Taint Engine

When taintEnabled: true (the default), the Taint Engine tracks secrets that have been transformed — summaries, embeddings, redacted copies. If a derived value appears in a later checkpoint, it is caught and redacted.

Usage

const taint = guard.getTaintEngine();
 
// Tag a derived value — mark it as originating from a secret
taint.tag('summary of sk-123', 'sec_abc123', 'manual');
 
// Later, when this value appears in state, it is caught
const clean = await guard.checkpoint({
  summary: 'summary of sk-123'  // ← tainted, will be vaulted
});

Propagation Rules

Operation	Taint behaviour
Direct assignment	Taint preserved
String concatenation	Result tainted if any operand is tainted
JSON.parse / JSON.stringify	Taint metadata survives round-trip
Object spread	Nested tainted values remain tainted

Both the vault reference token and the original secret are tagged — taint tracking catches “secret laundering” whether the agent uses the ref or the original value.

API

tag(value: any, secretId: string, source?: string): void
getTaints(value: any): TaintMetadata[]
propagate(sources: any[], derived: any): void
untaint(value: any): void

interface TaintMetadata {
  secretId: string;
  source: string;
  timestamp: number;
}