# The Gate Is Only as Honest as Its Contracts: ContractGuard for the Contract Layer of Risk-Aware Causal Gating

arXiv: https://arxiv.org/abs/2606.18550 · HTML: https://mlsanity.com/paper/2606.18550/

## Key facts

- Cited by 2 papers in the map (data through 14 Oct 2026).
- Placed in Agent threats, guardrails and governance, one of 16 directions in LLM agents and tool use.
- Builds on 13 of its 24 references that are in the map.
- First posted on arXiv 17 Jun 2026.

## Placed in

- LLM agents and tool use / [Agent threats, guardrails and governance](https://mlsanity.com/agents/agent-threats-guardrails-and-governance/)
- LLM safety and security / [Prompt injection and agent security](https://mlsanity.com/safety/prompt-injection-and-agent-security/)

## Builds on (most cited first, 13 of 13)

- [ReAct: Synergizing Reasoning and Acting in Language Models](https://mlsanity.com/paper/2210.03629/) (2022)
- [Toolformer: Language Models Can Teach Themselves to Use Tools](https://mlsanity.com/paper/2302.04761/) (2023)
- [ToolLLM: Facilitating Large Language Models to Master 16000+ Real-world APIs](https://mlsanity.com/paper/2307.16789/) (2023)
- [Not what you've signed up for: Compromising Real-World LLM-Integrated Applications with Indirect Prompt Injection](https://mlsanity.com/paper/2302.12173/) (2023)
- [AgentBench: Evaluating LLMs as Agents](https://mlsanity.com/paper/2308.03688/) (2023)
- [Model Cards for Model Reporting](https://mlsanity.com/paper/1810.03993/) (2018)
- [Ignore Previous Prompt: Attack Techniques For Language Models](https://mlsanity.com/paper/2211.09527/) (2022)
- [Identifying the Risks of LM Agents with an LM-Emulated Sandbox](https://mlsanity.com/paper/2309.15817/) (2023)
- [InjecAgent: Benchmarking Indirect Prompt Injections in Tool-Integrated Large Language Model Agents](https://mlsanity.com/paper/2403.02691/) (2024)
- [Defeating Prompt Injections by Design](https://mlsanity.com/paper/2503.18813/) (2025)
- [R-Judge: Benchmarking Safety Risk Awareness for LLM Agents](https://mlsanity.com/paper/2401.10019/) (2024)
- [Capability Minimization as a Safety Primitive: Risk-Aware Causal Gating for Least-Privilege LLM Agents](https://mlsanity.com/paper/2606.13884/) (2026)
- [Contract2Tool: Learning Preconditions and Effects for Reliable Tool-Augmented LLM Agents](https://mlsanity.com/paper/2606.07904/) (2026)

## Built on by (most cited first, 2 of 2)

- [Lingering Authority: Revocable Resource-and-Effect Capabilities for Coding Agents](https://mlsanity.com/paper/2606.22504/) (2026)
- [Risk Architecture for AI-Native Engineering Teams: An Organizational Framework for Agentic System Governance](https://mlsanity.com/paper/2607.01421/) (2026)

## Abstract (arXiv)

Risk-Aware Causal Gating (RACG) defends tool-augmented LLM agents against indirect prompt injection by removing dangerous tools from the agent's visible action space, so that even a fully injection-compliant agent cannot call a tool it cannot see. We make three points. First, this structural guarantee does not eliminate the trust assumption behind safe tool use; it relocates it into the integrity of the tool contracts -- declared preconditions, effects, risk, and authorization -- that the gate reads, so an attacker who corrupts a contract can make the gate mis-decide without ever persuading the agent. Second, forging a tool's effects is strictly more dangerous than tampering with its risk label, because RACG applies a causal gate before its admissibility gate: an off-path tool is never exposed, so risk-relabeling alone fails, whereas effect forgery routes the dangerous tool onto the causal path and succeeds. Effect integrity, not the risk label, is the load-bearing assumption. Third, we introduce ContractGuard, a verifier between the registry and the gate that layers signed provenance, typed contract attestation, and runtime effect verification; on a controlled benchmark it restores injection success to zero against every modeled attack -- including an exhaustive white-box adaptive attacker -- without over-rejecting honest contracts, and the structural prediction is confirmed on six current-generation hosted models (Claude Opus 4.8, Sonnet 4.6, Haiku 4.5; Amazon Nova Premier and Nova 2 Lite; GPT-OSS-120B).