fix(webapp): show changes works in every history feed, not just per-file (BEA-58) (#116)

The unified diff already shipped, but HistoryView passed the `diff` prop only
when the route targeted a single file. A reviewer who opened the project-wide
feed first — the natural entry point for "what did this agent run change?" —
found only Open this version / Download and concluded the product had no diff
at all.

Pass it unconditionally. `prevBlob` was already a per-path lookup over the
whole loaded window, so a mixed-path feed diffs each row against its own
predecessor with no new lookup; `run.idx[k]` does the same for rows inside a
run card. The existing gates are untouched: deletes never diff, a row with no
earlier version in the window says so, binary/too-large keep their
download-both message, and nothing fetches until a row is expanded.

The folder listing's "Recent changes" teaser stays diff-free on purpose: it
fetches n=20 with no Load more, so nearly every row would read "First version".

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/webapp/frontend/e2e/home.spec.ts

@@ -217,12 +217,68 @@ test("per-file history: a binary version says so instead of diffing", async ({ p
   await expect(dv.locator("a", { hasText: "download this version" })).toBeVisible();
 });
 
-test("the whole-project feed carries no diff controls", async ({ page }) => {
+// BEA-58: the diff shipped, but only the per-file page passed the prop, so a
+// reviewer who opened the whole-project feed first concluded the product had
+// no diff at all. Every feed offers it now — and the assertion that matters is
+// that a row in a MIXED-path feed diffs against its own path's predecessor.
+
+test("the whole-project feed diffs a row against its own predecessor", async ({ page }) => {
   await login(page);
   const pid = await wikiId(page);
   await page.goto(`/${pid}/history`);
-  await expect(page.locator(".history .hentry").first()).toBeVisible();
-  await expect(page.locator(".history .hdiff-btn")).toHaveCount(0);
+  // Never nth(0): the newest row is the run's, not guide.md's.
+  const row = page.locator(".history > .hentry", { hasText: "guide.md" }).first();
+  await expect(row).toContainText("edited");
+  await row.locator(".hdiff-btn").click();
+  const dv = row.locator(".dv");
+  await expect(dv).toBeVisible();
+  // guide.md's own first version — not whichever row sits below it in the feed.
+  await expect(dv.locator(".dv-rm")).toContainText("First version of the guide.");
+  await expect(dv.locator(".dv-ins")).toContainText("Second version of the guide, with more detail.");
+  await expect(dv.locator(".dv-add")).toHaveText("+1");
+  await expect(dv.locator(".dv-del")).toHaveText("−1");
+  // Expanding is not navigating.
+  await expect(page).toHaveURL(`/${pid}/history`);
+
+  // A delete has no content to diff, and says nothing at all — not "first
+  // version".
+  const del = page.locator(".hentry.delete", { hasText: "scratch.md" }).first();
+  await expect(del.locator(".hdiff-btn")).toHaveCount(0);
+  await expect(del.locator(".hdiff-none")).toHaveCount(0);
+  // index.md has one version only, so it says so rather than rendering an
+  // empty diff.
+  const only = page.locator(".history > .hentry", { hasText: "index.md" }).first();
+  await expect(only.locator(".hdiff-btn")).toHaveCount(0);
+  await expect(only.locator(".hdiff-none")).toContainText("nothing to compare against");
+  await expect(only.locator(".dv")).toHaveCount(0);
+
+  // Rows inside a run card get it too: run.idx[k] indexes back into the flat
+  // list, so the card's rows compare against their own paths — the rewritten
+  // file against its 24h-old version, and the file the run CREATED against
+  // nothing.
+  const inCard = page.locator(".hrun-body .hentry", { hasText: "notes/readme.md" }).first();
+  await inCard.locator(".hdiff-btn").click();
+  await expect(inCard.locator(".dv-rm")).toContainText("Nested folder content.");
+  await expect(inCard.locator(".dv-ins")).toContainText("Rewritten during the agent run.");
+  const created = page.locator(".hrun-body .hentry", { hasText: "runbook.md" }).first();
+  await expect(created.locator(".hdiff-btn")).toHaveCount(0);
+  await expect(created.locator(".hdiff-none")).toContainText("nothing to compare against");
+});
+
+test("the folder feed diffs a row against its own predecessor", async ({ page }) => {
+  await login(page);
+  const pid = await wikiId(page);
+  await page.goto(`/${pid}/history/notes`);
+  // The run touched one file inside notes/, so it is a bare row here, not a
+  // card. Its predecessor is the 24h-old version, further down this feed.
+  const row = page.locator(".history > .hentry", { hasText: "notes/readme.md" }).first();
+  await row.locator(".hdiff-btn").click();
+  const dv = row.locator(".dv");
+  await expect(dv).toBeVisible();
+  await expect(dv.locator(".dv-rm")).toContainText("Nested folder content.");
+  await expect(dv.locator(".dv-ins")).toContainText("Rewritten during the agent run.");
+  // Expanding is not navigating.
+  await expect(page).toHaveURL(`/${pid}/history/notes`);
 });
 
