OpenCode Filter sits between your codebase and AI assistants, automatically detecting and replacing sensitive information before it reaches the model. It ensures your API keys, passwords, tokens, and other secrets remain secure while you work with AI-powered development tools.

Key Features

230 Built-in Detection Patterns: Comprehensive coverage across 8 categories (Cloud, Code Hosting, Communication, Payment, Authentication, SaaS, Infrastructure, Generic)
Dual Detection Engine: Combines regex pattern matching with entropy analysis to catch even obfuscated secrets
95.12% Real-World Accuracy: Validated against 205 real secret examples from production environments
HMAC-SHA256 Placeholders: Replaces secrets with cryptographically secure, deterministic placeholders that preserve context without exposing data
Interactive Config Wizard: Easy setup with npx opencode-filter init
Visual Feedback: Status bar indicators, tooltips, and warnings show what's being filtered
Audit Logging: Structured logs for compliance and security review
Fail-Closed Security: If the filter fails, it defaults to blocking (not leaking) rather than allowing potentially sensitive data through
Performance Optimized: Sub-millisecond processing overhead with streaming support for large files
Zero Configuration: Works out of the box with sensible defaults, fully customizable when needed

Installation

Via npm/yarn/pnpm

npm install opencode-filter

OpenCode Configuration

Add to your opencode.json:

{
  "plugins": [
    "opencode-filter"
  ]
}

Or with configuration:

{
  "plugins": [
    ["opencode-filter", {
      "enabled": true,
      "mode": "redact",
      "entropyThreshold": 4.5
    }]
  ]
}

Quick Start

Install the plugin
Run the setup wizard: npx opencode-filter init
Start OpenCode - your secrets are now protected!

Features

🔒 192 Secret Patterns - Detects AWS, GitHub, Stripe, and 180+ more
🔔 Visual Feedback - Toast notifications when secrets are filtered
📊 Status Panel - View filter stats with /filter status
📝 Audit Logging - Track what was filtered (without storing secrets)
⚡ Performance - <1ms processing time
🛡️ Fail-Closed - Blocks on errors (security first)

Configuration

The filter reads configuration from filter.config.json in your project root (or a custom path via FILTER_CONFIG_PATH environment variable).

Default Configuration

Create a filter.config.json file:

{
  "enabled": true,
  "mode": "fail-closed",
  "patterns": {
    "builtIn": "all",
    "custom": []
  },
  "placeholder": {
    "type": "hmac-sha256",
    "prefix": "FILTERED_"
  },
  "performance": {
    "maxFileSize": "10MB",
    "streamingThreshold": "1MB",
    "cacheSize": 1000
  },
  "logging": {
    "level": "warn",
    "redactLogs": true
  }
}

Configuration Options

Option	Type	Default	Description
`enabled`	boolean	`true`	Enable/disable the filter globally
`mode`	string	`"fail-closed"`	Security mode: `"fail-closed"` (block on error) or `"fail-open"` (allow on error)
`patterns.builtIn`	string/array	`"all"`	Which built-in patterns to use: `"all"` or array of pattern names
`patterns.custom`	array	`[]`	Custom regex patterns with name and priority
`placeholder.type`	string	`"hmac-sha256"`	Placeholder algorithm: `"hmac-sha256"`, `"hash"`, or `"uuid"`
`placeholder.prefix`	string	`"FILTERED_"`	Prefix for generated placeholders
`performance.maxFileSize`	string	`"10MB"`	Maximum file size to process
`performance.streamingThreshold`	string	`"1MB"`	File size threshold for streaming mode
`performance.cacheSize`	number	`1000`	Size of the deduplication cache
`logging.level`	string	`"warn"`	Log level: `"error"`, `"warn"`, `"info"`, `"debug"`
`logging.redactLogs`	boolean	`true`	Whether to filter secrets from log output

Custom Patterns Example

{
  "patterns": {
    "builtIn": ["api-key", "database-url", "private-key"],
    "custom": [
      {
        "name": "internal-token",
        "pattern": "x-internal-[a-zA-Z0-9]{32}",
        "priority": 100,
        "entropyThreshold": 4.5
      },
      {
        "name": "company-secret",
        "pattern": "company-secret-[a-zA-Z0-9]+",
        "priority": 90
      }
    ]
  }
}

Built-in Pattern Categories (230 patterns)

Cloud Providers (30 patterns)

