FCoP: A File-Based Coordination Protocol for Governed Multi-Agent Systems

Abstract

Multi-agent work often outlives individual sessions and processes. A successor must identify not only an output but also the current task and attempt, the results submitted and accepted, and the evidence and authority for the next change. This paper systematically describes and studies FCoP 4.0, a protocol that expresses these coordination obligations in a project-visible filesystem workspace. Stable identities, four business-document types, path-authoritative lifecycle state, attempts, evidence binding, authorization, branch convergence, and durable receipts form an executable work contract that separates formal coordination records from transient actors. We explain the composition rationale and its tradeoffs, analyze freshness of completed commits under explicit storage, writer, and authority assumptions, and distinguish current-content coverage from acceptance-decision coverage. Using the frozen reference implementation, an end-to-end handoff proceeds through five successively terminated processes in each of three fresh workspaces, completing rejection, revision, acceptance, convergence, and archival. Four controlled cross-process commit orders, repeated three times each, exhibit the expected outcomes. Small-workspace measurements characterize local synthetic execution costs. Together with retained historical tests, failures, and boundary findings, the results support FCoP as an implementable, inspectable, and transferable persistent coordination protocol. They do not equate protocol acceptance with business truth or extend local validation to arbitrary Hosts or distributed deployments. This record contains the English paper, its Chinese edition, editable manuscript sources, and the frozen research supplement for one study. Preprint version 1.0; not peer reviewed. The earlier TMPA Architecture Paper A1.0, published in the TMPA V1.0 Publication System (DOI: 10.5281/zenodo.21888488), already introduced the architecture context and a file-based FCoP reference instantiation. This paper focuses on the concrete FCoP 4.0 contract and the frozen 4.0.3 implementation. It acknowledges that predecessor without claiming those foundational ideas as first introduced here or treating older TMPA/CodeFlowMu results as new-version conformance evidence. The supplement preserves original test failures, controlled-schedule interruptions, API findings, and environment-blocked installation preparation. Different evidence layers are not pooled into a single pass count. Experiments used synthetic workloads, one frozen implementation, and a local test Profile; they do not establish independent certification, live-Host interoperability, business truth, or arbitrary distributed deployment guarantees. AI assistance in research and manuscript preparation is disclosed in the paper. © 2026 Wei Zhu. The paper, original figures, and newly authored research materials are licensed under Creative Commons Attribution 4.0 International (CC BY 4.0): https://creativecommons.org/licenses/by/4.0/. Copying, sharing, adaptation, and commercial reuse are permitted with appropriate attribution, a license link, and an indication of changes; no endorsement may be implied. The frozen FCoP source remains under its original MIT license. Third-party material, quoted extracts, and other separately licensed material retain their own terms. This grant covers only rights the author can license and places no restrictions on public-domain facts.