feat(files): an HTML page opens in a modal over the screen

- Changes panel: Preview beside Whole file opens the page in a modal
  (HtmlViewerModal, shared with the File Explorer) instead of inside the
  panel; Changes and Whole file stay as they were.
- Chat: an HTML file's card, Outputs row or a path in a reply (in the
  workspace or not) opens FilePreview as a modal — Preview | Code, versions,
  Save to Artifacts kept — rather than the side panel or the Changes panel.
- Esc closes both modals: they stop every key from reaching the view below,
  which also kept useDialog's document listener from seeing it.

client/src/components/HtmlViewerModal.tsx

@@ -0,0 +1,109 @@
+/**
+ * @file HtmlViewerModal.tsx
+ * @description An HTML file shown as the page in a modal over the whole
+ * screen — the one viewer the File Explorer and the Changes panel's Preview
+ * open (the Chat's file preview opens its own panel as a modal instead, for
+ * its versions and Code tab). The page itself is `HtmlFrame`: the chat
+ * artifact's sandbox, its relative files read through the caller's guarded
+ * `fetchFile`. Keys and clicks stop at the modal, so a shortcut of the view
+ * underneath (the explorer's Delete) never fires from inside it.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { useRef, type ReactNode } from "react";
+import { createPortal } from "react-dom";
+import { useTranslation } from "react-i18next";
+import { Download, X } from "lucide-react";
+import { useDialog } from "../hooks/useDialog";
+import { HtmlFrame } from "./HtmlFrame";
+import type { FetchFile } from "../lib/htmlInline";
+
+export function HtmlViewerModal({
+  path,
+  html,
+  fetchFile,
+  onDownload,
+  onClose,
+  testId = "html-viewer",
+}: {
+  /** The file's path relative to the place `fetchFile` reads from; also its title. */
+  path: string;
+  /** The page's text; read through `fetchFile` when absent. */
+  html?: string;
+  fetchFile?: FetchFile | null;
+  onDownload?: () => void;
+  onClose: () => void;
+  testId?: string;
+}) {
+  const { t } = useTranslation(["lanes"]);
+  const panelRef = useRef<HTMLDivElement>(null);
+  useDialog(true, panelRef, onClose);
+  const name = path.slice(path.lastIndexOf("/") + 1);
+  return createPortal(
+    <div
+      className="fixed inset-0 z-[70] flex items-center justify-center bg-black/60 p-3"
+      onClick={(e) => {
+        e.stopPropagation();
+        onClose();
+      }}
+      onKeyDown={(e) => {
+        // Nothing reaches the view underneath — so Esc, which useDialog's
+        // document listener would never see, closes here.
+        e.stopPropagation();
+        if (e.key === "Escape") onClose();
+      }}
+      role="presentation"
+    >
+      <div
+        ref={panelRef}
+        role="dialog"
+        aria-modal="true"
+        aria-label={name}
+        data-testid={testId}
+        className="flex h-[92vh] w-[96vw] max-w-7xl flex-col overflow-hidden rounded-xl border border-border bg-surface-1 shadow-2xl shadow-black/50"
+        onClick={(e) => e.stopPropagation()}
+      >
+        <div className="flex items-center gap-2 border-b border-border px-3 py-2">
+          <span className="min-w-0 flex-1 truncate font-mono text-[13px] text-fg-primary">
+            {path}
+          </span>
+          {onDownload && (
+            <HeadButton label={t("fx.download")} onClick={onDownload}>
+              <Download className="h-4 w-4" />
+            </HeadButton>
+          )}
+          <HeadButton label={t("fx.close")} onClick={onClose}>
+            <X className="h-4 w-4" />
+          </HeadButton>
+        </div>
+        <HtmlFrame path={path} html={html} fetchFile={fetchFile} title={name} />
+      </div>
+    </div>,
+    document.body
+  );
+}
+
+function HeadButton({
+  label,
+  onClick,
+  children,
+}: {
+  label: string;
+  onClick: () => void;
+  children: ReactNode;
+}) {
+  return (
+    <button
+      type="button"
+      aria-label={label}
+      title={label}
+      onClick={(e) => {
+        e.stopPropagation();
+        onClick();
+      }}
+      className="rounded-md p-1.5 text-fg-secondary transition-colors hover:bg-surface-2 hover:text-fg-primary"
+    >
+      {children}
+    </button>
+  );
+}

