Providers

Providers are a name → config map: a new upstream is just another [providers.<name>] table — no code change. Two adapter kinds cover everything:

• kind = "anthropic" — the upstream speaks the Anthropic Messages API. shunt passes the request through, optionally injecting a different API key.
• kind = "responses" — the upstream speaks the OpenAI Responses API. shunt translates Anthropic Messages ⇄ Responses, including streaming.

Built-in providers

Name	Kind	Auth	Backend
anthropic	anthropic	passthrough	api.anthropic.com — forwards the caller’s own credential
openai	responses	api_key (OPENAI_API_KEY)	api.openai.com/v1
codex	responses	chatgpt_oauth	chatgpt.com/backend-api — reuses ~/.codex/auth.json

The codex provider (ChatGPT subscription)

Log in once with the Codex CLI; shunt reads and auto-refreshes ~/.codex/auth.json:

codex login

If the file is missing or expired, shunt returns an authentication_error telling you to run codex login.

Model slugs

The ChatGPT-account Codex backend rejects gpt-*-codex slugs — it only accepts the account’s live-entitled slugs. The authoritative catalog is openai/codex’s models.json. Current slugs are gpt-5.6-sol, gpt-5.6-terra, gpt-5.6-luna (frontier) and gpt-5.5 / gpt-5.4 / gpt-5.4-mini / gpt-5.2; older accounts may only be entitled to the earlier ones. Use upstream_model in a route to map any alias onto an entitled slug.

Adding an Anthropic-compatible backend

Most third-party “use Claude Code with X” gateways are Anthropic-Messages-compatible: kind = "anthropic" with auth = "api_key", differing only in base_url and the key env var. Ready-to-use bases:

Provider	base_url	Example model IDs
Kimi (Moonshot)	https://api.moonshot.ai/anthropic	kimi-k2.7-code
DeepSeek	https://api.deepseek.com/anthropic	deepseek-v4-pro, deepseek-v4-flash
Z.ai (GLM)	https://api.z.ai/api/anthropic	glm-5.2, glm-4.7
MiniMax	https://api.minimax.io/anthropic	see MiniMax docs
Mimo (Xiaomi)	https://api-mimo.mi.com/anthropic	see Mimo docs
OpenRouter	https://openrouter.ai/api	anthropic/claude-opus-4.8
Vercel AI Gateway	https://ai-gateway.vercel.sh	anthropic/claude-opus-4.8 (accepts x_api_key)

For example, to route Kimi’s model through shunt:

[providers.kimi]
kind = "anthropic"
base_url = "https://api.moonshot.ai/anthropic"
auth = "api_key"
api_key_env = "KIMI_API_KEY"

[[routes]]
model = "kimi-k2.7-code"
provider = "kimi"

Then export KIMI_API_KEY=…, point Claude Code at shunt, and select kimi-k2.7-code (via ANTHROPIC_CUSTOM_MODEL_OPTION or ANTHROPIC_MODEL). Run shunt check to validate — it reports an unknown provider in a route, a missing api_key_env, or a bad base_url.

Every provider key (kind, auth, api_key_header, count_tokens, …) is documented in the Configuration Reference.