}) => {
+  const [compareFrom, setCompareFrom] = useState(defaultCompareFrom);
+  const [compareTo, setCompareTo] = useState(defaultCompareTo);
+
+  // API hooks
+  const { data: branchesData, isLoading: isLoadingBranches } =
+    useGitBranches(projectId);
+  const { data: commitsData, isLoading: isLoadingCommits } =
+    useGitCommits(projectId);
+  const {
+    mutate: getDiff,
+    data: diffData,
+    isPending: isDiffLoading,
+    error: diffError,
+  } = useGitDiff();
+
+  // Transform branches and commits data to GitRef format
+  const gitRefs: GitRef[] =
+    branchesData?.success && branchesData.data
+      ? [
+          {
+            name: "working" as const,
+            type: "working" as const,
+            displayName: "Uncommitted changes",
+          },
+          {
+            name: "HEAD" as const,
+            type: "commit" as const,
+            displayName: "HEAD",
+          },
+          ...branchesData.data.map((branch) => ({
+            name: `branch:${branch.name}` as const,
+            type: "branch" as const,
+            displayName: branch.name + (branch.current ? " (current)" : ""),
+            sha: branch.commit,
+          })),
+          // Add commits from current branch
+          ...(commitsData?.success && commitsData.data
+            ? commitsData.data.map((commit) => ({
+                name: `commit:${commit.sha}` as const,
+                type: "commit" as const,
+                displayName: `${commit.message.substring(0, 50)}${commit.message.length > 50 ? "..." : ""}`,
+                sha: commit.sha,
+              }))
+            : []),
+        ]
+      : [];
+
+  const loadDiff = useCallback(() => {
+    if (compareFrom && compareTo && compareFrom !== compareTo) {
+      getDiff({
+        projectId,
+        fromRef: compareFrom,
+        toRef: compareTo,
+      });
+    }
+  }, [compareFrom, compareTo, getDiff, projectId]);
+
+  useEffect(() => {
+    if (isOpen && compareFrom && compareTo) {
+      loadDiff();
+    }
+  }, [isOpen, compareFrom, compareTo, loadDiff]);
+
+  const handleCompare = () => {
+    loadDiff();
+  };
+
+  return (
+    <Dialog open={isOpen} onOpenChange={onOpenChange}>
+      <DialogContent className="max-w-7xl w-[95vw] h-[90vh] overflow-hidden flex flex-col px-2 md:px-8">
+        <DialogHeader>
+          <DialogTitle>Preview Changes</DialogTitle>
+        </DialogHeader>
+
+        <div className="flex flex-col sm:flex-row gap-3 sm:items-end">
+          <div className="flex flex-col sm:flex-row gap-3 flex-1">
+            <RefSelector
+              label="Compare from"
+              value={compareFrom}
+              onValueChange={setCompareFrom}
+              refs={gitRefs.filter((ref) => ref.name !== "working")}
+            />
+            <RefSelector
+              label="Compare to"
+              value={compareTo}
+              onValueChange={setCompareTo}
+              refs={gitRefs}
+            />
+          </div>
+          <Button
+            onClick={handleCompare}
+            disabled={
+              isDiffLoading ||
+              isLoadingBranches ||
+              isLoadingCommits ||
+              compareFrom === compareTo
+            }
+            className="sm:self-end w-full sm:w-auto"
+          >
+            {isDiffLoading ? (
+              <>
+                <Loader2 className="w-4 h-4 mr-2 animate-spin" />
+                Loading...
+              </>
+            ) : (
+              <RefreshCcwIcon className="w-4 h-4" />
+            )}
+          </Button>
+        </div>
+
+        {diffError && (
+          <div className="bg-red-50 dark:bg-red-900/10 border border-red-200 dark:border-red-800 rounded-lg p-4">
+            <p className="text-red-600 dark:text-red-400 text-sm">
+              {diffError.message}
+            </p>
+          </div>
+        )}
+
+        {diffData?.success && (
+          <>
+            <DiffSummaryComponent
+              summary={{
+                filesChanged: diffData.data.files.length,
+                insertions: diffData.data.summary.totalAdditions,
+                deletions: diffData.data.summary.totalDeletions,
+                files: diffData.data.diffs.map((diff) => ({
+                  filename: diff.file.filePath,
+                  oldFilename: diff.file.oldPath,
+                  isNew: diff.file.status === "added",
+                  isDeleted: diff.file.status === "deleted",
+                  isRenamed: diff.file.status === "renamed",
+                  isBinary: false,
+                  hunks: diff.hunks,
+                  linesAdded: diff.file.additions,
+                  linesDeleted: diff.file.deletions,
+                })),
+              }}
+            />
+
+            <div className="flex-1 overflow-auto space-y-6">
+              {diffData.data.diffs.map((diff) => (
+                <DiffViewer
+                  key={diff.file.filePath}
+                  fileDiff={{
+                    filename: diff.file.filePath,
+                    oldFilename: diff.file.oldPath,
+                    isNew: diff.file.status === "added",
+                    isDeleted: diff.file.status === "deleted",
+                    isRenamed: diff.file.status === "renamed",
+                    isBinary: false,
+                    hunks: diff.hunks,
+                    linesAdded: diff.file.additions,
+                    linesDeleted: diff.file.deletions,
+                  }}
+                />
+              ))}
+            </div>
+          </>
+        )}
+
+        {isDiffLoading && (
+          <div className="flex-1 flex items-center justify-center">
+            <div className="text-center space-y-2">
+              <Loader2 className="w-8 h-8 animate-spin mx-auto" />
+              <p className="text-sm text-gray-500 dark:text-gray-400">
+                Loading diff...
