diff --git a/frontend/src/components/tasks/ConversationViewer.tsx b/frontend/src/components/tasks/ConversationViewer.tsx
index aad15e16..084d6e7f 100644
--- a/frontend/src/components/tasks/ConversationViewer.tsx
+++ b/frontend/src/components/tasks/ConversationViewer.tsx
@@ -17,6 +17,7 @@ import {
 interface JSONLLine {
   type: string;
   threadID?: string;
+  // Amp format
   messages?: [
     number,
     {
@@ -63,7 +64,31 @@ interface JSONLLine {
   state?: string;
   tool?: string;
   command?: string;
-  message?: string;
+  // Claude format
+  message?: {
+    role: "user" | "assistant" | "system";
+    content: Array<{
+      type: "text" | "tool_use" | "tool_result";
+      text?: string;
+      id?: string;
+      name?: string;
+      input?: any;
+      tool_use_id?: string;
+      content?: any;
+      is_error?: boolean;
+    }> | string;
+  };
+  // Tool rejection message (string format)
+  rejectionMessage?: string;
+  usage?: {
+    input_tokens: number;
+    output_tokens: number;
+    cache_creation_input_tokens?: number;
+    cache_read_input_tokens?: number;
+  };
+  result?: any;
+  duration_ms?: number;
+  total_cost_usd?: number;
   error?: string; // For parse errors
 }
 
@@ -89,6 +114,21 @@ const isValidMessage = (data: any): boolean => {
   );
 };
 
+const isValidClaudeMessage = (data: any): boolean => {
+  return (
+    typeof data.role === "string" &&
+    (typeof data.content === "string" || 
+     (Array.isArray(data.content) &&
+      data.content.every(
+        (item: any) =>
+          typeof item.type === "string" &&
+          (item.type !== "text" || typeof item.text === "string") &&
+          (item.type !== "tool_use" || typeof item.name === "string") &&
+          (item.type !== "tool_result" || typeof item.content !== "undefined")
+      )))
+  );
+};
+
 const isValidTokenUsage = (data: any): boolean => {
   return (
     data &&
@@ -97,11 +137,19 @@ const isValidTokenUsage = (data: any): boolean => {
   );
 };
 
+const isValidClaudeUsage = (data: any): boolean => {
+  return (
+    data &&
+    typeof data.input_tokens === "number" &&
+    typeof data.output_tokens === "number"
+  );
+};
+
 const isValidToolRejection = (data: any): boolean => {
   return (
     typeof data.tool === "string" &&
     typeof data.command === "string" &&
-    typeof data.message === "string"
+    (typeof data.message === "string" || typeof data.rejectionMessage === "string")
   );
 };
 
@@ -200,19 +248,50 @@ export function ConversationViewer({ jsonlOutput }: ConversationViewerProps) {
           isValidMessagesLine(line) &&
           line.messages
         ) {
+          // Amp format
           for (const [messageIndex, message] of line.messages) {
             items.push({
               type: "message",
-              ...message,
+              role: message.role,
+              content: message.content,
+              timestamp: message.meta?.sentAt,
               messageIndex,
               lineIndex: line._lineIndex,
             });
           }
+        } else if (
+          (line.type === "user" || line.type === "assistant" || line.type === "system") &&
+          line.message &&
+          isValidClaudeMessage(line.message)
+        ) {
+          // Claude format
+          const content = typeof line.message.content === "string" 
+            ? [{ type: "text", text: line.message.content }]
+            : line.message.content;
+          
+          items.push({
+            type: "message",
+            role: line.message.role === "system" ? "assistant" : line.message.role,
+            content: content,
+            lineIndex: line._lineIndex,
+          });
+        } else if (
+          line.type === "result" &&
+          line.usage &&
+          isValidClaudeUsage(line.usage)
+        ) {
+          // Claude usage info
+          tokenUsages.push({
+            used: line.usage.input_tokens + line.usage.output_tokens,
+            maxAvailable: line.usage.input_tokens + line.usage.output_tokens + 100000, // Approximate
+            lineIndex: line._lineIndex,
+          });
         } else if (
           line.type === "token-usage" &&
           line.tokenUsage &&
           isValidTokenUsage(line.tokenUsage)
         ) {
+          // Amp format
           tokenUsages.push({
             used: line.tokenUsage.used,
             maxAvailable: line.tokenUsage.maxAvailable,
@@ -231,7 +310,7 @@ export function ConversationViewer({ jsonlOutput }: ConversationViewerProps) {
             type: "tool-rejection",
             tool: line.tool,
             command: line.command,
-            message: line.message,
+            message: typeof line.message === "string" ? line.message : line.rejectionMessage || "Tool rejected",
             lineIndex: line._lineIndex,
           });
         } else {
@@ -602,12 +681,16 @@ export function ConversationViewer({ jsonlOutput }: ConversationViewerProps) {
                           <div key={contentIndex} className="mt-3">
                             <div className="flex items-center gap-2 mb-2">
                               <div className="w-4 h-4 flex items-center justify-center">
-                                {content.run?.status && (
+                                {content.run?.status ? (
                                   <div
                                     className={`w-2 h-2 rounded-full ${getToolStatusColor(
                                       content.run.status
                                     )}`}
                                   />
+                                ) : content.is_error ? (
+                                  <div className="w-2 h-2 rounded-full bg-red-500" />
+                                ) : (
+                                  <div className="w-2 h-2 rounded-full bg-green-500" />
                                 )}
                               </div>
                               <span className="text-sm text-muted-foreground">
@@ -618,12 +701,24 @@ export function ConversationViewer({ jsonlOutput }: ConversationViewerProps) {
                                   ({safeRenderString(content.run.status)})
                                 </span>
                               )}
+                              {content.is_error && (
+                                <span className="text-xs text-red-500">
+                                  (Error)
+                                </span>
+                              )}
                             </div>
+                            {/* Amp format result */}
                             {content.run?.result && (
                               <pre className="text-xs bg-muted/50 p-2 rounded overflow-x-auto max-h-32">
                                 {safeRenderString(content.run.result)}
                               </pre>
                             )}
+                            {/* Claude format result */}
+                            {content.content && !content.run && (
+                              <pre className="text-xs bg-muted/50 p-2 rounded overflow-x-auto max-h-32">
+                                {safeRenderString(content.content)}
+                              </pre>
+                            )}
                             {content.run?.toAllow && (
                               <div className="mt-2">
                                 <p className="text-xs text-muted-foreground mb-1">
diff --git a/frontend/src/components/tasks/ExecutionOutputViewer.tsx b/frontend/src/components/tasks/ExecutionOutputViewer.tsx
index 7cda06eb..2f32d0f2 100644
--- a/frontend/src/components/tasks/ExecutionOutputViewer.tsx
+++ b/frontend/src/components/tasks/ExecutionOutputViewer.tsx
@@ -1,4 +1,4 @@
-import { useState, useMemo } from "react";
+import { useState, useMemo, useEffect } from "react";
 import { Card, CardContent } from "@/components/ui/card";
 import { Button } from "@/components/ui/button";
 import { Badge } from "@/components/ui/badge";
@@ -15,27 +15,28 @@ export function ExecutionOutputViewer({
   executionProcess,
   executor,
 }: ExecutionOutputViewerProps) {
-  const [viewMode, setViewMode] = useState<"conversation" | "raw">(
-    executor === "amp" ? "conversation" : "raw"
-  );
+  const [viewMode, setViewMode] = useState<"conversation" | "raw">("raw");
 
