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Anthropic

The Anthropic provider connects Missy to Claude via the Messages API. It supports tool calling, streaming, and model tiers.

Setup

Step 1: Get an API key

  1. Go to console.anthropic.com.
  2. Create an API key under API Keys.
  3. Copy the key (starts with sk-ant-api).

Setup tokens are not supported

Keys starting with sk-ant-oat are setup tokens used for OAuth flows, not API keys. They will not work with the Messages API. Make sure your key starts with sk-ant-api.

Step 2: Configure

export ANTHROPIC_API_KEY="sk-ant-api03-..."

providers:
  anthropic:
    name: anthropic
    model: "claude-sonnet-4-6"
    enabled: true

providers:
  anthropic:
    name: anthropic
    model: "claude-sonnet-4-6"
    api_key: "sk-ant-api03-..."
    enabled: true

missy vault set anthropic_api_key "sk-ant-api03-..."

providers:
  anthropic:
    name: anthropic
    model: "claude-sonnet-4-6"
    api_key: "vault://anthropic_api_key"
    enabled: true

Step 3: Verify

missy providers

Expected output:

Providers:
  anthropic: available (claude-sonnet-4-6)

Test with a query:

missy ask "Hello, which model are you?" --provider anthropic

Models

Model Config value Use case
Claude Sonnet 4.6 claude-sonnet-4-6 Default -- balanced speed and capability
Claude Haiku 4.5 claude-haiku-4-5 Fast tier -- simple queries, low cost
Claude Opus 4.6 claude-opus-4-6 Premium tier -- complex reasoning

Model tiers

providers:
  anthropic:
    name: anthropic
    model: "claude-sonnet-4-6"
    fast_model: "claude-haiku-4-5"
    premium_model: "claude-opus-4-6"

The ModelRouter automatically selects the tier based on prompt complexity. Short, simple queries go to fast_model; complex tasks with many tools or long context go to premium_model.

Configuration reference

Field Type Default Description
name string "anthropic" Provider identifier
model string "claude-sonnet-4-6" Primary model
api_key string null API key (falls back to ANTHROPIC_API_KEY env var)
api_keys list [] Multiple keys for rotation
timeout int 30 Request timeout in seconds
fast_model string "" Model for fast/simple tier
premium_model string "" Model for premium/complex tier
enabled bool true Enable/disable this provider

Dependencies

The Anthropic provider requires the anthropic Python package. It is installed automatically with Missy's base dependencies:

pip install -e "."

If the package is not installed, is_available() returns false and the provider is skipped during registry initialization.