Anthropic

• Create an account at https://platform.claude.com/
• Go to https://platform.claude.com/settings/keys and get your api key
• You will need to set the following environment variable to your key or you can set it to user_provided for users to provide their own.

ANTHROPIC_API_KEY=user_provided

• You can determine which models you would like to have available with ANTHROPIC_MODELS.

ANTHROPIC_MODELS=claude-fable-5-1,claude-fable-5,claude-opus-5,claude-opus-4-8,claude-opus-4-7,claude-sonnet-5,claude-sonnet-4-6,claude-opus-4-6,claude-opus-4-20250514,claude-3-7-sonnet-20250219,claude-3-5-sonnet-20241022,claude-3-5-haiku-20241022

Notes:

• Claude Fable 5.1 and Fable 5 are included in LibreChat's default Anthropic model catalog. Fable/Mythos-class models use the modern Anthropic profile in LibreChat: 1M context, 128K max output, adaptive thinking, prompt caching, and thinkingDisplay support for summarized or omitted reasoning output. Fable 5.1 keeps Fable 5's $10 input and $50 output rates per million tokens, with $12.50 cache writes and $0.25 cache reads.
• Claude Opus 5 is available through direct Anthropic, Anthropic on Vertex AI, and AWS Bedrock. It has a 1M-token context window and 128K-token maximum output. Adaptive thinking is enabled unless explicitly disabled; when disabled, LibreChat limits xhigh or max effort to high to keep requests valid.
• Claude Sonnet 5 is available through direct Anthropic, Anthropic on Vertex AI, and AWS Bedrock. LibreChat assigns it a 1M-token context window and 128K-token maximum output, uses adaptive thinking with summarized display when thinking is enabled, and sends an explicit disabled setting when a user turns thinking off.
• Native Anthropic prompt-cache controls and 1M-context detection evaluate the configured Claude model ID directly. Compatible Sonnet and Opus IDs at version 4.6 or later, including matching later-version IDs, retain those controls without waiting for an exact catalog entry. Unsupported models keep prompt-cache controls hidden in the Agent Builder.
• Anthropic endpoint supports all Shared Endpoint Settings via the librechat.yaml configuration file, including streamRate, headers, titleModel, titleMethod, titlePrompt, titlePromptTemplate, and titleEndpoint
• To configure Anthropic or an Anthropic-compatible gateway as a separate custom endpoint, use provider: "anthropic".

Vertex AI

LibreChat supports running Anthropic Claude models through Google Cloud Vertex AI. This is useful if you:

• Already have Google Cloud infrastructure
• Want to use your existing GCP billing and credentials
• Need to comply with regional data residency requirements

Quick Setup (Environment Variables)

Set the following environment variables to enable Anthropic via Vertex AI:

# Enable Vertex AI mode for Anthropic
ANTHROPIC_USE_VERTEX=true

# Vertex AI region (optional, defaults to 'us-east5')
# Modern models such as Fable 5.1 and Opus 5 require global, us, or eu.
# Specific regions serve Sonnet 4.6 and earlier.
ANTHROPIC_VERTEX_REGION=global

# Path to Google service account key file (optional)
# If not specified, uses default path: api/data/auth.json
GOOGLE_SERVICE_KEY_FILE=/path/to/service-account.json

Prerequisites

1. Google Cloud Project with Vertex AI API enabled
2. Service Account with the following roles:
   • Vertex AI User (roles/aiplatform.user)
   • Or Vertex AI Administrator for full access
3. Claude models enabled in your Vertex AI Model Garden
4. Service Account Key (JSON file) downloaded and accessible to LibreChat

Advanced Configuration

For model name mapping and advanced settings (similar to Azure OpenAI configuration), use the librechat.yaml file:

endpoints:
  anthropic:
    vertex:
      region: global
      models:
        claude-fable-5-1:
          deploymentName: claude-fable-5-1
        claude-opus-5:
          deploymentName: claude-opus-5
        claude-sonnet-5:
          deploymentName: claude-sonnet-5
        claude-3.5-haiku:
          deploymentName: claude-3-5-haiku@20241022

For detailed YAML configuration options, see Anthropic Vertex AI Configuration.