Choose a provider

octo speaks two wire protocols natively — Anthropic Messages and OpenAI Chat Completions — so “which provider” really means “which of the two protocols does it speak.”

export ANTHROPIC_API_KEY=sk-ant-...
octo --provider anthropic --model claude-sonnet-5 "..."

export OPENAI_API_KEY=sk-...
octo --provider openai --model gpt-4o-mini "..."

DeepSeek, Bailian, and other OpenAI-compatible APIs use the same protocol.

Self-hosted and third-party endpoints (vLLM, OpenRouter, a proxy) use the custom vendor — the only one that takes a custom base URL. Its wire protocol (openai | anthropic) is chosen per config entry, so set it up once with octo config (choose Custom → pick the protocol → enter base URL + model):

CUSTOM_BASE_URL=https://api.deepseek.com/anthropic \
CUSTOM_API_KEY=sk-... \
  octo --model deepseek-chat "..."

Save it as your default

octo config        # interactive wizard
octo config show   # print the effective settings + where each came from
octo config path   # print the file location

octo config writes your default provider, model, (optionally) base URL, and reasoning settings to ~/.octo/config.yml, so a bare octo works without re-typing --provider/--model every time.

Extended reasoning

Reasoning models can deliberate before answering. Two knobs control it, both available as CLI flags and as octo config defaults:

--reasoning-effort low|medium|high|xhigh|max — the intensity. OpenAI-protocol backends receive it as reasoning_effort; Anthropic-protocol backends map it to adaptive thinking / an extended-thinking token budget, normalized per model family. Empty (the default) means off.
--show-reasoning (default off) — surface the reasoning/thinking trace for the Web UI (octo serve) to display. The terminal never renders the trace either way.

This unifies Anthropic thinking blocks and OpenAI reasoning_content behind one pair of controls.

Next: see the full schema in the config file reference.