Task responses with status.message not displayed in UI

# GitHub Issue for A2A Inspector

**Repository:** https://github.com/a2aproject/a2a-inspector
**Title:** Task responses with status.message not displayed in UI

---

## Description

The A2A Inspector UI displays "Task created with status: completed" instead of showing the actual agent response message when a task includes `status.message.parts[0].text`.

## Steps to Reproduce

1. Configure the inspector to connect to an A2A agent server
2. Send a message to the agent
3. Receive a task response with this structure:
```json
{
"jsonrpc": "2.0",
"id": "msg-1",
"result": {
"kind": "task",
"id": "task-123",
"contextId": "ctx-456",
"status": {
"state": "completed",
"message": {
"kind": "message",
"role": "agent",
"parts": [
{
"kind": "text",
"text": "Hello, how can I help you today?"
}
]
}
},
"history": [...]
}
}
```

## Expected Behavior

The UI should display:
```
task Hello, how can I help you today? ✅
```

## Actual Behavior

The UI displays:
```
task Task created with status: completed ✅
```

The actual message text is not shown.

## Technical Details

**Root Cause:** `frontend/src/script.ts` lines 1058-1068

The task event handler only displays `event.status.state` and ignores `event.status.message.parts[0].text`:

```typescript
} else if (event.status) {
// Only show task status if there are no artifacts
const statusHtml = `${event.kind} Task created with status: ${DOMPurify.sanitize(event.status.state)}`;
appendMessage('agent progress', statusHtml, displayMessageId, true, validationErrors);
}
```

## Inconsistency

The `status-update` event handler (lines 1071-1087) **correctly** extracts and displays the message:

```typescript
case 'status-update': {
const statusText = event.status?.message?.parts?.[0]?.text; // ✅ Correct
if (statusText) {
const renderedContent = DOMPurify.sanitize(marked.parse(statusText) as string);
const messageHtml = `${event.kind} Server responded with: ${renderedContent}`;
appendMessage('agent progress', messageHtml, ...);
}
}
```

The same logic should be applied to task events.

## Suggested Fix

Update the task event handler to check for and display `status.message.parts[0].text`:

```typescript
} else if (event.status) {
// Check if there's a message in the status
const statusText = event.status?.message?.parts?.[0]?.text;
if (statusText) {
// Display the actual message content
const renderedContent = DOMPurify.sanitize(
marked.parse(statusText) as string,
);
const messageHtml = `${event.kind} ${renderedContent}`;
appendMessage(
'agent',
messageHtml,
displayMessageId,
true,
validationErrors,
);
} else {
// Fallback: show task status if there's no message
const statusHtml = `${event.kind} Task created with status: ${DOMPurify.sanitize(event.status.state)}`;
appendMessage(
'agent progress',
statusHtml,
displayMessageId,
true,
validationErrors,
);
}
}
```

This mirrors the existing logic in the `status-update` handler and provides a fallback to the current behavior when no message is present.

## Impact

**Severity:** Medium
**Affected:** All A2A agents that return completed tasks with message content (standard A2A pattern)

## Current Workaround

Users can verify the response is actually present in the JSON by:
1. Checking browser DevTools Network tab
2. Using curl or other HTTP clients to see the raw JSON response
3. Using the backend logs (if available)

## Environment

- **Inspector Version:** Latest (as of 2026-01-16)
- **Browser:** Tested on multiple browsers
- **Test Server:** Custom A2A server implementing standard protocol

## Additional Context

The backend (`backend/app.py`) correctly passes through the full response including `status.message`, so no backend changes are needed. This is purely a frontend UI rendering issue.

The A2A protocol specification supports including messages in task status, and this is a common pattern for synchronous agent responses.

## Related Files

- `frontend/src/script.ts` (lines 1030-1121) - Event handlers
- `frontend/src/script.ts` (lines 23-48) - AgentResponseEvent interface

---

## Test Case for Verification

After the fix, test with this JSON-RPC request/response:

**Request:**
```json
{
"jsonrpc": "2.0",
"id": "test-1",
"method": "message/send",
"params": {
"contextId": "test-context",
"message": {
"messageId": "msg-1",
"role": "user",
"parts": [{"type": "text", "text": "Hello"}]
}
}
}
```

**Response:**
```json
{
"jsonrpc": "2.0",
"id": "test-1",
"result": {
"kind": "task",
"id": "task-123",
"status": {
"state": "completed",
"message": {
"kind": "message",
"parts": [{"kind": "text", "text": "Hi! How can I help?"}]
}
}
}
}
```

**Expected UI Display:**
```
task Hi! How can I help? ✅
```

---

Thank you for maintaining this excellent tool! Let me know if you need any additional information or testing assistance.