+              </p>
+            </div>
+          </div>
+        )}
+      </DialogContent>
+    </Dialog>
+  );
+};
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/DiffViewer.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/DiffViewer.tsx
@@ -0,0 +1,254 @@
+"use client";
+
+import { ChevronDownIcon, ChevronRightIcon, CopyIcon } from "lucide-react";
+import type { FC } from "react";
+import { useState } from "react";
+import { toast } from "sonner";
+import { cn } from "@/lib/utils";
+import { Button } from "../../../../../../../components/ui/button";
+import type { DiffHunk, FileDiff } from "./types";
+
+interface DiffViewerProps {
+  fileDiff: FileDiff;
+  className?: string;
+}
+
+interface DiffHunkProps {
+  hunk: DiffHunk;
+}
+
+const DiffHunkComponent: FC<DiffHunkProps> = ({ hunk }) => {
+  return (
+    <div className="relative flex overflow-x-auto">
+      {/* 行番号列（固定） */}
+      <div className="flex-shrink-0 sticky left-0 z-10 bg-white dark:bg-gray-900">
+        {/* 旧行番号列 */}
+        <div className="float-left w-10 bg-gray-50 dark:bg-gray-800/50 border-r border-gray-200 dark:border-gray-700">
+          {hunk.lines.map((line, index) => (
+            <div
+              key={`old-${line.oldLineNumber}-${index}`}
+              className="px-2 py-1 text-sm text-gray-400 dark:text-gray-600 font-mono text-right h-[28px]"
+            >
+              {line.type !== "added" &&
+              line.type !== "hunk" &&
+              line.oldLineNumber
+                ? line.oldLineNumber
+                : "　"}
+            </div>
+          ))}
+        </div>
+        {/* 新行番号列 */}
+        <div className="float-left w-10 bg-gray-50 dark:bg-gray-800/50 border-r border-gray-200 dark:border-gray-700">
+          {hunk.lines.map((line, index) => (
+            <div
+              key={`new-${line.newLineNumber}-${index}`}
+              className="px-2 py-1 text-sm text-gray-400 dark:text-gray-600 font-mono text-right h-[28px]"
+            >
+              {line.type !== "deleted" &&
+              line.type !== "hunk" &&
+              line.newLineNumber
+                ? line.newLineNumber
+                : "　"}
+            </div>
+          ))}
+        </div>
+      </div>
+
+      {/* コンテンツ列（スクロール可能） */}
+      <div className="flex-1 min-w-0">
+        {hunk.lines.map((line, index) => (
+          <div
+            key={`content-${line.content}-${line.oldLineNumber}-${line.newLineNumber}-${index}`}
+            className={cn("flex border-l-4", {
+              "bg-green-50 dark:bg-green-950/30 border-green-200 dark:border-green-800/50 border-l-green-400":
+                line.type === "added",
+              "bg-red-50 dark:bg-red-950/30 border-red-200 dark:border-red-800/50 border-l-red-400":
+                line.type === "deleted",
+              "bg-blue-50 dark:bg-blue-950/30 border-blue-200 dark:border-blue-800/50 border-l-blue-400":
+                line.type === "hunk",
+              "bg-white dark:bg-gray-900 border-gray-100 dark:border-gray-800 border-l-transparent":
+                line.type === "unchanged",
+            })}
+          >
+            <div className="flex-1 px-2 py-1">
+              <span className="font-mono text-sm whitespace-pre block">
+                <span
+                  className={cn({
+                    "text-green-600 dark:text-green-400": line.type === "added",
+                    "text-red-600 dark:text-red-400": line.type === "deleted",
+                    "text-blue-600 dark:text-blue-400 font-medium":
+                      line.type === "hunk",
+                    "text-gray-400 dark:text-gray-600":
+                      line.type === "unchanged",
+                  })}
+                >
+                  {line.type === "added"
+                    ? "+"
+                    : line.type === "deleted"
+                      ? "-"
+                      : line.type === "hunk"
+                        ? ""
+                        : " "}
+                </span>
+                {line.content || " "}
+              </span>
+            </div>
+          </div>
+        ))}
+      </div>
+    </div>
+  );
+};
+
+interface FileHeaderProps {
+  fileDiff: FileDiff;
+  isCollapsed: boolean;
+  onToggleCollapse: () => void;
+}
+
+const FileHeader: FC<FileHeaderProps> = ({
+  fileDiff,
+  isCollapsed,
+  onToggleCollapse,
+}) => {
+  const getFileStatusIcon = () => {
+    if (fileDiff.isNew)
+      return <span className="text-green-600 dark:text-green-400">A</span>;
+    if (fileDiff.isDeleted)
+      return <span className="text-red-600 dark:text-red-400">D</span>;
+    if (fileDiff.isRenamed)
+      return <span className="text-blue-600 dark:text-blue-400">R</span>;
+    return <span className="text-gray-600 dark:text-gray-400">M</span>;
+  };
+
+  const getFileStatusText = () => {
+    if (fileDiff.isNew) return "added";
+    if (fileDiff.isDeleted) return "deleted";
+    if (fileDiff.isRenamed) return `renamed from ${fileDiff.oldFilename ?? ""}`;
+    return "modified";
+  };
+
+  const handleCopyFilename = async (e: React.MouseEvent) => {
+    e.stopPropagation();
+    try {
+      await navigator.clipboard.writeText(fileDiff.filename);
+      toast.success("ファイル名をコピーしました");
+    } catch (err) {
+      console.error("Failed to copy filename:", err);
+      toast.error("ファイル名のコピーに失敗しました");
+    }
+  };
+
+  return (
+    <Button
+      onClick={onToggleCollapse}
+      className="w-full bg-gray-50 dark:bg-gray-800 px-4 py-4 hover:bg-gray-100 dark:hover:bg-gray-700 transition-colors min-h-[4rem]"
+    >
+      <div className="w-full space-y-1">
+        {/* Row 1: icon, status, and stats */}
+        <div className="flex items-center justify-between">
+          <div className="flex items-center gap-2">
+            {isCollapsed ? (
+              <ChevronRightIcon className="w-4 h-4 text-gray-500" />
+            ) : (
+              <ChevronDownIcon className="w-4 h-4 text-gray-500" />
+            )}
+            <div className="w-6 h-6 rounded-full bg-gray-100 dark:bg-gray-700 flex items-center justify-center text-xs font-mono">
+              {getFileStatusIcon()}
+            </div>
+            <span className="text-xs text-gray-500 dark:text-gray-400">
+              {getFileStatusText()}
+            </span>
+          </div>
+          <div className="flex items-center gap-4 text-xs text-gray-500 dark:text-gray-400">
+            {fileDiff.linesAdded > 0 && (
+              <span className="text-green-600 dark:text-green-400">
+                +{fileDiff.linesAdded}
+              </span>
