---
title: "Privileged/Quarantined Execution Model for Agentic AI Systems"
draft_name: draft-nennemann-ai-agent-dual-execution-00
intended_wg: SECDISPATCH → new WG
status: outline
gaps_addressed: [89, 92, 94]
camel_sections: [5.1]
date: 2026-03-09
---

# Privileged/Quarantined Execution Model for Agentic AI Systems

## 1. Problem Statement

Current AI agent architectures use a **single LLM** that simultaneously:

- Reads the user's trusted instructions
- Processes untrusted external data (emails, web pages, documents)
- Plans which tools to call
- Decides what arguments to pass

This architectural conflation is the root cause of prompt injection vulnerabilities. An adversary who can influence the external data can influence the plan and the arguments — because the same model processes both.

CaML (Debenedetti et al., 2025) implements the first concrete **Dual-LLM architecture** where a Privileged LLM (P-LLM) handles planning and a Quarantined LLM (Q-LLM) handles untrusted data parsing, with strict isolation between them. This separation is analogous to kernel/user-space separation in operating systems.

No IETF standard defines roles, isolation requirements, or behavioral contracts for multi-component AI agent architectures.

## 2. Scope

This document defines:

1. **Execution roles** for AI agent components (Privileged, Quarantined, Orchestrator)
2. **Isolation requirements** between roles
3. **Behavioral contracts** specifying what each role can and cannot do
4. **Communication channels** between roles with integrity guarantees
5. A **role negotiation protocol** for multi-agent systems

## 3. Execution Roles

### 3.1 Role Definitions

| Role | CaML Term | Privileges | Restrictions |
|------|-----------|-----------|-------------|
| **Planner** | Privileged LLM (P-LLM) | Sees user query; generates execution plan; selects tools | Never sees tool outputs or external data content |
| **Processor** | Quarantined LLM (Q-LLM) | Parses unstructured data into structured format | No tool access; cannot communicate arbitrary messages to Planner |
| **Orchestrator** | CaML Interpreter | Executes plan; maintains data flow graph; enforces policies | Deterministic; no LLM reasoning |
| **User** | Human | Approves policy violations; provides trusted input | — |

### 3.2 Role Isolation Matrix

```
             Can see:     User Query   Tool Outputs   Plan    External Data
Planner         ✓             ✗          ✓(own)        ✗
Processor       ✗             ✗          ✗             ✓
Orchestrator    ✓             ✓          ✓             ✓(metadata only)
User            ✓             ✓          ✓             ✓
```

Critical isolation: **The Planner never sees external data content. The Processor never has tool access.**

### 3.3 Communication Constraints

```
User ──(trusted query)──► Planner
Planner ──(plan code)──► Orchestrator
Orchestrator ──(tool calls)──► Tools
Tools ──(results)──► Orchestrator
Orchestrator ──(structured data + schema)──► Processor
Processor ──(structured output OR NotEnoughInfo)──► Orchestrator
Orchestrator ──(error type only, no content)──► Planner  [on error]
```

The Processor can only communicate back:
1. Structured data matching a Planner-specified schema (Pydantic-style)
2. A `NotEnoughInformation` boolean signal (no free-text explanation — that would be an injection vector)

## 4. Behavioral Contracts

*Addresses Gap #94: AI agent behavioral specification languages.*

### 4.1 Contract Format

Each role has a formal behavioral contract:

```json
{
  "contract:version": "1.0",
  "contract:role": "planner",
  "contract:invariants": [
    {
      "id": "inv-1",
      "description": "Planner never receives tool output content",
      "formal": "∀ step ∈ plan: planner.context ∩ tool_outputs = ∅",
      "enforcement": "orchestrator_enforced"
    },
    {
      "id": "inv-2",
      "description": "Plan is generated solely from user query and tool signatures",
      "formal": "plan = f(user_query, tool_signatures)",
      "enforcement": "architectural"
    },
    {
      "id": "inv-3",
      "description": "Planner output is deterministic code, not free-form text to tools",
      "formal": "planner.output ∈ restricted_python_subset",
      "enforcement": "parser_enforced"
    }
  ],
  "contract:capabilities": [
    "generate_plan",
    "select_tools",
    "define_schemas_for_processor",
    "call_print_for_user_output"
  ],
  "contract:prohibited": [
    "access_tool_outputs",
    "access_external_data",
    "communicate_with_processor_directly",
    "modify_orchestrator_state"
  ]
}
```

### 4.2 Processor Contract

```json
{
  "contract:version": "1.0",
  "contract:role": "processor",
  "contract:invariants": [
    {
      "id": "inv-1",
      "description": "Processor has no tool-calling capability",
      "formal": "processor.tools = ∅",
      "enforcement": "architectural"
    },
    {
      "id": "inv-2",
      "description": "Processor output conforms to Planner-specified schema",
      "formal": "processor.output ∈ schema(planner.request)",
      "enforcement": "schema_validation"
    },
    {
      "id": "inv-3",
      "description": "Processor cannot send free-text to Planner",
      "formal": "processor → planner: only {structured_data, NotEnoughInfo}",
      "enforcement": "orchestrator_enforced"
    }
  ],
  "contract:capabilities": [
    "parse_unstructured_to_structured",
    "signal_insufficient_information"
  ],
  "contract:prohibited": [
    "call_tools",
    "see_user_query",
    "send_arbitrary_text_to_planner",
    "access_other_tool_outputs"
  ]
}
```

