fix(agents): preview view_image tools with inline thumbnails and lightbox

- Add thumbnailSrc to compact developer tool summaries for http(s) and data:image sources
- Render a tiny inline thumbnail in Viewed image rows instead of a truncated URL
- Show a larger preview when the tool accordion expands and open a lightbox on click
- Route relay media URLs through rewriteRelayUrl and fall back to basename text for local paths
- Add unit tests for thumbnail extraction and local path fallback

desktop/src/features/agents/ui/AgentSessionToolItem.tsx

@@ -1,4 +1,5 @@
 import * as React from "react";
+import * as DialogPrimitive from "@radix-ui/react-dialog";
 import { ArrowUpRight, ChevronDown, CircleDot, Wrench } from "lucide-react";
 
 import { useAppNavigation } from "@/app/navigation/useAppNavigation";
@@ -7,6 +8,7 @@ import { resolveUserLabel } from "@/features/profile/lib/identity";
 import type { Channel, UserProfileSummary } from "@/shared/api/types";
 import { useChannelNavigation } from "@/shared/context/ChannelNavigationContext";
 import { cn } from "@/shared/lib/cn";
+import { rewriteRelayUrl } from "@/shared/lib/mediaUrl";
 import { Badge } from "@/shared/ui/badge";
 import { Tooltip, TooltipContent, TooltipTrigger } from "@/shared/ui/tooltip";
 import { UserAvatar } from "@/shared/ui/UserAvatar";
@@ -86,6 +88,7 @@ export function ToolItem({
             <CompactToolSummaryRow
               duration={duration}
               preview={compactSummary.preview}
+              thumbnailSrc={compactSummary.thumbnailSrc}
               label={compactSummary.label}
             />
           ) : (
@@ -137,6 +140,14 @@ export function ToolItem({
           description={buzzTool?.label}
           hasArgs={hasArgs}
           hasResult={hasResult}
+          imagePreview={
+            compactSummary?.kind === "view_image" && isExpanded
+              ? {
+                  src: compactSummary.thumbnailSrc,
+                  title: compactSummary.preview,
+                }
+              : null
+          }
           isError={item.isError}
           result={item.result}
         />
@@ -149,15 +160,33 @@ function CompactToolSummaryRow({
   duration,
   label,
   preview,
+  thumbnailSrc,
 }: {
   duration: string | null;
   label: string;
   preview: string | null;
+  thumbnailSrc: string | null;
 }) {
+  const [thumbnailFailed, setThumbnailFailed] = React.useState(false);
+  const resolvedThumbnail = React.useMemo(() => {
+    if (!thumbnailSrc || thumbnailFailed) return null;
+    return resolveImageSrc(thumbnailSrc);
+  }, [thumbnailFailed, thumbnailSrc]);
+
   return (
     <>
       <span className="shrink-0 text-sm font-semibold">{label}</span>
-      {preview ? (
+      {resolvedThumbnail ? (
+        <img
+          alt=""
+          className="h-5 w-auto max-w-12 shrink-0 rounded-sm object-cover"
+          decoding="async"
+          loading="lazy"
+          onError={() => setThumbnailFailed(true)}
+          src={resolvedThumbnail}
+          title={preview ?? undefined}
+        />
+      ) : preview ? (
         <span
           className="min-w-0 max-w-48 truncate text-sm text-muted-foreground/70"
           title={preview}
@@ -175,6 +204,112 @@ function CompactToolSummaryRow({
   );
 }
 