+            )}
+            {fileDiff.linesDeleted > 0 && (
+              <span className="text-red-600 dark:text-red-400">
+                -{fileDiff.linesDeleted}
+              </span>
+            )}
+          </div>
+        </div>
+
+        {/* Row 2: filename with copy button */}
+        <div className="w-full flex items-center gap-2">
+          <span className="font-mono text-sm font-medium text-black dark:text-white text-left truncate flex-1 min-w-0">
+            {fileDiff.filename}
+          </span>
+          <Button
+            onClick={handleCopyFilename}
+            variant="ghost"
+            size="sm"
+            className="flex-shrink-0 p-1 h-6 w-6 hover:bg-gray-200 dark:hover:bg-gray-600"
+          >
+            <CopyIcon className="w-3 h-3 text-gray-500 dark:text-gray-400" />
+          </Button>
+        </div>
+      </div>
+      {fileDiff.isBinary && (
+        <div className="mt-2 text-xs text-gray-500 dark:text-gray-400 text-left">
+          Binary file (content not shown)
+        </div>
+      )}
+    </Button>
+  );
+};
+
+export const DiffViewer: FC<DiffViewerProps> = ({ fileDiff, className }) => {
+  const [isCollapsed, setIsCollapsed] = useState(false);
+
+  const toggleCollapse = () => {
+    setIsCollapsed(!isCollapsed);
+  };
+
+  if (fileDiff.isBinary) {
+    return (
+      <div
+        className={cn(
+          "border border-gray-200 dark:border-gray-700 rounded-lg",
+          className,
+        )}
+      >
+        <FileHeader
+          fileDiff={fileDiff}
+          isCollapsed={isCollapsed}
+          onToggleCollapse={toggleCollapse}
+        />
+        {!isCollapsed && (
+          <div className="text-center py-8 text-gray-500 dark:text-gray-400 text-sm">
+            Binary file cannot be displayed
+          </div>
+        )}
+      </div>
+    );
+  }
+
+  return (
+    <div
+      className={cn(
+        "border border-gray-200 dark:border-gray-700 rounded-lg",
+        className,
+      )}
+    >
+      <FileHeader
+        fileDiff={fileDiff}
+        isCollapsed={isCollapsed}
+        onToggleCollapse={toggleCollapse}
+      />
+      {!isCollapsed && (
+        <div className="border-t border-gray-200 dark:border-gray-700">
+          {fileDiff.hunks.map((hunk, index) => (
+            <DiffHunkComponent
+              key={`${hunk.oldStart}-${hunk.newStart}-${index}`}
+              hunk={hunk}
+            />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+};
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/api-types.ts
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/api-types.ts
@@ -0,0 +1,76 @@
+// API response types for Git operations
+export interface GitBranch {
+  name: string;
+  current: boolean;
+  remote?: string;
+  commit: string;
+  ahead?: number;
+  behind?: number;
+}
+
+export interface GitBranchesResponse {
+  success: true;
+  data: GitBranch[];
+}
+
+export interface GitFileInfo {
+  filePath: string;
+  status: "added" | "modified" | "deleted" | "renamed" | "copied";
+  additions: number;
+  deletions: number;
+  oldPath?: string;
+}
+
+export interface GitDiffLine {
+  type: "added" | "deleted" | "unchanged" | "hunk";
+  oldLineNumber?: number;
+  newLineNumber?: number;
+  content: string;
+}
+
+export interface GitDiffHunk {
+  oldStart: number;
+  oldLines: number;
+  newStart: number;
+  newLines: number;
+  lines: GitDiffLine[];
+}
+
+export interface GitFileDiff {
+  file: GitFileInfo;
+  hunks: GitDiffHunk[];
+}
+
+export interface GitDiffSummary {
+  totalFiles: number;
+  totalAdditions: number;
+  totalDeletions: number;
+}
+
+export interface GitDiffResponse {
+  success: true;
+  data: {
+    files: GitFileInfo[];
+    diffs: GitFileDiff[];
+    summary: GitDiffSummary;
+  };
+}
+
+export interface GitErrorResponse {
+  success: false;
+  error: {
+    code:
+      | "NOT_A_REPOSITORY"
+      | "BRANCH_NOT_FOUND"
+      | "COMMAND_FAILED"
+      | "PARSE_ERROR";
+    message: string;
+    command?: string;
+    stderr?: string;
+  };
+}
+
+export type GitApiResponse =
+  | GitBranchesResponse
+  | GitDiffResponse
+  | GitErrorResponse;
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/index.ts
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/index.ts
@@ -0,0 +1,10 @@
+export { DiffModal } from "./DiffModal";
+export { DiffViewer } from "./DiffViewer";
+export type {
+  DiffHunk,
+  DiffLine,
+  DiffModalProps,
+  DiffSummary,
+  FileDiff,
+  GitRef,
+} from "./types";
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/types.ts
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/diffModal/types.ts
@@ -0,0 +1,48 @@
+export interface DiffLine {
+  type: "added" | "deleted" | "unchanged" | "hunk" | "context";
+  oldLineNumber?: number;
+  newLineNumber?: number;
+  content: string;
+}
+
+export interface DiffHunk {
+  oldStart: number;
+  // oldLines: number;
+  newStart: number;
+  // newLines: number;
+  lines: DiffLine[];
+}
+
+export interface FileDiff {
+  filename: string;
+  oldFilename?: string;
+  isNew: boolean;
+  isDeleted: boolean;
+  isRenamed: boolean;
+  isBinary: boolean;
+  hunks: DiffHunk[];
+  linesAdded: number;
+  linesDeleted: number;
+}
+
+export interface GitRef {
+  name: `branch:${string}` | `commit:${string}` | `HEAD` | "working";
+  type: "branch" | "commit" | "head" | "working";
+  sha?: string;
+  displayName: string;
+}
+
+export interface DiffSummary {
+  filesChanged: number;
+  insertions: number;
+  deletions: number;
+  files: FileDiff[];
+}
+
+export interface DiffModalProps {
+  projectId: string;
+  isOpen: boolean;
+  onOpenChange: (open: boolean) => void;
+  defaultCompareFrom?: string;
+  defaultCompareTo?: string;
+}
--- a/src/app/projects/[projectId]/sessions/[sessionId]/hooks/useGit.ts
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/hooks/useGit.ts
@@ -0,0 +1,69 @@
+import { useMutation, useQuery } from "@tanstack/react-query";
+import { honoClient } from "@/lib/api/client";
+
+export const useGitBranches = (projectId: string) => {
+  return useQuery({
+    queryKey: ["git", "branches", projectId],
+    queryFn: async () => {
+      const response = await honoClient.api.projects[
+        ":projectId"
+      ].git.branches.$get({
+        param: { projectId },
+      });
+
+      if (!response.ok) {
+        throw new Error(`Failed to fetch branches: ${response.statusText}`);
+      }
+
+      return response.json();
+    },
+    staleTime: 30000, // 30 seconds
+  });
+};
+
+export const useGitCommits = (projectId: string) => {
+  return useQuery({
