PII redaction proxy for LLM API calls

The idea

Every healthtech, legaltech, and fintech startup has the same stalled Jira epic: an LLM feature the compliance officer keeps vetoing because raw client text would leave the building. The engineers know the models are good enough; the blocker is purely that patient names, SSNs, and case details cannot legally transit a third-party API. Today teams either ship nothing or hand-roll a regex scrubber that misses half the entities and mangles the model’s output.

LLM Gateway proved developers happily route provider traffic through middleware. But gateways compete on routing and cost, which is a nice-to-have budget. This competes on the compliance checkbox: deterministic entity tokenization on the way in, re-hydration on the way out, and an audit log proving exactly what left the building. Adoption is one base-URL swap — the same near-zero integration cost that made gateways spread — but the purchase is made under regulatory pressure, which approves faster and churns slower.

Who pays

The buyer is an engineering lead at a seed-to-B healthtech, legaltech, or fintech company, unblocking a roadmap feature; the compliance officer is the internal champion. Price $99-499/mo across three tiers keyed to request volume, with BAA signing and self-hosting reserved for the top tier. Distribution: HIPAA-plus-LLM content SEO, HN and r/healthIT presence, and integration listings in the LangChain and Vercel AI SDK ecosystems.

MVP scope

• Reverse proxy supporting OpenAI and Anthropic chat endpoints, streaming included
• NER-based detection for names, SSNs, MRNs, DOBs, addresses, phones, emails, plus custom regex
• Deterministic per-conversation tokenization and response re-hydration
• Audit log with per-request redaction diffs, encrypted at rest
• Stripe billing on request volume
• Skip for v1: BAA/self-host tier, fine-tuned custom NER per customer, embeddings and image endpoints, SOC 2 (start the process, don’t wait on it)

Build Redactle, a PII redaction proxy for LLM API calls. Stack: a Go reverse proxy (Node acceptable for v1), local NER models for entity detection, Postgres for audit logs and config, Stripe for billing.

Core flow: customer swaps their OpenAI or Anthropic base URL for their Redactle endpoint and keeps their own provider key. The proxy intercepts each request, runs NER over every message, replaces detected entities with deterministic tokens (PERSON_1, SSN_1, DATE_3), forwards the sanitized request to the provider, then re-hydrates tokens in the response body before returning it. Streaming responses are re-hydrated chunk-by-chunk with a buffer that holds back partial token matches until enough characters arrive to resolve them.

Non-obvious details: tokenization must be deterministic within a conversation — the same name maps to the same token across turns, keyed by a per-request-supplied conversation ID — or multi-turn chats break. Store only entity hashes and token mappings encrypted per-customer, never raw values, so the audit log itself is not a liability.

Dashboard pages: setup (base-URL snippet per SDK), entity policy editor (toggle categories: names, SSNs, MRNs, addresses, custom regex), audit log with per-request diffs of what was stripped, usage, billing.

Pricing: Starter $99/mo (500k requests), Growth $249/mo (3M requests, custom entities), Compliance $499/mo (BAA, SSO, self-host option).