client/src/components/lanes/FileExplorer.tsx

@@ -91,7 +91,8 @@ import {
 } from "../../lib/api";
 import type { Lane } from "../../lib/types";
 import { useDialog } from "../../hooks/useDialog";
-import { HtmlFrame, fetchVia } from "../HtmlFrame";
+import { fetchVia } from "../HtmlFrame";
+import { HtmlViewerModal } from "../HtmlViewerModal";
 import { toast } from "../../lib/toast";
 import { confirmDialog } from "../../lib/confirm";
 import { formatBytes } from "../../lib/format";
@@ -1935,10 +1936,8 @@ export function FileExplorer({
   );
 }
 
-/** An HTML file shown as the page, over the explorer: its relative CSS,
- *  scripts and images read through the same download route (`HtmlFrame`).
- *  Keys and clicks stop here — through the portal they would otherwise reach
- *  the explorer's own shortcuts (Delete would trash the selection). */
+/** An HTML file as the page, in the shared modal viewer (`HtmlViewerModal`):
+ *  its relative CSS, scripts and images read through the same download route. */
 function HtmlViewer({
   entry,
   place,
@@ -1950,49 +1949,20 @@ function HtmlViewer({
   onDownload: () => void;
   onClose: () => void;
 }) {
-  const { t } = useTranslation(["lanes"]);
-  const panelRef = useRef<HTMLDivElement>(null);
-  useDialog(true, panelRef, onClose);
   const placeKey = JSON.stringify(place);
   const fetchFile = useMemo(
     () => fetchVia((p) => api.files.downloadUrl(place, p)),
     // eslint-disable-next-line react-hooks/exhaustive-deps
     [placeKey]
   );
-  return createPortal(
-    <div
-      className="fixed inset-0 z-[70] flex items-center justify-center bg-black/60 p-3"
-      onClick={(e) => {
-        e.stopPropagation();
-        onClose();
-      }}
-      onKeyDown={(e) => e.stopPropagation()}
-      role="presentation"
-    >
-      <div
-        ref={panelRef}
-        role="dialog"
-        aria-modal="true"
-        aria-label={entry.name}
-        data-testid="fx-html-viewer"
-        className="flex h-[92vh] w-[96vw] max-w-7xl flex-col overflow-hidden rounded-xl border border-border bg-surface-1 shadow-2xl shadow-black/50"
-        onClick={(e) => e.stopPropagation()}
-      >
-        <div className="flex items-center gap-2 border-b border-border px-3 py-2">
-          <span className="min-w-0 flex-1 truncate font-mono text-[13px] text-fg-primary">
-            {entry.path}
-          </span>
-          <HeadButton label={t("fx.download")} onClick={onDownload}>
-            <Download className="h-4 w-4" />
-          </HeadButton>
-          <HeadButton label={t("fx.close")} onClick={onClose}>
-            <X className="h-4 w-4" />
-          </HeadButton>
-        </div>
-        <HtmlFrame path={entry.path} fetchFile={fetchFile} title={entry.name} />
-      </div>
-    </div>,
-    document.body
+  return (
+    <HtmlViewerModal
+      path={entry.path}
+      fetchFile={fetchFile}
+      onDownload={onDownload}
+      onClose={onClose}
+      testId="fx-html-viewer"
+    />
   );
 }
 