AWS: Access keys, secret keys, session tokens, S3 credentials
Azure: Service principals, storage keys, connection strings
GCP: Service account keys, API keys, OAuth tokens

Code Hosting (15 patterns)

GitHub: Personal access tokens, OAuth apps, SSH keys
GitLab: Access tokens, CI/CD variables
Bitbucket: App passwords, access tokens

Communication (20 patterns)

Slack: Bot tokens, user tokens, webhooks
Discord: Bot tokens, webhooks
Teams: Webhooks, app credentials
Telegram: Bot tokens

Payment (15 patterns)

Stripe: Live/test keys, restricted keys, webhooks
PayPal: Client IDs, secrets, webhooks
Square: Application secrets, access tokens
Braintree: API keys, merchant IDs

Authentication (25 patterns)

JWT: HS256/RS256 tokens with various claim patterns
OAuth: Bearer tokens, refresh tokens, authorization codes
API Keys: Generic and provider-specific formats

SaaS Platforms (60 patterns)

Twilio, SendGrid, Mailgun (email/SMS)
PagerDuty, Datadog, New Relic (monitoring)
Shopify, WooCommerce (e-commerce)
And 40+ more services

Infrastructure (30 patterns)

Database URLs with embedded credentials
SSH private keys (RSA, ECDSA, Ed25519)
SSL/TLS certificates and keys
Docker registry credentials
Kubernetes secrets

Generic (15 patterns)

Password patterns in various formats
Secret key patterns
Token patterns
High-entropy strings

CLI Commands

Interactive Configuration Wizard

Set up the filter interactively with a guided wizard:

npx opencode-filter init

The wizard will guide you through:

Enable/disable the filter
Security mode: Fail-closed vs fail-open
Pattern selection: Choose which categories to enable
Performance settings: File size limits and caching
Visual feedback: Status bar and tooltip preferences
Audit logging: Enable structured logging for compliance

CLI Commands

View Audit Logs

View filtered secrets (without exposing actual values):

# Show recent activity
npx opencode-filter audit

# Show last 50 entries
npx opencode-filter audit --limit 50

# Show specific category
npx opencode-filter audit --category AWS

# Export to file
npx opencode-filter audit --export audit-log.json

Check Status

# Show filter status and statistics
npx opencode-filter status

Usage

Basic Usage

Once installed and configured, the filter automatically processes all input/output:

// This code contains a secret
const apiKey = "sk-live-abc123def456ghi789";

// The AI sees:
const apiKey = "FILTERED_a3f8c9d2e1b4";

Before and After Example

Original Input:

// config.js
export default {
  apiKey: "sk-live-51nN2h4xP9qR3tK8mJ7vW6yZ0aB1cD",
  databaseUrl: "postgres://user:password123@localhost:5432/mydb",
  jwtSecret: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."
};

What the AI Model Receives:

// config.js
export default {
  apiKey: "FILTERED_8f2a9c4d1e7b",
  databaseUrl: "postgres://FILTERED_3b5e8a1c9d2f:FILTERED_7c4b9e2a1d8f@localhost:5432/mydb",
  jwtSecret: "FILTERED_9d1e7b3a5c8f"
};

When Returned to You:

// config.js
export default {
  apiKey: "sk-live-51nN2h4xP9qR3tK8mJ7vW6yZ0aB1cD",
  databaseUrl: "postgres://user:password123@localhost:5432/mydb",
  jwtSecret: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."
};

Emergency Disable

If you need to temporarily disable the filter (not recommended):

# Environment variable (current session only)
export OPENCODE_FILTER_ENABLED=false

# Or in opencode.json
{
  "plugins": [
    ["opencode-filter", {
      "enabled": false
    }]
  ]
}

Warning: Disabling the filter exposes all secrets to the AI model. Use with extreme caution and only in trusted environments.