+    queryKey: ["git", "commits", projectId],
+    queryFn: async () => {
+      const response = await honoClient.api.projects[
+        ":projectId"
+      ].git.commits.$get({
+        param: { projectId },
+      });
+
+      if (!response.ok) {
+        throw new Error(`Failed to fetch commits: ${response.statusText}`);
+      }
+
+      return response.json();
+    },
+    staleTime: 30000, // 30 seconds
+  });
+};
+
+export const useGitDiff = () => {
+  return useMutation({
+    mutationFn: async ({
+      projectId,
+      fromRef,
+      toRef,
+    }: {
+      projectId: string;
+      fromRef: string;
+      toRef: string;
+    }) => {
+      const response = await honoClient.api.projects[
+        ":projectId"
+      ].git.diff.$post({
+        param: { projectId },
+        json: { fromRef, toRef },
+      });
+
+      if (!response.ok) {
+        throw new Error(`Failed to get diff: ${response.statusText}`);
+      }
+
+      return response.json();
+    },
+  });
+};
--- a/src/components/ui/select.tsx
+++ b/src/components/ui/select.tsx
@@ -0,0 +1,175 @@
+"use client";
+
+import * as SelectPrimitive from "@radix-ui/react-select";
+import { Check, ChevronDown, ChevronUp } from "lucide-react";
+import type * as React from "react";
+
+import { cn } from "@/lib/utils";
+
+function Select({
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Root>) {
+  return <SelectPrimitive.Root {...props} />;
+}
+
+function SelectGroup({
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Group>) {
+  return <SelectPrimitive.Group {...props} />;
+}
+
+function SelectValue({
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Value>) {
+  return <SelectPrimitive.Value {...props} />;
+}
+
+function SelectTrigger({
+  className,
+  children,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Trigger>) {
+  return (
+    <SelectPrimitive.Trigger
+      className={cn(
+        "flex h-10 w-full items-center justify-between rounded-md border bg-background px-3 py-2 text-sm ring-offset-background placeholder:text-muted-foreground focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 [&>span]:line-clamp-1",
+        className,
+      )}
+      {...props}
+    >
+      {children}
+      <SelectPrimitive.Icon asChild>
+        <ChevronDown className="h-4 w-4 opacity-50" />
+      </SelectPrimitive.Icon>
+    </SelectPrimitive.Trigger>
+  );
+}
+
+function SelectScrollUpButton({
+  className,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.ScrollUpButton>) {
+  return (
+    <SelectPrimitive.ScrollUpButton
+      className={cn(
+        "flex cursor-default items-center justify-center py-1",
+        className,
+      )}
+      {...props}
+    >
+      <ChevronUp className="h-4 w-4" />
+    </SelectPrimitive.ScrollUpButton>
+  );
+}
+
+function SelectScrollDownButton({
+  className,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.ScrollDownButton>) {
+  return (
+    <SelectPrimitive.ScrollDownButton
+      className={cn(
+        "flex cursor-default items-center justify-center py-1",
+        className,
+      )}
+      {...props}
+    >
+      <ChevronDown className="h-4 w-4" />
+    </SelectPrimitive.ScrollDownButton>
+  );
+}
+
+function SelectContent({
+  className,
+  children,
+  position = "popper",
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Content>) {
+  return (
+    <SelectPrimitive.Portal>
+      <SelectPrimitive.Content
+        className={cn(
+          "relative z-50 max-h-96 min-w-[8rem] overflow-hidden rounded-md border bg-popover text-popover-foreground shadow-md data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2",
+          position === "popper" &&
+            "data-[side=bottom]:translate-y-1 data-[side=left]:-translate-x-1 data-[side=right]:translate-x-1 data-[side=top]:-translate-y-1",
+          className,
+        )}
+        position={position}
+        {...props}
+      >
+        <SelectScrollUpButton />
+        <SelectPrimitive.Viewport
+          className={cn(
+            "p-1",
+            position === "popper" &&
+              "h-[var(--radix-select-trigger-height)] w-full min-w-[var(--radix-select-trigger-width)]",
+          )}
+        >
+          {children}
+        </SelectPrimitive.Viewport>
+        <SelectScrollDownButton />
+      </SelectPrimitive.Content>
+    </SelectPrimitive.Portal>
+  );
+}
+
+function SelectLabel({
+  className,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Label>) {
+  return (
+    <SelectPrimitive.Label
+      className={cn("py-1.5 pl-8 pr-2 text-sm font-semibold", className)}
+      {...props}
+    />
+  );
+}
+
+function SelectItem({
+  className,
+  children,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Item>) {
+  return (
+    <SelectPrimitive.Item
+      className={cn(
+        "relative flex w-full cursor-default select-none items-center rounded-sm py-1.5 pl-8 pr-2 text-sm outline-none focus:bg-accent focus:text-accent-foreground data-[disabled]:pointer-events-none data-[disabled]:opacity-50",
+        className,
+      )}
+      {...props}
+    >
+      <span className="absolute left-2 flex h-3.5 w-3.5 items-center justify-center">
+        <SelectPrimitive.ItemIndicator>
+          <Check className="h-4 w-4" />
+        </SelectPrimitive.ItemIndicator>
+      </span>
+
+      <SelectPrimitive.ItemText>{children}</SelectPrimitive.ItemText>
+    </SelectPrimitive.Item>
+  );
+}
+
+function SelectSeparator({
+  className,
+  ...props
+}: React.ComponentProps<typeof SelectPrimitive.Separator>) {
+  return (
+    <SelectPrimitive.Separator
+      className={cn("-mx-1 my-1 h-px bg-muted", className)}
+      {...props}
+    />
+  );
+}
+
+export {
+  Select,
+  SelectContent,
+  SelectGroup,
+  SelectItem,
+  SelectLabel,
+  SelectScrollDownButton,
+  SelectScrollUpButton,
+  SelectSeparator,
+  SelectTrigger,
+  SelectValue,
+};
--- a/src/components/ui/sonner.tsx
+++ b/src/components/ui/sonner.tsx
@@ -0,0 +1,25 @@
+"use client";
+
+import { useTheme } from "next-themes";
+import { Toaster as Sonner, type ToasterProps } from "sonner";
+
+const Toaster = ({ ...props }: ToasterProps) => {
+  const { theme = "system" } = useTheme();
+
+  return (
+    <Sonner
+      theme={theme as ToasterProps["theme"]}
+      className="toaster group"
+      style={
+        {
+          "--normal-bg": "var(--popover)",
+          "--normal-text": "var(--popover-foreground)",
+          "--normal-border": "var(--border)",
+        } as React.CSSProperties
+      }
+      {...props}
+    />
+  );
+};
+
+export { Toaster };
--- a/src/server/hono/route.ts
+++ b/src/server/hono/route.ts
