diff --git a/apps/web/src/components/pullRequest/PullRequestSummaryTab.test.tsx b/apps/web/src/components/pullRequest/PullRequestSummaryTab.test.tsx
new file mode 100644
index 0000000000000000000000000000000000000000..6bf532e5aefdc069b5eca64e26d8b6d1cd4c3be8
--- /dev/null
+++ b/apps/web/src/components/pullRequest/PullRequestSummaryTab.test.tsx
@@ -0,0 +1,141 @@
+import { EnvironmentId, ProjectId, type PullRequestDetailView } from "@t3tools/contracts";
+import { act } from "react";
+import { create, type ReactTestRenderer } from "react-test-renderer";
+import { afterEach, beforeEach, expect, it, vi } from "vite-plus/test";
+
+vi.mock("~/state/use-atom-command", () => ({ useAtomCommand: () => vi.fn() }));
+vi.mock("~/state/pullRequests", () => ({ pullRequestEnvironment: {} }));
+vi.mock("~/browser/useOpenLink", () => ({ useOpenLink: () => vi.fn() }));
+vi.mock("./PullRequestMarkdown", () => ({
+  PullRequestMarkdown: ({ text }: { text: string }) => <p>{text}</p>,
+}));
+
+import { PullRequestSummaryTab } from "./PullRequestSummaryTab";
+
+const detail: PullRequestDetailView = {
+  provider: "github",
+  projectId: ProjectId.make("project"),
+  projectTitle: "Project",
+  workspaceRoot: "/workspace",
+  repository: "owner/repo",
+  number: 1,
+  title: "Test pull request",
+  body: "Original description",
+  url: "https://github.com/owner/repo/pull/1",
+  author: { login: "author", name: null, avatarUrl: null },
+  viewer: "author",
+  state: "open",
+  isDraft: false,
+  mergeability: "mergeable",
+  additions: 1,
+  deletions: 0,
+  changedFiles: 1,
+  headBranch: "feature",
+  baseBranch: "main",
+  createdAt: "2026-09-01T00:00:00Z",
+  updatedAt: "2026-09-01T00:00:00Z",
+  mergedAt: null,
+  closedAt: null,
+  reviewers: [],
+  labels: [],
+  checks: [{ name: "Unit tests", status: "success", description: null, url: null }],
+  comments: [],
+  commentCount: 0,
+  commentsTruncated: false,
+  reviewThreads: [],
+  commits: [],
+  mergeCapabilities: { merge: false, squash: false, rebase: false },
+  capabilities: {
+    diff: true,
+    comment: true,
+    search: true,
+    actions: [],
+    mergeMethods: [],
+    review: { inlineComment: false, reply: false, resolve: false, verdicts: [] },
+    reviewers: { request: false, listCandidates: false },
+    edit: { changeRequest: true, comment: true },
+  },
+  viewerPermissions: {
+    actions: [],
+    comment: true,
+    resolve: false,
+    verdicts: [],
+    requestReviewers: false,
+  },
+};
+
+let renderer: ReactTestRenderer;
+beforeEach(() => vi.stubGlobal("IS_REACT_ACT_ENVIRONMENT", true));
+afterEach(() => {
+  act(() => renderer?.unmount());
+  vi.unstubAllGlobals();
+});
+
+function render(value = detail) {
+  return (
+    <PullRequestSummaryTab
+      environmentId={EnvironmentId.make("environment")}
+      threadRef={null}
+      reference={value}
+      detail={value}
+      activityPending={false}
+      activityError={null}
+      onRefresh={() => {}}
+    />
+  );
+}
+
+function heading(title: string) {
+  const section = renderer.root
+    .findAllByType("section")
+    .find((section) => section.props["aria-label"] === title)!;
+  return section
+    .findAllByType("button")
+    .find((button) => button.findAllByType("span").some((span) => span.children.includes(title)))!;
+}
+
+function click(title: string) {
+  act(() =>
+    heading(title).props.onClick({ nativeEvent: {}, preventDefault() {}, stopPropagation() {} }),
+  );
+}
+
+it("toggles checks from their heading and resets sections for another pull request", () => {
+  act(() => {
+    renderer = create(render());
+  });
+  expect(
+    renderer.root.findAllByType("span").some((span) => span.children.includes("Unit tests")),
+  ).toBe(false);
+  click("Checks");
+  expect(
+    renderer.root.findAllByType("span").some((span) => span.children.includes("Unit tests")),
+  ).toBe(true);
+  click("Checks");
+  expect(heading("Checks").props["aria-expanded"]).toBe(false);
+  click("Checks");
+  click("Description");
+  act(() =>
+    renderer.update(render({ ...detail, url: "https://github.com/owner/repo/pull/2", number: 2 })),
+  );
+  expect(heading("Checks").props["aria-expanded"]).toBe(false);
+  expect(heading("Description").props["aria-expanded"]).toBe(true);
+});
+
+it("keeps an unsaved description when collapsed and reopened", () => {
+  act(() => {
+    renderer = create(render());
+  });
+  act(() => renderer.root.findByProps({ "aria-label": "Edit description" }).props.onClick());
+  act(() =>
+    renderer.root.findByType("textarea").props.onChange({
+      target: { value: "Unsaved description" },
+      currentTarget: { value: "Unsaved description" },
+      nativeEvent: {},
+    }),
+  );
+  click("Description");
+  expect(heading("Description").props["aria-expanded"]).toBe(false);
+  click("Description");
+  expect(renderer.root.findByType("textarea").props.value).toBe("Unsaved description");
+});
diff --git a/apps/web/src/components/pullRequest/PullRequestSummaryTab.tsx b/apps/web/src/components/pullRequest/PullRequestSummaryTab.tsx
index 26aa05bd8b48973a2501d835456728a37fab3e08..7c7c72d8d163e9346a6b249189a9b8e4e912b56a 100644
--- a/apps/web/src/components/pullRequest/PullRequestSummaryTab.tsx
+++ b/apps/web/src/components/pullRequest/PullRequestSummaryTab.tsx
@@ -15,7 +15,7 @@ import {
   TagIcon,
   UsersIcon,
 } from "lucide-react";
-import { useId, useRef, useState, type ReactNode } from "react";
+import { useRef, useState, type ReactNode } from "react";
 
