A Policy Algebra for Trust-Preserving Agentic AI Execution
Organizations: Volkswagen Digital Services · Scania CV AB
Abstract
Large language model-based agentic frameworks primarily optimize capability: whether an agent can reason, retrieve information, call tools, delegate work, and complete a goal. Enterprise execution requires a stronger property. A successful result is not reliable if it was produced through unauthorized data access, widened delegated authority, unapproved side effects, unrecoverable budget consumption, or incomplete evidence. This paper defines reliable capability as a path property: an agent is reliably capable only when it completes a task through action events that remain admissible under identity, profile, tool, data, memory, budget, artifact, approval, and audit constraints. We propose a policy algebra that defines the reliability envelope within which agent capability may be exercised. Security profiles and runtime obligations compose through joins, intersections, budget narrowing, approval inheritance, and evidence accumulation; the resulting composition is both trust-preserving and the least restrictive state satisfying all governing inputs. The algebra also propagates restrictions across multi-agent calls and introduces cost-aware artifact materialization, which redirects open-ended execution toward a recoverable outcome as budget exposure grows. The evaluation is interpreted as a reliability-capability trade-off rather than a capability benchmark: the policy-algebra runtime intervenes on 94.8% of policy-violating events while retaining an 86.9% task-completion rate, eliminates the observed profile-monotonicity and zero-artifact-exhaustion violations, and increases audit completeness to 98.6%. The method provides researchers and practitioners with formal correctness conditions, executable decision semantics, and trace evidence for building agents that are not only capable, but reliably capable.
Figures & tables
| No. | Work or standard | Main focus and contribution | Gap addressed by this paper |
|---|---|---|---|
| 1 | OWASP AISVS [ 1 ] | AI security verification through testable control categories and levels | Action-level enforcement inside an agent loop |
| 2 | NIST AI RMF and GenAI profile [ 2 , 3 ] | AI risk governance through the Govern, Map, Measure, and Manage cycle | Runtime semantics for the risk cycle |
| 3 | MAESTRO [ 4 ] | Agentic threat modeling through layered analysis of agentic systems | Translation from layer finding to policy gate |
| 4 | MITRE ATLAS [ 5 ] | AI adversary tactics and techniques for AI systems | Runtime use of tactics as control requirements |
| 5 | Agentic Security Hub [ 6 ] | Aggregated standards, threats, components, architectures, and mappings | Compilation into executable runtime constraints |
| 6 | Agent and multi-agent systems foundations [ 19 , 20 , 21 , 22 ] | Autonomy, interaction, coordination, and multi-agent system design | Runtime security semantics for tool-using agentic systems |
| No. | Profile | Models/tools | Memory/data | Approval | Audit/budget |
|---|---|---|---|---|---|
| 1 | Low | Safe defaults; built-in tools | Short-lived memory; no sensitive RAG | None by default | Basic logs |
| 2 | Medium | Approved models/tools; limited connectors | Retention, redaction, classified RAG | Destructive actions | Tool parameters, costs, per-run budget |
| 3 | High | Whitelisted tools/connectors | Limited memory; vector decay; strict classes | External side effects and writes | Step traces, rate limits, anomaly detection |
| 4 | VeryHigh | Deterministic tools for regulated actions | Sanitized knowledge only; strict retention | All regulated/external actions | Immutable evidence, fixed budgets, alerts |
| No. | Component | Implementation status |
|---|---|---|
| 1 | Security profiles and cascade | Implemented in configuration and UI; formal semantics defined in ( 15 ) |
| 2 | Policy-intersected tool authorization | Implemented in permission gate and executor paths |
| 3 | Trust boundary propagation | Implemented for profile and depth; formal verification remains future work |
| 4 | Human approval inheritance | Implemented for core paths; asynchronous workflow queues under development |
| 5 | RAG and memory governance | Classification and access checks exist; advanced cross-session retention remains partial |
