fix: keep Activity commit details after browser Back

frontend/src/App.activity-back-navigation.browser.svelte.ts

@@ -0,0 +1,183 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vite-plus/test";
+import { page } from "vite-plus/test/browser";
+
+import { mountBrowserApp, pressKey, resetKeyboardModuleState, type MountedBrowserApp } from "./test/browserAppHarness.js";
+import { jsonResponse, mockSettings, type MockRouteOverride } from "./test/mockApiFetch.js";
+
+const WAIT = 10_000;
+
+const repo = {
+  provider: "github",
+  platform_host: "github.com",
+  owner: "acme",
+  name: "widgets",
+  repo_path: "acme/widgets",
+  capabilities: {},
+};
+
+const activityItems = [
+  {
+    id: "a1",
+    cursor: "a1",
+    activity_type: "comment",
+    author: "marius",
+    body_preview: "",
+    created_at: "2026-03-30T14:00:00Z",
+    item_number: 42,
+    item_state: "open",
+    item_title: "PR 42 title",
+    item_type: "pr",
+    item_url: "https://github.com/acme/widgets/pull/42",
+    repo,
+  },
+  {
+    id: "b1",
+    cursor: "b1",
+    activity_type: "comment",
+    author: "marius",
+    body_preview: "",
+    created_at: "2026-03-30T13:00:00Z",
+    item_number: 55,
+    item_state: "open",
+    item_title: "Issue 55 title",
+    item_type: "issue",
+    item_url: "https://github.com/acme/widgets/issues/55",
+    repo,
+  },
+  {
+    id: "c1",
+    cursor: "c1",
+    activity_type: "default_branch_commit",
+    author: "marius",
+    body_preview: "Bump dependency",
+    created_at: "2026-03-30T12:00:00Z",
+    item_number: 0,
+    item_state: "",
+    item_title: "",
+    item_type: "pr",
+    item_url: "https://github.com/acme/widgets/commit/abcdef1234567890",
+    branch_name: "main",
+    commit_sha: "abcdef1234567890",
+    repo,
+  },
+];
+
+function activityOverrides(): MockRouteOverride[] {
+  return [
+    (req) => {
+      if (req.method !== "GET" || req.url.pathname !== "/api/v1/settings") return null;
+      return jsonResponse({
+        ...mockSettings,
+        activity: {
+          ...mockSettings.activity,
+          view_mode: "flat",
+          collapse_threads: false,
+        },
+      });
+    },
+    (req) => {
+      if (req.method !== "GET" || req.url.pathname !== "/api/v1/activity") return null;
+      return jsonResponse({ capped: false, items: activityItems });
+    },
+  ];
+}
+
+function activityRow(text: string): Element {
+  return Array.from(document.querySelectorAll(".activity-row")).find((row) =>
+    (row.textContent ?? "").includes(text),
+  )!;
+}
+
+async function openSelection(text: string): Promise<string> {
+  await vi.waitFor(() => expect(document.querySelector(".activity-row")).not.toBeNull(), WAIT);
+  const row = activityRow(text);
+  expect(row).not.toBeUndefined();
+  await page.elementLocator(row).click();
+  await vi.waitFor(() => expect(document.querySelector(".activity-detail")).not.toBeNull(), WAIT);
+  return window.location.pathname + window.location.search;
+}
+
+async function leaveAndRestore(destination: "/pulls" | "/issues"): Promise<void> {
+  const { navigate } = await import("./lib/stores/router.svelte.js");
+  navigate(destination);
+  await vi.waitFor(() => expect(document.querySelector(".activity-detail")).toBeNull(), WAIT);
+  window.history.back();
+  await vi.waitFor(() => expect(document.querySelector(".activity-detail")).not.toBeNull(), WAIT);