@@ -12,6 +12,9 @@ import { getEventBus } from "../service/events/EventBus";
 import { getFileWatcher } from "../service/events/fileWatcher";
 import { sseEventResponse } from "../service/events/sseEventResponse";
 import { getFileCompletion } from "../service/file-completion/getFileCompletion";
+import { getBranches } from "../service/git/getBranches";
+import { getCommits } from "../service/git/getCommits";
+import { getDiff } from "../service/git/getDiff";
 import { getMcpList } from "../service/mcp/getMcpList";
 import { getProject } from "../service/project/getProject";
 import { getProjects } from "../service/project/getProjects";
@@ -202,6 +205,81 @@ export const routes = (app: HonoAppType) => {
        });
      })

+      .get("/projects/:projectId/git/branches", async (c) => {
+        const { projectId } = c.req.param();
+        const { project } = await getProject(projectId);
+
+        if (project.meta.projectPath === null) {
+          return c.json({ error: "Project path not found" }, 400);
+        }
+
+        try {
+          const result = await getBranches(project.meta.projectPath);
+          return c.json(result);
+        } catch (error) {
+          console.error("Get branches error:", error);
+          if (error instanceof Error) {
+            return c.json({ error: error.message }, 400);
+          }
+          return c.json({ error: "Failed to get branches" }, 500);
+        }
+      })
+
+      .get("/projects/:projectId/git/commits", async (c) => {
+        const { projectId } = c.req.param();
+        const { project } = await getProject(projectId);
+
+        if (project.meta.projectPath === null) {
+          return c.json({ error: "Project path not found" }, 400);
+        }
+
+        try {
+          const result = await getCommits(project.meta.projectPath);
+          return c.json(result);
+        } catch (error) {
+          console.error("Get commits error:", error);
+          if (error instanceof Error) {
+            return c.json({ error: error.message }, 400);
+          }
+          return c.json({ error: "Failed to get commits" }, 500);
+        }
+      })
+
+      .post(
+        "/projects/:projectId/git/diff",
+        zValidator(
+          "json",
+          z.object({
+            fromRef: z.string().min(1, "fromRef is required"),
+            toRef: z.string().min(1, "toRef is required"),
+          }),
+        ),
+        async (c) => {
+          const { projectId } = c.req.param();
+          const { fromRef, toRef } = c.req.valid("json");
+          const { project } = await getProject(projectId);
+
+          if (project.meta.projectPath === null) {
+            return c.json({ error: "Project path not found" }, 400);
+          }
+
+          try {
+            const result = await getDiff(
+              project.meta.projectPath,
+              fromRef,
+              toRef,
+            );
+            return c.json(result);
+          } catch (error) {
+            console.error("Get diff error:", error);
+            if (error instanceof Error) {
+              return c.json({ error: error.message }, 400);
+            }
+            return c.json({ error: "Failed to get diff" }, 500);
+          }
+        },
+      )
+
      .get("/mcp/list", async (c) => {
        const { servers } = await getMcpList();
        return c.json({ servers });
--- a/src/server/service/git/getBranches.ts
+++ b/src/server/service/git/getBranches.ts
@@ -0,0 +1,130 @@
+import type { GitBranch, GitResult } from "./types";
+import { executeGitCommand, parseLines } from "./utils";
+
+/**
+ * Get all branches (local and remote) in the repository
+ */
+export async function getBranches(
+  cwd: string,
+): Promise<GitResult<GitBranch[]>> {
+  // Get all branches with verbose information
+  const result = await executeGitCommand(["branch", "-vv", "--all"], cwd);
+
+  if (!result.success) {
+    return result as GitResult<GitBranch[]>;
+  }
+
+  try {
+    const lines = parseLines(result.data);
+    const branches: GitBranch[] = [];
+    const seenBranches = new Set<string>();
+
+    for (const line of lines) {
+      // Parse branch line format: "  main     abc1234 [origin/main: ahead 1] Commit message"
+      const match = line.match(
+        /^(\*?\s*)([^\s]+)\s+([a-f0-9]+)(?:\s+\[([^\]]+)\])?\s*(.*)/,
+      );
+      if (!match) continue;
+
+      const [, prefix, name, commit, tracking] = match;
+      if (!prefix || !name || !commit) continue;
+
+      const current = prefix.includes("*");
+
+      // Skip remote tracking branches if we already have the local branch
+      const cleanName = name.replace("remotes/origin/", "");
+      if (name.startsWith("remotes/origin/") && seenBranches.has(cleanName)) {
+        continue;
+      }
+
+      // Parse tracking information
+      let remote: string | undefined;
+      let ahead: number | undefined;
+      let behind: number | undefined;
+
+      if (tracking) {
+        const remoteMatch = tracking.match(/^([^:]+)/);
+        if (remoteMatch?.[1]) {
+          remote = remoteMatch[1];
+        }
+
+        const aheadMatch = tracking.match(/ahead (\d+)/);
+        const behindMatch = tracking.match(/behind (\d+)/);
+        if (aheadMatch?.[1]) ahead = parseInt(aheadMatch[1], 10);
+        if (behindMatch?.[1]) behind = parseInt(behindMatch[1], 10);
+      }
+
+      branches.push({
+        name: cleanName,
+        current,
+        remote,
+        commit,
+        ahead,
+        behind,
+      });
+
+      seenBranches.add(cleanName);
+    }
+
+    return {
+      success: true,
+      data: branches,
+    };
+  } catch (error) {
+    return {
+      success: false,
+      error: {
+        code: "PARSE_ERROR",
+        message: `Failed to parse branch information: ${error instanceof Error ? error.message : "Unknown error"}`,
+      },
+    };
+  }
+}
+
+/**
+ * Get current branch name
+ */
+export async function getCurrentBranch(
+  cwd: string,
+): Promise<GitResult<string>> {
+  const result = await executeGitCommand(["branch", "--show-current"], cwd);
+
+  if (!result.success) {
+    return result as GitResult<string>;
+  }
+
+  const currentBranch = result.data.trim();
+
+  if (!currentBranch) {
+    return {
+      success: false,
+      error: {
+        code: "COMMAND_FAILED",
+        message: "Could not determine current branch (possibly detached HEAD)",
+      },
+    };
+  }
+
+  return {
+    success: true,
+    data: currentBranch,
+  };
+}
+
+/**
+ * Check if a branch exists
+ */
+export async function branchExists(
+  cwd: string,
+  branchName: string,
