You are an expert frontend engineer and product designer. Extend the existing **Jupyter-like deep research notebook** prototype with advanced capabilities for **tool integration**, **human checkpoints**, and **traceability**.

### New Requirements

#### 1. Tool Integration

* Support connecting each cell to **external tools or APIs**, such as:

* MCP (Model Context Protocol) services.
* Research or data APIs (e.g., arXiv, PubMed, financial data).
* Custom backend endpoints.
* Each cell may declare:

```json
{
"tools": ["search_api", "data_cleaner", "plot_generator"]
}
```
* When a cell runs, it may show:

* Which tools were invoked.
* Input/output logs for each tool.
* API call status, latency, and result preview.
* Allow users to **configure tool parameters** or **reconnect tools** via a modal.

#### 2. Human Checkpoints

* Enable **human-in-the-loop review** for specific cells or workflow stages:

* Cells can be marked as “🧍 Human Checkpoint Required”.
* The system pauses execution until the user verifies or edits the intermediate result.
* Human reviewers can:

* Approve/Reject the result.
* Add comments or corrections inline.
* Re-run or reassign the cell to an agent.
* Display human checkpoint states (pending, approved, rejected) with clear badges and timeline markers.

#### 3. Traceability and Provenance

* Every cell’s output must include structured metadata:

```json
{
"version_hash": "sha256:abcd1234...",
"source_citations": [
{"title": "WHO Data Report", "url": "https://who.int/..."},
{"title": "OECD Dataset", "url": "https://oecd.org/..."}
],
"verification_score": 0.87
}
```
* Display this metadata in a collapsible “Provenance” panel under each output.
* Add:

* **Citations viewer:** Render links and allow hover previews for referenced sources.
* **Version hashes:** Allow copy/share for reproducibility.
* **Verification scores:** Show confidence badges (e.g., ✅ High, ⚠️ Medium, ❌ Low).

#### 4. UI and Interaction Enhancements

* Add an **Execution Timeline View** that tracks all runs, tool calls, and human reviews.
* Provide a **Cell History Panel** for version comparison and rollback.
* Maintain full **trace graph** of data and tool dependencies.
* Continue using **React + TailwindCSS**, ensuring minimal yet data-rich visualization.

### Deliverable

Generate an updated **React frontend prototype** implementing:

* Tool integration panel per cell.
* Human checkpoint workflow.
* Provenance and traceability metadata display.
* Version and verification tracking.
Use mock data and simulated API responses to demonstrate all these features visually.

