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Overview

Klaus requires API keys from three providers to function:
  • Anthropic — Vision and reasoning via Claude
  • OpenAI — Text-to-speech
  • Tavily — Web search (free tier available)
The setup wizard will prompt you for these keys on first launch. On macOS, keys are stored securely in Apple Keychain. On Windows, they’re stored in ~/.klaus/config.toml.

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Getting Your API Keys

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Anthropic (Claude)

Purpose: Vision analysis and reasoning Model used: claude-sonnet-4-6
1

Sign up or log in

Go to console.anthropic.com
2

Create an API key

  • Navigate to Settings > API Keys
  • Click Create Key
  • Copy the key immediately (it won’t be shown again)
3

Add credits

Anthropic requires prepaid credits. Go to Settings > Billing and add a balance.
Estimated costs:
  • 10 questions: ~$0.05
  • 50 questions: ~$0.25
  • 100 questions/day: ~$2.50-3.50/day
Key format: Starts with sk-ant-

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OpenAI (Text-to-Speech)

Purpose: Convert Claude’s text responses to speech Model used: gpt-4o-mini-tts
1

Sign up or log in

Go to platform.openai.com/api-keys
2

Create an API key

  • Click Create new secret key
  • Give it a name (e.g., “Klaus”)
  • Copy the key immediately
3

Add credits (if needed)

New accounts may have free trial credits. Go to Settings > Billing to add more.
TTS costs: 0.015perminuteofgeneratedaudio( 0.015 per minute of generated audio (~0.01-0.02 per response)
Key format: Starts with sk-proj- or sk-
Purpose: Search the web when Klaus is uncertain about a claim Free tier: 1,000 searches per month
1

Sign up

Go to app.tavily.com/home
2

Get your API key

  • After signing in, your API key is displayed on the home page
  • Copy it for use in Klaus
Key format: Starts with tvly-
Free tier limits:The free tier includes 1,000 searches per month, which is typically sufficient for most users. Klaus only triggers search when Claude is uncertain, not on every question.

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Entering Keys in Klaus

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During First Run

The setup wizard (step 2) will prompt you to enter all three keys:
  1. Launch klaus
  2. On the “API Keys” step, paste each key into the corresponding field
  3. Klaus validates the format (prefix + length) before proceeding
  4. Click Next to continue
Keys are validated by format only, not with live API calls. If you enter an invalid key, Klaus will fail when trying to use the API later.

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After Setup

To update API keys after the initial setup:
  1. Open Klaus
  2. Click the settings button (gear icon)
  3. Go to the API Keys tab
  4. Update any keys as needed
  5. Click Save
Klaus will reload the API clients with the new keys.

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Key Storage

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macOS (Keychain)

API keys are stored securely in Apple Keychain. Klaus resolves keys in this order:
  1. Environment variable (ANTHROPIC_API_KEY, OPENAI_API_KEY, TAVILY_API_KEY)
  2. Apple Keychain
  3. Legacy ~/.klaus/config.toml under [api_keys] (fallback)
Migration: If you have plaintext keys in config.toml, Klaus automatically migrates them to Keychain on first launch.

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Windows (config.toml)

API keys are stored in ~/.klaus/config.toml under the [api_keys] section: 
[api_keys]
anthropic = "sk-ant-..."
openai = "sk-proj-..."
tavily = "tvly-..."
Klaus also checks for environment variables and .env files as fallbacks.

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Using Environment Variables

If you prefer not to store keys in config files, set environment variables: 
export ANTHROPIC_API_KEY="sk-ant-..."
export OPENAI_API_KEY="sk-proj-..."
export TAVILY_API_KEY="tvly-..."
Or create a .env file in ~/.klaus/: 
ANTHROPIC_API_KEY=sk-ant-...
OPENAI_API_KEY=sk-proj-...
TAVILY_API_KEY=tvly-...
Klaus loads .env automatically via python-dotenv.

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Troubleshooting

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”Invalid API key” errors

  • Verify the key format matches the expected prefix
  • Check for extra spaces or line breaks when pasting
  • Ensure you copied the entire key
  • Regenerate the key from the provider’s console

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Keys not persisting

  • On macOS, check Keychain Access for entries named klaus_anthropic_key, klaus_openai_key, klaus_tavily_key
  • On Windows, verify ~/.klaus/config.toml contains the [api_keys] section
  • Ensure Klaus has write permissions to ~/.klaus/

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Quota exceeded errors

  • Check your billing dashboard at the provider’s console
  • Add credits or upgrade your plan
  • For Tavily, monitor your monthly search usage

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Next Steps

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