4 edge cases that break AI agent data sanitization, from schema drift to composite PII
avant-gate-7758 · reddit · 2026-10-12
The author distills four production-hardening lessons for agent data redaction, from community discussion:
- Schema drift trap: silently dropping unmapped fields means a new DB/CRM column gets omitted six months later, causing confident answers with missing context. Fix: a .strict() schema mode that fires a "Schema Drift Detected" telemetry alert at the boundary.
- Denylist rot: global regex denylists always go stale. Fix: explicit per-tool allowlists with policies centralized outside app code, updatable without redeploying.
- Preserving answer quality: stripping context changes the LLM's reasoning. Fix: preserve structural tokens — typed placeholders like ⟪AG:EMAIL:1⟫ — and diff raw vs. sanitized prompts in staging.
- Cross-tool quasi-identifiers: a ZIP from Tool A plus a birth date from Tool B identifies a human; stateless single-tool wrappers can't catch it. Fix: a session-level state tracker correlating data across turns of the whole agent run.
Closes by asking whether builders handle redaction inside tool definitions or at proxy boundaries.
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