Anthropic: API key and base URL
Claude models, direct API or ant CLI subscription. Bring your own key; nothing is billed by us.
What the harness already knows
| Provider id | anthropic |
| Base URL | https://api.anthropic.com |
| Protocol | Anthropic Messages API |
| API key | ANTHROPIC_API_KEY |
| Model discovery | No — models come from the catalogue and from what you configure. |
Connecting it
The endpoint above is built in, so there is nothing to configure. Put the key in the environment and the provider appears in the model picker:
export ANTHROPIC_API_KEY="..."Keys are issued by Anthropic — where to get one.
Models on Anthropic
The newest models Anthropic serves that can call tools, from the models.dev snapshot OHarness ships.
| Model id | Context / output | $/M in / cached / out | Reasoning |
|---|---|---|---|
claude-fable-5-1 | 1M / 128K | 10 / 0.25 / 50 | Yes |
claude-opus-5 | 1M / 128K | 5 / 0.5 / 25 | Yes |
claude-sonnet-5 | 1M / 128K | 2 / 0.2 / 10 | Yes |
claude-fable-5 | 1M / 128K | 10 / 1 / 50 | Yes |
claude-opus-4-8 | 1M / 128K | 5 / 0.5 / 25 | Yes |
claude-opus-4-7 | 1M / 128K | 5 / 0.5 / 25 | Yes |
claude-sonnet-4-6 | 1M / 128K | 3 / 0.3 / 15 | Yes |
claude-opus-4-6 | 1M / 128K | 5 / 0.5 / 25 | Yes |
claude-opus-4-5 | 200K / 64K | 5 / 0.5 / 25 | Yes |
claude-opus-4-5-20251101 | 200K / 64K | 5 / 0.5 / 25 | Yes |
List prices in USD per million tokens, read from models.dev on 2026-09-19. Anthropic changes its prices and models; its own pricing page is the authority. Start a session on the newest:
oharness -m anthropic/claude-fable-5-1Pointing it somewhere else
A regional host, a gateway, or a server of your own. Overrides in ~/.oharness/config.json are field level, so changing the endpoint does not mean restating the rest of the provider — this is the whole block, shown holding the default so the shape is clear:
{
"providers": {
"anthropic": {
"baseUrl": "https://api.anthropic.com"
}
}
}What you get either way
The same agent loop, the same tools, the same MCP servers and the same permission rules, whichever provider is underneath — and switching between them mid-session converts nothing, because history is never stored in a vendor’s shape. What an agent harness is covers why that is the hard part, and the providers reference covers the catalogue itself.