feat(maestro): show image previews in user message bubbles

Uploaded images now render as thumbnails in the user bubble instead of
showing only the server file path as text.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/structured.ts

@@ -85,10 +85,10 @@ export function createStructuredConnection(
       <div class="structured-main">
         <div class="structured-scroll">
           <div class="structured-rows"></div>
-        </div>
-        <div class="structured-activity" role="status" aria-live="polite" hidden>
-          <span class="structured-activity-pulse" aria-hidden="true"></span>
-          <span class="structured-activity-text">Thinking</span>
+          <div class="structured-activity" role="status" aria-live="polite" hidden>
+            <span class="structured-activity-pulse" aria-hidden="true"></span>
+            <span class="structured-activity-text">Thinking</span>
+          </div>
         </div>
         <form class="structured-composer">
           <button type="button" class="btn btn-ghost btn-icon structured-attach" aria-label="Attach files" title="Attach files (up to 20 MiB each)">
@@ -253,6 +253,8 @@ export function createStructuredConnection(
   let activityTimer: number | null = null;
   const promptQueue: QueuedPrompt[] = [];
   let promptRequestPending = false;
+  /** Server path → object URL for uploaded images, so user bubbles can show previews. */
+  const imageObjectUrls = new Map<string, string>();
 
   // Within 64px, wheel and touch imprecision should still count as following.
   const FOLLOW_BOTTOM_THRESHOLD_PX = 64;
@@ -383,6 +385,9 @@ export function createStructuredConnection(
     }
   }
 
+  /** Pattern matching `Attached file "name": "path"` references appended by dispatchPrompt. */
+  const attachedFileRe = /Attached file "(?:[^"\\]|\\.)*": "((?:[^"\\]|\\.)*)"/g;
+
   function buildRowElement(row: TranscriptRow): HTMLElement | null {
     const el = buildTranscriptRow(
       row,
@@ -399,6 +404,39 @@ export function createStructuredConnection(
     if (el.querySelector(".st-tool-head")?.getAttribute("aria-expanded") !== "true") {
       expandedRowIds.delete(row.id);
     }
+    // Inject image previews into user message bubbles and strip the path text.
+    if (row.kind === "user" && imageObjectUrls.size > 0) {
+      const data = row.data as { content?: { type: string; text?: string } } | undefined;
+      const text = data?.content?.type === "text" ? data.content.text ?? "" : "";
+      const body = el.querySelector(".st-body");
+      if (body && text) {
+        const images: string[] = [];
+        attachedFileRe.lastIndex = 0;
+        let match: RegExpExecArray | null;
+        while ((match = attachedFileRe.exec(text)) !== null) {
+          const serverPath = JSON.parse(`"${match[1]}"`);
+          const objectUrl = imageObjectUrls.get(serverPath);
+          if (objectUrl) images.push(objectUrl);
+        }
+        if (images.length > 0) {
+          // Strip attachment reference lines from the displayed text.
+          const userText = body.querySelector(".st-user-text");
+          if (userText) {
+            const cleaned = text.replace(/\n\nAttached file "[^"]*": "[^"]*"/g, "").trim();
+            userText.textContent = cleaned;
+            if (!cleaned) userText.remove();
+          }
+          for (const src of images) {
+            const img = document.createElement("img");
+            img.className = "st-user-image";
+            img.src = src;
+            img.alt = "Uploaded image";
+            img.loading = "lazy";
+            body.appendChild(img);
+          }
+        }
+      }
+    }
     return el;
   }
 
@@ -717,6 +755,7 @@ export function createStructuredConnection(
 
   function renderActivity(): void {
     const active = state.turn.responding || state.turn.thinking || awaitingBeginGeneration !== null;
+    const wasHidden = activityEl.hidden;
     activityEl.hidden = !active;
     if (!active) {
       optimisticTurnStartedAt = null;
@@ -739,6 +778,11 @@ export function createStructuredConnection(
     }
     activityText.textContent = parts.join(" · ");
     if (activityTimer === null) activityTimer = window.setInterval(renderActivity, 1_000);
+    // Activity lives inside the scroll area; nudge scroll when it first appears.
+    if (wasHidden && followingBottom) {
+      beginTranscriptLayout(true);
+      finishTranscriptLayout();
+    }
   }
 
   function reconcileAwaitingBegin(): void {
@@ -985,6 +1029,9 @@ export function createStructuredConnection(
       for (const attachment of submittedAttachments) {
         if (disposed) return;
         if (!attachment.path) attachment.path = (await uploadStructuredFile(sessionId, attachment.file)).path;
+        if (attachment.path && attachment.file.type.startsWith("image/")) {
+          imageObjectUrls.set(attachment.path, URL.createObjectURL(attachment.file));
+        }
       }
       if (disposed) return;
       const references = submittedAttachments.map(({ file, path }) =>
@@ -1224,6 +1271,8 @@ export function createStructuredConnection(
       closeCurrentSocket();
       expandedRowIds.clear();
       expandedGroupIds.clear();
+      for (const url of imageObjectUrls.values()) URL.revokeObjectURL(url);
+      imageObjectUrls.clear();
       scrollEl.removeEventListener("scroll", onTranscriptScroll);
       scrollEl.removeEventListener("click", onTranscriptClick, true);
       scrollEl.removeEventListener("wheel", stopSmoothFollow);

web/src/styles.css

@@ -2318,9 +2318,7 @@ input.leaf-rename:focus {
   gap: var(--sp-2);
   min-height: 30px;
   padding: var(--sp-1) var(--sp-3);
-  border-top: 1px solid var(--border);
   color: var(--muted);
-  background: var(--surface-2);
   font-size: var(--fs-11);
   font-variant-numeric: tabular-nums;
 }
@@ -2382,6 +2380,15 @@ input.leaf-rename:focus {
   overflow-wrap: anywhere;
 }
 
+.st-user-image {
+  display: block;
+  max-width: min(100%, 480px);
+  max-height: 360px;
+  margin-top: var(--sp-2);
+  border-radius: var(--r-1);
+  object-fit: contain;
+}
+
 /* agent prose: no card, no background — plain text is the point */
 .st-row-agent .st-body p {
   margin: 0 0 var(--sp-2);