Virtual Models

Use GoModel virtual models to expose stable model names and test model swaps without changing app code.

What virtual models do

A virtual model is a model you define, instead of one a provider advertises. GoModel picks the kind from whether you give it a target:

• A redirect (an alias) is a stable name that points to a concrete provider model. Your app sends the name in the model field, and GoModel resolves it before sending the request upstream.
• An access policy has no target. It gates an existing model selector by user_path — or disables it entirely — without adding a new name. See User Path for access control.

Create and manage both in the admin dashboard at Models -> New virtual model. Fill Target model to make a redirect; leave it empty to make an access policy on the Source selector.

The rest of this page covers redirects.

Use stable names

You can expose names like regular and smarter instead of provider-specific model IDs.

• regular -> anthropic/claude-sonnet-4-6
• smarter -> anthropic/claude-opus-4-6

Your app can then send:

{
  "model": "regular",
  "messages": []
}

Load balance across models

A redirect can point at several target models and spread requests across them. Add more than one target in the editor (Add target) and pick a strategy:

• Round-robin (default) rotates requests evenly across the targets. Set a per-target weight to bias the share — a target with weight 2 receives twice the traffic of a target with weight 1.
• Lowest cost routes every request to the cheapest currently-available target, ranked by the model registry’s input + output per-token price. When a target has no registry pricing it is skipped while a priced target exists; if none are priced, the first listed target is used.

Targets that the gateway cannot currently serve (unknown model, provider down) are skipped automatically, so a redirect keeps working as long as one target is available. A redirect with a single target behaves exactly like a plain alias.

{
  "model": "smart",
  "messages": []
}

For example, point smart at both openai/gpt-4o and anthropic/claude-sonnet-4-6 with the round-robin strategy to split load, or at a premium and a budget model with the cost strategy to always take the cheaper one.

Rename or repoint a redirect

Open a redirect in the dashboard and edit its Source to rename it. GoModel moves the definition to the new name in one step — the old name stops resolving, so update any app still sending it. Renaming onto a name that already belongs to another virtual model is rejected; renaming onto a concrete model name shadows that model (see Shadow a model).

Redirects that shadow a model can be edited the same way — use the model row’s Edit redirect action. Virtual models declared as code keep their source fixed in configuration; rename them by editing the declaration.

Define virtual models as code

Operators who manage configuration as infrastructure-as-code can declare virtual models in config.yaml or the VIRTUAL_MODELS environment variable instead of the dashboard. Declarative entries are applied at startup, override any admin-store row with the same source, and are shown read-only in the dashboard (a Config badge). Edit the configuration to change them.

In config.yaml:

virtual_models:
  # A plain alias.
  - source: regular
    target: anthropic/claude-sonnet-4-6

  # A weighted round-robin load balancer.
  - source: smart
    strategy: round_robin
    targets:
      - model: openai/gpt-4o
        weight: 2
      - model: anthropic/claude-sonnet-4-6

  # A cost-based load balancer.
  - source: cheap
    strategy: cost
    targets:
      - { model: openai/gpt-4o }
      - { model: groq/llama-3.3-70b }

The same list as a single environment variable (JSON), which overrides config.yaml entries with a matching source:

VIRTUAL_MODELS=[{"source":"smart","strategy":"cost","targets":[{"model":"openai/gpt-4o"},{"model":"groq/llama-3.3-70b"}]}]

Each entry accepts source, a single target (shorthand) or a targets list, strategy (round_robin or cost), user_paths, description, and enabled. Leave the targets empty to declare an access policy on the source selector. An invalid declaration (unknown strategy, missing or self-referential target) fails startup with a clear error.

Expose only redirects

To hide provider models from GET /v1/models, set:

KEEP_ONLY_ALIASES_AT_MODELS_ENDPOINT=true

When this is enabled, GoModel returns enabled redirects from /v1/models instead of the full provider model list. The setting is also listed in .env.template.

Shadow a model

A redirect can “shadow” a model by using the same name as an existing model and pointing it somewhere else. This lets you override a requested model without changing application code.

For example:

• source: anthropic/claude-opus-4-6
• target model: anthropic/claude-sonnet-4-6

Your app can keep sending anthropic/claude-opus-4-6, while GoModel routes the request to anthropic/claude-sonnet-4-6.

A/B testing

Redirects are useful for short model experiments. Move a redirect from one target to another, then compare app behavior, latency, and usage.

For example, point smarter at Opus for one test and Sonnet for another. You can also shadow opus-4-6 with sonnet-4-6 to check whether the same app flow still works.