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Xynthis talks to any LLM through a provider abstraction. Providers live in ~/.xynthis/config.toml; the active one is a single line you can change from the CLI, the app, or the file itself.

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The config file

[models]
active = "anthropic"

[providers.anthropic]
kind = "anthropic-messages"
base_url = "https://api.anthropic.com/v1/messages"
default_model = "claude-sonnet-4-5"

[providers.ollama]
kind = "openai-chat"
base_url = "http://localhost:11434/v1"
default_model = "llama3.3"

[providers.claude-code]
kind = "subprocess"
command = "claude"
args = ["--print"]
model_arg = "--model"
[models] active takes "<provider>" (uses that provider’s default_model) or "<provider>/<model>" for an explicit model. An optional [models] fast names a cheaper target the agent can use for low-effort follow-up turns; unset, every turn goes to active. Each [providers.<name>] table supports:
FieldApplies toMeaning
kindallHow Xynthis calls the provider (see below)
base_urlHTTP kindsFor openai-chat, the API root without /chat/completions; for anthropic-messages, the full /messages endpoint
default_modelallModel id used when the target doesn’t name one
command, args, model_argsubprocessCLI to spawn, its fixed args, and the flag used to pass a model name
litelocal modelsPlain-chat mode for small models; see Local models
launch_commandlocal modelsShell command that starts the provider’s local server; see Local models
kind is one of:
  • anthropic-messages: Anthropic’s /v1/messages API with an API key.
  • openai-chat: any OpenAI-compatible /v1/chat/completions endpoint: OpenAI, Ollama, llama.cpp, Groq, DeepSeek, Gemini, xAI, LM Studio, and self-hosted servers.
  • subprocess: spawn an installed CLI such as claude or codex and pipe the message through it. Uses the CLI’s own auth. Plain text only: no tool use, so the agent can’t act, only answer.
  • claude-oauth: call Anthropic directly with the OAuth token the Claude Code CLI stores in the macOS Keychain. Billed against your Claude subscription, with full tool use; it is the working alternative to subprocess for agent work. The claude-fable preset uses the same credential pinned to the Claude Fable model, so it appears as its own choice in the picker.
  • codex-oauth: the equivalent for a ChatGPT subscription via the codex CLI’s stored token. This targets a private, undocumented endpoint and may break without notice. The model set is what the ChatGPT account allows; unsupported model names are rejected with a 400.
  • xynthis-llm: the on-device Xynthis model server on 127.0.0.1:8080. See On-device model.
  • echo: a deterministic, network-free fallback used when nothing else is configured.

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Switching models

From the CLI: 
xynthis models list --all        # configured + built-in presets
xynthis models set anthropic     # provider's default model
xynthis models set openai/gpt-4o # explicit model
xynthis models test              # probe the active target with a tiny completion
xynthis models status
From the app: the model picker in the chat bar lists every configured provider. Picking one writes config.toml and restarts the daemon: the chat model is constructed at daemon startup, so the restart is what makes the switch take effect. Local providers that aren’t running are shown with a start action and are launched via their launch_command. If you edit config.toml by hand, one-shot CLI commands pick the change up on their next run, but a running daemon does not. Restart it (or switch once from the app’s picker, which restarts it for you). For a single invocation, override without touching config: xynthis --llm ollama/llama3.3 chat "...", or set XYNTHIS_LLM_OVERRIDE.

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API keys

Three places a key can live, checked in this order:
  1. macOS Keychain. The app’s Settings → Models tab stores keys under the com.xynthis.app service, one entry per provider (account <provider>-api-key). The CLI reads these too, so a key entered in the app works everywhere. macOS only.
  2. ~/.xynthis/auth.json. xynthis login <provider> prompts for a key interactively and stores it here. xynthis models add <provider> --api-key <key> does the same non-interactively.
  3. Environment variables, via discovery: xynthis auth scan finds ANTHROPIC_API_KEY, OPENAI_API_KEY, GROQ_API_KEY, XAI_API_KEY, DEEPSEEK_API_KEY, and GEMINI_API_KEY/GOOGLE_API_KEY, plus Claude/Codex OAuth tokens and running local servers (Ollama, LM Studio), and offers to wire what it finds into your config.
xynthis doctor diagnoses config, auth, and binary problems when a provider won’t respond.