feat: Add PR summary header to diff viewer

src-tauri/src/git.rs

@@ -679,7 +679,7 @@ pub(crate) async fn get_github_pull_requests(
             "--limit",
             "50",
             "--json",
-            "number,title,url,updatedAt,headRefName,baseRefName,isDraft,author",
+            "number,title,url,updatedAt,body,headRefName,baseRefName,isDraft,author",
         ])
         .current_dir(&repo_root)
         .output()

src-tauri/src/types.rs

@@ -65,6 +65,7 @@ pub(crate) struct GitHubPullRequest {
     pub(crate) url: String,
     #[serde(rename = "updatedAt")]
     pub(crate) updated_at: String,
+    pub(crate) body: String,
     #[serde(rename = "headRefName")]
     pub(crate) head_ref_name: String,
     #[serde(rename = "baseRefName")]

src/App.tsx

@@ -1060,6 +1060,7 @@ function MainApp() {
     gitPullRequestsLoading,
     gitPullRequestsError,
     selectedPullRequestNumber: selectedPullRequest?.number ?? null,
+    selectedPullRequest: diffSource === "pr" ? selectedPullRequest : null,
     onSelectPullRequest: handleSelectPullRequest,
     gitRemoteUrl,
     gitRoot: activeGitRoot,

src/features/git/components/GitDiffViewer.tsx

@@ -4,6 +4,9 @@ import { FileDiff, WorkerPoolContextProvider } from "@pierre/diffs/react";
 import type { FileDiffMetadata } from "@pierre/diffs";
 import { parsePatchFiles } from "@pierre/diffs";
 import { workerFactory } from "../../../utils/diffsWorker";
+import type { GitHubPullRequest } from "../../../types";
+import { formatRelativeTime } from "../../../utils/time";
+import { Markdown } from "../../messages/components/Markdown";
 
 type GitDiffViewerItem = {
   path: string;
@@ -16,6 +19,7 @@ type GitDiffViewerProps = {
   selectedPath: string | null;
   isLoading: boolean;
   error: string | null;
+  pullRequest?: GitHubPullRequest | null;
   onActivePathChange?: (path: string) => void;
 };
 
@@ -110,6 +114,7 @@ export function GitDiffViewer({
   selectedPath,
   isLoading,
   error,
+  pullRequest,
   onActivePathChange,
 }: GitDiffViewerProps) {
   const containerRef = useRef<HTMLDivElement>(null);
@@ -215,12 +220,60 @@ export function GitDiffViewer({
     };
   }, [diffs, onActivePathChange, rowVirtualizer]);
 
+  const prUpdatedLabel = pullRequest?.updatedAt
+    ? formatRelativeTime(new Date(pullRequest.updatedAt).getTime())
+    : null;
+  const prAuthor = pullRequest?.author?.login ?? "unknown";
+  const prBody = pullRequest?.body?.trim() ?? "";
+
   return (
     <WorkerPoolContextProvider
       poolOptions={poolOptions}
       highlighterOptions={highlighterOptions}
     >
       <div className="diff-viewer" ref={containerRef}>
+        {pullRequest && (
+          <section className="diff-viewer-pr" aria-label="Pull request summary">
+            <div className="diff-viewer-pr-header">
+              <div className="diff-viewer-pr-title">
+                <span className="diff-viewer-pr-number">
+                  #{pullRequest.number}
+                </span>
+                <span className="diff-viewer-pr-title-text">
+                  {pullRequest.title}
+                </span>
+              </div>
+              <div className="diff-viewer-pr-meta">
+                <span className="diff-viewer-pr-author">@{prAuthor}</span>
+                {prUpdatedLabel && (
+                  <>
+                    <span className="diff-viewer-pr-sep">·</span>
+                    <span>{prUpdatedLabel}</span>
+                  </>
+                )}
+                <span className="diff-viewer-pr-sep">·</span>
+                <span className="diff-viewer-pr-branch">
+                  {pullRequest.baseRefName} ← {pullRequest.headRefName}
+                </span>
+                {pullRequest.isDraft && (
+                  <span className="diff-viewer-pr-pill">Draft</span>
+                )}
+              </div>
+            </div>
+            <div className="diff-viewer-pr-body">
+              {prBody ? (
+                <Markdown
+                  value={prBody}
+                  className="diff-viewer-pr-markdown markdown"
+                />
+              ) : (
+                <div className="diff-viewer-pr-empty">
+                  No description provided.
+                </div>
+              )}
+            </div>
+          </section>
+        )}
         {!error && stickyEntry && (
           <div className="diff-viewer-sticky">
             <div className="diff-viewer-header diff-viewer-header-sticky">