client/src/components/lanes/LaneChangesPanel.tsx

@@ -14,9 +14,9 @@
  *              is unsaved): Changes folds the unchanged lines away, Whole file
  *              shows them; any other file opens on its read-only diff; a
  *              whole markdown file can also be read rendered (Preview), an HTML
- *              file shown as the page by Preview beside Whole file
- *              (`HtmlFrame`, its relative CSS, scripts and images read like
- *              downloads), and an
+ *              file's Preview beside Whole file opens the page in a modal
+ *              (`HtmlViewerModal`, its relative CSS, scripts and images read
+ *              like downloads), and an
  *              image file is shown as the picture (`GET …/git/raw`)
  *   history  — recent commits; opening one shows that commit's diff
  *   browse   — quick-open by path, or the repo's tracked file tree (the
@@ -139,7 +139,8 @@ import { LaneConflictView } from "./LaneConflictView";
 import { FileExplorer } from "./FileExplorer";
 import { ContextMenu, MenuItem, MenuSeparator, useContextMenu } from "../ContextMenu";
 import { MarkdownPreview, isMarkdown } from "../MarkdownPreview";
-import { HtmlFrame, fetchVia } from "../HtmlFrame";
+import { fetchVia } from "../HtmlFrame";
+import { HtmlViewerModal } from "../HtmlViewerModal";
 import { LaneGitHeader, useLaneGitFacts } from "./LaneGitHeader";
 import { changeTree, treeFiles, type ChangeTreeDir } from "../../lib/changeTree";
 import { dragProjectPath } from "../../lib/promptAttach";
@@ -198,7 +199,7 @@ function Delta({
   );
 }
 
-/** An HTML page, which the viewer can show rendered (`HtmlFrame`). */
+/** An HTML page, which Preview opens as the page (`HtmlViewerModal`). */
 const isHtml = (p: string | null | undefined) => !!p && /\.html?$/i.test(p);
 
 /** What the viewer shows as a picture (`readImageAt`'s list on the server). */
@@ -890,11 +891,13 @@ export function LaneChangesPanel({
   const [layout, setLayout] = useState<DiffLayout>(wide ? "split" : "unified");
   useEffect(() => setLayout(wide ? "split" : "unified"), [wide]);
   const [whole, setWhole] = useState(false);
-  // A whole markdown or HTML file shown rendered instead of as source; per
-  // file, markdown opening as Settings → Appearance says
-  // (`lib/markdownView.ts`), an HTML page only once Preview is clicked.
+  // A whole markdown file shown rendered instead of as source; per file,
+  // opening as Settings → Appearance says (`lib/markdownView.ts`).
   const [mdPreview, setMdPreview] = useState(readMarkdownPreview);
-  useEffect(() => setMdPreview(!isHtml(openFile) && readMarkdownPreview()), [openFile]);
+  useEffect(() => setMdPreview(readMarkdownPreview()), [openFile]);
+  // An HTML file's page, open in the modal viewer (Preview beside Whole file).
+  const [htmlOpen, setHtmlOpen] = useState(false);
+  useEffect(() => setHtmlOpen(false), [openFile, mode]);
   const [data, setData] = useState<LaneChanges | null>(null);
   // A folder that is not a repo (an empty new workspace, a parent of clones)
   // has no changes, review or history — only its files, which Files reads
@@ -2059,10 +2062,8 @@ export function LaneChangesPanel({
     });
 