   const isAmpExecutor = executor === "amp";
+  const isClaudeExecutor = executor === "claude";
   const hasStdout = !!executionProcess.stdout;
   const hasStderr = !!executionProcess.stderr;
 
-  // Check if stdout looks like JSONL (for Amp executor)
-  const isValidJsonl = useMemo(() => {
-    if (!isAmpExecutor || !executionProcess.stdout) return false;
+  // Check if stdout looks like JSONL (for Amp or Claude executor)
+  const { isValidJsonl, jsonlFormat } = useMemo(() => {
+    if ((!isAmpExecutor && !isClaudeExecutor) || !executionProcess.stdout) {
+      return { isValidJsonl: false, jsonlFormat: null };
+    }
 
     try {
       const lines = executionProcess.stdout
         .split("\n")
         .filter((line) => line.trim());
-      if (lines.length === 0) return false;
+      if (lines.length === 0) return { isValidJsonl: false, jsonlFormat: null };
 
       // Try to parse at least the first few lines as JSON
       const testLines = lines.slice(0, Math.min(3, lines.length));
-      return testLines.every((line) => {
+      const allValid = testLines.every((line) => {
         try {
           JSON.parse(line);
           return true;
@@ -43,10 +44,42 @@ export function ExecutionOutputViewer({
           return false;
         }
       });
+
+      if (!allValid) return { isValidJsonl: false, jsonlFormat: null };
+
+      // Detect format by checking for Amp vs Claude structure
+      let hasAmpFormat = false;
+      let hasClaudeFormat = false;
+
+      for (const line of testLines) {
+        try {
+          const parsed = JSON.parse(line);
+          if (parsed.type === "messages" || parsed.type === "token-usage") {
+            hasAmpFormat = true;
+          }
+          if (parsed.type === "user" || parsed.type === "assistant" || parsed.type === "system" || parsed.type === "result") {
+            hasClaudeFormat = true;
+          }
+        } catch {
+          // Skip invalid lines
+        }
+      }
+
+      return {
+        isValidJsonl: true,
+        jsonlFormat: hasAmpFormat ? "amp" : hasClaudeFormat ? "claude" : "unknown"
+      };
     } catch {
-      return false;
+      return { isValidJsonl: false, jsonlFormat: null };
     }
-  }, [isAmpExecutor, executionProcess.stdout]);
+  }, [isAmpExecutor, isClaudeExecutor, executionProcess.stdout]);
+
+  // Set initial view mode based on JSONL detection
+  useEffect(() => {
+    if (isValidJsonl) {
+      setViewMode("conversation");
+    }
+  }, [isValidJsonl]);
 
   if (!hasStdout && !hasStderr) {
     return (
@@ -64,13 +97,18 @@ export function ExecutionOutputViewer({
     <Card className="">
       <CardContent className="p-3">
         <div className="space-y-3">
-          {/* View mode toggle for Amp executor with valid JSONL */}
-          {isAmpExecutor && isValidJsonl && hasStdout && (
+          {/* View mode toggle for executors with valid JSONL */}
+          {isValidJsonl && hasStdout && (
             <div className="flex items-center justify-between">
               <div className="flex items-center gap-2">
                 <Badge variant="outline" className="text-xs">
                   {executor} output
                 </Badge>
+                {jsonlFormat && (
+                  <Badge variant="secondary" className="text-xs">
+                    {jsonlFormat} format
+                  </Badge>
+                )}
               </div>
               <div className="flex items-center gap-1">
                 <Button
@@ -98,7 +136,7 @@ export function ExecutionOutputViewer({
           {/* Output content */}
           {hasStdout && (
             <div>
-              {isAmpExecutor && isValidJsonl && viewMode === "conversation" ? (
+              {isValidJsonl && viewMode === "conversation" ? (
                 <ConversationViewer
                   jsonlOutput={executionProcess.stdout || ""}
                 />