Microsoft Corporation

US rdurga@microsoft.com

Security HTTPAPI / DISPATCH Working Group Agentic AI MCP A2A JCS Ed25519 Zero Trust When autonomous AI agents execute write operations against enterprise Systems of Record (ERP, MES, WMS, CRM, ITSM), traditional HTTP idempotency keys (RFC 9110) and post-hoc Saga orchestrators cannot guarantee deterministic recovery if a stochastic multi-step plan halts mid-flight or hallucinates downstream parameters. This document specifies the Pre-Release Transactional Compensation Lease (PTCL) protocol: a fail-closed wire contract requiring an agent runtime to acquire a cryptographically signed recovery reservation lease, prove a bounded rollback window (T_req <= T_granted), and present a Compare-And-Swap (CAS) epoch fencing token prior to committing any state mutation.

Introduction and Problem Statement Existing HTTP API and MCP tool-execution protocols treat write operations as fire-and-forget mutations or rely on application-layer Saga compensations after state has already been mutated and observed by concurrent processes. No internet standard defines a pre-mutation cryptographic reservation lease that binds an inverse compensation payload, a strict recovery window inequality (T_req <= T_granted), and a monotonic CAS fencing epoch before the target System of Record releases the write lock. This specification complements the foundational execution-trace verification architecture defined in draft-durga-agenttrust-trace-verification-00 by introducing deterministic, fail-closed wire semantics specifically addressing Agent Transactional Compensation Leases.

Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 ( ) when, and only when, they appear in all capitals, as shown here.

Pre-Release Transactional Compensation Lease (PTCL) Wire Format Before executing a state-mutating request against a conforming System of Record, the agent gateway MUST obtain and attach a signed PTCL object carried in the Agent-Compensation-Lease HTTP header or MCP _meta.compensationLease field:

Normative Fail-Closed Verification Rules Conforming verifiers and relying-party gateways MUST enforce the following deterministic invariants before releasing any downstream side effect:

1. RECOVERY_WINDOW_INEQUALITY: The System of Record verifier MUST verify that t_req_ms <= t_granted_ms and that the current monotonic clock has not exceeded the lease expiration timestamp prior to applying the mutation.
2. MONOTONIC_CAS_FENCING: If the target resource's current state epoch is greater than or equal to cas_fence_epoch, or if the current state digest does not match pre_image_state_hash, the write MUST abort with HTTP 409 Conflict (ERR_STALE_FENCE_EPOCH).
3. FOUR_MODE_RESERVATION_MANDATE: Every lease MUST declare one of four deterministic recovery modes (COMPENSATING_ACTION, SNAPSHOT_RESTORE, DRY_RUN_SHADOW, or HUMAN_ESCROW) and pre-stage the signed inverse payload prior to lock release.

Security Considerations All pre-image objects MUST be canonicalized using RFC 8785 JSON Canonicalization Scheme (JCS) prior to signature generation or verification under RFC 8032 Ed25519. Any clock skew exceeding 60 seconds, digest mismatch, or missing cryptographic binding MUST cause the verifier to fail closed and emit an auditable security rejection receipt.

IANA Considerations This document requests IANA registration of the media type application/agent-tx-lease+json and the registry IETF Agent Transactional Recovery Modes (COMPENSATING_ACTION, SNAPSHOT_RESTORE, DRY_RUN_SHADOW, HUMAN_ESCROW), alongside the following header fields:

• HTTP/MCP Header Field: Agent-Compensation-Lease
• HTTP/MCP Header Field: Agent-Fence-Token
• HTTP/MCP Header Field: Agent-Commit-Receipt

Normative References