components/cell.js

@@ -40,9 +40,100 @@ class AgenticCell extends HTMLElement {
             <style>
                 :host {
                     display: block;
+                    position: relative;
                 }
-                
-                .cell-container {
+
+                .tool-badge {
+                    display: inline-flex;
+                    align-items: center;
+                    padding: 0.25rem 0.5rem;
+                    margin-right: 0.5rem;
+                    margin-bottom: 0.5rem;
+                    font-size: 0.75rem;
+                    border-radius: 0.25rem;
+                    background-color: #f3f4f6;
+                    color: #4b5563;
+                }
+
+                .checkpoint-badge {
+                    position: absolute;
+                    top: 0.5rem;
+                    right: 0.5rem;
+                    padding: 0.25rem 0.5rem;
+                    border-radius: 0.25rem;
+                    font-size: 0.75rem;
+                    font-weight: 500;
+                }
+
+                .checkpoint-pending {
+                    background-color: #fef3c7;
+                    color: #92400e;
+                }
+
+                .checkpoint-approved {
+                    background-color: #d1fae5;
+                    color: #065f46;
+                }
+
+                .checkpoint-rejected {
+                    background-color: #fee2e2;
+                    color: #991b1b;
+                }
+
+                .provenance-panel {
+                    margin-top: 1rem;
+                    padding: 0.75rem;
+                    background-color: #f9fafb;
+                    border-radius: 0.375rem;
+                    border: 1px solid #e5e7eb;
+                }
+
+                .provenance-header {
+                    display: flex;
+                    align-items: center;
+                    cursor: pointer;
+                    font-weight: 500;
+                    color: #4b5563;
+                }
+
+                .provenance-content {
+                    margin-top: 0.5rem;
+                    padding-top: 0.5rem;
+                    border-top: 1px solid #e5e7eb;
+                }
+
+                .citation-item {
+                    margin-bottom: 0.5rem;
+                    padding: 0.5rem;
+                    background-color: white;
+                    border-radius: 0.25rem;
+                    border: 1px solid #e5e7eb;
+                }
+
+                .verification-badge {
+                    display: inline-flex;
+                    align-items: center;
+                    padding: 0.25rem 0.5rem;
+                    border-radius: 0.25rem;
+                    font-size: 0.75rem;
+                    font-weight: 500;
+                }
+
+                .verification-high {
+                    background-color: #d1fae5;
+                    color: #065f46;
+                }
+
+                .verification-medium {
+                    background-color: #fef3c7;
+                    color: #92400e;
+                }
+
+                .verification-low {
+                    background-color: #fee2e2;
+                    color: #991b1b;
+                }
+.cell-container {
                     border-radius: 0.5rem;
                     box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
                     background-color: white;
@@ -168,8 +259,13 @@ class AgenticCell extends HTMLElement {
                         <span class="cell-timestamp">${new Date(timestamp).toLocaleString()}</span>
                     ` : ''}
                 </div>
-                
-                <div class="cell-content">
+                ${output?.metadata?.requires_human_check ? `
+                    <div class="checkpoint-badge checkpoint-${output.metadata.human_check_status || 'pending'}">
+                        ${output.metadata.human_check_status === 'approved' ? '✅ Approved' : 
+                          output.metadata.human_check_status === 'rejected' ? '❌ Rejected' : '🧍 Pending Review'}
+                    </div>
+                ` : ''}
+<div class="cell-content">
                     <textarea class="input-area" placeholder="Enter your prompt or reference other cells with {{cell_id.output}}">${input}</textarea>
                     
                     <div class="actions">
@@ -178,19 +274,77 @@ class AgenticCell extends HTMLElement {
                             Run
                         </button>
                     </div>
-                    
                     <div class="output-container">
                         ${output ? `
                             <div class="output-header">
                                 <i data-feather="file-text" class="mr-2"></i>
                                 Output
                             </div>
+                            ${output.tools_used ? `
+                                <div class="mt-2 mb-3">
+                                    <div class="text-xs text-gray-500 mb-1">Tools used:</div>
+                                    ${output.tools_used.map(tool => `
+                                        <span class="tool-badge">
+                                            <i data-feather="${tool.icon || 'tool'}" class="w-3 h-3 mr-1"></i>
+                                            ${tool.name}
+                                        </span>
+                                    `).join('')}
+                                </div>
+                            ` : ''}
                             <agentic-output-viewer output='${JSON.stringify(output)}'></agentic-output-viewer>
+                            
+                            ${output.metadata ? `
+                                <div class="provenance-panel">
+                                    <div class="provenance-header" onclick="this.nextElementSibling.classList.toggle('hidden')">
+                                        <i data-feather="info" class="mr-2"></i>
+                                        Provenance & Metadata
+                                        <i data-feather="chevron-down" class="ml-auto w-4 h-4"></i>
+                                    </div>
+                                    <div class="provenance-content hidden">
+                                        ${output.metadata.version_hash ? `
+                                            <div class="mb-2">
+                                                <div class="text-xs text-gray-500">Version:</div>
+                                                <div class="flex items-center mt-1">
+                                                    <code class="text-xs bg-gray-100 p-1 rounded mr-2">${output.metadata.version_hash.substring(0, 12)}...</code>
+                                                    <button class="text-xs text-blue-600 hover:text-blue-800" onclick="navigator.clipboard.writeText('${output.metadata.version_hash}')">Copy</button>
+                                                </div>
+                                            </div>
+                                        ` : ''}
+                                        
+                                        ${output.metadata.verification_score ? `
+                                            <div class="mb-2">
+                                                <div class="text-xs text-gray-500">Verification:</div>
+                                                <div class="mt-1">
+                                                    <span class="verification-badge ${output.metadata.verification_score > 0.8 ? 'verification-high' : 
+                                                      output.metadata.verification_score > 0.5 ? 'verification-medium' : 'verification-low'}">
+                                                        ${output.metadata.verification_score > 0.8 ? '✅ High' : 
+                                                          output.metadata.verification_score > 0.5 ? '⚠️ Medium' : '❌ Low'} (${Math.round(output.metadata.verification_score * 100)}%)
+                                                    </span>
+                                                </div>
+                                            </div>
+                                        ` : ''}
+                                        
+                                        ${output.metadata.source_citations?.length > 0 ? `
+                                            <div>
+                                                <div class="text-xs text-gray-500">Citations:</div>
+                                                <div class="mt-1">
+                                                    ${output.metadata.source_citations.map(cite => `
+                                                        <div class="citation-item">
+                                                            <a href="${cite.url}" target="_blank" class="text-sm text-blue-600 hover:underline">${cite.title}</a>
+                                                            ${cite.description ? `<div class="text-xs text-gray-500 mt-1">${cite.description}</div>` : ''}
+                                                        </div>
+                                                    `).join('')}
+                                                </div>
+                                            </div>
+                                        ` : ''}
+                                    </div>
+                                </div>
+                            ` : ''}
                         ` : `
                             <div class="empty-output">No output yet. Run the cell to see results.</div>
                         `}
                     </div>
-                </div>
+</div>
             </div>
         `;
         

