Self-hosted Cerb is free. Create as many workers as you like, and sign in as many of them at once as you like – neither is limited, with or without a subscription.

Your subscription is entered at Setup » Configure » Subscription.

• What a subscription raises
• Seat usage
• When a subscription lapses
• Cerb Cloud

What a subscription raises

A subscription raises concurrency: how much work your installation runs at the same time.

A Concurrency panel draws what this installation runs at once, wherever there's a ceiling worth drawing. Each slot in the pool is one block, on two rows – Batch jobs and Agent turns – and the slots that both rows cover are the ones either kind of work may take. This is a Community installation's, with its three slots:

A licensed self-hosted installation doesn't see that panel. A subscription removes the ceiling entirely, so there's nothing left to draw here, and the pool it sizes for itself is drawn on Setup » Configure » Queues alongside the controls that set it. The panel appears where a real ceiling exists – a Community installation, whose three slots are a limit, and Cerb Cloud, whose pool is provisioned rather than self-sized.

Concurrency slots are what background work draws from – queue drains, bulk updates, imports, exports, scheduler jobs that run in parallel, and AI agent turns. More slots means more of that work happening at once rather than in sequence. Every installation has a floor of three, and a subscription carrying fewer than three grants three.

Agent turns per slot is a multiplier on top of that. An agent turn spends nearly all of its life waiting on a model provider rather than working, so one slot can hold several turns at once and take the next as each finishes. That's usually the number a busy installation feels most.

The two multiply into the ceiling the panel states in words, which on a three-slot installation reads 2 of 3 slots can run agent turns (2 sessions each, max 4). Note it's 2 of 3, not 3: only the slow lane and the commons run agent turns, so the multiplier applies to the slots that can take one rather than to the whole pool.

It's a ceiling rather than a reservation. Scheduled jobs draw from the same lane, and a provider's own rate limits apply on top of it.

This page answers how much capacity you have. Setup » Configure » Queues answers what that capacity is doing right now – the same lane split, with a live view of which slots are busy.

Seat usage

Cerb reports your seat count on this page, so it's never something to work out by hand. The panel is headed with the figure itself – N seats average over M months – and draws one row per month below it, with one block for each seat that month against a fixed track.

A seat is a person who signed in, counted once for the month whether they worked one day of it or all of them. Two things mark a worker active – signing in, and sending mail – so a worker who drives Cerb entirely through the API, and never holds a session, still counts as the worker it acts as.

The average divides by the months on record, not by twelve. A month with no recorded activity produces no row and isn't counted against you, and a new installation averages over the months it has actually run. A track is at least ten cells wide, so a small installation reads as small rather than as full.

Seats are how a subscription is priced, never something enforced. Nothing here blocks a login, ends a session, or warns you for going over – the number is reported so you can price against it, and running above it interrupts nobody.

This panel is shown on every installation, including Community and Cerb Cloud.

When a subscription lapses

A subscription is time-based. Concurrency follows the subscription term rather than the version you installed, so it ends when the term does, on whatever version you're running.

An expired subscription drops concurrency back to the community floor – three slots, at two agent turns each. Every feature keeps working, workers and logins stay unlimited, and no data is touched – the installation simply runs less at once until the subscription is renewed.

Cerb Cloud

If you have a Cerb Cloud subscription, what you won't see is the key-entry form – your subscription is managed with your account rather than with a key, and Cerb refuses the change server-side rather than merely hiding the form. Everything else on the page is there: the plan chip, the Concurrency panel drawing the pool we provision for you, and your seat usage.