API Keys and Providers

Megasthenes delegates provider and credential resolution to pi-ai. Any provider pi-ai supports works with megasthenes, and the matching env var is picked up automatically — you never pass a key into the Client.

For the full list of providers, env-var mappings, fallback chains (Anthropic OAuth, Bedrock credential chain, Vertex ADC), and OAuth flows, see the pi-ai docs:

• Supported providers and model IDs
• Environment Variables
• OAuth Providers

Per-session selection

provider and model are required per session at connect() time — there is no library-level default. Both are passed through to pi-ai’s getModel(provider, id).

import { Client } from "@nilenso/megasthenes";

const client = new Client();
const session = await client.connect({
  repo: { url: "https://github.com/owner/repo" },
  model: { provider: "anthropic", id: "claude-sonnet-4-6" },
  maxIterations: 20,
});

If the matching env var for your chosen provider isn’t set, connect() or the first ask() throws. See Handling Errors to classify by errorType.

Per-ask override

Swap the model for a single turn without rebuilding the client. Other turns in the same session keep the session default:

await session.ask("Summarize the architecture.", {
  model: { provider: "openai", id: "o3" },
  thinking: { effort: "low" },
}).result();

maxIterations and thinking can be overridden on a single ask() the same way — see AskOptions.