+function resolveImageSrc(source: string): string {
+  if (source.startsWith("data:image/")) {
+    return source;
+  }
+  return rewriteRelayUrl(source);
+}
+
+function ViewImageToolPreview({
+  src,
+  title,
+}: {
+  src: string;
+  title: string | null;
+}) {
+  const [lightboxOpen, setLightboxOpen] = React.useState(false);
+  const [imageFailed, setImageFailed] = React.useState(false);
+  const resolvedSrc = React.useMemo(() => resolveImageSrc(src), [src]);
+  const alt = title ?? "Viewed image";
+
+  if (imageFailed) {
+    return null;
+  }
+
+  return (
+    <>
+      {/* biome-ignore lint/a11y/useKeyWithClickEvents: opens lightbox on click */}
+      <img
+        alt={alt}
+        className="block max-h-64 max-w-sm cursor-pointer rounded-md object-contain"
+        decoding="async"
+        loading="lazy"
+        onClick={() => setLightboxOpen(true)}
+        onError={() => setImageFailed(true)}
+        src={resolvedSrc}
+        title={title ?? undefined}
+      />
+      <ImageLightbox
+        alt={alt}
+        onOpenChange={setLightboxOpen}
+        open={lightboxOpen}
+        src={resolvedSrc}
+      />
+    </>
+  );
+}
+
+function ImageLightbox({
+  alt,
+  onOpenChange,
+  open,
+  src,
+}: {
+  alt: string;
+  onOpenChange: (open: boolean) => void;
+  open: boolean;
+  src: string;
+}) {
+  return (
+    <DialogPrimitive.Root open={open} onOpenChange={onOpenChange}>
+      <DialogPrimitive.Portal>
+        <DialogPrimitive.Overlay className="fixed inset-0 z-50 bg-black/80 data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0" />
+        <DialogPrimitive.Content
+          className="fixed inset-0 z-50 flex items-center justify-center p-8"
+          onInteractOutside={(event) => event.preventDefault()}
+          onPointerDownOutside={(event) => event.preventDefault()}
+        >
+          <DialogPrimitive.Title className="sr-only">
+            {alt}
+          </DialogPrimitive.Title>
+          <DialogPrimitive.Description className="sr-only">
+            Full-size image preview. Press Escape or click outside the image to
+            close.
+          </DialogPrimitive.Description>
+          <DialogPrimitive.Close
+            aria-label="Close lightbox"
+            className="absolute inset-0 cursor-default"
+          />
+          <img
+            alt={alt}
+            className="relative max-h-[90vh] max-w-[90vw] rounded-lg object-contain"
+            src={src}
+          />
+          <DialogPrimitive.Close className="absolute right-4 top-4 rounded-full bg-black/50 p-2 text-white/80 transition-colors hover:bg-black/70 hover:text-white focus:outline-hidden focus:ring-2 focus:ring-white/30">
+            <svg
+              aria-hidden="true"
+              fill="none"
+              height="20"
+              viewBox="0 0 24 24"
+              width="20"
+              xmlns="http://www.w3.org/2000/svg"
+            >
+              <path
+                d="M18 6L6 18M6 6l12 12"
+                stroke="currentColor"
+                strokeLinecap="round"
+                strokeLinejoin="round"
+                strokeWidth="2"
+              />
+            </svg>
+          </DialogPrimitive.Close>
+        </DialogPrimitive.Content>
+      </DialogPrimitive.Portal>
+    </DialogPrimitive.Root>
+  );
+}
+
 function getToolDuration(item: Extract<TranscriptItem, { type: "tool" }>) {
   if (item.startedAt && item.completedAt) {
     return formatDuration(item.startedAt, item.completedAt);
@@ -222,6 +357,7 @@ function ToolDetailBlocks({
   description,
   hasArgs,
   hasResult,
+  imagePreview,
   isError,
   result,
 }: {
@@ -229,6 +365,7 @@ function ToolDetailBlocks({
   description?: string;
   hasArgs: boolean;
   hasResult: boolean;
+  imagePreview: { src: string | null; title: string | null } | null;
   isError: boolean;
   result: string;
 }) {
@@ -239,6 +376,12 @@ function ToolDetailBlocks({
           {description}
         </p>
       ) : null}
+      {imagePreview?.src ? (
+        <ViewImageToolPreview
+          src={imagePreview.src}
+          title={imagePreview.title}
+        />
+      ) : null}
       {hasArgs ? (
         <ToolCodeBlock
           label="Parameters"

desktop/src/features/agents/ui/agentSessionToolSummary.test.mjs

@@ -63,19 +63,31 @@ test("buildCompactToolSummary formats shell command preview", () => {
   assert.equal(summary.preview, "git status");
 });
 