   const dirty = draft !== null && draft !== text?.lines.join("\n");
-  // Rendered only where the toggle is offered: a whole markdown or HTML file.
-  const mdShown = mdPreview && whole && (isMarkdown(openFile) || isHtml(openFile));
-  // The HTML page is showing (the Preview view of the Changes / Whole file / Preview group).
-  const htmlShown = mdShown && isHtml(openFile);
+  // Rendered only where the toggle is offered: a whole markdown file.
+  const mdShown = mdPreview && whole && isMarkdown(openFile);
   // An HTML page's relative CSS/scripts/images, read like a download — only
   // from the working tree: a commit's page would get today's files.
   const htmlFetch = useMemo(
@@ -2562,11 +2563,8 @@ export function LaneChangesPanel({
                     <button
                       key={String(w)}
                       type="button"
-                      aria-pressed={whole === w && !htmlShown}
+                      aria-pressed={whole === w}
                       onClick={() => {
-                        // Changes and Whole file show an HTML page's source;
-                        // only Preview runs it.
-                        if (htmlShown) setMdPreview(false);
                         if (whole === w) return;
                         // Both views of a working file are the same editor: the
                         // draft goes along, unsaved or not.
@@ -2580,7 +2578,7 @@ export function LaneChangesPanel({
                         });
                       }}
                       className={`rounded px-2 py-0.5 text-[11px] transition-colors ${
-                        whole === w && !htmlShown
+                        whole === w
                           ? "bg-surface-4 text-fg-primary"
                           : "text-fg-secondary hover:text-fg-primary"
                       }`}
@@ -2588,28 +2586,33 @@ export function LaneChangesPanel({
                       {t(w ? "changes.wholeFile" : "changes.changesView")}
                     </button>
                   ))}
-                  {/* An HTML file's third view: the page itself. */}
-                  {isHtml(openFile) && (
-                    <button
-                      type="button"
-                      data-testid="lane-file-preview"
-                      aria-pressed={htmlShown}
-                      disabled={dirty}
-                      onClick={() => {
-                        setMdPreview(true);
-                        setWhole(true);
-                      }}
-                      className={`rounded px-2 py-0.5 text-[11px] transition-colors disabled:cursor-not-allowed disabled:opacity-40 ${
-                        htmlShown
-                          ? "bg-surface-4 text-fg-primary"
-                          : "text-fg-secondary hover:text-fg-primary"
-                      }`}
-                    >
-                      {t("changes.preview")}
-                    </button>
-                  )}
                 </div>
               )}
+              {/* An HTML file opens as the page in a modal over the screen;
+                  a commit's page once its text is read (Whole file). */}
+              {mode === "file" && isHtml(openFile) && (
+                <button
+                  type="button"
+                  data-testid="lane-file-preview"
+                  disabled={dirty || (range === "commit" && !text)}
+                  onClick={() => setHtmlOpen(true)}
+                  className="flex items-center gap-1 rounded border border-border bg-surface-2 px-2 py-1 text-[11px] text-fg-secondary hover:text-fg-primary disabled:cursor-not-allowed disabled:opacity-40"
+                >
+                  <Eye className="h-3 w-3" />
+                  {t("changes.preview")}
+                </button>
+              )}
+              {htmlOpen && openFile && (
+                <HtmlViewerModal
+                  path={openFile}
+                  // A commit's page is its text at that commit (no sibling
+                  // files); a working one is read whole from the disk.
+                  html={range === "commit" ? text?.lines.join("\n") : undefined}
+                  fetchFile={htmlFetch}
+                  onDownload={!local && range !== "commit" ? () => download(openFile) : undefined}
+                  onClose={() => setHtmlOpen(false)}
+                />
+              )}
             </div>
           )}
         </div>
@@ -3164,17 +3167,7 @@ export function LaneChangesPanel({
                     </Suspense>
                   )
                 ) : whole ? (
-                  text && mdShown && isHtml(openFile) ? (
-                    <HtmlFrame
-                      key={openFile}
-                      path={text.path}
-                      // A cut-off page is read whole through the download.
-                      html={text.truncated && htmlFetch ? undefined : text.lines.join("\n")}
-                      fetchFile={htmlFetch}
-                      title={text.path}
-                      className="rounded border border-border-light"
-                    />
-                  ) : text && mdShown ? (
+                  text && mdShown ? (
                     <div className="min-h-0 flex-1 overflow-auto rounded border border-border-light bg-surface-0 p-4">
                       <MarkdownPreview text={text.lines.join("\n")} />
                     </div>

client/src/components/lanes/__tests__/LaneChangesPanel.test.tsx

@@ -544,7 +544,7 @@ describe("LaneChangesPanel", () => {
     expect(screen.queryByTestId("lane-file-editor")).toBeNull();
   });
 