 import { useAtomCommand } from "~/state/use-atom-command";
 import { pullRequestEnvironment } from "~/state/pullRequests";
@@ -237,11 +237,13 @@ function MetaRow({
 function Section({
   title,
   defaultOpen = true,
+  keepMounted = false,
   actions,
   children,
 }: {
   title: string;
   defaultOpen?: boolean;
+  keepMounted?: boolean;
   /** Heading controls stay separate from the collapse trigger so they remain independently usable. */
   actions?: ReactNode;
   children: ReactNode;
@@ -271,6 +273,7 @@ function Section({
     <Collapsible
       open={open}
       onOpenChange={setOpenWithScrollAnchor}
+      render={<section aria-label={title} />}
       data-pull-request-summary-section
     >
       {/* The heading rides the top of the scroll box the way a diff's file header does, so a
@@ -292,7 +295,7 @@ function Section({
         </CollapsibleTrigger>
         {actions}
       </div>
-      <CollapsiblePanel>
+      <CollapsiblePanel keepMounted={keepMounted}>
         <div className="px-4 pb-4">{children}</div>
       </CollapsiblePanel>
     </Collapsible>
@@ -334,9 +337,6 @@ export function PullRequestSummaryTab({
   // Keyed by the pull request, so opening another one starts at the end of its conversation
   // rather than wherever the last one had been read back to.
   const [shown, setShown] = useState({ url: detail.url, count: COMMENT_PAGE });
-  const checksId = useId();
-  const [expandedChecksUrl, setExpandedChecksUrl] = useState<string | null>(null);
-  const showChecks = expandedChecksUrl === detail.url;
   const shownComments = shown.url === detail.url ? shown.count : COMMENT_PAGE;
   // Windowed by recency regardless of display order: expanding always reaches further back in
   // time, whether the newest comment currently reads first or last.
@@ -472,7 +472,7 @@ export function PullRequestSummaryTab({
 
   return (
     <div className="h-full overflow-y-auto" data-pull-request-summary-scroll>
-      <section className="px-4 py-2.5">
+      <section className="px-4 pt-2.5 pb-1">
         <div className="space-y-2">
           <MetaRow icon={<UsersIcon className="size-3.5" />} label="Reviewers">
             <span className="flex min-w-0 flex-wrap items-center gap-1.5">
@@ -601,7 +601,7 @@ export function PullRequestSummaryTab({
         </div>
       </section>
 
-      <section aria-label="Description" className="px-4 pt-2 pb-1">
+      <Section key={`description:${detail.url}`} title="Description" keepMounted>
         <div className="group">
           {bodyScope === detail.url ? (
             <PullRequestMarkdownEditor
@@ -640,78 +640,58 @@ export function PullRequestSummaryTab({
             </div>
           )}
         </div>
-      </section>
+      </Section>
 
