Anthropic via oh-my-pi (UH-27)

What this runbook covers

Routing Claude models through Ultimate Harness without building a native Anthropic adapter — by using the existing oh-my-pi adapter (shipped in UH-25) and the new mission-level runtime_config_overrides (UH-27) to select an Anthropic-tier model per mission.

# .harness/missions/<id>/mission.yaml
runtime_config_overrides:
  model: anthropic/claude-opus-4-7
  thinking: medium

Adapter manifest at .harness/adapters/oh-my-pi.yaml does NOT need to change; the default model: "" stays empty so other missions keep their own model choice.

Auth & ToS posture — read this before adopting

OMP’s anthropic provider authenticates against Claude Pro/Max via a PKCE flow that uses Claude Code’s OAuth client_id (base64-decoded in packages/ai/src/utils/oauth/anthropic.ts). On the wire, OMP additionally applies a “stealth surface” so Anthropic’s server-side detection does not reject the request:

Claude Code system-prompt prefix: "You are a Claude agent, built on Anthropic's Claude Agent SDK." (see OMP claudeCodeSystemInstruction)
proxy_* tool name prefix (matches Claude Code’s convention)
User-Agent: claude-cli/<version> plus claudeCodeHeaders and the Claude Code beta-feature header set
Node TLS ciphersuite ordering matching Claude Code’s binary (CLAUDE_CODE_TLS_CIPHERS = tls.DEFAULT_CIPHERS)

Anthropic Consumer ToS (Feb 20, 2026) explicitly prohibits using subscription OAuth tokens outside Claude Code. Server-side detection has been live since Jan 9, 2026 (it killed OpenCode, Roo Code, Cline). OMP’s stealth surface currently bypasses that detection — but this is a cat-and-mouse posture, not a stable contract:

If Anthropic tightens detection (e.g. adds tool-name-pattern matching), every mission using this route fails together until OMP catches up.
A ToS escalation by Anthropic against the client_id would invalidate every Claude Max user’s tokens.
Reputationally, UH’s posture inherits OMP’s posture; if that becomes a problem, switch missions to a paid ANTHROPIC_API_KEY route (a future UH issue may add a native adapter).

You are responsible for accepting this risk on your Anthropic account. This runbook does not endorse the route — it documents it because UH-26 made the override path explicit and UH-27 chose to wire it.

Prerequisites

OMP installed and on PATH (omp --version ≥ 15.1.3).
Claude Pro or Claude Max subscription, logged in via OMP:
```
omp auth login anthropic
```
This runs the PKCE flow on localhost:54545; on success OMP stores a refreshable OAuth token in its credential database.
UH .harness/adapters/oh-my-pi.yaml present (created by uh init). The manifest’s config.runtime_config.model: may stay empty — the mission-level override fills it in per-mission.

Smoke test sequence

The reference mission lives at examples/missions/anthropic-via-omp-smoke.yaml. Copy it under .harness/missions/<id>/mission.yaml in a host project to exercise the path:

uh mission dry-run .harness/missions/anthropic-via-omp-smoke/mission.yaml \
  --runtime oh-my-pi

The dry-run output should include --model anthropic/claude-opus-4-7 in the planned args. Then:

uh mission run .harness/missions/anthropic-via-omp-smoke/mission.yaml \
  --runtime oh-my-pi

Watch .harness/missions/<id>/runtime.stdout.log for OMP’s NDJSON event stream. A successful run produces:

runtime-final.txt containing the assistant’s last message
events.ndjson with runtime.started → oh-my-pi.message* → runtime.finished
runtime-result.yaml with status: passed

Failure modes & what to do

Symptom	Likely cause	Remediation
`401 Unauthorized` in stderr	OMP token expired or revoked	`omp auth login anthropic` to refresh
`runtime-result.yaml: status: blocked` + “auth or quota error”	Detected by `detectOhMyPiQuotaError`; usually a tightened Anthropic server-side block	Check OMP release notes for stealth-surface updates; pin a known-good OMP version
`Mission runtime_config_overrides validation failed`	Typo or unknown key in mission override	Diff against `OhMyPiRuntimeConfigSchema` in `src/adapters/oh-my-pi.ts`
Hangs without final message	OMP exited before emitting an assistant event	`runtime-result.yaml: status: blocked`; inspect stderr; common cause is upstream rate-limit

Mission override schema

Mission-level runtime_config_overrides is validated by the same strict OhMyPiRuntimeConfigSchema as the adapter manifest, after merging. Valid keys:

mode: json | text | rpc | rpc-ui (default json; rpc-ui is rejected for headless runs)
thinking: "" | minimal | low | medium | high | xhigh
allow_extensions: boolean
allow_skills: boolean
model: arbitrary string; OMP routes anthropic/..., openai/..., openrouter/..., etc.

Unknown keys raise a load-time Zod error — same typo safety as the adapter manifest after UH-26.

Out of scope for UH-27

Per-runtime override merging for hermes and codex adapters (parity follow-up: file UH-31 when needed).
Native Anthropic adapter using ANTHROPIC_API_KEY (the ToS-clean alternative; file as UH-29 when desired).
OpenRouter/Vercel AI Gateway routing (file as UH-30).

v0.8.0 graduation (2026-05-25 — #156)

oh-my-pi graduated from status: experimental to status: active in Ultimate Harness v0.8.0 (GitHub issue #156). The graduation inherits the ToS posture documented above (§ “Auth & ToS posture — read this before adopting”) rather than restating it. Mirrors the v0.7.0 pi adapter graduation: the runbook is authoritative; users opt in.

Graduation evidence (local, 2026-05-25):

Adapter probe: uh adapter check oh-my-pi → [PASS] against omp/15.2.4 (the current released OMP build at graduation time).
Reference mission examples/missions/anthropic-via-omp-smoke.yaml remains the canonical live smoke; running it consumes Anthropic tokens and is left to the operator’s local environment, since the smoke outcome reflects the OMP stealth surface plus the operator’s Pro/Max subscription status (both outside this repo).
No adapter behavior change. The runtime_config_overrides.model: override path documented above is unchanged.

What changed in the repo for graduation:

.harness/adapters/oh-my-pi.yaml — status: active.
src/harness/adapter-add.ts — uh adapter add oh-my-pi scaffold template flipped to status: active; header comment in sync.
README.md — capability summary, adapter table row, and CLI example list reflect oh-my-pi as active.
docs/ROADMAP.md — Adapters considered table row updated.
apps/docs/content/docs/index.mdx — docs-site adapter mirror updated.
CHANGELOG.md — [0.8.0] entry covers the graduation in the v0.8.0 release notes.

If OMP’s stealth surface gets tightened (Anthropic detection adds a pattern OMP doesn’t yet bypass), every mission using this route fails together with runtime-result.yaml: status: blocked until OMP catches up. Pin a known-good OMP version in your local env (see § “Failure modes & what to do” above) or switch to the native ANTHROPIC_API_KEY adapter (planned v0.9.0). The graduation does not change UH’s responsibility model: this is still an opt-in route documented for adopters who have accepted the ToS posture.