| 6 | Publication profile freezing | Implemented using publication snapshots and review triggers |
| No. | Threat | Layers | AISVS categories | Components | Runtime controls | Audit evidence |
|---|---|---|---|---|---|---|
| 1 | Memory poisoning | Data, framework, observability | C8, C12 | Memory, RAG, tools | Save/publish/run validation; retrieval audit; classification; retention limits | Source ID, classifier result, retrieval hash, action result |
| 2 | Tool misuse | Tools, runtime | C5, C9, C12 | Tool integration, runtime | Intersected permission; sandbox; schema validation; HITL | Tool, params hash, policy predicates, approver, cost |
| 3 | Privilege compromise | Framework, ecosystem | C5, C9, C10 | Orchestration, runtime | RBAC; cascade; monotone trust; depth limits | Caller, callee, profile join, denied/escalated reason |
| 4 | Resource overload | Runtime, observability | C12 | Runtime | Token/cost budgets; rate limits; loop controls | Budget before/after, rate decision, loop counter |
| 5 | Overwhelming HITL | Framework, ecosystem | C13 | Orchestration | Risk-adaptive approval; batching; deterministic tools | Approval queue state, decision latency, approver |
| 6 | Unexpected RCE | Tools, runtime | C4, C5, C9 | Tool integration, runtime | Sandbox; command allowlist; network blocking | Command hash, sandbox ID, network policy, result |
| Research question | Hypothesis | Metric, equation, or evidence | Evaluation location |
|---|---|---|---|
| RQ1 | H1: Coverage | in Eq. ( 34 ); design-coverage matrix | Section 9 |
| RQ2 | H2: Compilation | in Eq. ( 33 ); runtime predicate, gate, audit-field, profile-floor, or regression-test mapping | Section 9 |
| RQ3 | H3: Tool control | Unsafe intervention rate and false intervention rate in Eq. ( 35 ) and Eq. ( 36 ); governed tool-call protocol | Section 10 ; Section 11 |
| RQ4 | H4: Delegation | Trust violation rate in Eq. ( 37 ); profile-monotonicity violations | Section 10 ; Section 11 |
| RQ5 | H5: Evidence | Audit completeness in Eq. ( 38 ); trace reconstruction fields | Section 11 |
| RQ6 | H6: Artifact materialization | Zero-artifact exhaustion rate; materialization redirects and artifact-state evidence | Section 10 ; Section 11 |
| No. | Artifact family | Coverage criterion | Runtime control path |
|---|---|---|---|
| 1 | AISVS categories | Each category maps to an enforcement or audit surface | Profile rules, input validation, output filtering, memory policy, tool gate, audit schema |
| 2 | NIST AI RMF functions | Each function maps to a lifecycle or runtime mechanism | Governance cascade, asset mapping, monitoring, policy repair |
| 3 | MAESTRO layers | Each layer maps to one or more runtime controls | Model gateway, RAG gate, tool gate, sandbox, observability, trust chain |
| 4 | T1–T15 threat classes | Each threat maps to a control, evidence field, and test case | Threat-to-control matrix, profile floor, HITL, monitoring, trace field |
| 5 | KC1–KC6 components | Each component maps to scoped runtime constraints | Model, orchestration, memory, tool, and operational policies |
| 6 | Agent architecture patterns | Each pattern maps to profile floors and delegation constraints | Sequential, hierarchical, swarm, reactive, and RAG agent policies |
| No. | Invariant | Formal condition | Runtime mechanism |
|---|---|---|---|
| 1 | Profile monotonicity | for delegated execution | Profile cascade and profile join |
| 2 | Tool authorization | before execution | Intersected permission gate |
| 3 | HITL inheritance | Approval propagation over the call chain | |
| 4 | Budget narrowing | Budget attribution and sub-budget allocation | |
| 5 | Artifact materialization | Cost-governance and artifact-state gate | |
| 6 | Publication freeze | participates in until review | Published service profile snapshot |
| No. | Scenario | Targeted rule | Expected decision | Evidence field |
|---|---|---|---|---|
| 1 | Prompt injection calls blocked tool | Eq. ( 16 ) | Deny | Failed predicate |
| 2 | Medium agent invokes Very High service | Eq. ( 15 ); Eq. ( 19 ) | Deny or run at stricter profile | Effective profile |
| 3 | Sub-agent widens tools | Algorithm 3 | Deny | Delegated tool set |
| 4 | External app calls unpublished service | in Eq. ( 16 ) | Deny | Service status |
| 5 | Sensitive data enters RAG context | Eq. ( 17 ) | Deny retrieval | Data class and clearance |
| 6 | Memory poisoning attempt | Eq. ( 18 ) | Deny write | Provenance and redaction |
