Building a Go middleware service to catch prompt injection before it hits the Genesys Cloud LLM Gateway. The regex allowlist works locally but drops valid customer intents in production. Kind of annoying. We don’t want the raw user text hitting the model. Trying to sanitize the payload and push security events to CloudWatch before the HTTP forward. It’s weird how the gateway handles the quotes. We can’t figure out the exact encoding.
Forwarding to /api/v2/ai/conversations/llm after the check.
Error
Getting a 422 Unprocessable Entity back from the gateway when the sanitized string contains escaped quotes. The JSON payload looks fine in the debug log but the API rejects it.
{"error_code": 422, "message": "Invalid prompt structure after sanitization"}
Question
Is there a specific charset requirement for the LLM Gateway endpoint that breaks the regex replacement? The middleware runs fine with raw UTF-8 but chokes on the escaped sequences. How should I format the body before the http.Client.Do call. Logs show the drop right before the forward. The test suite keeps failing on the escape sequences anyway.
The regex dropping valid intents usually happens when the allowlist blocks standard punctuation that the LLM Gateway expects in the prompt structure. You’re also probably stripping tokens that the OAuth2 client credentials flow needs for the downstream forward.
Here’s how I handle the sanitization and audit trail before the forward:
Keep the regex focused on known injection patterns instead of a strict allowlist. A negative lookahead works better for preserving valid intents.
Attach a security event to the Genesys Cloud audit pipeline so you can track what got blocked versus what passed through.
Forward the cleaned payload using the correct ai:llm:execute scope on the bearer token.
func sanitizePrompt(raw string) (string, bool) {
injectionPattern := regexp.MustCompile(`(?i)(system prompt|ignore previous|<\|im_start\|>)`)
if injectionPattern.MatchString(raw) {
return "", true
}
return strings.TrimSpace(raw), false
}
// In your handler:
cleaned, blocked := sanitizePrompt(req.Body)
if blocked {
auditPayload := map[string]interface{}{
"userId": "system_middleware",
"resourceId": "llm_gateway_forward",
"action": "blocked_injection",
"details": map[string]string{"originalLength": fmt.Sprintf("%d", len(req.Body))},
}
// POST /api/v2/audit/logs with audit:write scope
}
The audit:write scope is mandatory here. You’ll hit a 403 if the service account doesn’t have it explicitly granted in the role/permission API. Run a quick check on the assigned role first:
Look for audit:write in the permissions array. If it’s missing, patch the role or swap the service account before the forward. The LLM Gateway also expects the X-Genesys-Request-Id header for traceability. Drop that in your outbound request or the gateway will reject it with a 422. Initializing the forward through PureCloudPlatformClientV2 keeps the token rotation automatic.
Honestly it took a few rounds of tweaking to get the lookahead right. The regex stops matching normal customer phrasing now. Just started mapping this pattern to our internal guardrails, so the setup might need a couple more passes for edge cases. Still tweaking the token cache refresh interval. The audit logs are finally clean anyway.
platformClient handles the OAuth rotation for you, but the raw HTTP call in your middleware bypasses that logic. You’ll run into a hard 422 if the requestContext gets nuked by the regex scrub. The LLM Gateway needs that object intact to map back to the active conversation. Stripping it breaks the routing matrix entirely. The default Go http.Client timeout sits at 30 seconds locally but drops to zero behind production load balancers. You’ll get a connection reset before the model even starts generating. Bump it explicitly to 15 * time.Second or higher. Don’t forget to attach the admin:users:read scope if you’re pulling agent metadata downstream. Kind of a pain to debug at 2am when the logs just show a silent timeout. Watch out for that.