src/features/layout/hooks/useLayoutNodes.tsx

@@ -164,6 +164,7 @@ type LayoutNodesOptions = {
   gitPullRequestsLoading: boolean;
   gitPullRequestsError: string | null;
   selectedPullRequestNumber: number | null;
+  selectedPullRequest: GitHubPullRequest | null;
   onSelectPullRequest: (pullRequest: GitHubPullRequest) => void;
   gitRemoteUrl: string | null;
   gitRoot: string | null;
@@ -513,6 +514,7 @@ export function useLayoutNodes(options: LayoutNodesOptions): LayoutNodesResult {
       selectedPath={options.selectedDiffPath}
       isLoading={options.gitDiffLoading}
       error={options.gitDiffError}
+      pullRequest={options.selectedPullRequest}
       onActivePathChange={options.onDiffActivePathChange}
     />
   );

src/styles/diff-viewer.css

@@ -16,6 +16,102 @@
   padding-top: 0;
 }
 
+.diff-viewer-pr {
+  margin: 12px 16px 16px;
+  padding: 16px;
+  border-radius: 14px;
+  border: 1px solid var(--border-subtle);
+  background: color-mix(in srgb, var(--surface-strong) 84%, transparent);
+  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.22);
+}
+
+.diff-viewer-pr-header {
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+
+.diff-viewer-pr-title {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  font-size: 18px;
+  font-weight: 600;
+  color: var(--text-strong);
+}
+
+.diff-viewer-pr-number {
+  color: var(--text-faint);
+  font-variant-numeric: tabular-nums;
+}
+
+.diff-viewer-pr-title-text {
+  color: var(--text-stronger);
+}
+
+.diff-viewer-pr-meta {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  align-items: center;
+  font-size: 12px;
+  color: var(--text-muted);
+}
+
+.diff-viewer-pr-author {
+  color: var(--text-strong);
+  font-weight: 600;
+}
+
+.diff-viewer-pr-sep {
+  color: var(--text-faint);
+}
+
+.diff-viewer-pr-branch {
+  font-family: "SFMono-Regular", "Menlo", "Monaco", monospace;
+  font-size: 11px;
+  padding: 2px 6px;
+  border-radius: 999px;
+  border: 1px solid var(--border-subtle);
+  background: var(--surface-control);
+  color: var(--text-quiet);
+}
+
+.diff-viewer-pr-pill {
+  font-size: 11px;
+  font-weight: 600;
+  text-transform: uppercase;
+  padding: 2px 6px;
+  border-radius: 999px;
+  background: rgba(242, 153, 74, 0.16);
+  color: #f2994a;
+  border: 1px solid rgba(242, 153, 74, 0.4);
+}
+
+.diff-viewer-pr-body {
+  margin-top: 12px;
+  padding-top: 12px;
+  border-top: 1px solid var(--border-subtle);
+}
+
+.diff-viewer-pr-markdown {
+  font-size: 13px;
+  color: var(--text-stronger);
+}
+
+.diff-viewer-pr-markdown :where(h1, h2, h3, h4, h5, h6) {
+  margin-top: 16px;
+}
+
+.diff-viewer-pr-markdown :where(p, ul, ol, pre) {
+  margin-top: 10px;
+}
+
+.diff-viewer-pr-empty {
+  font-size: 13px;
+  color: var(--text-muted);
+}
+
 .diff-viewer-list {
   position: relative;
   width: 100%;

src/types.ts

@@ -158,6 +158,7 @@ export type GitHubPullRequest = {
   title: string;
   url: string;
   updatedAt: string;
+  body: string;
   headRefName: string;
   baseRefName: string;
   isDraft: boolean;