# Claude Code

Facts from the Claude Code documentation (2026-10-15):
- Model: `--model`, `/model`, `ANTHROPIC_MODEL`, `model` in settings; aliases `haiku`, `sonnet`, `opus`, `fable`,
  `opusplan` (Opus in plan mode, Sonnet to execute); `CLAUDE_CODE_SUBAGENT_MODEL`; a sub-agent can pin `model` and
  `effort` in its frontmatter.
- Effort: `--effort`, `/effort`, `CLAUDE_CODE_EFFORT_LEVEL`, `effortLevel` in settings; levels `low`, `medium`, `high`,
  `xhigh`, `max` (`max` not accepted in `effortLevel`); `ultrathink` in a prompt raises depth for one turn.
- Gateway: `ANTHROPIC_BASE_URL` + `ANTHROPIC_AUTH_TOKEN`. **Anthropic does not support routing Claude Code to
  non-Claude models through a gateway**: keep the pool to Claude models.
- With `CLAUDE_CODE_GATEWAY_HINT_HEADERS=1` (v2.1.273+) a custom gateway receives `x-claude-code-session-id`,
  `x-claude-code-prompt-id` (one id per user prompt), `x-claude-code-request-class` (`main`, `subagent`, `workflow`,
  `compaction`, `auxiliary`).

## 1. Simplest: choose at launch (*documented flags, router untested*)
```bash
python integrations/serve.py --model scombat/s1d1-router --policy integrations/policy.example.yaml &
python integrations/routed.py claude "refactor the parser and add tests"
```
`routed.py` asks the router about your first prompt and starts `claude --model <model> --effort <effort> "<prompt>"`.
The session keeps that model; use `/model` and `/effort` to change it. Nothing is intercepted.

## 2. Per request, through a gateway (*untested end to end*)
```bash
export ANTHROPIC_BASE_URL=http://localhost:4000
export ANTHROPIC_AUTH_TOKEN=<litellm key>
export CLAUDE_CODE_GATEWAY_HINT_HEADERS=1
claude --model s1d1-auto
```
with the LiteLLM hook of `02-litellm.md` (A). The hook routes on the last human text of the request (tool results are
skipped), remembers one decision per `x-claude-code-prompt-id`, and leaves `auxiliary` requests alone.
Cautions from the gateway guide:
- keep forwarding `anthropic-beta`/`anthropic-version` and the `system` array unchanged; do not rewrite bodies except
  `model` and the effort field;
- changing the model between turns can make the API reject old thinking blocks ("bound to a different conversation");
  Claude Code then drops earlier thinking and retries, at the price of the cache. This is why the policy is
  escalate-only per session;
- a rejected `output_config.effort` is retried without it by Claude Code.

## 3. No router at all: the same policy as static settings
```json
{
  "model": "sonnet",
  "effortLevel": "medium",
  "availableModels": ["haiku", "sonnet", "opus", "fable"]
}
```
plus `CLAUDE_CODE_SUBAGENT_MODEL=haiku` for exploration sub-agents, a sub-agent frontmatter with `model: haiku` and
`effort: low` for cheap searches, and `opusplan` to plan with Opus and execute with Sonnet. The router replaces these
fixed choices with a choice per prompt.