-      <section aria-label="Checks" className="px-4 py-3">
+      <Section key={`checks:${detail.url}`} title="Checks" defaultOpen={false}>
         {detail.checks.length === 0 ? (
           <p className="text-xs text-muted-foreground">No checks reported.</p>
         ) : (
-          <div>
-            <div className="flex items-center gap-1 text-xs">
-              <span className="font-medium text-muted-foreground">Checks</span>
-              <Button
-                size="icon-xs"
-                variant="ghost-muted"
-                aria-label={showChecks ? "Hide checks" : "Show checks"}
-                aria-expanded={showChecks}
-                aria-controls={checksId}
-                onClick={() => setExpandedChecksUrl(showChecks ? null : detail.url)}
+          detail.checks.map((check, index) => {
+            const finding = { kind: "check", check } as const;
+            const failing = check.status === "failure" || check.status === "cancelled";
+            return (
+              <div
+                // Position too: the host decides how many runs share a name, and a repeated
+                // key would be a rendering fault on top of whatever the list already says.
+                key={`${index}:${check.name}:${check.url ?? ""}`}
+                className="group flex items-center gap-2 rounded-md pr-1 hover:bg-accent/60"
               >
-                <ChevronRightIcon
-                  aria-hidden
-                  className={cn("size-3.5 text-muted-foreground/60", showChecks && "rotate-90")}
-                />
-              </Button>
-            </div>
-            <div id={checksId} className={showChecks ? "mt-2" : "hidden"}>
-              {(showChecks ? detail.checks : []).map((check, index) => {
-                const finding = { kind: "check", check } as const;
-                const failing = check.status === "failure" || check.status === "cancelled";
-                return (
-                  <div
-                    // Position too: the host decides how many runs share a name, and a repeated
-                    // key would be a rendering fault on top of whatever the list already says.
-                    key={`${index}:${check.name}:${check.url ?? ""}`}
-                    className="group flex items-center gap-2 rounded-md pr-1 hover:bg-accent/60"
-                  >
-                    <button
-                      type="button"
-                      disabled={!check.url}
-                      onClick={() => check.url && openCheck(check.url)}
-                      className={cn(
-                        "flex min-w-0 flex-1 items-start gap-2 rounded-md px-2 py-2 text-left text-xs leading-5 [&>svg]:mt-0.5",
-                        check.url ? "cursor-pointer" : "cursor-default",
-                      )}
-                    >
-                      <PullRequestCheckStatusIcon status={check.status} />
-                      <span className="min-w-0 flex-1 wrap-anywhere">{check.name}</span>
-                      <span className="shrink-0 text-muted-foreground">
-                        {pullRequestCheckStatusLabel(check)}
-                      </span>
-                    </button>
-                    {/* Only where there is something to fix. A passing check has no failure to
+                <button
+                  type="button"
+                  disabled={!check.url}
+                  onClick={() => check.url && openCheck(check.url)}
+                  className={cn(
+                    "flex min-w-0 flex-1 items-start gap-2 rounded-md px-2 py-2 text-left text-xs leading-5 [&>svg]:mt-0.5",
+                    check.url ? "cursor-pointer" : "cursor-default",
+                  )}
+                >
+                  <PullRequestCheckStatusIcon status={check.status} />
+                  <span className="min-w-0 flex-1 wrap-anywhere">{check.name}</span>
+                  <span className="shrink-0 text-muted-foreground">
+                    {pullRequestCheckStatusLabel(check)}
+                  </span>
+                </button>
+                {/* Only where there is something to fix. A passing check has no failure to
                       reproduce, and the button would be an invitation to waste a thread. */}
-                    {onFixFinding && failing ? (
-                      <Button
-                        size="xs"
-                        variant="ghost"
-                        className="shrink-0"
-                        disabled={pendingFinding !== null && pendingFinding !== undefined}
-                        onClick={() => onFixFinding(finding)}
-                      >
-                        <HammerIcon className="size-3" />
-                        {pendingFinding === pullRequestFindingKey(finding)
-                          ? "Preparing..."
-                          : fixCheckLabel}
-                      </Button>
-                    ) : null}
-                  </div>
-                );
-              })}
-            </div>
-          </div>
+                {onFixFinding && failing ? (
+                  <Button
+                    size="xs"
+                    variant="ghost"
+                    className="shrink-0"
+                    disabled={pendingFinding !== null && pendingFinding !== undefined}
+                    onClick={() => onFixFinding(finding)}
+                  >
+                    <HammerIcon className="size-3" />
+                    {pendingFinding === pullRequestFindingKey(finding)
+                      ? "Preparing..."
+                      : fixCheckLabel}
+                  </Button>
+                ) : null}
+              </div>
+            );
+          })
         )}
-      </section>
+      </Section>
 
       <Section
         title="Comments"