components/timeline.js

@@ -0,0 +1,115 @@
+```javascript
+class AgenticTimeline extends HTMLElement {
+    constructor() {
+        super();
+        this.attachShadow({ mode: 'open' });
+    }
+
+    connectedCallback() {
+        this.render();
+    }
+
+    render() {
+        this.shadowRoot.innerHTML = `
+            <style>
+                :host {
+                    display: block;
+                    margin-top: 2rem;
+                }
+                
+                .timeline-header {
+                    display: flex;
+                    align-items: center;
+                    margin-bottom: 1rem;
+                }
+                
+                .timeline-container {
+                    position: relative;
+                    padding-left: 1.5rem;
+                    border-left: 2px solid #e5e7eb;
+                }
+                
+                .timeline-item {
+                    position: relative;
+                    padding-bottom: 1.5rem;
+                }
+                
+                .timeline-dot {
+                    position: absolute;
+                    left: -1.5rem;
+                    top: 0;
+                    width: 1rem;
+                    height: 1rem;
+                    border-radius: 50%;
+                    background-color: #3b82f6;
+                    transform: translateX(-50%);
+                }
+                
+                .timeline-content {
+                    padding: 0.75rem;
+                    background-color: white;
+                    border-radius: 0.375rem;
+                    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
+                }
+                
+                .timeline-time {
+                    font-size: 0.75rem;
+                    color: #6b7280;
+                    margin-bottom: 0.25rem;
+                }
+                
+                .timeline-title {
+                    font-weight: 500;
+                    margin-bottom: 0.25rem;
+                }
+                
+                .timeline-desc {
+                    font-size: 0.875rem;
+                    color: #4b5563;
+                }
+                
+                .tool-call {
+                    margin-top: 0.5rem;
+                    padding: 0.5rem;
+                    background-color: #f9fafb;
+                    border-radius: 0.25rem;
+                    font-size: 0.75rem;
+                }
+                
+                .human-review {
+                    margin-top: 0.5rem;
+                    padding: 0.5rem;
+                    border-radius: 0.25rem;
+                    font-size: 0.75rem;
+                }
+                
+                .review-approved {
+                    background-color: #d1fae5;
+                    color: #065f46;
+                }
+                
+                .review-pending {
+                    background-color: #fef3c7;
+                    color: #92400e;
+                }
+            </style>
+            
+            <div class="timeline-header">
+                <h3 class="text-lg font-medium">Execution Timeline</h3>
+            </div>
+            
+            <div class="timeline-container">
+                <div class="timeline-item">
+                    <div class="timeline-dot"></div>
+                    <div class="timeline-content">
+                        <div class="timeline-time">2 minutes ago</div>
+                        <div class="timeline-title">Cell #3 Completed</div>
+                        <div class="timeline-desc">Data visualization generated</div>
+                        
+                        <div class="human-review review-pending">
+                            <div>🧍 Human Review Required</div>
+                            <div class="mt-1">Status: Pending</div>
+                        </div>
+                        
+                        <div class="tool-call">
+                            <div>

