Virtual models

Configure virtual models with weighted, failover, and conditional routing in simplified LLM mode.

Virtual models let you publish one client-facing model name and route requests across one or more internal target models.

Use llm.virtualModels[] to define the virtual entrypoint and llm.models[] as the concrete upstream targets.

Public and internal models

Use llm.models[].visibility to control whether a model is directly exposed to clients or kept as an internal target.

public: The model can be requested directly by clients and can also be used as a virtual model target.
internal: The model is intended for internal routing targets and is not exposed as a direct client model.

Route selection modes

Each virtual model defines its routing strategy under routing. The routing targets in a virtual model point to concrete llm.models[] entries.

Weighted routing

Use routing.weighted.targets to split traffic between targets with weight.

llm:
  models:
  - name: gpt-4o-public
    visibility: public
    provider: openAI
    params:
      model: gpt-4o
      apiKey: "$OPENAI_API_KEY"
  - name: gpt-4o-primary
    visibility: internal
    provider: openAI
    params:
      model: gpt-4o
      apiKey: "$OPENAI_API_KEY"
  - name: gpt-4o-fallback
    visibility: internal
    provider: openAI
    params:
      model: gpt-4o-mini
      apiKey: "$OPENAI_API_KEY"

  virtualModels:
  - name: smart
    routing:
      weighted:
        targets:
        - model: gpt-4o-primary
          weight: 90
        - model: gpt-4o-fallback
          weight: 10

Failover routing

Use routing.failover.targets and priority to define ordered failover targets. Targets with the same priority are load balanced across based on health and latency.

llm:
  models:
  - name: claude-primary
    visibility: internal
    provider: anthropic
    params:
      model: claude-sonnet-4-0
      apiKey: "$ANTHROPIC_API_KEY"
  - name: claude-backup-a
    visibility: internal
    provider: anthropic
    params:
      model: claude-3-5-haiku-20241022
      apiKey: "$ANTHROPIC_API_KEY"
  - name: claude-backup-b
    visibility: internal
    provider: anthropic
    params:
      model: claude-3-5-haiku-20241022
      apiKey: "$ANTHROPIC_API_KEY"

  virtualModels:
  - name: resilient
    routing:
      failover:
        targets:
        - model: claude-primary
          priority: 1
        - model: claude-backup-a
          priority: 2
        - model: claude-backup-b
          priority: 2

Conditional routing

Use routing.conditional.targets and when expressions to select targets by request context.

llm:
  models:
  - name: openai-public
    visibility: public
    provider: openAI
    params:
      model: gpt-4o-mini
      apiKey: "$OPENAI_API_KEY"
  - name: openai-fast
    visibility: internal
    provider: openAI
    params:
      model: gpt-4o-mini
      apiKey: "$OPENAI_API_KEY"
  - name: openai-smart
    visibility: internal
    provider: openAI
    params:
      model: gpt-4o
      apiKey: "$OPENAI_API_KEY"

  virtualModels:
  - name: adaptive
    routing:
      conditional:
        targets:
        - model: openai-fast
          when: request.headers["x-tier"] == "free"
        - model: openai-smart
          when: request.headers["x-tier"] == "pro"

For reusable provider defaults in simplified mode, see Multiple LLM providers.

Virtual key management Model costs

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