diff --git a/frontend/src/components/UnifiedChat.tsx b/frontend/src/components/UnifiedChat.tsx
index 176db243..5e1c2040 100644
--- a/frontend/src/components/UnifiedChat.tsx
+++ b/frontend/src/components/UnifiedChat.tsx
@@ -4506,6 +4506,64 @@ export function UnifiedChat({ isVisible = true }: { isVisible?: boolean }) {
         ) {
           throw new Error("Response stream ended before completion");
         }
+
+        // Check if response completed but produced no useful output.
+        // This can happen when the model tries to use a tool that was available in
+        // previous conversation turns but is not in the current request's tools array.
+        if (terminalState === "completed") {
+          const finalSnapshot = runtimeStore.get(runtimeKey);
+          if (finalSnapshot) {
+            const ownedMessages = (finalSnapshot.messages as Message[]).filter((msg) =>
+              ownedItemIds.has(msg.id)
+            );
+
+            // Check if we have any assistant message content
+            const hasAssistantContent = ownedMessages.some((msg) => {
+              if (msg.type === "message" && (msg as ExtendedMessage).role === "assistant") {
+                const content = (msg as ExtendedMessage).content;
+                return content && content.length > 0 && content.some((part) => {
+                  if ("text" in part && typeof part.text === "string") {
+                    return part.text.trim().length > 0;
+                  }
+                  return false;
+                });
+              }
+              return false;
+            });
+
+            // Check if there are failed tool calls (tool call with no output)
+            const toolCallIds = new Set<string>();
+            const toolOutputCallIds = new Set<string>();
+            ownedMessages.forEach((msg) => {
+              if (isToolCallItem(msg)) {
+                toolCallIds.add(msg.call_id);
+              }
+              if (isToolOutputItem(msg)) {
+                toolOutputCallIds.add(msg.call_id);
+              }
+            });
+            const hasFailedToolCalls = toolCallIds.size > 0 &&
+              Array.from(toolCallIds).some(callId => !toolOutputCallIds.has(callId));
+
+            if (!hasAssistantContent) {
+              console.warn("Response completed with no assistant content", {
+                hasFailedToolCalls,
+                toolCallIds: Array.from(toolCallIds),
+                toolOutputCallIds: Array.from(toolOutputCallIds)
+              });
+
+              let errorMessage = "The response didn't produce any output.";
+              if (hasFailedToolCalls) {
+                errorMessage = "The model attempted to use a feature that's not currently available. Try rephrasing your request without requiring that feature.";
+              }
+
+              runtimeStore.updateForRun(runtimeKey, runToken, (snapshot) => ({
+                ...snapshot,
+                error: errorMessage
+              }));
+            }
+          }
+        }
       } catch (error) {
         // Commit the final partial frame before changing its status. UI cancel
         // and account teardown clear run ownership before aborting, so their
@@ -4672,6 +4730,36 @@ export function UnifiedChat({ isVisible = true }: { isVisible?: boolean }) {
       if (originalDocumentText) {
         finalText = originalDocumentText + (trimmedInput ? `\n\n${trimmedInput}` : "");
       }
+
+      // Prepend Maple UX context for new conversations to help the assistant
+      // understand the interface and guide users through the app
+      const hasConversationHistory = existingConversationId && isFollowUpConversation;
+      const isFirstMessage = !hasConversationHistory;
+
+      if (isFirstMessage) {
+        const mapleUxContext = `[System: You are the Maple AI assistant. The user is interacting with you through the Maple app interface. You can reference these UI elements:
+
+- **Web Search Toggle**: Globe icon in the composer toolbar (bottom). Currently ${requestWebSearchEnabled ? "ENABLED" : "DISABLED"}. Tell users "tap the globe icon" to toggle it.
+- **File Uploads**: Plus (+) icon opens attachment menu with "Add Images" and "Add Document" options.
+- **Project Picker**: Folder icon to organize conversations into projects.
+- **Model Selection**: Quick (fast) or Powerful (vision-enabled, required for images).