### 4.3 Contract Verification

Contracts can be verified at three levels:

1. **Architectural**: enforced by system design (Processor literally has no tool access)
2. **Parser-enforced**: Planner output parsed and validated against restricted grammar
3. **Runtime-monitored**: Orchestrator checks invariants at each step

## 5. Practical Considerations

### 5.1 Model Selection

CaML shows that the Processor role can use a **cheaper, weaker model**:

- P-LLM: Claude Sonnet, GPT-4o, o3 (needs strong reasoning)
- Q-LLM: Claude Haiku, GPT-4o-mini (only needs structured extraction)

Using a local model for the Processor improves **privacy**: the P-LLM provider never sees tool outputs (which may contain sensitive data).

### 5.2 Error Handling

When the Processor encounters an error:

1. Processor signals `NotEnoughInformation` (boolean, no details)
2. Orchestrator reports to Planner: error type + location (but **not** the data content)
3. Planner generates alternative code
4. Retry up to N times (CaML uses N=10)

Important: error messages from untrusted data must be **redacted** before reaching the Planner, as they could contain prompt injections.

### 5.3 Limitations

CaML identifies inherent limitations of the Dual-LLM pattern:

- **"Data requires action" failure**: when the required actions depend on untrusted data content, the Planner cannot plan without seeing the data
- **Not enough context for Processor**: when the Processor needs information that wasn't passed to it, and cannot request it (that would be a communication channel)

## 6. Multi-Agent Role Mapping

*Addresses Gap #89: Adversarial AI agent detection in real-time.*

In multi-agent systems, each agent declares its role:

```json
{
  "agent:id": "agent-a@org1.example",
  "agent:role_declaration": {
    "architecture": "dual_llm",
    "planner": {
      "model_family": "claude-sonnet",
      "contract_ref": "https://org1.example/contracts/planner-v2"
    },
    "processor": {
      "model_family": "claude-haiku",
      "contract_ref": "https://org1.example/contracts/processor-v1"
    },
    "orchestrator": {
      "type": "deterministic_interpreter",
      "contract_ref": "https://org1.example/contracts/orchestrator-v1"
    }
  },
  "agent:attestation": "<signed by org1.example>"
}
```

Peer agents can verify:
- The counterpart uses a recognized execution model
- Role contracts meet minimum security requirements
- Attestations are valid and current

### 6.1 Detecting Adversarial Agents

An agent that violates its declared contracts can be detected by:

1. **Behavioral anomaly**: actions inconsistent with declared role contracts
2. **Provenance inconsistency**: data claimed as "trusted" but provenance chain shows untrusted origins
3. **Policy violation patterns**: repeated attempts to bypass policies suggest compromise

## 7. Ethical Conflict Resolution

*Partially addresses Gap #92: AI agent ethical decision conflict resolution.*

When agents with different ethical frameworks collaborate:

1. Each agent's Planner operates under its organization's ethical guidelines (encoded in its system prompt)
2. The Orchestrator enforces policy-level ethical constraints
3. When ethical conflicts arise at data exchange boundaries, the Policy Federation framework (Draft 4) handles resolution
4. The execution model ensures ethical guidelines cannot be overridden by injected data

This is a partial solution — the execution model prevents **external manipulation** of ethical decisions, but does not resolve **genuine disagreements** between organizations' ethical frameworks.

## 8. Security Considerations

- Role isolation must be enforced architecturally, not just by prompting
- The Orchestrator is the most critical component — if compromised, all guarantees fail
- Model selection for Processor should consider adversarial robustness, not just capability
- Role declarations should be verified, not just trusted

## 9. Open Questions

1. **Standardizing the restricted language**: CaML uses a Python subset. Should the standard mandate a specific language or allow alternatives?
2. **Role granularity**: are Planner/Processor/Orchestrator sufficient, or do we need more fine-grained roles?
3. **Recursive planning**: when a Planner needs to plan based on intermediate results, how to maintain isolation?
4. **Multi-turn conversations**: how do roles work across conversation turns where context accumulates?

## 10. References

- Debenedetti et al. "Defeating Prompt Injections by Design." arXiv:2503.18813, 2025.
- Willison. "The Dual LLM pattern for building AI assistants that can resist prompt injection." 2023.
- Wu et al. "IsolateGPT: An Execution Isolation Architecture for LLM-Based Agentic Systems." NDSS, 2025.
- Shi et al. "Progent: Programmable Privilege Control for LLM Agents." arXiv:2504.11703, 2025.