+): Promise<GitResult<boolean>> {
+  const result = await executeGitCommand(
+    ["rev-parse", "--verify", branchName],
+    cwd,
+  );
+
+  return {
+    success: true,
+    data: result.success,
+  };
+}
--- a/src/server/service/git/getCommits.ts
+++ b/src/server/service/git/getCommits.ts
@@ -0,0 +1,51 @@
+import type { GitCommit, GitResult } from "./types";
+import { executeGitCommand, parseLines } from "./utils";
+
+/**
+ * Get the last 20 commits from the current branch
+ */
+export async function getCommits(cwd: string): Promise<GitResult<GitCommit[]>> {
+  // Get commits with oneline format and limit to 20
+  const result = await executeGitCommand(
+    ["log", "--oneline", "-n", "20", "--format=%H|%s|%an|%ad", "--date=iso"],
+    cwd,
+  );
+
+  if (!result.success) {
+    return result as GitResult<GitCommit[]>;
+  }
+
+  try {
+    const lines = parseLines(result.data);
+    const commits: GitCommit[] = [];
+
+    for (const line of lines) {
+      // Parse commit line format: "sha|message|author|date"
+      const parts = line.split("|");
+      if (parts.length < 4) continue;
+
+      const [sha, message, author, date] = parts;
+      if (!sha || !message || !author || !date) continue;
+
+      commits.push({
+        sha: sha.trim(),
+        message: message.trim(),
+        author: author.trim(),
+        date: date.trim(),
+      });
+    }
+
+    return {
+      success: true,
+      data: commits,
+    };
+  } catch (error) {
+    return {
+      success: false,
+      error: {
+        code: "PARSE_ERROR",
+        message: `Failed to parse commit information: ${error instanceof Error ? error.message : "Unknown error"}`,
+      },
+    };
+  }
+}
--- a/src/server/service/git/getDiff.ts
+++ b/src/server/service/git/getDiff.ts
@@ -0,0 +1,283 @@
+import parseGitDiff, {
+  type AnyChunk,
+  type AnyFileChange,
+} from "parse-git-diff";
+import type {
+  GitComparisonResult,
+  GitDiff,
+  GitDiffFile,
+  GitDiffHunk,
+  GitDiffLine,
+  GitResult,
+} from "./types";
+import { executeGitCommand, parseLines } from "./utils";
+
+/**
+ * Convert parse-git-diff file change to GitDiffFile
+ */
+function convertToGitDiffFile(
+  fileChange: AnyFileChange,
+  fileStats: Map<string, { additions: number; deletions: number }>,
+): GitDiffFile {
+  let filePath: string;
+  let status: GitDiffFile["status"];
+  let oldPath: string | undefined;
+
+  switch (fileChange.type) {
+    case "AddedFile":
+      filePath = fileChange.path;
+      status = "added";
+      break;
+    case "DeletedFile":
+      filePath = fileChange.path;
+      status = "deleted";
+      break;
+    case "RenamedFile":
+      filePath = fileChange.pathAfter;
+      oldPath = fileChange.pathBefore;
+      status = "renamed";
+      break;
+    case "ChangedFile":
+      filePath = fileChange.path;
+      status = "modified";
+      break;
+    default:
+      // Fallback for any unknown types
+      filePath = "";
+      status = "modified";
+  }
+
+  // Get stats from numstat
+  const stats = fileStats.get(filePath) ||
+    fileStats.get(oldPath || "") || { additions: 0, deletions: 0 };
+
+  return {
+    filePath,
+    status,
+    additions: stats.additions,
+    deletions: stats.deletions,
+    oldPath,
+  };
+}
+
+/**
+ * Convert parse-git-diff chunk to GitDiffHunk
+ */
+function convertToGitDiffHunk(chunk: AnyChunk): GitDiffHunk {
+  if (chunk.type !== "Chunk") {
+    // For non-standard chunks, return empty hunk
+    return {
+      oldStart: 0,
+      oldCount: 0,
+      newStart: 0,
+      newCount: 0,
+      header: "",
+      lines: [],
+    };
+  }
+
+  const lines: GitDiffLine[] = [];
+
+  for (const change of chunk.changes) {
+    let line: GitDiffLine;
+
+    switch (change.type) {
+      case "AddedLine":
+        line = {
+          type: "added",
+          content: change.content,
+          newLineNumber: change.lineAfter,
+        };
+        break;
+      case "DeletedLine":
+        line = {
+          type: "deleted",
+          content: change.content,
+          oldLineNumber: change.lineBefore,
+        };
+        break;
+      case "UnchangedLine":
+        line = {
+          type: "context",
+          content: change.content,
+          oldLineNumber: change.lineBefore,
+          newLineNumber: change.lineAfter,
+        };
+        break;
+      case "MessageLine":
+        // This is likely a hunk header or context line
+        line = {
+          type: "context",
+          content: change.content,
+        };
+        break;
+      default:
+        // Fallback for unknown line types
+        line = {
+          type: "context",
+          content: "",
+        };
+    }
+
+    lines.push(line);
+  }
+
+  return {
+    oldStart: chunk.fromFileRange.start,
+    oldCount: chunk.fromFileRange.lines,
+    newStart: chunk.toFileRange.start,
+    newCount: chunk.toFileRange.lines,
+    header: `@@ -${chunk.fromFileRange.start},${chunk.fromFileRange.lines} +${chunk.toFileRange.start},${chunk.toFileRange.lines} @@${chunk.context ? ` ${chunk.context}` : ""}`,
+    lines,
+  };
+}
+
+const extractRef = (refText: string) => {
+  const [group, ref] = refText.split(":");
+  if (group === undefined || ref === undefined) {
+    if (refText === "HEAD") {
+      return "HEAD";
+    }
+
+    if (refText === "working") {
+      return undefined;
+    }
+
+    throw new Error(`Invalid ref text: ${refText}`);
+  }
+
+  return ref;
+};
+
+/**
+ * Get Git diff between two references (branches, commits, tags)
+ */
+export const getDiff = async (
+  cwd: string,
+  fromRefText: string,
+  toRefText: string,
+): Promise<GitResult<GitComparisonResult>> => {
+  const fromRef = extractRef(fromRefText);
+  const toRef = extractRef(toRefText);
+
+  if (fromRef === toRef) {
+    return {
+      success: true,
+      data: {
+        diffs: [],
+        files: [],
+        summary: {
+          totalFiles: 0,
+          totalAdditions: 0,
+          totalDeletions: 0,
+        },
+      },
+    };
+  }
+
+  if (fromRef === undefined) {
+    throw new Error(`Invalid fromRef: ${fromRefText}`);
+  }
+
+  const commandArgs = toRef === undefined ? [fromRef] : [fromRef, toRef];
+
+  // Get diff with numstat for file statistics
+  const numstatResult = await executeGitCommand(
+    ["diff", "--numstat", ...commandArgs],
+    cwd,
+  );
+
+  if (!numstatResult.success) {
+    return numstatResult;
+  }
+
+  // Get diff with full content
+  const diffResult = await executeGitCommand(
+    ["diff", "--unified=5", ...commandArgs],
+    cwd,
+  );
+
+  if (!diffResult.success) {
+    return diffResult;
