diff --git a/webui/src/web-components/demo/mermaid-test/mermaid-test.ts b/webui/src/web-components/demo/mermaid-test/mermaid-test.ts
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index 0000000..7d8e04f
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+++ b/webui/src/web-components/demo/mermaid-test/mermaid-test.ts
@@ -0,0 +1,136 @@
+import { html, css, LitElement } from 'lit';
+import { customElement } from 'lit/decorators.js';
+import '../../sketch-timeline-message.ts';
+// Using simple objects matching the AgentMessage interface
+
+@customElement('mermaid-test-component')
+export class MermaidTestComponent extends LitElement {
+  static styles = css`
+    :host {
+      display: block;
+    }
+    .test-section {
+      margin-bottom: 30px;
+    }
+    h2 {
+      margin-top: 0;
+      color: #444;
+    }
+  `;
+
+  render() {
+    // Create a sample message with Mermaid diagrams
+    const flowchartMessage = {
+      id: 'test-1',
+      type: 'agent',
+      content: `# Mermaid Flowchart Example
+
+This is a test of a flowchart diagram in Mermaid syntax:
+
+\`\`\`mermaid
+graph TD
+    A[Start] --> B{Is it working?}
+    B -->|Yes| C[Great!]
+    B -->|No| D[Try again]
+    C --> E[Continue]
+    D --> B
+\`\`\`
+
+The above should render as a Mermaid diagram.`,
+      timestamp: new Date().toISOString(),
+    };
+
+    const sequenceDiagramMessage = {
+      id: 'test-2',
+      type: 'agent',
+      content: `# Mermaid Sequence Diagram Example
+
+Here's a sequence diagram showing a typical HTTP request:
+
+\`\`\`mermaid
+sequenceDiagram
+    participant Browser
+    participant Server
+    Browser->>Server: GET /index.html
+    Server-->>Browser: HTML Response
+    Browser->>Server: GET /style.css
+    Server-->>Browser: CSS Response
+    Browser->>Server: GET /script.js
+    Server-->>Browser: JS Response
+\`\`\`
+
+Complex diagrams should render properly.`,
+      timestamp: new Date().toISOString(),
+    };
+
+    const classDiagramMessage = {
+      id: 'test-3',
+      type: 'agent',
+      content: `# Mermaid Class Diagram Example
+
+A simple class diagram in Mermaid:
+
+\`\`\`mermaid
+classDiagram
+    class Animal {
+        +string name
+        +makeSound() void
+    }
+    class Dog {
+        +bark() void
+    }
+    class Cat {
+        +meow() void
+    }
+    Animal <|-- Dog
+    Animal <|-- Cat
+\`\`\`
+
+This represents a basic inheritance diagram.`,
+      timestamp: new Date().toISOString(),
+    };
+
+    const normalMarkdownMessage = {
+      id: 'test-4',
+      type: 'agent',
+      content: `# Regular Markdown
+
+This is regular markdown with:
+
+- A bullet list
+- **Bold text**
+- *Italic text*
+
+\`\`\`javascript
+// Regular code block
+const x = 10;
+console.log('This is not Mermaid');
+\`\`\`
+
+Regular markdown should continue to work properly.`,
+      timestamp: new Date().toISOString(),
+    };
+
+    return html`
+      <div class="test-section">
+        <h2>Flowchart Diagram Test</h2>
+        <sketch-timeline-message .message=${flowchartMessage}></sketch-timeline-message>
+      </div>
+      
+      <div class="test-section">
+        <h2>Sequence Diagram Test</h2>
+        <sketch-timeline-message .message=${sequenceDiagramMessage}></sketch-timeline-message>
+      </div>
+
+      <div class="test-section">
+        <h2>Class Diagram Test</h2>
+        <sketch-timeline-message .message=${classDiagramMessage}></sketch-timeline-message>
+      </div>
+
+      <div class="test-section">
+        <h2>Normal Markdown Test</h2>
+        <sketch-timeline-message .message=${normalMarkdownMessage}></sketch-timeline-message>
+      </div>
+    `;
+  }
+}