CoMemBench: Benchmarking Collaborative Memory Boundaries across Multi-Agent Workflow Topologies

Multi-agent workflows require task-relevant information to be shared across agents, while irrelevant, stale, unverified, or incompatible information must remain isolated. We call this task-conditioned scope of information a collaborative memory boundary. Workflow topology determines which intermediate artifacts are applicable to which downstream workers and when they cease to be valid, thereby providing a structural stress dimension for sharing and isolation. Existing memory benchmarks primarily evaluate retention and retrieval, whereas multi-agent benchmarks emphasize coordination and end-to-end completion, leaving topology-conditioned memory boundaries largely unmeasured. We introduce COMEMBENCH, an executiongrounded benchmark for collaborative memory sharing and isolation across multiagent workflow topologies. It constructs 800 composite workflows across four domains from source-grounded dependency graphs, with node-local specifications, verifiable artifact handoffs, native evaluators, and matched isolation challenges.COMEMBENCH measures workflow completion, verified node progress, requiredhandoff reliability, isolation robustness, and token cost. Experiments reveal a sharing–isolation trade-off: broader context improves information availability but can weaken isolation, while system rankings shift across topologies and artifact violations. COMEMBENCH is available at https://huggingface.co/datasets/anonymoussubmission-333/anonymous-submission.