-  it("opens a whole HTML file as its source, the page after Preview, the source after Whole file", async () => {
+  it("opens a whole HTML file as its source, the page in a modal after Preview", async () => {
     vi.mocked(api.lanes.gitTree).mockResolvedValue({
       available: true,
       path: "",
@@ -560,22 +560,31 @@ describe("LaneChangesPanel", () => {
       lines: ["<p>deck</p>"],
       sha: "c".repeat(40),
     });
-    const user = userEvent.setup();
-    render(<LaneChangesPanel laneId={7} full />);
-    const sidebar = await screen.findByTestId("lane-changes-sidebar");
-    await user.click(await within(sidebar).findByText("deck.html"));
-    expect(await screen.findByTestId("lane-file-editor")).toHaveValue("<p>deck</p>");
-    expect(screen.queryByTestId("html-frame")).toBeNull();
-    await user.click(screen.getByTestId("lane-file-preview"));
-    const frame = await screen.findByTestId("html-frame");
-    expect(frame.getAttribute("srcdoc")).toContain("<p>deck</p>");
-    expect(screen.getByRole("button", { name: "Preview", pressed: true })).toBeInTheDocument();
-    await user.click(screen.getByRole("button", { name: "Whole file", pressed: false }));
-    expect(await screen.findByTestId("lane-file-editor")).toHaveValue("<p>deck</p>");
-    expect(screen.queryByTestId("html-frame")).toBeNull();
+    const fetchSpy = vi
+      .spyOn(globalThis, "fetch")
+      .mockResolvedValue(new Response("<p>deck</p>", { status: 200 }));
+    try {
+      const user = userEvent.setup();
+      render(<LaneChangesPanel laneId={7} full />);
+      const sidebar = await screen.findByTestId("lane-changes-sidebar");
+      await user.click(await within(sidebar).findByText("deck.html"));
+      expect(await screen.findByTestId("lane-file-editor")).toHaveValue("<p>deck</p>");
+      expect(screen.queryByTestId("html-frame")).toBeNull();
+      await user.click(screen.getByTestId("lane-file-preview"));
+      const modal = await screen.findByTestId("html-viewer");
+      const frame = await within(modal).findByTestId("html-frame");
+      expect(frame.getAttribute("srcdoc")).toContain("<p>deck</p>");
+      expect(frame.getAttribute("sandbox")).not.toContain("allow-same-origin");
+      await user.keyboard("{Escape}");
+      await waitFor(() => expect(screen.queryByTestId("html-viewer")).toBeNull());
+      // The source stayed where it was, under the modal.
+      expect(screen.getByTestId("lane-file-editor")).toHaveValue("<p>deck</p>");
+    } finally {
+      fetchSpy.mockRestore();
+    }
   });
 
-  it("opens a changed HTML file on its Changes, the page only after Preview", async () => {
+  it("offers Preview on a changed HTML file's Changes, opening the page in a modal", async () => {
     vi.mocked(api.lanes.changes).mockResolvedValue(
       changes({
         files: [
@@ -583,28 +592,21 @@ describe("LaneChangesPanel", () => {
         ],
       })
     );
-    vi.mocked(api.lanes.gitFile).mockResolvedValue({
-      available: true,
-      path: "deck.html",
-      rev: "work",
-      binary: false,
-      truncated: false,
-      lines: ["<p>deck</p>"],
-      sha: "c".repeat(40),
-    });
-    const user = userEvent.setup();
-    render(<LaneChangesPanel laneId={7} />);
-    await user.click(await screen.findByTitle("deck.html"));
-    await screen.findByRole("button", { name: "Changes", pressed: true });
-    expect(screen.queryByTestId("html-frame")).toBeNull();
-    await user.click(await screen.findByTestId("lane-file-preview"));
-    const frame = await screen.findByTestId("html-frame");
-    expect(frame.getAttribute("srcdoc")).toContain("<p>deck</p>");
-    expect(frame.getAttribute("sandbox")).not.toContain("allow-same-origin");
-    // Back to Changes: the diff again, not the page.
-    await user.click(screen.getByRole("button", { name: "Changes", pressed: false }));
-    await screen.findByRole("button", { name: "Changes", pressed: true });
-    await waitFor(() => expect(screen.queryByTestId("html-frame")).toBeNull());
+    const fetchSpy = vi
+      .spyOn(globalThis, "fetch")
+      .mockResolvedValue(new Response("<p>deck</p>", { status: 200 }));
+    try {
+      const user = userEvent.setup();
+      render(<LaneChangesPanel laneId={7} />);
+      await user.click(await screen.findByTitle("deck.html"));
+      await screen.findByRole("button", { name: "Changes", pressed: true });
+      await user.click(await screen.findByTestId("lane-file-preview"));
+      const modal = await screen.findByTestId("html-viewer");
+      expect(await within(modal).findByTestId("html-frame")).toBeInTheDocument();
+      expect(screen.getByRole("button", { name: "Changes", pressed: true })).toBeInTheDocument();
+    } finally {
+      fetchSpy.mockRestore();
+    }
   });
 