 test("folder listing's Full history goes to the subtree feed", async ({ page }) => {

internal/webapp/frontend/src/components/HistoryRow.tsx

@@ -61,14 +61,14 @@ export function HistoryRow({
 }: {
   entry: HistoryEntry;
   // Its own prop, not something nested in `diff`: the version controls below
-  // belong on every feed, and `diff` is per-file-only by design.
+  // belong on every row that has content, diff or no diff.
   apiBase: string;
   // The row's own version (e.blob) rides along: a row is an address for the
   // bytes it describes, not a shortcut to whatever the file says now.
   onOpen: (path: string, version?: string) => void;
-  // Present only in the per-file history view, where "the previous version"
-  // is unambiguous. `prev` is the sha of the entry before this one on the
-  // same path; absent means this is the first version.
+  // Present in every paged history feed. `prev` is the sha of the entry
+  // before this one ON THE SAME PATH; absent means there is no earlier
+  // version in the loaded window.
   diff?: { apiBase: string; prev?: string };
   restore?: RestoreAction;
   // Only ever offered on an add inside a run card, where "this run created

internal/webapp/frontend/src/components/HistoryView.tsx

@@ -89,9 +89,6 @@ export function HistoryView(props: {
     />
   );
   if (!data) return bar ? <div className="history">{bar}</div> : null;
-  // Diffs are a per-file affair: the subtree feed mixes paths, and each row
-  // there would need its own predecessor lookup for no review benefit.
-  const perFile = !!target && !isFolder(target);
   // Entries arrive newest-first, so a row's predecessor is the next entry
   // below it on the same path that still has content. This keeps scanning the
   // flat list, never a group: it is a per-path lookup, and grouping must not
@@ -144,7 +141,6 @@ export function HistoryView(props: {
             run={item.run}
             onOpen={props.onOpen}
             apiBase={apiBase}
-            perFile={perFile}
             prevBlob={prevBlob}
             restoreSha={restoreSha}
             restore={restore}
@@ -156,7 +152,12 @@ export function HistoryView(props: {
             entry={entries[item.i]}
             apiBase={apiBase}
             onOpen={props.onOpen}
-            diff={perFile ? { apiBase, prev: prevBlob(item.i) } : undefined}
+            /* Every feed, not just the per-file one (BEA-58): prevBlob is a
+               per-path lookup, so a mixed-path feed diffs each row against its
+               own predecessor. A review-focused reader opens the whole-project
+               feed first, and finding no diff there read as "this product has
+               none". */
+            diff={{ apiBase, prev: prevBlob(item.i) }}
             restore={restore}
             restoreSha={restoreSha(item.i)}
             /* no `remove`: an add outside a run card isn't attributable to a
@@ -185,7 +186,6 @@ function RunGroup({
   run,
   onOpen,
   apiBase,
-  perFile,
   prevBlob,
   restoreSha,
   restore,
@@ -194,7 +194,6 @@ function RunGroup({
   run: Run;
   onOpen: (path: string, version?: string) => void;
   apiBase: string;
-  perFile: boolean;
   prevBlob: (i: number) => string | undefined;
   restoreSha: (i: number) => string | undefined;
   restore?: RestoreAction;
@@ -240,7 +239,10 @@ function RunGroup({
               entry={e}
               apiBase={apiBase}
               onOpen={onOpen}
-              diff={perFile ? { apiBase, prev: prevBlob(run.idx[k]) } : undefined}
+              /* run.idx[k] indexes back into the flat list, so a row inside a
+                 card compares against its own predecessor, not its neighbour
+                 in the card. */
+              diff={{ apiBase, prev: prevBlob(run.idx[k]) }}
               restore={restore}
               remove={remove}
               restoreSha={restoreSha(run.idx[k])}

internal/webapp/static/index.html

@@ -5,7 +5,7 @@
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>BearDrive</title>
 <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32' fill='%23f5a623'><rect x='4' y='4' width='5.6' height='24'/><rect x='11.2' y='4' width='14.4' height='11.2'/><rect x='11.2' y='16.8' width='16.8' height='11.2'/></svg>">
-  <script type="module" crossorigin src="/assets/index-w2PDXp5a.js"></script>
+  <script type="module" crossorigin src="/assets/index-BMdHuKLj.js"></script>
   <link rel="stylesheet" crossorigin href="/assets/index-DKdbhP6i.css">
 </head>
 <body>