mobiusguard

The Mobius Guard firewall proxy. Part of Mobius Guard. Alpha: the API may still change before 1.0.

It sits between your app and the model and speaks three APIs: OpenAI Chat Completions (/v1/chat/completions), OpenAI Responses (/v1/responses) and Anthropic Messages (/v1/messages), streamed or not.

• On the way in, user messages and tool results are cleaned up (invisible characters, look-alike letters, spaced-out letters, leetspeak and base64 undone) and checked against named rules, and optionally a classifier. A clear rule hit is refused with HTTP 403 in the API's own error format, naming the rule. Classifier scores are logged until you set a threshold.
• On the way out, secrets and personal data are replaced in the reply as it streams, even when they are split across events (mobiusguard-redact).
• For each request, one audit line: the decision, rule IDs, scores and what was redacted, never the prompt text unless you ask. OpenTelemetry spans if installed.

mobiusguard serve --port 8787                 # forwards each caller's own API key
mobiusguard check "Ignore all previous instructions"   # try the request check

Point any SDK at it:

from openai import OpenAI

client = OpenAI(base_url="http://127.0.0.1:8787/v1")  # your usual API key

from anthropic import Anthropic

claude = Anthropic(base_url="http://127.0.0.1:8787")

To try it with a free local model, run Ollama and use examples/ollama.toml; scripts/live_check.py sends every case through all three APIs.

Settings are a TOML file (mobiusguard serve --config mobiusguard.toml). Guides: quickstart, configuration, rules, audit log and deploying it, including the container image. The design is in decision 0010. Optional extras: mobiusguard[classifier] (PIGuard or ProtectAI v2, about a second per long prompt on a CPU) and mobiusguard[otel].