| Workload family | Traces | Events | Unsafe events | Safe events |
|---|---|---|---|---|
| Prompt-injection and tool-misuse tasks | 154 | 491 | 245 | 246 |
| RAG and memory-governance tasks | 137 | 438 | 202 | 236 |
| Multi-agent delegation tasks | 121 | 386 | 162 | 224 |
| Publication and service-invocation tasks | 88 | 281 | 108 | 173 |
| Budget, artifact-materialization, HITL, and sandbox tasks | 112 | 340 | 125 | 215 |
| Total | 612 | 1,936 | 842 | 1,094 |
| Metric | RBAC + allowlist | Policy algebra | Difference | Target direction |
|---|---|---|---|---|
| Unsafe intervention rate | 67.1% | 94.8% | +27.7 pp | Higher is better |
| False intervention rate | 2.1% | 4.2% | +2.1 pp | Lower is better |
| Profile monotonicity violations | 31/188 | 0/188 | -31 | Lower is better |
| Zero-artifact budget exhaustions | 18/44 | 0/44 | -18 | Lower is better |
| Audit completeness | 71.9% | 98.6% | +26.7 pp | Higher is better |
| Task completion rate | 90.7% | 86.9% | -3.8 pp | Higher is better |
| Scenario | Unsafe events | Intervened | Intervention rate | Main residual failure mode |
|---|---|---|---|---|
| Prompt injection triggers blocked tool | 133 | 126 | 94.7% | Ambiguous tool intent |
| Unauthorized tool execution | 112 | 104 | 92.9% | Incomplete tool metadata |
| RAG over-access | 116 | 111 | 95.7% | Misclassified document label |
| Memory poisoning write | 86 | 79 | 91.9% | Semantic poisoning not caught by exact filter |
| Profile laundering through sub-agent | 104 | 104 | 100.0% | None observed |
| External side effect without HITL | 128 | 121 | 94.5% | Missing action-risk tag |
| No. | Failed case | Repair action | Regression case |
|---|---|---|---|
| 1 | Unsafe tool allowed | Add tool profile floor and HITL rule | Re-run blocked tool-call test |
| 2 | Profile downgrade in delegation | Enforce profile join on call chain | Re-run delegation test |
| 3 | Unauthorized document retrieved | Restrict RAG source and add classification check | Re-run RAG access test |
| 4 | Missing audit field | Add required field to audit schema | Re-run audit completeness test |
| 5 | Published service changed profile | Require re-approval before invocation | Re-run publication-freeze test |
| 6 | Budget exhausted without artifact | Lower materialization threshold and require checkpoint | Re-run artifact-materialization test |
Appendix figures & tables3 assets
Supplementary material from the paper’s appendix.
Appendix
| Symbol | Meaning |
|---|---|
| Set of agents. | |
| Set of tools. | |
| Set of data sources or data objects. | |
| Set of published services. | |
| Set of security profiles. | |
| or | Profile join, equal to the stricter profile under the profile order. |
| Dimension | Low | Medium | High | Very High |
|---|---|---|---|---|
| Models | Approved general models | Approved models with logging | Restricted models | Restricted models; deterministic tools for regulated action |
| Tools | Built-in low-risk tools | Approved tools | Tool calls require stricter validation | Deterministic or schema-bound tools |
| Memory | Short-lived | Scoped with retention | Scoped, redacted, audited | Minimal retention; strong isolation |
| RAG | Public or low-risk sources | Approved internal sources | Classified sources with provenance | Sanitized sources only; stronger review |
| HITL | None by default | Destructive actions | External side effects and high-risk writes | Most external actions |
| Budget | Basic run limit | User/team budget | Strict budget and rate limit | Fixed budget and approval for increase |
| No. | Artifact | Example category | Runtime effect | Evidence |
|---|---|---|---|---|
| 1 | AISVS | Access control | RBAC predicate, data-source access check, service invocation check | Role, resource, decision |
| 2 | AISVS | Agentic action security | Tool authorization, HITL, sandbox, schema validation | Tool, parameters, decision |
| 3 | AISVS | Memory/vector security | , , retention, redaction, isolation | Source, memory key, class |
| 4 | AISVS | Monitoring | Trace completeness, anomaly detection, alerts | Trace ID, metric |
| 5 | NIST | Govern; accountability | Owner, reviewer, profile floor, approval path | Owner, approver |
| 6 | NIST | Map; context and assets | Agent inventory, tool list, data classification map | Asset ID |
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