+  }
+
+  try {
+    // Parse numstat output to get file statistics
+    const fileStats = new Map<
+      string,
+      { additions: number; deletions: number }
+    >();
+    const numstatLines = parseLines(numstatResult.data);
+
+    for (const line of numstatLines) {
+      const parts = line.split("\t");
+      if (parts.length >= 3 && parts[0] && parts[1] && parts[2]) {
+        const additions = parts[0] === "-" ? 0 : parseInt(parts[0], 10);
+        const deletions = parts[1] === "-" ? 0 : parseInt(parts[1], 10);
+        const filePath = parts[2];
+        fileStats.set(filePath, { additions, deletions });
+      }
+    }
+
+    // Parse diff output using parse-git-diff
+    const parsedDiff = parseGitDiff(diffResult.data);
+
+    const files: GitDiffFile[] = [];
+    const diffs: GitDiff[] = [];
+    let totalAdditions = 0;
+    let totalDeletions = 0;
+
+    for (const fileChange of parsedDiff.files) {
+      // Convert to GitDiffFile format
+      const file = convertToGitDiffFile(fileChange, fileStats);
+      files.push(file);
+
+      // Convert chunks to hunks
+      const hunks: GitDiffHunk[] = [];
+      for (const chunk of fileChange.chunks) {
+        const hunk = convertToGitDiffHunk(chunk);
+        hunks.push(hunk);
+      }
+
+      diffs.push({
+        file,
+        hunks,
+      });
+
+      totalAdditions += file.additions;
+      totalDeletions += file.deletions;
+    }
+
+    return {
+      success: true,
+      data: {
+        files,
+        diffs,
+        summary: {
+          totalFiles: files.length,
+          totalAdditions,
+          totalDeletions,
+        },
+      },
+    };
+  } catch (error) {
+    return {
+      success: false,
+      error: {
+        code: "PARSE_ERROR",
+        message: `Failed to parse diff: ${error instanceof Error ? error.message : "Unknown error"}`,
+      },
+    };
+  }
+};
+
+/**
+ * Compare between two branches (shorthand for getDiff)
+ */
+export async function compareBranches(
+  cwd: string,
+  baseBranch: string,
+  targetBranch: string,
+): Promise<GitResult<GitComparisonResult>> {
+  return getDiff(cwd, baseBranch, targetBranch);
+}
--- a/src/server/service/git/getStatus.ts
+++ b/src/server/service/git/getStatus.ts
@@ -0,0 +1,172 @@
+import type { GitDiffFile, GitResult, GitStatus } from "./types";
+import {
+  executeGitCommand,
+  getFileStatus,
+  parseLines,
+  parseStatusLine,
+} from "./utils";
+
+/**
+ * Get git status information including staged, unstaged, and untracked files
+ */
+export async function getStatus(cwd: string): Promise<GitResult<GitStatus>> {
+  // Get porcelain status for consistent parsing
+  const statusResult = await executeGitCommand(
+    ["status", "--porcelain=v1", "-b"],
+    cwd,
+  );
+
+  if (!statusResult.success) {
+    return statusResult as GitResult<GitStatus>;
+  }
+
+  try {
+    const lines = parseLines(statusResult.data);
+    const staged: GitDiffFile[] = [];
+    const unstaged: GitDiffFile[] = [];
+    const untracked: string[] = [];
+    const conflicted: string[] = [];
+
+    let branch = "HEAD";
+    let ahead = 0;
+    let behind = 0;
+
+    for (const line of lines) {
+      // Parse branch line
+      if (line.startsWith("##")) {
+        const branchMatch = line.match(/^##\s+(.+?)(?:\.\.\.|$)/);
+        if (branchMatch?.[1]) {
+          branch = branchMatch[1];
+        }
+
+        const aheadMatch = line.match(/ahead (\d+)/);
+        const behindMatch = line.match(/behind (\d+)/);
+        if (aheadMatch?.[1]) ahead = parseInt(aheadMatch[1], 10);
+        if (behindMatch?.[1]) behind = parseInt(behindMatch[1], 10);
+        continue;
+      }
+
+      // Parse file status lines
+      const { status, filePath, oldPath } = parseStatusLine(line);
+      const indexStatus = status[0]; // Staged changes
+      const workTreeStatus = status[1]; // Unstaged changes
+
+      // Handle conflicts (both index and work tree have changes)
+      if (
+        indexStatus === "U" ||
+        workTreeStatus === "U" ||
+        (indexStatus !== " " &&
+          indexStatus !== "?" &&
+          workTreeStatus !== " " &&
+          workTreeStatus !== "?")
+      ) {
+        conflicted.push(filePath);
+        continue;
+      }
+
+      // Handle staged changes (index status)
+      if (indexStatus !== " " && indexStatus !== "?") {
+        staged.push({
+          filePath,
+          status: getFileStatus(`${indexStatus} `),
+          additions: 0, // We don't have line counts from porcelain status
+          deletions: 0,
+          oldPath,
+        });
+      }
+
+      // Handle unstaged changes (work tree status)
+      if (workTreeStatus !== " " && workTreeStatus !== "?") {
+        if (workTreeStatus === "?") {
+          untracked.push(filePath);
+        } else {
+          unstaged.push({
+            filePath,
+            status: getFileStatus(` ${workTreeStatus}`),
+            additions: 0,
+            deletions: 0,
+            oldPath,
+          });
+        }
+      }
+
+      // Handle untracked files
+      if (status === "??") {
+        untracked.push(filePath);
+      }
+    }
+
+    return {
+      success: true,
+      data: {
+        branch,
+        ahead,
+        behind,
+        staged,
+        unstaged,
+        untracked,
+        conflicted,
+      },
+    };
+  } catch (error) {
+    return {
+      success: false,
+      error: {
+        code: "PARSE_ERROR",
+        message: `Failed to parse git status: ${error instanceof Error ? error.message : "Unknown error"}`,
+      },
+    };
+  }
+}
+
+/**
+ * Get uncommitted changes (both staged and unstaged)
+ */
+export async function getUncommittedChanges(
+  cwd: string,
+): Promise<GitResult<GitDiffFile[]>> {
+  const statusResult = await getStatus(cwd);
+
+  if (!statusResult.success) {
+    return statusResult as GitResult<GitDiffFile[]>;
+  }
+
+  const { staged, unstaged } = statusResult.data;
+  const allChanges = [...staged, ...unstaged];
+
+  // Remove duplicates (files that are both staged and unstaged)
+  const uniqueChanges = allChanges.reduce((acc: GitDiffFile[], change) => {
+    const existing = acc.find((c) => c.filePath === change.filePath);
+    if (!existing) {
+      acc.push(change);
+    }
+    return acc;
+  }, [] as GitDiffFile[]);
+
+  return {
+    success: true,
+    data: uniqueChanges,
+  };
+}
+
+/**
+ * Check if the working directory is clean (no uncommitted changes)
+ */
+export async function isWorkingDirectoryClean(
+  cwd: string,
+): Promise<GitResult<boolean>> {
+  const statusResult = await getStatus(cwd);
+
