strangerDanger

Secret and PII redaction guard for AI coding agents.

The Problem

Every secret scanner checks your files. None check what goes into the LLM's context window. A secret can be clean in your repo and still get sent to a cloud API inside a prompt, checkpoint, or shell summary. strangerDanger operates at three layers to catch what others miss.

How It Works — Three Layers of Protection

• Layer 1: File-level (before reads) — Intercepts file reads, redacts secrets in-place before the agent sees them.
• Layer 2: Context-level (before compaction) — Scans everything injected into the LLM context during session compaction. Also scans outbound user messages.
• Layer 3: Output-level (after tool execution) — Scans tool outputs before they're written to disk.

Installation

OpenCode Plugin

Add to your opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["@gitdamnit/stranger-danger"]
}

Standalone CLI

npm install -g @gitdamnit/stranger-danger

Use with envsitter-guard

strangerDanger and envsitter-guard are complementary:

• envsitter-guard blocks .env* file reads entirely
• strangerDanger scans everything else and protects the context window

Use both for complete coverage.

Quick Start

Plugin

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["@gitdamnit/stranger-danger"]
}

CLI

sd scan .                    # Scan current directory
sd scan src/config.ts        # Scan a single file
sd scan - < file.txt         # Scan stdin
sd redact src/config.ts      # Redact secrets in-place (creates .backup)
sd audit                     # Show audit log
sd rules                     # List all active rules

Detection Rules

• ~160 rules vendored from gitleaks (MIT)
• ~12 clean-room additions for AI/ML providers (Groq, DeepSeek, Replicate, ElevenLabs, etc.)
• 3 entropy-based detectors (Base64, Hex, Alphanumeric)

Key Providers Covered

| Category | Providers | |----------|-----------| | Cloud | AWS, GCP, Azure, Alibaba, DigitalOcean, Heroku, Cloudflare | | AI/ML | OpenAI, Anthropic, Groq, DeepSeek, Cohere, HuggingFace, Replicate, ElevenLabs | | Version Control | GitHub, GitLab, Bitbucket | | Communication | Slack, Discord, Telegram, Twilio, SendGrid, Mailgun | | Payment | Stripe, Square, PayPal, Coinbase, Plaid | | Databases | MongoDB, PostgreSQL, Redis (connection strings) | | Generic | Private keys, JWTs, high-entropy strings |

OpenCode Plugin Tools

• sd_status — Show rule count, findings, audit log path
• sd_audit — Show audit log with timestamps and rule IDs
• sd_allowlist_add — Add allowlist entry
• sd_allowlist_show — Show current allowlist
• sd_scan — Manually scan content

Allowlist

Create .strangerdanger-allowlist.toml in your project root:

[[entries]]
description = "Known test key"
fingerprint = "a3f7b2c1"

[[entries]]
description = "Ignore generic-api-key in test files"
ruleId = "generic-api-key"
path = "test/"

Entry types: fingerprint, ruleId, path, regex.

Audit Log

Location: .opencode/state/strangerdanger-audit.jsonl

Format: one JSON line per finding. Logs fingerprint, rule ID, timestamp, and source. Never logs the actual secret value.

Architecture

src/engine/     → Core detection engine (zero OpenCode deps)
src/plugin/     → OpenCode plugin hooks
src/cli/        → Standalone CLI (sd binary)

Zero runtime dependencies beyond @opencode-ai/plugin. Node.js built-ins only.

Development

npm install          # Install dependencies
npm run build:rules  # Compile gitleaks TOML → TypeScript
npm run build        # Build all TypeScript
npm run typecheck    # Type check
npm test             # Run tests

Adding New Rules

Edit scripts/compile-rules.ts to add clean-room rules. The gitleaks TOML is compiled automatically at build time.

Attribution

• gitleaks/gitleaks (MIT) — Secret detection rules vendored from config/gitleaks.toml. https://github.com/gitleaks/gitleaks
• Yelp/detect-secrets (Apache-2.0) — Shannon entropy detection approach referenced for high-entropy string detectors. Clean-room TypeScript implementation. https://github.com/Yelp/detect-secrets
• boxpositron/envsitter-guard (MIT) — Complementary plugin. strangerDanger coordinates with envsitter-guard to avoid duplicating .env* file blocking. https://github.com/boxpositron/envsitter-guard

License

MIT. See LICENSE.