+- **Settings**: Access via app menu for Preferences, Account, Billing, etc.
+
+When users ask about app features or how to do things in Maple, reference these specific UI elements. If they mention "API" or "proxy", they're NOT in the app - use capability language instead.]
+
+`;
+        finalText = mapleUxContext + finalText;
+      } else {
+        // Prepend tool availability context to help the model understand what tools
+        // are available for this specific request, especially when it differs from
+        // previous turns in the conversation.
+        if (requestWebSearchEnabled) {
+          finalText = `[System context: Web search is available for this request.]\n\n${finalText}`;
+        } else {
+          finalText = `[System context: Web search is not available for this request. Please respond without using web search capabilities.]\n\n${finalText}`;
+        }
+      }
+
       if (finalText) {
         messageContent.push({
           type: "input_text",
diff --git a/frontend/src/instructions/maple-ux-context.ts b/frontend/src/instructions/maple-ux-context.ts
new file mode 100644
index 00000000..4456bfa1
--- /dev/null
+++ b/frontend/src/instructions/maple-ux-context.ts
@@ -0,0 +1,77 @@
+// Maple UX Context System Instruction
+// This instruction is automatically loaded to help the Maple assistant
+// understand the UI and guide users through the application.
+
+export const MAPLE_UX_INSTRUCTION = `# Maple Assistant - UI Context
+
+You are the Maple AI assistant. When users interact with you through the Maple app, you have knowledge of the interface they're using.
+
+## Interface Detection
+
+IMPORTANT: Only reference UI elements when the user is clearly using the Maple desktop or mobile app.
+
+If user mentions "API", "proxy", "CLI" → they are NOT in the app, use capability language instead.
+
+## Core UI Features (Maple App Only)
+
+### Web Search Toggle
+- **Icon**: Globe icon in composer toolbar (bottom)
+- **Function**: Enable/disable web search
+- **Default**: Enabled
+- **How to use**: "Tap/click the globe icon to toggle web search"
+
+### File Uploads
+- **Icon**: Plus (+) icon in composer toolbar
+- **Opens**: Attachment menu
+
+**Add Images**:
+- Upload photos, screenshots, diagrams
+- Requires vision-capable model (Powerful)
+- **How to use**: "Tap + icon → Add Images"
+
+**Add Document**:
+- Upload PDF files (OCR on desktop)
+- Desktop: Full support | Web: Use desktop app prompt
+- **How to use**: "Tap + icon → Add Document"
+
+### Project Picker
+- **Icon**: Folder icon in composer toolbar
+- **Function**: Organize conversations by project
+- **States**: Gray (no project) | Colored (project selected)
+- **How to use**: "Tap the folder icon to select a project"
+
+### Model Selection
+- **Quick**: Fast, everyday responses
+- **Powerful**: Deeper thinking, vision-enabled (required for images)
+
+### Settings
+Access via app menu → Settings
+
+Sections:
+- **Preferences**: System prompt, chat appearance, text-to-speech
+- **Account, Security, Billing, API, History, About**
+
+## Response Guidelines
+
+**In Maple app**:
+✅ "Tap the globe icon to enable web search"
+✅ "Use the + button to upload an image"
+
+**Via API/proxy**:
+✅ "Web search can be enabled in your request"
+✅ "You can include images in your API call"
+
+**When uncertain**: Ask "Are you using the Maple app, or accessing via API?"
+
+## Platform Differences
+
+- **Desktop**: Full PDF OCR, all features
+- **Web**: Limited document upload (directs to desktop)
+- **Mobile**: Touch-optimized, camera integration
+
+Remember: Only reference UI elements when user is clearly in the Maple app. For API users, focus on capabilities.
+`;
+
+export const MAPLE_UX_INSTRUCTION_NAME = "Maple UX Context";
+export const MAPLE_UX_INSTRUCTION_DESCRIPTION =
+  "Helps the Maple assistant understand the UI and guide users through the application";