+  if (!statusResult.success) {
+    return statusResult as GitResult<boolean>;
+  }
+
+  const { staged, unstaged, untracked } = statusResult.data;
+  const isClean =
+    staged.length === 0 && unstaged.length === 0 && untracked.length === 0;
+
+  return {
+    success: true,
+    data: isClean,
+  };
+}
--- a/src/server/service/git/index.ts
+++ b/src/server/service/git/index.ts
@@ -0,0 +1,32 @@
+// Git service utilities for claude-code-viewer
+// Provides comprehensive Git operations including branch management, diff generation, and status checking
+
+export * from "./getBranches";
+// Re-export main functions for convenience
+export { branchExists, getBranches, getCurrentBranch } from "./getBranches";
+export * from "./getCommits";
+export { getCommits } from "./getCommits";
+export * from "./getDiff";
+export { compareBranches, getDiff } from "./getDiff";
+export * from "./getStatus";
+export {
+  getStatus,
+  getUncommittedChanges,
+  isWorkingDirectoryClean,
+} from "./getStatus";
+// Types re-export for convenience
+export type {
+  GitBranch,
+  GitCommit,
+  GitComparisonResult,
+  GitDiff,
+  GitDiffFile,
+  GitDiffHunk,
+  GitDiffLine,
+  GitError,
+  GitResult,
+  GitStatus,
+} from "./types";
+export * from "./types";
+export * from "./utils";
+export { executeGitCommand, isGitRepository } from "./utils";
--- a/src/server/service/git/types.ts
+++ b/src/server/service/git/types.ts
@@ -0,0 +1,85 @@
+export type GitBranch = {
+  name: string;
+  current: boolean;
+  remote?: string;
+  commit: string;
+  ahead?: number;
+  behind?: number;
+};
+
+export type GitCommit = {
+  sha: string;
+  message: string;
+  author: string;
+  date: string;
+};
+
+export type GitDiffFile = {
+  filePath: string;
+  status: "added" | "modified" | "deleted" | "renamed" | "copied";
+  additions: number;
+  deletions: number;
+  oldPath?: string; // For renamed files
+};
+
+export type GitDiffHunk = {
+  oldStart: number;
+  oldCount: number;
+  newStart: number;
+  newCount: number;
+  header: string;
+  lines: GitDiffLine[];
+};
+
+export type GitDiffLine = {
+  type: "context" | "added" | "deleted";
+  content: string;
+  oldLineNumber?: number;
+  newLineNumber?: number;
+};
+
+export type GitDiff = {
+  file: GitDiffFile;
+  hunks: GitDiffHunk[];
+};
+
+export type GitComparisonResult = {
+  files: GitDiffFile[];
+  diffs: GitDiff[];
+  summary: {
+    totalFiles: number;
+    totalAdditions: number;
+    totalDeletions: number;
+  };
+};
+
+export type GitStatus = {
+  branch: string;
+  ahead: number;
+  behind: number;
+  staged: GitDiffFile[];
+  unstaged: GitDiffFile[];
+  untracked: string[];
+  conflicted: string[];
+};
+
+export type GitError = {
+  code:
+    | "NOT_A_REPOSITORY"
+    | "BRANCH_NOT_FOUND"
+    | "COMMAND_FAILED"
+    | "PARSE_ERROR";
+  message: string;
+  command?: string;
+  stderr?: string;
+};
+
+export type GitResult<T> =
+  | {
+      success: true;
+      data: T;
+    }
+  | {
+      success: false;
+      error: GitError;
+    };
--- a/src/server/service/git/utils.ts
+++ b/src/server/service/git/utils.ts
@@ -0,0 +1,142 @@
+import { execFile } from "node:child_process";
+import { existsSync } from "node:fs";
+import { resolve } from "node:path";
+import { promisify } from "node:util";
+
+import type { GitError, GitResult } from "./types";
+
+const execFileAsync = promisify(execFile);
+
+/**
+ * Execute a git command in the specified directory
+ */
+export async function executeGitCommand(
+  args: string[],
+  cwd: string,
+): Promise<GitResult<string>> {
+  try {
+    // Check if the directory exists and contains a git repository
+    if (!existsSync(cwd)) {
+      return {
+        success: false,
+        error: {
+          code: "NOT_A_REPOSITORY",
+          message: `Directory does not exist: ${cwd}`,
+          command: `git ${args.join(" ")}`,
+        },
+      };
+    }
+
+    if (!existsSync(resolve(cwd, ".git"))) {
+      return {
+        success: false,
+        error: {
+          code: "NOT_A_REPOSITORY",
+          message: `Not a git repository: ${cwd}`,
+          command: `git ${args.join(" ")}`,
+        },
+      };
+    }
+
+    const { stdout } = await execFileAsync("git", args, {
+      cwd,
+      maxBuffer: 10 * 1024 * 1024, // 10MB buffer for large diffs
+      timeout: 30000, // 30 second timeout
+    });
+
+    return {
+      success: true,
+      data: stdout,
+    };
+  } catch (error: unknown) {
+    const err = error as { code?: string; stderr?: string; message?: string };
+
+    let errorCode: GitError["code"] = "COMMAND_FAILED";
+    let errorMessage = err.message || "Unknown git command error";
+
+    if (err.stderr) {
+      if (err.stderr.includes("not a git repository")) {
+        errorCode = "NOT_A_REPOSITORY";
+        errorMessage = "Not a git repository";
+      } else if (err.stderr.includes("unknown revision")) {
+        errorCode = "BRANCH_NOT_FOUND";
+        errorMessage = "Branch or commit not found";
+      }
+    }
+
+    return {
+      success: false,
+      error: {
+        code: errorCode,
+        message: errorMessage,
+        command: `git ${args.join(" ")}`,
+        stderr: err.stderr,
+      },
+    };
+  }
+}
+
+/**
+ * Check if a directory is a git repository
+ */
+export function isGitRepository(cwd: string): boolean {
+  return existsSync(cwd) && existsSync(resolve(cwd, ".git"));
+}
+
+/**
+ * Safely parse git command output that might be empty
+ */
+export function parseLines(output: string): string[] {
+  return output
+    .trim()
+    .split("\n")
+    .filter((line) => line.trim() !== "");
+}
+
+/**
+ * Parse git status porcelain output
+ */
+export function parseStatusLine(line: string): {
+  status: string;
+  filePath: string;
+  oldPath?: string;
+} {
+  const status = line.slice(0, 2);
+  const filePath = line.slice(3);
+
+  // Handle renamed files (R  old -> new)
+  if (status.startsWith("R")) {
+    const parts = filePath.split(" -> ");
+    return {
+      status,
+      filePath: parts[1] || filePath,
+      oldPath: parts[0],
+    };
+  }
+
+  return { status, filePath };
+}
+
+/**
+ * Convert git status code to readable status
+ */
+export function getFileStatus(
+  statusCode: string,
+): "added" | "modified" | "deleted" | "renamed" | "copied" {
+  const firstChar = statusCode[0];
+
+  switch (firstChar) {
+    case "A":
+      return "added";
+    case "M":
+      return "modified";
+    case "D":
+      return "deleted";
+    case "R":
+      return "renamed";
+    case "C":
+      return "copied";
+    default:
+      return "modified";
+  }
+}