fix(web): PDF previews keep their page when the agent responds

apps/web/src/components/files/AttachmentFilePreview.browser.test.tsx

@@ -2345,6 +2345,72 @@ it("toggles a Mermaid attachment between diagram and source through the lazy pre
   expect(screen.container.querySelector('[role="alert"]')).toBeNull();
 });
 
+it("keeps a workspace PDF open across URL renewals and reloads it when the file changes", async () => {
+  const { WorkspaceBrowserPreview } = await import("./FilePreviewPanel");
+  using _native = vi.spyOn(navigator, "pdfViewerEnabled", "get").mockReturnValue(true);
+  const original = URL.createObjectURL(new Blob(["%PDF-1.4"], { type: "application/pdf" }));
+  const edited = URL.createObjectURL(new Blob(["%PDF-1.4 edited"], { type: "application/pdf" }));
+  const preview = (mutation: string) => (
+    <WorkspaceBrowserPreview
+      environmentId={EnvironmentId.make("test")}
+      threadRef={{ environmentId: EnvironmentId.make("test"), threadId: ThreadId.make("test") }}
+      draft={false}
+      workspaceRoot="/repo"
+      absolutePath="/repo/planning.pdf"
+      title="Planning PDF"
+      workspaceMutationId={mutation}
+    />
+  );
+  assetUrlState.mockReturnValue({
+    _tag: "Success",
+    url: `${original}#initial`,
+    expiresAt: 0,
+    fileRevision: "one",
+  });
+  try {
+    await using screen = await render(preview("first"));
+    const opened = screen.container.querySelector("iframe");
+    expect(opened?.src.startsWith(original)).toBe(true);
+
+    // An agent command renews the signed URL but leaves the file alone.
+    assetUrlState.mockReturnValue({
+      _tag: "Success",
+      url: `${original}#renewed`,
+      expiresAt: 0,
+      fileRevision: "one",
+    });
+    await screen.rerender(preview("second"));
+    expect(assetUrlState).toHaveBeenLastCalledWith(expect.anything(), expect.anything(), "second");
+    expect(screen.container.querySelector("iframe")).toBe(opened);
+
+    assetUrlState.mockReturnValue({
+      _tag: "Success",
+      url: edited,
+      expiresAt: 0,
+      fileRevision: "two",
+    });
+    await screen.rerender(preview("third"));
+    const reloaded = screen.container.querySelector("iframe");
+    expect(reloaded).not.toBe(opened);
+    expect(reloaded?.src.startsWith(edited)).toBe(true);
+
+    // Servers without revisions hold the preview back until a fresh grant arrives.
+    assetUrlState.mockReturnValue({
+      _tag: "Success",
+      url: `${edited}#stale`,
+      expiresAt: 0,
+      waiting: true,
+    });
+    await screen.rerender(preview("fourth"));
+    expect(screen.container.querySelector("iframe")).toBeNull();
+    assetUrlState.mockReturnValue({ _tag: "Success", url: original, expiresAt: 0 });
+    await screen.rerender(preview("fourth"));
+    expect(screen.container.querySelector("iframe")?.src.startsWith(original)).toBe(true);
+  } finally {
+    URL.revokeObjectURL(original);
+    URL.revokeObjectURL(edited);
+  }
+});
 it("unwraps one text attachment without turning off the word wrap setting", async () => {
   const file = new Blob(["a long line"], { type: "text/plain" });
   await using screen = await render(

apps/web/src/components/files/FilePreviewPanel.tsx

@@ -222,7 +222,7 @@ function WorkspaceImagePreview(props: {
   );
 }
 
-function WorkspaceBrowserPreview(props: {
+export function WorkspaceBrowserPreview(props: {
   readonly environmentId: EnvironmentId;
   readonly threadRef: ScopedThreadRef;
   readonly draft: boolean;
@@ -231,18 +231,25 @@ function WorkspaceBrowserPreview(props: {
   readonly title: string;
   readonly workspaceMutationId: string | null;
 }) {
+  const pdf = isPdfPreviewFile(props.absolutePath);
   const resource = workspaceAssetResource({
-    kind: "workspace-file",
+    kind: pdf ? "media-file" : "workspace-file",
     threadRef: props.threadRef,
     draft: props.draft,
     workspaceRoot: props.workspaceRoot,
     absolutePath: props.absolutePath,
   });
-  const assetUrl = useAssetUrlState(props.environmentId, resource);
+  const assetUrl = useAssetUrlState(
+    props.environmentId,
+    resource,
+    pdf ? props.workspaceMutationId : undefined,
+  );
+  const fileRevision = pdf && assetUrl._tag === "Success" ? assetUrl.fileRevision : undefined;
+  const revision = fileRevision ?? props.workspaceMutationId;
   const revisionSuffix =
-    props.workspaceMutationId === null
+    revision === null
       ? ""
-      : `${assetUrl._tag === "Success" && assetUrl.url.includes("?") ? "&" : "?"}workspace-revision=${encodeURIComponent(props.workspaceMutationId)}`;
+      : `${assetUrl._tag === "Success" && assetUrl.url.includes("?") ? "&" : "?"}${fileRevision !== undefined ? "file" : "workspace"}-revision=${encodeURIComponent(revision)}`;
 
   if (assetUrl._tag === "Failure") {
     return (
@@ -251,7 +258,10 @@ function WorkspaceBrowserPreview(props: {
       </div>
     );
   }
-  if (assetUrl._tag !== "Success") {
+  if (
+    assetUrl._tag !== "Success" ||
+    (pdf && assetUrl.fileRevision === undefined && assetUrl.waiting)
+  ) {
     return (
       <div className="flex min-h-0 flex-1 items-center justify-center text-muted-foreground">
         <Spinner size="lg" />
@@ -261,9 +271,9 @@ function WorkspaceBrowserPreview(props: {
   return (
     <BrowserDocumentFrame
       src={`${assetUrl.url}${revisionSuffix}`}
-      documentKey={`${props.environmentId}:${resource._tag}:${props.threadRef.threadId}:${props.absolutePath}:${props.workspaceMutationId}`}
+      documentKey={`${props.environmentId}:${resource._tag}:${props.threadRef.threadId}:${props.absolutePath}:${revision}`}
       title={props.title}
-      pdf={isPdfPreviewFile(props.absolutePath)}
+      pdf={pdf}
     />
   );
 }