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A warm slot keeps one prewarmed machine ready for a project at a specific VM size. Assigning a slot means choosing both the project and the size: small, medium, or large. Projects do not have a hardware default. A single project can hold slots at several sizes, and each (project, size) pair is a separate warm pool. The number of slots assigned to that pair is the number of prewarmed machines Aether keeps ready for it.

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How Warm Starts Match Tasks

Every task chooses its VM size when it is created. A task starts immediately only when its project has a ready machine in the warm pool for that exact size. If no matching machine is ready, Aether cold-starts a machine at the requested size.
Aether never substitutes another size during startup. A large task cannot consume a ready medium machine; without a ready large machine, it cold-starts at large. You can resize its workspace later.
The web composer uses availability for the selected project. It shows a Warm badge on sizes that currently have ready machines and a Warming badge on sizes with configured slots but no ready machine.

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Tier-Bounded Quota

The number of warm slots you can use is set by your subscription tier: Slots beyond your tier’s quota cannot be assigned. The web app renders a fixed grid of slot cards sized to your tier; empty cards show as unassigned. aether warm-slot list prints the same numbered slots as rows. Every plan can assign slots at any of the three sizes. The sizes differ in shape and credits/hour, not plan availability.

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Requirements

A slot assignment must meet two conditions:
  • The project is linked to a GitHub repository so Aether can build its prewarmed environment from the repository source.
  • The selected size maps to a pool-eligible runtime class. Pool eligibility belongs to the size’s runtime class, not to the project.
Assigning a project and size to an occupied slot evicts the assignment that was there before.

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Slot Statuses

Building or rebuilding a pool’s prewarmed environment does not consume credits.

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Managing Slots

Open the warm-slots grid in settings, choose a slot, then select the project and machine size. Both selections are required. Release a slot when you no longer want Aether to keep that machine ready.
You can also manage slots over the API — see warm-slot endpoints.