Hatchet is a platform for orchestrating background tasks, AI agents, and durable workflows at scale. Prior to 0.95.3, the V1 DurableTask stream handler stores worker-supplied task_external_id values in the durableInvocations routing map before tenant ownership is verified, and callback delivery resolves that map by task UUID without tenant identity. An authenticated tenant worker that knows another tenant's durable task UUID and keeps a stream open on the same dispatcher process can receive that task's durable callback result payload. UUIDv4 values are not enumerable, and single-tenant deployments are unaffected in practice. This issue is fixed in version 0.95.3.