Sensitive Data Filter

The Sensitive Data Filter is a span processor that automatically redacts sensitive information from your AI traces before they're exported. This ensures that passwords, API keys, tokens, and other confidential data never leave your application or get stored in observability platforms.

Default Configuration

By default, the Sensitive Data Filter is automatically enabled when you use the standard Mastra configuration:

src/mastra/index.ts

export const mastra = new Mastra({
  observability: {
    default: { enabled: true }, // Automatically includes SensitiveDataFilter
  },
  storage: new LibSQLStore({
    url: "file:./mastra.db",
  }),
});

With the default configuration, the filter automatically redacts these common sensitive field names:

• password
• token
• secret
• key
• apikey
• auth
• authorization
• bearer
• bearertoken
• jwt
• credential
• clientsecret
• privatekey
• refresh
• ssn

note

Field matching is case-insensitive and normalizes separators. For example, api-key, api_key, and Api Key are all treated as apikey.

How It Works

The Sensitive Data Filter processes spans before they're sent to exporters, scanning through:

• Attributes - Span metadata and properties
• Metadata - Custom metadata attached to spans
• Input - Data sent to agents, tools, and LLMs
• Output - Responses and results
• Error Information - Stack traces and error details

When a sensitive field is detected, its value is replaced with [REDACTED] by default. The filter handles nested objects, arrays, and circular references safely.

Custom Configuration

You can customize which fields are redacted and how redaction appears:

src/mastra/index.ts

import { SensitiveDataFilter, DefaultExporter } from "@mastra/core/ai-tracing";

export const mastra = new Mastra({
  observability: {
    configs: {
      production: {
        serviceName: "my-service",
        exporters: [new DefaultExporter()],
        processors: [
          new SensitiveDataFilter({
            // Add custom sensitive fields
            sensitiveFields: [
              // Default fields
              "password",
              "token",
              "secret",
              "key",
              "apikey",
              // Custom fields for your application
              "creditCard",
              "bankAccount",
              "routingNumber",
              "email",
              "phoneNumber",
              "dateOfBirth",
            ],
            // Custom redaction token
            redactionToken: "***SENSITIVE***",
            // Redaction style
            redactionStyle: "full", // or 'partial'
          }),
        ],
      },
    },
  },
});

Redaction Styles

The filter supports two redaction styles:

Full Redaction (Default)

Replaces the entire value with a fixed token:

// Before
{
  "apiKey": "sk-abc123xyz789def456",
  "userId": "user_12345"
}

// After
{
  "apiKey": "[REDACTED]",
  "userId": "user_12345"
}

Partial Redaction

Shows the first and last 3 characters, useful for debugging without exposing full values:

new SensitiveDataFilter({
  redactionStyle: "partial",
});

// Before
{
  "apiKey": "sk-abc123xyz789def456",
  "creditCard": "4111111111111111"
}

// After
{
  "apiKey": "sk-…456",
  "creditCard": "411…111"
}

Values shorter than 7 characters are fully redacted to prevent information leakage.

Field Matching Rules

The filter uses intelligent field matching:

1. Case-Insensitive: APIKey, apikey, and ApiKey are all matched
2. Separator-Agnostic: api-key, api_key, and apiKey are treated identically
3. Exact Matching: After normalization, fields must match exactly
   • token matches token, Token, TOKEN
   • token does NOT match promptTokens or tokenCount

Nested Object Handling

The filter recursively processes nested structures:

// Before
{
  "user": {
    "id": "12345",
    "credentials": {
      "password": "SuperSecret123!",
      "apiKey": "sk-production-key"
    }
  },
  "config": {
    "auth": {
      "jwt": "eyJhbGciOiJIUzI1NiIs..."
    }
  }
}

// After
{
  "user": {
    "id": "12345",
    "credentials": {
      "password": "[REDACTED]",
      "apiKey": "[REDACTED]"
    }
  },
  "config": {
    "auth": {
      "jwt": "[REDACTED]"
    }
  }
}

Performance Considerations

The Sensitive Data Filter is designed to be lightweight and efficient:

• Synchronous Processing: No async operations, minimal latency impact
• Circular Reference Handling: Safely handles complex object graphs
• Error Recovery: If filtering fails, the field is replaced with an error marker rather than crashing

Disabling the Filter

If you need to disable sensitive data filtering (not recommended for production):

src/mastra/index.ts

export const mastra = new Mastra({
  observability: {
    configs: {
      debug: {
        serviceName: "debug-service",
        processors: [], // No processors, including no SensitiveDataFilter
        exporters: [new DefaultExporter()],
      },
    },
  },
});

warning

Only disable sensitive data filtering in controlled environments. Never disable it when sending traces to external services or shared storage.

Common Use Cases

Healthcare Applications

new SensitiveDataFilter({
  sensitiveFields: [
    // HIPAA-related fields
    "ssn",
    "socialSecurityNumber",
    "medicalRecordNumber",
    "mrn",
    "healthInsuranceNumber",
    "diagnosisCode",
    "icd10",
    "prescription",
    "medication",
  ],
});

Financial Services

new SensitiveDataFilter({
  sensitiveFields: [
    // PCI compliance fields
    "creditCard",
    "ccNumber",
    "cardNumber",
    "cvv",
    "cvc",
    "securityCode",
    "expirationDate",
    "expiry",
    "bankAccount",
    "accountNumber",
    "routingNumber",
    "iban",
    "swift",
  ],
});

Error Handling

If the filter encounters an error while processing a field, it replaces the field with a safe error marker:

{
  "problematicField": {
    "error": {
      "processor": "sensitive-data-filter"
    }
  }
}

This ensures that processing errors don't prevent traces from being exported or cause application crashes.

Related

• SensitiveDataFilter API
• Basic AI Tracing Example