Linden: Linear-Typed Agent Collaboration

Collaboration among language-model agents is becoming increasingly common, making safe coordination over shared resources a central systems concern. Sandboxing provides a meaningful initial authority boundary, but not a dynamic mechanism for reallocating and transferring authority as collaboration evolves. We present **Linden**, a system for agent collaboration grounded in linear types. Linden represents resources and their update authority as linear values—values that must be consumed exactly once rather than duplicated—thereby enforcing unique ownership while allowing authority to move between participants. Resource versions and collections follow the same typed ownership discipline. A read-only projection separates shared access from update authority, while a $\mathtt{Share}$ monad captures runtime-mediated observations of shared state. Humans, agents, and terminals inhabit a common participant tree whose parent–child relationships constrain resource and authority transfers. We formalize Linden in a core calculus and prove type safety, unique ownership, role authenticity, capability confinement, and atomic observation. An executable language and a runtime authority manager enforce these guarantees during agent execution. Beyond semantic conformance tests and runtime microbenchmarks, we evaluate Linden on general-purpose terminal tasks, small-team coding, and large-scale multi-agent collaboration. On Terminal-Bench 2.1, Linden improves task success by 8.1 percentage points over a conventional sandbox baseline. On CooperBench Flash, Linden-Coop scores 3.4 points above Pi-Coop, while Linden-Team reaches 89.7%, the highest success rate among all evaluated conditions, including Shepherd. On Silo-Bench, Linden reaches 76% success on the common completed set, 28 percentage points above the strongest baseline, and coordinates 100 Agents in a chain-structured task through direct handoffs and independent recomputation.