Ship AI agents with real-time budget, policy, and human-approval gates.
Zero-refactor cost control, tool policy enforcement, and audit trail for any LLM-powered agent — works with OpenAI, Anthropic, LangGraph, CrewAI, AutoGen, LlamaIndex, and your own stack.
Quickstart · Docs · Examples
⚠️ Status: alpha (v0.14.7, protocol v3.31.6). The public API may shift between minor versions. Pin your dependency and read the CHANGELOG before upgrading.
AI agents can overspend, call dangerous tools, and act without audit trails. Existing observability tools tell you after the fact. NullRun enforces before the action.
| Without NullRun | With NullRun |
|---|---|
Agent calls gpt-4o 10,000 times → surprise $5,000 invoice |
Hard budget cap → SDK blocks at 402 before invocation |
Agent runs bash rm -rf / |
Tool policy → SDK blocks at 403 before execution |
| Sensitive action with no human in the loop | Approval flow → SDK pauses and waits for WS approval_resolved push |
| Cost & calls scattered across 4 libraries | Single source of truth: per-org, per-workflow, per-execution |
Runaway SDK loop calling /gate without /track |
Per-reservation rate cap → 402 budget error (see docs/errors/NR-R001.md) |
| Hard & soft budget gates — atomic Redis-enforced, no client-trust model | Tool policy enforcement — block dangerous tools before execution |
Human-in-the-loop approvals — pause agent and await approval_resolved via WS push |
Immutable audit trail — every decision, every tool call, every cent |
Zero-code instrumentation — nullrun.init() patches httpx once for any vendor |
LangGraph, CrewAI, AutoGen, LlamaIndex — first-class integrations |
| Memory-safe streaming — 16 MiB response body cap (anti-OOM); full body for usage extraction | Lightweight — no LLM-key storage, no proxy required |
| Server-authoritative cost — wire protocol v3.31, server-minted execution IDs | MCP support — expose tools to agents via Model Context Protocol |
%%{init: {
'flowchart': {
'curve': 'basis',
'htmlLabels': true,
'nodeSpacing': 80,
'rankSpacing': 90
}
}}%%
flowchart LR
%% =========================
%% AI RUNTIME
%% =========================
subgraph USER ["👤 AI Runtime"]
direction TB
A["🤖 Agent"]
end
%% =========================
%% NULLRUN LAYER
%% =========================
subgraph LIB ["📦 NullRun Enforcement Layer"]
direction TB
B["NullRun SDK<br/>Interceptor"]
C["🚦 Runtime Gate"]
P["📜 Policy Engine"]
H["👤 Human Approval"]
end
%% =========================
%% PRODUCTION
%% =========================
subgraph PROD ["⚙️ Production Actions"]
direction TB
T["🛠 Tools"]
API["🌐 External APIs"]
DB["🗄 Databases"]
end
STATE["🗂 Audit + Runtime State"]
%% =========================
%% FLOW
%% =========================
A -->|"protected action"| B
B -->|"authorize"| C
C --> P
P -->|"allow"| T
P -->|"allow"| API
P -->|"allow"| DB
C -->|"require approval"| H
H -->|"approved"| T
C --> STATE
%% =========================
%% COLORS
%% =========================
classDef user fill:#dbeafe,stroke:#2563eb,color:#0f172a
classDef sdk fill:#dcfce7,stroke:#16a34a,color:#0f172a
classDef srv fill:#fed7aa,stroke:#ea580c,color:#0f172a
classDef store fill:#f5d0fe,stroke:#a21caf,color:#0f172a
classDef ok fill:#bbf7d0,stroke:#16a34a,color:#0f172a
classDef wait fill:#fef08a,stroke:#ca8a04,color:#0f172a
class A user
class B sdk
class C,P,H srv
class STATE store
class T,API,DB ok
class H wait
style USER fill:#f8fafc,stroke:#64748b,stroke-width:1px
style LIB fill:#f8fafc,stroke:#64748b,stroke-width:1px
style PROD fill:#f8fafc,stroke:#64748b,stroke-width:1px
The gate is server-authoritative — the SDK never trusts client-supplied cost. Redis is the source of truth for budget and tool-policy state; Postgres holds the immutable audit log.
sequenceDiagram
participant Agent
participant SDK
participant Gate
participant Policy
participant Human
participant Tool
Agent->>SDK: execute(tool)
SDK->>Gate: authorize(action)
Gate->>Policy: evaluate rules
alt Allowed
Policy-->>Gate: allow
Gate-->>SDK: continue
SDK->>Tool: execute
else Approval required
Policy-->>Gate: approval_required
Gate-->>SDK: wait
Gate->>Human: request approval
Human-->>Gate: approved
Gate-->>SDK: resume
SDK->>Tool: execute
else Blocked
Policy-->>Gate: deny
Gate-->>SDK: exception
end
Install:
pip install nullrun
export NULLRUN_API_KEY="nr_..." # get one at https://nullrun.io/control-center/api-keysfrom nullrun import protect
@protect
def my_agent(prompt: str) -> str:
return call_llm(prompt)| NullRun | LangChain callbacks | Helicone | Portkey | OpenLLMetry | |
|---|---|---|---|---|---|
| Enforce before execution | ✅ | ❌ observe-only | ❌ | ||
| Server-authoritative budget | ✅ | ❌ | ❌ | ❌ | ❌ |
| Tool-call policy | ✅ | ❌ | ❌ | ❌ | |
| Human-in-the-loop approvals | ✅ | ❌ | ❌ | ❌ | ❌ |
| Zero-code instrumentation | ✅ | ✅ | ✅ | ✅ | ✅ |
| Immutable audit trail | ✅ | ✅ | ✅ | ✅ | |
| Streaming memory cap (anti-OOM) | ✅ | ❌ | ❌ | ||
| MCP support | ✅ | ❌ | ❌ |
NullRun is the only option that blocks expensive or dangerous calls before they happen, not just observes them.
Runnable, copy-pastable examples live in a separate repo so you can adapt without cloning the SDK source:
- LangGraph — multi-node agent with budget + approval →
- CrewAI — multi-agent crew with shared budget →
- AutoGen — group-chat agent with policy gating →
- LlamaIndex — RAG pipeline with cost-per-query enforcement →
- Custom tools — register your own tools for policy →
- Multi-agent — shared budget across sub-agents →
| Version | Status | Highlights |
|---|---|---|
| v0.14.x (current) | ✅ alpha | Wire protocol v3.31, server-minted execution IDs, MCP, anti-OOM streaming cap |
| v0.15 | 🚧 in progress | OpenTelemetry exporter, Redis-backed offline queue, hardened init contract |
| v0.16 | 📋 planned | Cost prediction from prompt, semantic tool policy (regex → AST) |
| v1.0 | 🎯 beta target | Stable wire contract, full async support, type-safe decisions |
git clone https://github.com/nullrunio/nullrun-sdk-python
cd nullrun-sdk-python
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pytest -qWe follow Conventional Commits,
require tests for new public API, and run ruff + mypy in CI.
NullRun does not store or proxy your LLM provider keys — it sits beside your existing clients and observes the calls. The gate is server-authoritative for cost: even a malicious SDK cannot inflate spend by sending a fake cost_cents to /track.
See the security policy at https://github.com/nullrunio/nullrun-sdk-python/security/policy for the threat model and disclosure policy.
To report a vulnerability: support@nullrun.io.
- GitHub Issues: https://github.com/nullrunio/nullrun-sdk-python/issues
- GitHub Discussions: https://github.com/nullrunio/nullrun-sdk-python/discussions
- Enterprise support: support@nullrun.io
Made with care by NullRun and contributors.