   it("shows an image file as the picture, with no edit control", async () => {

client/src/components/run/ChatFilePreview.tsx

@@ -12,6 +12,8 @@
  * text file it read, wrote or named (a generated report) anywhere else through
  * `GET /api/sessions/:id/file`.
  * Anything else (or a file those routes refuse) shows its path only. A Windows path's `\` counts as `/` throughout.
+ * `FilePreview` with `modal` (an HTML page, from PaneChat) is the same view in
+ * a modal over the whole screen.
  * `SkillListModal` is the same dialog over the session's skills, each one's
  * SKILL.md found by name (`plugin:name` from the plugin list, else the user's
  * or the project's); a built-in skill has no file and shows by name only.
@@ -357,6 +359,7 @@ export function FilePreview({
   onClose,
   className = "",
   messages,
+  modal = false,
 }: {
   path: string;
   scope: PreviewScope;
@@ -364,12 +367,16 @@ export function FilePreview({
   className?: string;
   /** The conversation, for the versions its Write/Edit calls left. */
   messages?: TranscriptMessage[];
+  /** A modal over the whole screen (backdrop, Esc closes) instead of a panel. */
+  modal?: boolean;
 }) {
   const { t } = useTranslation("run");
   const kind = artifactKind(path);
   const loaded = useContent(path, scope);
   const [view, setView] = useState<View>(() => defaultView(path));
   const [full, setFull] = useState(false);
+  const modalRef = useRef<HTMLDivElement>(null);
+  useDialog(modal, modalRef, onClose);
   const [sharing, setSharing] = useState(false);
   const versions = useMemo(
     () => (messages ? artifactVersions(messages, path) : []),
@@ -424,7 +431,9 @@ export function FilePreview({
     <section
       data-testid="chat-file-preview"
       className={
-        full
+        modal
+          ? "flex h-[92vh] w-[96vw] max-w-7xl min-h-0 min-w-0 flex-col overflow-hidden rounded-xl border border-border bg-surface-1 shadow-2xl shadow-black/50"
+          : full
           ? "fixed inset-4 z-[200] flex min-h-0 min-w-0 flex-col overflow-hidden rounded-xl border border-border bg-surface-1 shadow-2xl"
           : `flex min-h-0 min-w-0 flex-col overflow-hidden bg-surface-1 ${className}`
       }
@@ -522,16 +531,18 @@ export function FilePreview({
               <Share2 className="h-3.5 w-3.5" />
             )}
           </button>
-          <button
-            type="button"
-            data-testid="artifact-expand"
-            onClick={() => setFull((f) => !f)}
-            title={t(full ? "chat.artifact.collapse" : "chat.artifact.expand")}
-            aria-label={t(full ? "chat.artifact.collapse" : "chat.artifact.expand")}
-            className={iconBtn}
-          >
-            {full ? <Minimize2 className="h-3.5 w-3.5" /> : <Maximize2 className="h-3.5 w-3.5" />}
-          </button>
+          {!modal && (
+            <button
+              type="button"
+              data-testid="artifact-expand"
+              onClick={() => setFull((f) => !f)}
+              title={t(full ? "chat.artifact.collapse" : "chat.artifact.expand")}
+              aria-label={t(full ? "chat.artifact.collapse" : "chat.artifact.expand")}
+              className={iconBtn}
+            >
+              {full ? <Minimize2 className="h-3.5 w-3.5" /> : <Maximize2 className="h-3.5 w-3.5" />}
+            </button>
+          )}
           <button
             type="button"
             onClick={onClose}
@@ -546,6 +557,32 @@ export function FilePreview({
       <Body path={path} content={content} view={view} scope={scope} />
     </section>
   );
+  if (modal) {
+    return createPortal(
+      <div
+        className="fixed inset-0 z-[70] flex items-center justify-center bg-black/60 p-3"
+        onClick={onClose}
+        onKeyDown={(e) => {
+          // Nothing reaches the view underneath — so Esc, which useDialog's
+          // document listener would never see, closes here.
+          e.stopPropagation();
+          if (e.key === "Escape") onClose();
+        }}
+        role="presentation"
+      >
+        <div
+          ref={modalRef}
+          role="dialog"
+          aria-modal="true"
+          aria-label={displayName(path)}
+          onClick={(e) => e.stopPropagation()}
+        >
+          {panel}
+        </div>
+      </div>,
+      document.body
+    );
+  }
   // Full screen: over the whole page, where a pane's edges cannot clip it.
   return full ? createPortal(panel, document.body) : panel;
 }

