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Agent model selection

Every agent run picks exactly one model. You control it per agent with the model field; when you omit that field the agent uses the platform default model. This page explains both paths and the resolution order the platform follows so you can predict — and pin — which model a tenant’s agents run on.

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Set the model per agent

Pass model on create or update. Agent runs route through Anthropic only, and the API accepts a fixed allowlist of Claude model ids rather than every id Anthropic currently serves. The supported ids are: Send the id exactly as listed, including the dated snapshot: claude-haiku-4-5-20251001 is accepted, but the bare alias claude-haiku-4-5 is not. Any id outside this list is rejected at the write boundary with a 422 and the error.code INVALID_MODEL — see When a model id is rejected below. That includes a Claude model Anthropic has released but Orbit has not yet added: a new Anthropic release is not accepted automatically. Orbit adds support for each id before an agent can pin it, so treat the four ids above as the current set. Call GET /api/v1/agents/models for the live, authoritative list of currently selectable ids, or check back here when you need a newer model.
GET /api/v1/agents/models returns only the ids you can newly select, so while a model is export-suspended it is a strict subset of the table above. claude-fable-5 is the current example: it stays in this table because create and update still accept it (requests pinned to it fall back to claude-opus-4-7) and agents already pinned to it keep running, but because you cannot newly select a suspended id it is omitted from the endpoint response until the suspension lifts. If an id appears in this table but not in the endpoint response, check whether the table marks it export-suspended.
If you leave model unset, the agent resolves to the platform default at run time — you are never required to pin a model per agent.

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When a model id is rejected

Every path that writes an agent rejects a model outside the supported list, and all three write boundaries return the same error code on the 422 — INVALID_MODEL. One branch on error.code covers every path: Every path carries HTTP 422 and error.code INVALID_MODEL in the standard error envelope, so a single branch on error.code === 'INVALID_MODEL' handles a rejected model id from create, update, or config import. An id Anthropic has released but Orbit has not yet added is rejected the same way; a new Anthropic release is not accepted automatically.

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The platform default

The platform default is the model an agent uses when its own model field is unset. It is resolved fresh by the agent runtime, in this order:
  1. Admin pin. If a platform admin has pinned a model, that id wins and auto-discovery is bypassed. Use this to hold every tenant on a known-good model when a new release breaks a flow.
  2. Auto-discovery. Otherwise the runtime queries Anthropic for the available models, selects the newest in the default agent family, and caches the result for 24 hours. When Anthropic ships a newer model in that family, every tenant flows onto it within 24 hours of the next agent run — no redeploy. (This path is paused today — see the status note below.)
  3. Boot fallback. If Anthropic’s model listing is unreachable and no admin pin is set, the runtime falls back to a configured boot default (see below).
Discovery never returns an id the provider does not serve, so a tenant agent always resolves to a live model.
Current status. The default agent family is Fable, but Anthropic’s Fable models are export-suspended: they still appear in the model listing, yet completions against them return a 404. Auto-discovery skips any suspended id, so the Fable step currently returns nothing and resolution falls through to the Opus fallback. Every tenant runs on claude-opus-4-7 today. The auto-discovery-onto-the-newest-Fable behaviour described above is the design for normal operation and resumes automatically once the suspension lifts — no redeploy. To hold tenants on a specific model in the meantime, set an admin pin (model.tenant_default).

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Platform-default configuration (operators)

These settings are owned by platform operators, not tenants. They are documented in full in the agent default model runbook.
claude-opus-4-7 is the current live Opus boot fallback. It takes effect when both the admin pin and auto-discovery are unavailable — and because Fable-family discovery is currently export-suspended (see the status note above), the Opus branch is the path every tenant is on today. When the suspension lifts, auto-discovery selects the newest model in the default agent family again. If you need a tenant to stay on a specific model regardless of discovery, set an explicit admin pin (model.tenant_default) rather than relying on the boot fallback.
To override auto-discovery without a redeploy, a platform admin pins the default in platform config rather than changing the boot fallback. The boot fallback only takes effect when both the admin pin and live discovery are unavailable.