Anthropic adapter setup (UH-136)

The anthropic adapter is a first-class HTTP client for the official pay-per-token Anthropic Messages API (POST https://api.anthropic.com/v1/messages). It talks directly to Anthropic’s metered API with your own key.

Status: experimental.

ToS / posture: this is the official, sanctioned, pay-per-token API. It is distinct from:

hermes-proxy — OAuth-backed subscription routing via a local Hermes proxy, and

oh-my-pi (and docs/runbooks/anthropic-via-omp.md) — routing through the OMP credential store.

Use anthropic when you want to pay Anthropic per token with your own API key, with no proxy in the path.

1. Get an API key

Create a key at https://console.anthropic.com/settings/keys. Export it (the adapter reads it from the environment and never persists it to the manifest):

export ANTHROPIC_API_KEY="sk-ant-..."

2. Add the adapter manifest

uh adapter add anthropic

This writes .harness/adapters/anthropic.yaml:

schema_version: uh.adapter.v0
id: anthropic
name: Anthropic
runtime: anthropic
capabilities:
  - messages-api
  - http-transport
  - sentinel-protocol
  - pay-per-token
status: experimental
config:
  runtime_config:
    base_url: "https://api.anthropic.com/v1"
    model: "claude-sonnet-4-6"
    max_tokens: 8192
    request_timeout_ms: 120000
    extra_headers: {}

3. Verify connectivity

uh adapter check anthropic

A healthy check prints the reachable endpoint and the number of models the key can see. A missing key degrades gracefully (found:false) so CI can skip the live smoke job.

4. Run a mission

uh run <mission-id> --runtime anthropic

Notes

The API key is read from ANTHROPIC_API_KEY and never written to the manifest.
The Messages API requires max_tokens; the manifest default is 8192.
The pinned API version header is anthropic-version: 2023-06-01.
request_timeout_ms bounds each HTTP call (default 120 000 ms).
base_url can be overridden (e.g. for a gateway); the adapter appends /messages and /models.
extra_headers lets you pass any forward-compat header (e.g. anthropic-beta).
Token usage is captured from the response usage object ({ input_tokens, output_tokens }) and emitted as a runtime.usage event.
See docs/runbooks/openrouter-setup.md for the cheapest OpenAI-compat pay-per-token alternative, and docs/runbooks/anthropic-via-omp.md for the subscription-routing path and its ToS posture.