feat(notifications): implement complete MCP notification system

[kargnas]

Resolves #43

• Add HTTP 202 response support for notifications per MCP specification
• Create make:mcp-notification command for generating notification handlers
• Implement notification handler framework with void return type
• Add comprehensive notification stub template with examples
• Create standard notification handlers (Progress, Cancelled, Message, Initialized)
• Add robust error handling and logging for notifications
• Add ProcessMessageData.isNotification flag for proper response routing
• Include test coverage for notification HTTP 202 behavior
• Add practical documentation with real-world examples for beginners

[claude]

Claude finished @kargnas's task —— View job

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Code Review for MCP Notification System Implementation

I've completed a comprehensive review of this pull request that implements the MCP notification system. Overall, this is a well-architected implementation that properly follows the MCP specification for notifications.

Review Progress

• Analyze notification handler framework architecture
• Review console command implementation
• Check protocol changes and HTTP response handling
• Examine notification handler implementations
• Verify test coverage and quality
• Review documentation updates
• Assess security and performance considerations
• Provide final recommendations

---

✅ Strengths

1. Excellent MCP Specification Compliance

• HTTP 202 Response: Correctly implements HTTP 202 with empty body for notifications per MCP spec (StreamableHttpController.php:43-45)
• Void Return Type: Proper void return type in NotificationHandler::execute() (NotificationHandler.php:24)
• JSON-RPC Compliance: Proper handling of notification vs request differentiation in MCPProtocol.php:122-124

2. Robust Error Handling

• Exception Isolation: Notifications errors are logged but don't propagate to clients (MCPProtocol.php:215-230)
• Unknown Method Handling: Graceful handling of unregistered notification methods with appropriate logging (MCPProtocol.php:233-243)
• Comprehensive Logging: Good error context in logs including method, client ID, params, and stack traces

3. Developer Experience

• Excellent Console Command: MakeMcpNotificationCommand provides great UX with automatic class naming, registration instructions, and usage examples
• Comprehensive Stub Template: The notification stub (notification.stub) includes extensive documentation and practical examples
• Clear Documentation: Well-documented classes with practical examples in docblocks

4. Clean Architecture

• Separation of Concerns: Clear separation between protocol handling, notification execution, and transport layers
• Consistent Patterns: Follows established patterns from the existing codebase
• Type Safety: Good use of PHP type declarations and enums

---

⚠️ Areas for Improvement

1. Potential Security Concerns

Log Injection Risk (MCPProtocol.php:218-224, ProgressHandler.php:25-32)

\Log::error('MCP Notification Handler Error', [
    'method' => $method,  // Unvalidated user input
    'params' => $notificationData->params,  // Could contain malicious data
]);

Recommendation: Sanitize or limit the size of logged parameters to prevent log injection attacks.

Input Validation Missing

• No validation of notification parameters in any handlers
• Potential for DoS through large payloads

Recommendation: Add parameter validation in notification handlers:

public function execute(?array $params = null): void
{
    $validated = validator($params ?? [], [
        'progressToken' => 'string|max:255',
        'progress' => 'integer|min:0',
        'total' => 'integer|min:1'
    ])->validate();
    
    // Use $validated instead of $params
}

2. Performance Considerations

Synchronous Logging (Multiple handlers)

• All notification handlers perform synchronous logging operations
• Could impact response times under high load

Recommendation: Consider async logging or queued processing for non-critical notifications.

No Rate Limiting

• Notifications can be sent without any rate limiting
• Potential for DoS through notification flooding

3. Code Quality Issues

Direct Log Facade Usage (Multiple files)

\Log::info('MCP Progress Update', [...]);  // Anti-pattern

Recommendation: Inject logger dependency or use Laravel's logging standards:

use Illuminate\Support\Facades\Log;

Log::info('MCP Progress Update', [...]);

Magic Numbers in Progress Calculation (ProgressHandler.php:30)

'percentage' => $total ? round(($progress / $total) * 100, 2) : null,

Recommendation: Extract to named constants for clarity.

