PHI Guard

Every AI request on the HASP platform flows through PHI Guard before it reaches an upstream model. PHI Guard is a mandatory compliance layer — it cannot be disabled — and it operates on the raw message content before any inference is performed.

What it does

PHI Guard scans outbound messages for Protected Health Information (PHI) using a combination of statistical NER and rule-based detectors (powered by Microsoft Presidio). On detection, it applies your org’s configured phi_mode.

phi_mode values

Mode	Behavior
`redact` (default)	Detected PHI entities are replaced with placeholders (e.g., `[PERSON]`, `[US_SSN]`) before the message is sent upstream. The response streams normally. The stored message row contains both the original encrypted content and the redaction metadata.
`block`	Any message containing PHI returns `403 PHI_BLOCKED` immediately — no inference is performed. The error response includes `details.entity_types` listing what was detected.

phi_mode=off is not a valid state. Every organization operates under a compliance posture. Configure phi_mode in Settings → AI Workspace → PHI Mode.

What counts as PHI

The scanner detects the 18 HIPAA identifier categories, including:

Names, geographic data, dates (other than year), phone numbers, fax numbers
Email addresses, SSNs, medical record numbers, account numbers
Certificate/license numbers, vehicle identifiers, device identifiers
URLs, IP addresses, biometric identifiers, full-face photos

PHI_BLOCKED error (phi_mode=block)

{
  "success": false,
  "error": {
    "code": "PHI_BLOCKED",
    "type": "forbidden",
    "message": "Message contains PHI that cannot be sent without redaction.",
    "param": "messages[0].content",
    "details": {
      "entity_types": ["US_SSN", "PERSON"]
    },
    "retryable": false,
    "request_id": "req_01JQREQ000000000000000000",
    "docs_hint": "https://docs.usehasp.com/ai-api/concepts/phi-guard"
  },
  "meta": { "request_id": "req_01JQREQ000000000000000000" }
}

Tool schema scanning

PHI Guard also scans tool definitions (function schemas) passed in the request. If a tool name, description, or parameter description contains PHI, the request is rejected with 400 PHI_IN_TOOL_SCHEMA regardless of phi_mode. This rule cannot be relaxed — tool schemas are stored in plaintext in the model provider’s infrastructure and are not subject to the redaction pipeline.

PHI Guard on /v1/messages (Anthropic-compat)

PHI Guard applies identically on the Anthropic-compat endpoint. The error shape uses the HASP envelope with Anthropic-compatible type: "invalid_request_error" for PHI_IN_TOOL_SCHEMA; PHI_BLOCKED returns 403 using the standard HASP error envelope (not Anthropic’s shape, since Anthropic has no equivalent concept).

Audit trail

Every PHI scan result — regardless of whether PHI was found — is recorded in the HIPAA audit log. The AI gateway writes an audit event for each of the three pipeline phases: pre-flight, scan, and post-stream credit deduction. Audit records are available via GET /v1/audit and in Settings → Compliance → Audit Log.

AI Studio

Platform

AI API

App Builder SDK

What it does

phi_mode values

What counts as PHI

PHI_BLOCKED error (phi_mode=block)

Tool schema scanning

PHI Guard on /v1/messages (Anthropic-compat)

Audit trail

​What it does

​phi_mode values

​What counts as PHI

​PHI_BLOCKED error (phi_mode=block)

​Tool schema scanning

​PHI Guard on /v1/messages (Anthropic-compat)

​Audit trail

What it does

phi_mode values

What counts as PHI

PHI_BLOCKED error (phi_mode=block)

Tool schema scanning

PHI Guard on /v1/messages (Anthropic-compat)

Audit trail