script.js

@@ -9,22 +9,53 @@ document.addEventListener('DOMContentLoaded', () => {
             input: 'Find recent breakthroughs in quantum computing',
             output: {
                 type: 'markdown',
-                content: '## Quantum Computing Breakthroughs (2023)\n\n1. **IBM Quantum Heron Processor** - 133-qubit processor with improved error rates\n2. **Google Quantum Supremacy 2.0** - Demonstrated 70-qubit processor\n3. **Microsoft Topological Qubits** - More stable qubit design\n4. **Quantum Networking** - First multi-node quantum network demonstrated'
+                content: '## Quantum Computing Breakthroughs (2023)\n\n1. **IBM Quantum Heron Processor** - 133-qubit processor with improved error rates\n2. **Google Quantum Supremacy 2.0** - Demonstrated 70-qubit processor\n3. **Microsoft Topological Qubits** - More stable qubit design\n4. **Quantum Networking** - First multi-node quantum network demonstrated',
+                tools_used: [
+                    { name: 'arXiv Search', icon: 'search', status: 'success', latency: '420ms' },
+                    { name: 'Research Summarizer', icon: 'file-text', status: 'success', latency: '320ms' }
+                ],
+                metadata: {
+                    version_hash: 'sha256:9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08',
+                    source_citations: [
+                        {
+                            title: 'IBM Quantum Heron Processor Announcement',
+                            url: 'https://research.ibm.com/blog/quantum-heron-processor',
+                            description: 'Official announcement of the 133-qubit processor'
+                        },
+                        {
+                            title: 'Nature: Quantum Computing Advances 2023',
+                            url: 'https://www.nature.com/quantum-2023',
+                            description: 'Comprehensive review of quantum computing milestones'
+                        }
+                    ],
+                    verification_score: 0.92,
+                    requires_human_check: true,
+                    human_check_status: 'approved'
+                }
             },
             status: 'success',
             timestamp: new Date(Date.now() - 3600000).toISOString()
-        },
+},
         {
             id: 'cell-2',
             agentType: 'analyst',
             input: 'Summarize the key points from cell-1 into bullet points',
             output: {
                 type: 'markdown',
-                content: '- IBM released 133-qubit processor\n- Google demonstrated 70-qubit processor\n- Microsoft developed more stable qubit design\n- Multi-node quantum networks achieved'
+                content: '- IBM released 133-qubit processor\n- Google demonstrated 70-qubit processor\n- Microsoft developed more stable qubit design\n- Multi-node quantum networks achieved',
+                tools_used: [
+                    { name: 'Text Summarizer', icon: 'align-left', status: 'success', latency: '210ms' }
+                ],
+                metadata: {
+                    version_hash: 'sha256:5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8',
+                    source_citations: [],
+                    verification_score: 0.85,
+                    requires_human_check: false
+                }
             },
             status: 'success',
             timestamp: new Date(Date.now() - 1800000).toISOString()
-        },
+},
         {
             id: 'cell-3',
             agentType: 'data-visualizer',
@@ -38,11 +69,22 @@ document.addEventListener('DOMContentLoaded', () => {
                         ['Google', '70', 'Supremacy 2.0'],
                         ['Microsoft', 'N/A', 'Topological stability']
                     ]
+                },
+                tools_used: [
+                    { name: 'Table Generator', icon: 'grid', status: 'success', latency: '380ms' },
+                    { name: 'Data Validator', icon: 'check-circle', status: 'success', latency: '290ms' }
+                ],
+                metadata: {
+                    version_hash: 'sha256:a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e',
+                    source_citations: [],
+                    verification_score: 0.78,
+                    requires_human_check: true,
+                    human_check_status: 'pending'
                 }
             },
             status: 'success',
             timestamp: new Date(Date.now() - 900000).toISOString()
-        }
+}
     ];
 
     // Create notebook with initial cells