4. Testing Gaps

Limited Test Coverage

• Only one test for HTTP 202 response (StreamableHttpTest.php:41-52)
• No tests for individual notification handlers
• No tests for error scenarios

Recommendations:

1. Add tests for each notification handler
2. Test error handling scenarios
3. Test parameter validation
4. Test logging behavior

5. Documentation Issues

Inconsistent Method Naming (MakeMcpNotificationCommand.php:158-160)

if (! Str::startsWith($method, 'notifications/')) {
    $method = 'notifications/'.ltrim($method, '/');
}

Issue: Automatically prefixes with 'notifications/' but MCP spec allows other notification types.

---

🔧 Specific Recommendations

1. Add Input Validation

Create a base validation method in NotificationHandler:

protected function validateParams(array $rules, ?array $params = null): array
{
    return validator($params ?? [], $rules)->validate();
}

2. Improve Error Handling

Add structured exception handling:

try {
    $handler->execute(params: $notificationData->params);
} catch (ValidationException $e) {
    Log::warning('Invalid notification parameters', ['errors' => $e->errors()]);
} catch (Exception $e) {
    Log::error('Notification handler failed', ['exception' => $e]);
}

3. Enhance Test Coverage

test('progress notification logs correctly', function () {
    $payload = [
        'jsonrpc' => '2.0',
        'method' => 'notifications/progress',
        'params' => ['progressToken' => 'test', 'progress' => 50, 'total' => 100]
    ];
    
    Log::shouldReceive('info')->once()->with('MCP Progress Update', Mockery::any());
    
    $response = $this->postJson('/mcp', $payload);
    $response->assertStatus(202);
});

4. Add Rate Limiting

Consider adding rate limiting middleware for notification endpoints.

---

📊 Overall Assessment

Aspect	Rating	Notes
Architecture	⭐⭐⭐⭐⭐	Clean, well-structured, follows MCP spec
Code Quality	⭐⭐⭐⭐	Good patterns, minor issues with facade usage
Security	⭐⭐⭐	Needs input validation and log sanitization
Performance	⭐⭐⭐⭐	Good, but consider async logging
Testing	⭐⭐	Basic coverage, needs expansion
Documentation	⭐⭐⭐⭐⭐	Excellent docs and examples

✅ Final Recommendation

APPROVE with suggestions for follow-up improvements. This is a solid implementation that correctly implements the MCP notification specification. The core functionality is sound, and the identified issues are primarily around security hardening and testing completeness rather than fundamental flaws.

Priority fixes for security:

1. Add input validation to notification handlers
2. Sanitize logged parameters
3. Consider rate limiting

Follow-up enhancements:

1. Expand test coverage
2. Add async logging option
3. Create validation base class

Great work on implementing a comprehensive notification system! 🎉

---

[claude]

Claude finished @kargnas's task —— View job

---

Code Review: MCP Notification System Implementation

I've completed a comprehensive review of this merged pull request that implements the MCP notification system. This is a well-architected implementation that properly follows the MCP specification.

✅ Strengths

1. Excellent MCP Specification Compliance

• HTTP 202 Response: Correctly implements HTTP 202 with empty body for notifications per MCP spec (StreamableHttpController.php:43-45)
• Void Return Type: Proper void return type in NotificationHandler::execute() (NotificationHandler.php:24)
• JSON-RPC Compliance: Proper handling of notification vs request differentiation in MCPProtocol.php:122-124

2. Robust Error Handling

• Exception Isolation: Notification errors are logged but don't propagate to clients (MCPProtocol.php:215-230)
• Unknown Method Handling: Graceful handling of unregistered notification methods with appropriate logging (MCPProtocol.php:233-243)
• Comprehensive Logging: Good error context in logs including method, client ID, params, and stack traces

3. Outstanding Developer Experience

• Excellent Console Command: MakeMcpNotificationCommand provides great UX with automatic class naming, registration instructions, and usage examples
• Comprehensive Stub Template: The notification stub includes extensive documentation and practical examples (notification.stub)
• Clear Documentation: Well-documented classes with practical examples in docblocks and README updates

4. Clean Architecture

• Separation of Concerns: Clear separation between protocol handling, notification execution, and transport layers
• Consistent Patterns: Follows established patterns from the existing codebase
• Type Safety: Good use of PHP type declarations and enums

---

⚠️ Areas for Improvement

1. Security Concerns

Log Injection Risk (MCPProtocol.php:218-224, ProgressHandler.php:25-32)

Log::error('MCP Notification Handler Error', [
    'method' => $method,  // Unvalidated user input
    'params' => $notificationData->params,  // Could contain malicious data
]);

Recommendation: Sanitize or limit the size of logged parameters to prevent log injection attacks.

