OpenRouter

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Unified API for hundreds of AI models from multiple providers with intelligent routing and fallback.

Configuration

OPENROUTER_API_KEY=sk-or-...

Provider Options

Passed via :provider_options keyword:

Model Routing

openrouter_models

  • Type: List of strings
  • Purpose: Specify fallback models for automatic routing
  • Example:
    provider_options: [
  openrouter_models: [
    "anthropic/claude-3.5-sonnet",
    "anthropic/claude-3-haiku",
    "openai/gpt-4o"
  ]
]

openrouter_route

  • Type: String
  • Purpose: Routing strategy (e.g., "fallback")
  • Example: provider_options: [openrouter_route: "fallback"]

openrouter_provider

  • Type: Map
  • Purpose: Provider preferences for routing
  • Keys:
    • order: List of preferred providers
    • require_parameters: Boolean
  • Example:
    provider_options: [
  openrouter_provider: %{
    order: ["Together", "Fireworks"],
    require_parameters: true
  }
]

Prompt Transforms

openrouter_transforms

  • Type: List of strings
  • Purpose: Apply transforms to prompts
  • Example: provider_options: [openrouter_transforms: ["middle-out"]]

Sampling Parameters

openrouter_top_k

  • Type: Integer
  • Purpose: Top-k sampling
  • Note: Not available for all models (e.g., OpenAI models)
  • Example: provider_options: [openrouter_top_k: 40]

openrouter_repetition_penalty

  • Type: Float
  • Purpose: Reduce repetitive text
  • Example: provider_options: [openrouter_repetition_penalty: 1.1]

openrouter_min_p

  • Type: Float
  • Purpose: Minimum probability threshold for sampling
  • Example: provider_options: [openrouter_min_p: 0.05]

openrouter_top_a

  • Type: Float
  • Purpose: Top-a sampling parameter
  • Example: provider_options: [openrouter_top_a: 0.1]

openrouter_top_logprobs

  • Type: Integer
  • Purpose: Number of top log probabilities to return
  • Example: provider_options: [openrouter_top_logprobs: 5]

Usage & Plugins

openrouter_usage

  • Type: Map
  • Purpose: Configure usage reporting
  • Example: provider_options: [openrouter_usage: %{include: true}]

openrouter_plugins

  • Type: List of maps
  • Purpose: Enable OpenRouter plugins (e.g., web search)
  • Example: provider_options: [openrouter_plugins: [%{id: "web"}]]

App Attribution

app_referer

  • Type: String
  • Purpose: HTTP-Referer header for app identification
  • Benefit: App discoverability in OpenRouter rankings
  • Example: provider_options: [app_referer: "https://myapp.com"]

app_title

  • Type: String
  • Purpose: X-Title header for app title
  • Benefit: App ranking in OpenRouter
  • Example: provider_options: [app_title: "My Awesome App"]

Prompt Caching (Anthropic Models)

When using Anthropic models via OpenRouter, you can enable prompt caching by adding cache_control metadata to your ContentPart structs:

alias ReqLLM.Message.ContentPart

# Create content with cache_control metadata
system_content = ContentPart.text(
  "You are a helpful assistant with extensive knowledge...",
  %{cache_control: %{type: "ephemeral"}}
)

# Use in a message
context = ReqLLM.Context.new([
  ReqLLM.Context.system([system_content]),
  ReqLLM.Context.user("Hello!")
])

# The cache_control will be passed through to Anthropic
{:ok, response} = ReqLLM.generate_text(
  "openrouter:anthropic/claude-sonnet-4-20250514",
  context
)

The cache_control metadata is passed directly to the underlying Anthropic API, enabling prompt caching for system prompts, tools, and message content.

Note: This differs from the direct Anthropic provider which uses anthropic_prompt_cache: true option. Through OpenRouter, you have fine-grained control over exactly which content blocks get cached.

Model Discovery

Browse available models:

Pricing

Dynamic pricing based on underlying provider. Check response usage:

{:ok, response} = ReqLLM.generate_text("openrouter:model", "Hello")
IO.puts("Cost: $#{response.usage.total_cost}")

Key Benefits

  • Single API for multiple providers
  • Automatic fallback routing
  • Cost optimization through model selection
  • No vendor lock-in

Resources