client/src/components/run/PaneChat.tsx

@@ -35,7 +35,9 @@
  * of files or the used skills a list with a preview (`FileListModal`,
  * `SkillListModal`). Anything there drags into the prompt box. A file in a turn's
  * "Edited N files" card opens in the Workspace's Changes panel
- * (`openInChanges`) when it lies in the pane's folder. The unsent prompt and
+ * (`openInChanges`) when it lies in the pane's folder. An HTML file — a card,
+ * an Outputs row, a path in a reply — opens instead as the page, the same
+ * preview in a modal over the whole screen. The unsent prompt and
  * its attachments are kept per session (`lib/chatDraft.ts`), so a reload
  * leaves them as typed; switching to the terminal pastes them into its input
  * box and back brings that box's text here (`ChatToggle`). A send scrolls the
@@ -582,6 +584,12 @@ export const PaneChat = memo(function PaneChat({
     setPreview(null);
   };
   const [preview, setPreview] = useState<string | null>(null);
+  // An HTML file shown as the page, in a modal over the screen.
+  const [htmlView, setHtmlView] = useState<string | null>(null);
+  const show = useCallback(
+    (path: string) => (/\.html?$/i.test(path) ? setHtmlView(path) : setPreview(path)),
+    []
+  );
   // The side panel's width as a fraction of the pane: the dragged one, else
   // a default per content (a preview wants more room than the panel).
   const [dragged, setDragged] = useState(storedSide);
@@ -757,20 +765,21 @@ export const PaneChat = memo(function PaneChat({
   // not the workspace's Changes panel a plain file link goes to.
   const openArtifact = useCallback(
     (named: string) => {
-      setPreview(resolveIn(cwd, named));
+      show(resolveIn(cwd, named));
     },
-    [cwd]
+    [cwd, show]
   );
   const openFile = useCallback(
     (named: string) => {
       // A relative path in a reply (`server/lib/x.js`) is relative to this pane's folder.
       const path = resolveIn(cwd, named);
+      if (/\.html?$/i.test(path)) return show(path);
       // The workspace's Changes panel when the file is in its folder;
       // else this view's own preview.
       if (laneId !== null && openInChanges(laneId, cwd, path)) return;
       setPreview(path);
     },
-    [laneId, cwd]
+    [laneId, cwd, show]
   );
 
   // Before the session starts the CLI may be asking in the terminal (trust
@@ -984,7 +993,7 @@ export const PaneChat = memo(function PaneChat({
           <ChatOutline
             outline={activity}
             onClose={() => openOutline(false)}
-            onOpenFile={setPreview}
+            onOpenFile={show}
             onOpenList={setList}
           />
         )
@@ -1006,6 +1015,15 @@ export const PaneChat = memo(function PaneChat({
           />
         </div>
       )}
+      {htmlView && (
+        <FilePreview
+          path={htmlView}
+          scope={scope}
+          messages={convMessages}
+          onClose={() => setHtmlView(null)}
+          modal
+        />
+      )}
       {list === "skills" && (
         <SkillListModal
           title={t("chat.outline.skills")}

client/src/components/run/__tests__/ChatFilePreview.test.tsx

@@ -217,6 +217,17 @@ describe("the artifact view", () => {
     cleanup();
   });
 
+  it("shows a page as a modal over the screen, closed by Esc", async () => {
+    const onClose = vi.fn();
+    render(<FilePreview path="/w/page.html" scope={scope} onClose={onClose} modal />);
+    const dialog = await screen.findByRole("dialog", { name: "page.html" });
+    expect(dialog.parentElement?.parentElement).toBe(document.body);
+    expect(await screen.findByTestId("artifact-frame")).toBeInTheDocument();
+    expect(screen.queryByTestId("artifact-expand")).toBeNull();
+    fireEvent.keyDown(screen.getByTestId("artifact-tab-code"), { key: "Escape" });
+    expect(onClose).toHaveBeenCalled();
+  });
+
   it("steps back to an older version the conversation wrote", async () => {
     html(["<p>two</p>"]);
     const tool = (id: string, input: Record<string, unknown>, name = "Write") => ({