-test("buildCompactToolSummary formats view_image source preview", () => {
+test("buildCompactToolSummary formats view_image thumbnail source", () => {
+  const source =
+    "https://sprout-oss.stage.blox.sqprod.co/media/ffd1b2721f2d52e19f0ca2be9aa7842cdec5b4e0215aaab2a67c26a2a76a6a83.png";
   const summary = buildCompactToolSummary(
     makeTool({
       toolName: "buzz-dev-mcp__view_image",
-      args: {
-        source:
-          "https://sprout-oss.stage.blox.sqprod.co/media/ffd1b2721f2d52e19f0ca2be9aa7842cdec5b4e0215aaab2a67c26a2a76a6a83.png",
-      },
+      args: { source },
     }),
   );
 
   assert.equal(summary.label, "Viewed image");
-  assert.ok(summary.preview?.startsWith("https://sprout-oss"));
+  assert.equal(summary.thumbnailSrc, source);
+  assert.equal(summary.preview, source);
+});
+
+test("buildCompactToolSummary uses basename for local view_image paths", () => {
+  const summary = buildCompactToolSummary(
+    makeTool({
+      toolName: "view_image",
+      args: { source: "desktop/assets/screenshot.png" },
+    }),
+  );
+
+  assert.equal(summary.thumbnailSrc, null);
+  assert.equal(summary.preview, "screenshot.png");
 });
 
 test("buildCompactToolSummary formats read_file path preview", () => {

desktop/src/features/agents/ui/agentSessionToolSummary.ts

@@ -19,6 +19,8 @@ export type CompactToolSummary = {
   kind: CompactToolKind;
   label: string;
   preview: string | null;
+  /** When set, the compact row renders a tiny image instead of text preview. */
+  thumbnailSrc: string | null;
 };
 
 const DEVELOPER_TOOL_BASES = new Set([
@@ -44,11 +46,12 @@ export function isCompactDeveloperTool(item: ToolItem): boolean {
 /** Build the compact summary label and preview for developer MCP tool rows. */
 export function buildCompactToolSummary(item: ToolItem): CompactToolSummary {
   const kind = resolveDeveloperToolKind(item) ?? "dev_mcp";
-  const preview = extractCompactToolPreview(item, kind);
+  const { preview, thumbnailSrc } = extractCompactToolPreview(item, kind);
   return {
     kind,
     label: compactToolLabel(kind, item.status, item.isError),
     preview,
+    thumbnailSrc,
   };
 }
 
@@ -153,33 +156,70 @@ function compactToolLabel(
   return set.completed;
 }
 
+type CompactToolPreview = {
+  preview: string | null;
+  thumbnailSrc: string | null;
+};
+
 function extractCompactToolPreview(
   item: ToolItem,
   kind: CompactToolKind,
-): string | null {
+): CompactToolPreview {
   const args = item.args;
 
   switch (kind) {
     case "shell":
-      return getToolString(args, ["command"]);
+      return textPreview(getToolString(args, ["command"]));
     case "read_file":
     case "str_replace":
-      return getToolString(args, ["path"]);
+      return textPreview(getToolString(args, ["path"]));
     case "view_image":
-      return getToolString(args, ["source"]);
+      return getViewImagePreview(getToolString(args, ["source"]));
     case "todo":
-      return getTodoPreview(args);
+      return textPreview(getTodoPreview(args));
     case "stop_hook":
     case "post_compact_hook":
-      return null;
+      return emptyPreview();
     case "dev_mcp":
-      return (
+      return textPreview(
         getToolString(args, ["command", "path", "source", "query", "name"]) ??
-        null
+          null,
       );
   }
 }
 
+function textPreview(preview: string | null): CompactToolPreview {
+  return { preview, thumbnailSrc: null };
+}
+
+function emptyPreview(): CompactToolPreview {
+  return { preview: null, thumbnailSrc: null };
+}
+
+function getViewImagePreview(source: string | null): CompactToolPreview {
+  if (!source) {
+    return emptyPreview();
+  }
+
+  const trimmed = source.trim();
+  if (
+    trimmed.startsWith("data:image/") ||
+    trimmed.startsWith("http://") ||
+    trimmed.startsWith("https://")
+  ) {
+    return {
+      preview: trimmed,
+      thumbnailSrc: trimmed,
+    };
+  }
+
+  const basename = trimmed.split(/[/\\]/).pop() ?? trimmed;
+  return {
+    preview: basename,
+    thumbnailSrc: null,
+  };
+}
+
 function getTodoPreview(args: Record<string, unknown>): string | null {
   const todos = args.todos;
   if (!Array.isArray(todos)) {