Missing Input Validation

• No validation of notification parameters in any handlers
• Potential for DoS through large payloads or malformed data

Recommendation: Add parameter validation in notification handlers:

public function execute(?array $params = null): void
{
    $validated = validator($params ?? [], [
        'progressToken' => 'string|max:255',
        'progress' => 'integer|min:0',
        'total' => 'integer|min:1'
    ])->validate();
    
    // Use $validated instead of raw $params
}

2. Performance Considerations

Synchronous Logging (Multiple handlers)

• All notification handlers perform synchronous logging operations
• Could impact response times under high load

No Rate Limiting

• Notifications can be sent without any rate limiting
• Potential for DoS through notification flooding

Recommendation: Consider async logging or queued processing for non-critical notifications.

3. Code Quality Issues

Direct Log Facade Usage (Multiple files)

\Log::info('MCP Progress Update', [...]);  // Anti-pattern

Recommendation: Use proper facade imports:

use Illuminate\Support\Facades\Log;

Log::info('MCP Progress Update', [...]);

Magic Numbers (ProgressHandler.php:31)

'percentage' => $total ? round(($progress / $total) * 100, 2) : null,

Recommendation: Extract to named constants for clarity.

4. Test Coverage Gaps

Limited Test Coverage

• Only one test for HTTP 202 response (StreamableHttpTest.php:41-52)
• No tests for individual notification handlers
• No tests for error scenarios or parameter validation

Recommendations:

• Add tests for each notification handler
• Test error handling scenarios
• Test parameter validation
• Test logging behavior

---

🔧 Specific Recommendations

1. Add Input Validation Base Class

abstract class NotificationHandler
{
    protected function validateParams(array $rules, ?array $params = null): array
    {
        return validator($params ?? [], $rules)->validate();
    }
}

2. Improve Error Handling

try {
    $handler->execute(params: $notificationData->params);
} catch (ValidationException $e) {
    Log::warning('Invalid notification parameters', ['errors' => $e->errors()]);
} catch (Exception $e) {
    Log::error('Notification handler failed', ['exception' => $e]);
}

3. Enhance Test Coverage

test('progress notification logs correctly', function () {
    Log::shouldReceive('info')->once()->with('MCP Progress Update', Mockery::any());
    
    $payload = [
        'jsonrpc' => '2.0',
        'method' => 'notifications/progress',
        'params' => ['progressToken' => 'test', 'progress' => 50, 'total' => 100]
    ];
    
    $response = $this->postJson('/mcp', $payload);
    $response->assertStatus(202);
});

---

📊 Overall Assessment

Aspect	Rating	Notes
Architecture	⭐⭐⭐⭐⭐	Clean, well-structured, follows MCP spec
Code Quality	⭐⭐⭐⭐	Good patterns, minor facade usage issues
Security	⭐⭐⭐	Needs input validation and log sanitization
Performance	⭐⭐⭐⭐	Good, but consider async logging
Testing	⭐⭐	Basic coverage, needs expansion
Documentation	⭐⭐⭐⭐⭐	Excellent docs and examples

✅ Final Recommendation

APPROVE with suggestions for follow-up improvements. This is a solid implementation that correctly implements the MCP notification specification. The core functionality is sound, and the identified issues are primarily around security hardening and testing completeness rather than fundamental flaws.

Priority fixes for security:

1. Add input validation to notification handlers
2. Sanitize logged parameters
3. Consider rate limiting

Follow-up enhancements:

1. Expand test coverage
2. Add async logging option
3. Create validation base class

Great work on implementing a comprehensive notification system! 🎉

---