+}
+
+describe("Activity detail restoration after browser Back", () => {
+  vi.setConfig({ testTimeout: 30_000 });
+
+  let mounted: MountedBrowserApp | null = null;
+
+  beforeEach(async () => {
+    await page.viewport(1280, 900);
+  });
+
+  afterEach(async () => {
+    mounted?.unmount();
+    mounted = null;
+    vi.restoreAllMocks();
+    localStorage.clear();
+    sessionStorage.clear();
+    await resetKeyboardModuleState();
+  });
+
+  it("restores the commit detail pane after leaving Activity and pressing Back", async () => {
+    mounted = await mountBrowserApp("/", { overrides: activityOverrides() });
+    const activityUrl = await openSelection("Bump dependency");
+
+    await leaveAndRestore("/pulls");
+
+    expect(document.querySelector(".commit-diff-panel")).not.toBeNull();
+    expect(document.querySelector(".activity-detail-header")?.textContent).toContain("acme/widgets");
+    expect(document.querySelector(".activity-detail-header")?.textContent).toContain("main");
+    expect(document.querySelector(".activity-detail-header")?.textContent).toContain("abcdef123456");
+    const selected = new URL(activityUrl, window.location.origin).searchParams;
+    expect(selected.get("selected")).toBe("commit:abcdef1234567890");
+    expect(selected.get("provider")).toBe("github");
+    expect(selected.get("platform_host")).toBe("github.com");
+    expect(selected.get("repo_path")).toBe("acme/widgets");
+    expect(selected.get("branch")).toBe("main");
+  });
+
+  it("restores a PR selection after leaving Activity and pressing Back", async () => {
+    mounted = await mountBrowserApp("/", { overrides: activityOverrides() });
+    await openSelection("PR 42 title");
+
+    await leaveAndRestore("/pulls");
+
+    expect(document.querySelector(".activity-detail")).not.toBeNull();
+    expect(document.querySelector(".activity-detail-header")?.textContent).toContain("acme/widgets#42");
+  });
+
+  it("restores an issue selection after leaving Activity and pressing Back", async () => {
+    mounted = await mountBrowserApp("/", { overrides: activityOverrides() });
+    await openSelection("Issue 55 title");
+
+    await leaveAndRestore("/issues");
+
+    expect(document.querySelector(".activity-detail")).not.toBeNull();
+    expect(document.querySelector(".activity-detail-header")?.textContent).toContain("acme/widgets#55");
+  });
+
+  it("Escape closes a restored commit pane", async () => {
+    mounted = await mountBrowserApp("/", { overrides: activityOverrides() });
+    await openSelection("Bump dependency");
+    await leaveAndRestore("/pulls");
+
+    pressKey("Escape");
+    await vi.waitFor(() => expect(document.querySelector(".activity-detail")).toBeNull(), WAIT);
+    expect(new URL(window.location.href).searchParams.has("selected")).toBe(false);
+  });
+
+  it("replaces a commit selection when an item row is selected", async () => {
+    mounted = await mountBrowserApp("/", { overrides: activityOverrides() });
+    await openSelection("Bump dependency");
+
+    await page.getByText("PR 42 title").click();
+    await vi.waitFor(() => expect(document.querySelector(".activity-detail-header")?.textContent).toContain("acme/widgets#42"), WAIT);
+    expect(new URL(window.location.href).searchParams.get("selected")).toBe("pr:42");
+    expect(document.querySelector(".commit-diff-panel")).toBeNull();
+  });
+});

