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Neo

Providers

The Simple Idea

Section titled “The Simple Idea”

A provider is the adapter between Neo and a model API. Neo speaks its own small internal language; providers translate that into Anthropic, OpenAI, OpenRouter, or Gemini requests.

The Problem

Section titled “The Problem”

Different model APIs use different request shapes, response shapes, tool-call formats, auth methods, retry behavior, and token accounting. OpenRouter uses an OpenAI-compatible Chat Completions shape while OpenAI itself uses the newer Responses API in Neo.

Neo should not bake any one provider into the agent loop.

How Neo Solves It

Section titled “How Neo Solves It”

Neo defines one provider interface:

type Provider interface {
    Name() string
    Complete(ctx context.Context, req Request) (*Response, error)
}

The core loop sends an llm.Request. The provider returns an llm.Response. Everything provider-specific stays behind the adapter.

Streaming

Section titled “Streaming”

Complete is blocking by design and always returns a finished response, but the Anthropic adapter uses the streaming endpoint underneath and reassembles the events in stream.go. Nothing is emitted as it arrives: Neo renders completed blocks, so streaming here is a transport decision, not a UI one.

Two reasons for it:

  • No fixed client deadline. A http.Client.Timeout caps how long one generation may take regardless of progress. The Anthropic client sets no timeout and lets the caller’s context bound the request; every caller has one (Ctrl-C in chat, --timeout headless).
  • The Messages API requires streaming above a max_tokens threshold, so raising defaultMaxTokens will not need another transport change.

Adapters must propagate the error from reading a response body. Discarding it turns a cancelled request into an apparently successful empty body, which then surfaces as a decode failure rather than the cancellation that happened.

Current Providers

Section titled “Current Providers”
Provider config Auth Adapter
provider: anthropic ANTHROPIC_API_KEY internal/llm/anthropic
provider: openai + openai_auth: api_key OPENAI_API_KEY internal/llm/openai.Client
provider: openai + openai_auth: subscription neo login device-code credentials internal/llm/openai.CodexClient
provider: openrouter OPENROUTER_API_KEY internal/llm/openrouter
provider: google GOOGLE_API_KEY internal/llm/google

How Models Are Chosen

Section titled “How Models Are Chosen”

The config model value is passed through to the provider. If omitted, Neo chooses a provider-aware default.

In the TUI, /model opens a model picker. It changes the active model for the current session and saves that session metadata.

What To Be Careful About

Section titled “What To Be Careful About”
  • Provider adapters should translate, not decide product behavior.
  • Retry and response parsing belong in provider packages.
  • The core agent loop should not care whether a response came from Anthropic, OpenAI, OpenRouter, or Google.
  • Subscription/Codex auth is experimental and should be documented carefully.

Where To Look

Section titled “Where To Look”
  • internal/llm/provider.go: provider-neutral types.
  • internal/llm/anthropic: Anthropic adapter.
  • internal/llm/openai: OpenAI adapters.
  • internal/llm/chatcompletions: reusable OpenAI-compatible Chat Completions translation.
  • internal/llm/openrouter: OpenRouter adapter wiring.
  • internal/llm/google: Google Gemini adapter.
  • internal/auth: subscription credential storage and refresh.
  • cmd/neo/main.go: provider selection.