Day 0 Support: Claude Opus 5.5

LiteLLM now supports Claude Opus 5.5 on Day 0. Use it across Anthropic, Bedrock, Gemini Enterprise Agent Platform, and Azure through the LiteLLM AI Gateway. Call it with the same OpenAI-compatible request you already use, and track spend, rate limits, and logging in one place.

What's new in Opus 5.5

Key changes (details from Anthropic):

• 20% cheaper than Opus 5: $4 / MTok input and $20 / MTok output, down from $5 and $25
• Cheaper cache reads: $0.20 / MTok, with 5-minute writes at $5 and 1-hour writes at $8
• Stronger agentic coding: Terminal-Bench 4.0 at 66.4% and OSWorld 2.0 at 81.8%
• Faster and leaner: Anthropic reports output more than 30% faster, using fewer tokens per task
• Thinking is always on: effort is the only control, and its default is medium
• Fast mode: about 2x the base price, down from Opus 5's $10 / $50

Context window and max output are unchanged from Opus 5 at 1M and 128K.

Enabling Opus 5.5

Pricing landed in PR #42489, and most proxies do not need to upgrade at all. On the default remote cost map, open the Price Data tab under Models + Endpoints in the UI and click Reload Price Data (or POST /reload/model_cost_map as a proxy admin), on any version v1.76.0 or newer.

The exception is LITELLM_LOCAL_MODEL_COST_MAP=true, which bakes the cost map into the image and puts it out of the Reload button's reach. That path needs an image built after #42489 merged.

Usage

Pick your provider below. Each tab wires up claude-opus-5-5 for that provider; the request you send afterward is identical everywhere.

Anthropic

1. Setup config.yaml

model_list:
  - model_name: claude-opus-5-5
    litellm_params:
      model: anthropic/claude-opus-5-5
      api_key: os.environ/ANTHROPIC_API_KEY

2. Start the proxy

docker run -d \
  -p 4000:4000 \
  -e ANTHROPIC_API_KEY=$ANTHROPIC_API_KEY \
  -v $(pwd)/config.yaml:/app/config.yaml \
  ghcr.io/berriai/litellm:v1.103.0-rc.1 \
  --config /app/config.yaml

Bedrock

1. Setup config.yaml

model_list:
  - model_name: claude-opus-5-5
    litellm_params:
      model: bedrock/anthropic.claude-opus-5-5
      aws_access_key_id: os.environ/AWS_ACCESS_KEY_ID
      aws_secret_access_key: os.environ/AWS_SECRET_ACCESS_KEY
      aws_region_name: us-east-1

2. Start the proxy

docker run -d \
  -p 4000:4000 \
  -e AWS_ACCESS_KEY_ID=$AWS_ACCESS_KEY_ID \
  -e AWS_SECRET_ACCESS_KEY=$AWS_SECRET_ACCESS_KEY \
  -v $(pwd)/config.yaml:/app/config.yaml \
  ghcr.io/berriai/litellm:v1.103.0-rc.1 \
  --config /app/config.yaml

Gemini Enterprise Agent Platform

1. Setup config.yaml

model_list:
  - model_name: claude-opus-5-5
    litellm_params:
      model: vertex_ai/claude-opus-5-5
      vertex_project: os.environ/VERTEX_PROJECT
      vertex_location: global

2. Start the proxy

docker run -d \
  -p 4000:4000 \
  -e VERTEX_PROJECT=$VERTEX_PROJECT \
  -e GOOGLE_APPLICATION_CREDENTIALS=/app/credentials.json \
  -v $(pwd)/config.yaml:/app/config.yaml \
  -v $(pwd)/credentials.json:/app/credentials.json \
  ghcr.io/berriai/litellm:v1.103.0-rc.1 \
  --config /app/config.yaml

Azure

1. Setup config.yaml

model_list:
  - model_name: claude-opus-5-5
    litellm_params:
      model: azure_ai/claude-opus-5-5
      api_key: os.environ/AZURE_AI_API_KEY
      api_base: os.environ/AZURE_AI_API_BASE  # https://<resource>.services.ai.azure.com

2. Start the proxy

docker run -d \
  -p 4000:4000 \
  -e AZURE_AI_API_KEY=$AZURE_AI_API_KEY \
  -e AZURE_AI_API_BASE=$AZURE_AI_API_BASE \
  -v $(pwd)/config.yaml:/app/config.yaml \
  ghcr.io/berriai/litellm:v1.103.0-rc.1 \
  --config /app/config.yaml

3. Test it!

The request is the same regardless of which provider you configured above:

curl --location 'http://0.0.0.0:4000/chat/completions' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer $LITELLM_KEY' \
--data '{
  "model": "claude-opus-5-5",
  "messages": [
    {
      "role": "user",
      "content": "what llm are you"
    }
  ]
}'

Fast Mode

info

Fast mode is only supported on the Anthropic provider (anthropic/claude-opus-5-5). It is not available on Bedrock, Gemini Enterprise Agent Platform, or Azure, and it cannot be combined with the Batch API.

Opus 5.5 runs faster with speed: "fast", billed at $8 / MTok input and $40 / MTok output, 2x the standard rate and down from the $10 / $50 on Opus 5. LiteLLM adds the fast-mode-2026-02-01 beta header and tracks the premium in cost calculations automatically.

curl --location 'http://0.0.0.0:4000/v1/chat/completions' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer $LITELLM_KEY' \
--data '{
  "model": "claude-opus-5-5",
  "messages": [
    {
      "role": "user",
      "content": "Refactor this module..."
    }
  ],
  "max_tokens": 4096,
  "speed": "fast"
}'

Worth knowing

Forced tool use returns a 400. With drop_params on, LiteLLM downgrades tool_choice to auto and logs a warning, so the call succeeds and the model is free not to call your tool.

Thinking cannot be disabled, and the default effort is now medium where Opus 5's was high, so a request that never set effort thinks less than it used to.

Thinking blocks are tied to the model. Only Fable 5.1 and Mythos 5.1 read Opus 5.5's, so a fallback to Sonnet or Haiku runs those turns without the reasoning.

Feedback

Running Claude Opus 5.5 through LiteLLM and hitting something unexpected? Share it on GitHub discussion #42494.