flyyy-guard

Block prompt injection before it reaches your LLM, using FLYYY's guardrail check.

The user's prompt is sent once to FLYYY's /api/v1/guardrails/check endpoint before the agent starts, where an LLM judge decides whether it is a prompt injection. If it is, the agent stops and returns a refusal; neither the model nor any tool is called. Otherwise the agent runs normally with no further checks. Every check shows up in FLYYY → AI Governance → GenAI Governance → your project → Guardrails.

Quickstart (LangChain create_agent)

1. Install:

   pip install "flyyy-guard[langchain]"
   # or, in a uv project
   uv add "flyyy-guard[langchain]"
   

2. Add FLYYY_URL to the .env that already holds your project's Langfuse keys. The guard authenticates with those same keys, so no extra key is needed:

   LANGFUSE_PUBLIC_KEY=pk-lf-...
   LANGFUSE_SECRET_KEY=sk-lf-...
   FLYYY_URL=https://<your-flyyy-backend>
   

   If you were given a guardrail key (FLYYY_GUARDRAIL_KEY=fg_...), it is used instead.
3. Add the middleware where you create the agent:

   from flyyy_guard import FlyyyGuardMiddleware
   
   agent = create_agent(
       model=model,
       tools=tools,
       system_prompt=system_prompt,
       checkpointer=checkpointer,
       middleware=[FlyyyGuardMiddleware()],
   )
   

Nothing else changes: agent.invoke(...), your Langfuse CallbackHandler, tools and prompts stay as they are. The conversation's thread_id is sent as the session id automatically.

When a prompt is blocked, agent.invoke returns normally and the last message is "Your request was blocked by policy.". Its response_metadata["flyyy_guard"] holds the attack type, risk score and FLYYY request id. The blocked text is replaced in the stored conversation so it is never sent to the model on later turns.

Any other framework

pip install flyyy-guard

from flyyy_guard import check

decision = check(user_prompt, session_id=session_id)
if not decision.allowed:
    return "Your request was blocked by policy."
response = llm.invoke(user_prompt)

check_or_raise(...) does the same but raises PromptBlockedError.

Options

A rejected or revoked guardrail key always blocks, whatever the fail-open setting, so a misconfiguration is noticed instead of silently turning protection off.

Privacy

The guard sends only the text being checked and the session id. It never logs your key or the prompt text. FLYYY stores a short preview of each checked input for the Guardrails view.