frontend/src/App.svelte

@@ -127,7 +127,9 @@
   import {
     buildActivitySelectionSearch,
     parseActivitySelection,
+    type ActivityCommitSelection,
     type ActivityDetailTab,
+    type ActivitySelection,
   } from "./lib/utils/activitySelection.js";
   import { docsHref } from "./lib/api/docs/route.js";
   import {
@@ -899,17 +901,23 @@
     const route = getRoute();
     const page = route.page;
 
-    if (page !== "activity") {
-      drawerItem = null;
-    } else if (!stores.settings.hasConfiguredRepos()) {
+    if (page !== "activity" || !stores.settings.hasConfiguredRepos()) {
       drawerItem = null;
+      commitItem = null;
     } else {
-      const nextDrawer = parseActivitySelection(
+      const nextSelection = parseActivitySelection(
         window.location.search,
       );
+      const nextDrawer =
+        nextSelection && nextSelection.itemType !== "commit" ? nextSelection : null;
+      const nextCommit =
+        nextSelection && nextSelection.itemType === "commit" ? nextSelection : null;
       if (!sameActivitySelection(drawerItem, nextDrawer)) {
         drawerItem = nextDrawer;
       }
+      if (!sameActivityCommitSelection(commitItem, nextCommit)) {
+        commitItem = nextCommit;
+      }
     }
 
     if (route.page === "pulls") {
@@ -961,6 +969,9 @@
   };
 
   let drawerItem = $state<DrawerItem | null>(null);
+  // Owned here for the same reason drawerItem is: the Activity selection lives
+  // in the page's query string, and only this component writes it.
+  let commitItem = $state<ActivityCommitSelection | null>(null);
 
   function sameActivitySelection(
     left: DrawerItem | null,
@@ -978,8 +989,26 @@
       && left.detailTab === right.detailTab;
   }
 
+  function sameActivityCommitSelection(
+    left: ActivityCommitSelection | null,
+    right: ActivityCommitSelection | null,
+  ): boolean {
+    if (left === right) return true;
+    if (left === null || right === null) return false;
+    // `title` is display text the feed supplies and the URL does not carry, so
+    // it is deliberately not part of identity: comparing it would let a
+    // reparse downgrade a live commit subject to the short SHA.
+    return left.provider === right.provider
+      && left.platformHost === right.platformHost
+      && left.repoPath === right.repoPath
+      && left.owner === right.owner
+      && left.name === right.name
+      && left.branchName === right.branchName
+      && left.commitSha === right.commitSha;
+  }
+
   function updateDrawerURL(
-    item: DrawerItem | null,
+    item: ActivitySelection | null,
   ): void {
     if (getPage() !== "activity") return;
     const sp = buildActivitySelectionSearch(
@@ -1017,6 +1046,7 @@
       ...selectedItem,
       detailTab: "conversation",
     };
+    commitItem = null;
     updateDrawerURL(drawerItem);
   }
 
@@ -1035,6 +1065,14 @@
     updateDrawerURL(drawerItem);
   }
 
+  function handleActivityCommitSelect(
+    item: ActivityCommitSelection,
+  ): void {
+    drawerItem = null;
+    commitItem = item;
+    updateDrawerURL(commitItem);
+  }
+
   function handleResponsiveStackMemberNavigate(
     ref: PullRequestRouteRef,
   ): boolean | void {
@@ -1049,6 +1087,7 @@
 
   function closeDrawer(): void {
     drawerItem = null;
+    commitItem = null;
     updateDrawerURL(null);
   }
 
@@ -1076,7 +1115,7 @@
         scope: "global",
         binding: { key: "Escape" },
         priority: 50,
-        when: (ctx) => ctx.page === "activity" && drawerItem !== null,
+        when: (ctx) => ctx.page === "activity" && (drawerItem !== null || commitItem !== null),
         handler: () => closeDrawer(),
       },
     ]);
@@ -1452,6 +1491,8 @@
           detailTab={drawerItem?.detailTab ?? "conversation"}
           onDetailTabChange={handleActivityDetailTabChange}
           onDrawerItemChange={handleActivityDrawerItemChange}
+          {commitItem}
+          onSelectCommit={handleActivityCommitSelect}
           inlineWorkspace={getInlineWorkspaceController("activity")}
           {workspacePaneControls}
         />

frontend/src/lib/stores/keyboard/actions.test.ts

@@ -335,6 +335,18 @@ describe("defaultActions", () => {
     expect(locationPath()).toBe(
       "/repo/browser?provider=gitlab&platform_host=gitlab.example.com&repo_path=group%2Fproject",
     );
+
+    window.history.replaceState(
+      null,
+      "",
+      "/?selected=commit:abcdef1234567890&provider=github&platform_host=github.com&repo_path=acme%2Fwidgets&branch=main",
+    );
+    const commitContext = ctx("activity", { selectedPR: staleSelected });
+    expect(action.when(commitContext)).toBe(true);
+    action.handler(commitContext);
+    expect(locationPath()).toBe(
+      "/repo/browser?provider=github&platform_host=github.com&repo_path=acme%2Fwidgets",
+    );
   });
 
   it("opens the repo browser from the route-selected issue before stale issue store state", () => {