Security Considerations

How Secrets Are Protected

Detection: The filter scans all input using a combination of:
- Known pattern regex matching for common secret formats
- Entropy analysis to detect high-randomness strings that may be secrets
- Contextual analysis to reduce false positives
Replacement: Detected secrets are replaced with:
- HMAC-SHA256 hash of the secret (using a session key)
- Consistent prefix for easy identification
- Deterministic generation (same secret = same placeholder)
Session Key Management: Each OpenCode session uses a unique key for HMAC generation, ensuring:
- Placeholders cannot be reversed to original values without the session key
- Keys are ephemeral and destroyed when the session ends
- No secrets are persisted in placeholder form
Reconstruction: When the AI response returns, placeholders are matched back to original values using:
- In-memory mapping (secret hash -> original value)
- No disk storage or logging of secret mappings
- Automatic cleanup on session termination

Fail-Closed Mode

By default, the filter operates in "fail-closed" mode. This means:

If pattern loading fails: Input is blocked
If detection engine crashes: Input is blocked
If replacement fails: Output is blocked
If any unexpected error occurs: Data flow stops

This ensures sensitive data never leaks due to a malfunction. To change this behavior (not recommended):

{
  "mode": "fail-open"
}

Session Management

All secret mappings exist only in memory
No persistence to disk, even temporarily
Keys are rotated every 24 hours or on session restart
Memory is wiped on graceful shutdown

Visual Feedback

The filter provides visual indicators to keep you informed about what's happening:

Status Bar

🔒 Filtered 3 secrets

Shows the number of secrets filtered in the current session.

Tooltips

Hover over filtered content to see details:

1 AWS Key, 2 Password patterns detected

Warning Indicators

When high-severity secrets are detected:

⚠️  Critical secrets detected (AWS, Stripe)

Enable/Disable Visual Feedback

{
  "feedback": {
    "enabled": true,
    "showStatusBar": true,
    "showTooltips": true,
    "showWarnings": true,
    "minSeverity": "medium"
  }
}

Performance

Benchmarks

Tested on AMD Ryzen 7 5800X with 32GB RAM:

Input Size	Processing Time	Memory Usage
1KB	68μs (p95)	<1MB
10KB	827μs (p95)	<2MB
100KB	27.3ms (p95)	<5MB

Optimization Tips

Use streaming mode for files >1MB
Adjust cache size based on your typical file count
Selective pattern loading - only enable patterns you need
Enable streaming threshold for large repositories

Best Practices

Keep the filter enabled: Only disable in true emergencies
Use custom patterns: Add company-specific secret formats
Monitor logs: Check for false positives (legitimate text being filtered)
Review AI output: Always verify reconstructed content looks correct
Rotate secrets: If you suspect a leak, rotate the exposed secret immediately

Troubleshooting

Common Issues

Issue: Legitimate code/text is being filtered

Symptoms: Non-secret strings are replaced with placeholders.

Solutions:

Adjust the entropy threshold in custom patterns
Add exceptions using negative lookaheads in regex
Disable specific built-in patterns if they cause issues:

{
  "patterns": {
    "builtIn": ["api-key", "aws-key", "github-token"]
  }
}

Issue: Secrets are not being detected

Symptoms: API keys appear in AI responses.

Solutions:

Enable debug logging to see what patterns are loaded
Check if the pattern exists for your secret format
Add a custom pattern for your specific secret type
Verify the filter is enabled in configuration

Issue: Performance slowdown

Symptoms: Noticeable delay in file processing.

Solutions:

Increase the streaming threshold for large files
Reduce cache size if memory is constrained
Disable entropy detection for non-critical files
Use pattern allowlists to limit which patterns are checked

Debug Mode

Enable detailed logging:

{
  "logging": {
    "level": "debug",
    "redactLogs": false
  }
}

Warning: Setting redactLogs to false may log detected secrets for debugging. Only use in isolated environments.

Performance Tips

Use streaming for large files: Files over 1MB automatically stream
Limit pattern scope: Only enable patterns you need
Adjust cache size: Balance memory usage vs. deduplication efficiency
Pre-filter known safe files: Use .filterignore for directories with only safe content

Getting Help

Documentation: https://docs.opencode.dev/filter
Issues: https://github.com/opencode/filter/issues
Discord: OpenCode Community
Email: security@opencode.dev (for security-related issues only)

Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines on:

Setting up the development environment
Running tests
Submitting pull requests
Adding new detection patterns
Security disclosure process

Quick Start for Contributors

git clone https://github.com/opencode/filter.git
cd filter
npm install
npm test

License

OpenCode Filter is released under the MIT License.

MIT License

Copyright (c) 2024 OpenCode

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Security Note: This filter provides defense-in-depth but is not a substitute for proper secret management. Always use dedicated secret management solutions (like HashiCorp Vault, AWS Secrets Manager, or environment variables) for production credentials.

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